Detroit Diesel 6V71, 8V71, 12V71, 16V71 Engine Tune Up

June 30, 2022

Guide To Engine Tune Up Your 71 V Series Engine Engine

There is no scheduled interval for performing an engine tune-up. As long as the engine performance is satisfactory, no tune-up should be needed. Minor adjustments in the valve and injector operating mechanism, governor, etc. should only be required periodically to compensate for normal wear and tear on parts.

To comply with emission regulations, injector timing, exhaust valve clearance, engine idle and no-load speeds, and throttle delay or fuel modulator settings must be checked and adjusted, if necessary, at 50,000 mile intervals.

Normally, when performing tune-up on an engine in service, it is only necessary to check the various adjustments for a possible change in settings. However, if a cylinder head, governor, or injectors have been replaced or overhauled, then certain tune-up adjustments are required. Accurate tune up adjustments are very important if maximum performance and economy are to be obtained.

NOTICE: If a supplementary governing device such as a throttle delay mechanism is used, it must be disconnected prior to the tune-up. After the governor and injector rack adjustments are completed, the supplementary governing device must be reconnected.

CAUTION: To eliminate the possibility of personal injury when air inlet piping is removed, do not operate an engine with a blower-mounted or front center-mounted turbo charger unless the compressor inlet guard assembly or turbo inlet shield J-26554-A is installed.

Use new valve rocker cover gaskets after the tune-up is completed.

Time Up Sequence for Mechanical Governor

Before starting an engine after an engine speed control adjustment or after removal of the engine governor cover, the service technician must determine that the injector racks move to the no-fuel position when the governor stop lever is placed in the stop position. Engine overspeed will result if the injector racks cannot be positioned at no-fuel with the governor stop lever. An overspeeding engine can result in engine damage which can result in personal injury.

Adjust the exhaust valves.
Time the fuel injectors.
Adjust the governor gap.
Position the injector rack control levers.
Adjust the maximum no-load speed.
Adjust the idle speed.
Adjust the Belleville spring for “TT” horsepower.
Adjust the buffer screw.
Adjust the throttle booster spring
Adjust the supplementary governing device if used.

Exhaust Valve Clearance Adjustment

The correct exhaust valve clearance at normal operating temperature is important for smooth, efficient operation of the engine.

Insufficient valve clearance can result in loss of compression, misfiring cylinders and, eventually, burned valve seats and valve seat inserts. Excessive valve clearance will result in noisy operation, increased valve face wear and valve lock damage.

When the cylinder head is overhauled, the exhaust valves are reconditioned or replaced, or the valve operating mechanism is replaced or disturbed in any way, the valve clearance must be adjusted to the cold setting to allow for normal expansion of engine parts during the warm-up period. This will ensure a valve setting that is close enough to the specified clearance to prevent damage to the valves when the engine is started.

All of the exhaust valves may be adjusted in firing order sequence during one full rotation of the crankshaft. Refer to General Specifications at the front of your service manual for the engine firing order.

Service Manual For 6V71, 8V71, 12V71, 16V71 Detroit Diesel Engines

Engines With Two Valve Cylinder Heads

Valve Clearance Adjustment (Cold Engine)

Remove the loose dirt from the valve rocker covers and remove covers. Discard the gaskets.
Place the governor speed control lever in the idle speed position. If a stop lever is provided, secur it in the stop position.
Rotate the crankshaft, with engine barring tool J22582 or with the starting motor, until the injector follower is fully depressed on the cylinder to be adjusted. If a wrench or barring tool is used on the crankshaft bolt at the front of the engine, do not turn the crankshaft in a left-hand direction of rotation because the bolt could be loosened.

CAUTION: To reduce the risk of personal injury when barring over or “bumping” the starter while performing an engine tune-up, personnel should keep their hands and clothing away from the engine as there is a remote possibility the engine could start.

Loosen the exhaust valve rocker arm push rod locknut.
Place a 0.12” feeler gage (J9708-01) between the end of the exhaust valve stem and the rocker arm bridge. Adjust the push rod to obtain a smooth “pull” on the feeler gage.
Remove the feeler gage. Hold the push rod with a 5/16” wrench and tighten the locknut with a ½” wrench.
Recheck the clearance. At this time, if the adjustment is correct, the 0.11” feeler gage will pass freely between the valve stem and the rocker arm, but the 0.13” feeler gage will not pass through. Readjust the push rod, if necessary.
Adjust and check the remaining exhaust valves in the same manner as above.

Valve Clearance Adjustment (Hot Engine)

It is not necessary to make a final hot engine exhaust valve clearance adjustment after a cold engine adjustment has been performed. However, if a hot engine adjustment is desired, use the following procedure.

Maintaining normal engine operating temperature is particularly important when making the hot engine exhaust valve clearance adjustment. If the engine is allowed to cool before setting any of the valves, the clearance, when running at full load may become insufficient.

NOTICE: Since the adjustments are normally made while the engine is stopped, it may be necessary to run the engine between adjustments to maintain normal operating temperature.

With the engine at normal operating temperature set the exhaust valve clearance with feeler gage J9708-01. At this time, if the valve clearance is correct, the 0.008” feeler gage will pass freely between the exhaust valve stem and the rocker arm and 0.010” feeler gage will not pass through. Readjust the push rod, if necessary.
After the exhaust valve clearance has been adjusted check the fuel injector timing.

Check Exhaust Valve Clearance Adjustment

With the engine at 100 degrees fahrenheit (38 degrees celsius) or less, check the valve clearance.
If a 0.012” feeler gage plus or minus 0.004” will pass between the end of the exhaust valve stem and the rocker arm, the valve clearance is satisfactory. If necessary, adjust the push rod.

Engines With Four Valve Cylinder Heads

The exhaust valve bridges must be adjusted and the adjustment screws locked securely at the time the cylinder head is installed on the engine

The exhaust valve bridge balance should be checked when a general valve adjustment is performed . After the bridges are balanced, adjust the valve clearance at the push rod only. Do not disturb the exhaust valve bridge adjusting screw.

Valve Clearance Adjustment (Cold Engine)

Remove the loose dirt from the rocker covers and remove the covers. Discard the gaskets.

NOTICE: On certain 12V turbocharged engines, it is necessary to remove the air inlet housing to remove the rocker covers.

Place the governor speed control lever in the idle speed position. If a stop lever is provided, secure it in the stop position.

Rotate the crankshaft, with engine barring tool J22582 or with the starting motor, until the injector follower is fully depressed on the particular cylinder to be adjusted. If a wrench or barring tool is used on the crankshaft bolt at the front of the engine, do not turn the crankshaft in a left hand direction of rotation because the bolt could be loosened.

Loosen the exhaust valve rocker arm push rod locknut.
Place a 0.016” feeler gage (J 9708-01) between the end of the exhaust valve stem and the valve bridge adjusting screw (spring loaded bridge only) or between the valve bridge and valve rocker arm pallet (unloaded bridge only). Adjust the push rod to obtain a smooth “pull” on the feeler gage.
Remove the feeler gage. Hold the push rod with a 5/16” wrench and tighten the locknut with a 1/2 “ wrench.
Recheck the clearance. At this time, if the adjustment is correct, the 0.015” feeler gage will pass freely between the valve stem and the adjusting screw (spring-loaded bridge) or between the valve bridge and rocker arm pallet (unloaded bridge), but the 0.017” feeler gage will not pass through. Readjust the push rod, if necessary.
Adjust and check the remaining exhaust valves in the same manner as above.

Valve Clearance Adjustment (Hot Engine)

It is not necessary to make final hot engine exhaust valve clearance adjustments after a cold engine adjustment has been performed. However, if a hot engine adjustment is desired, use the following procedures.

NOTICE: Since these adjustments are normally made while the engine is stopped, it may be necessary to run the engine between adjustments to maintain normal operating temperature.

With the engine at normal operating temperature, recheck the exhaust valve clearance with feeler gage J 9708-01. At this time, if the valve clearance is correct, the 0.013” feeler gage will pass freely between the valve stem and the valve bridge adjusting screw (spring loaded bridge) or between the valve bridge and the valve rocker arm pallet (unloaded bridge), but the 0.015” feeler gage will not pass through. Readjust the push rod, if necessary.
After the exhaust valve clearance has been adjusted, check the fuel injector timing.

Check Exhaust Valve Clearance Adjustment

With the engine at 100 degrees fahrenheit (38 degrees celsius) or less, check the valve clearance.
If 0.016” feeler gage plus or minus 0.004” will pass between the end of the exhaust valve stem and the valve bridge adjusting screw (spring-loaded bridge) or between the valve bridge and the valve rocker arm pallet (unloaded bridge), the valve clearance is satisfactory. If necessary, adjust the push rod.

Fuel Injector Timing

To time an injector properly, the injector follower must be adjusted to a definite height in relation to the injector body.

All of the injectors can be timed in firing order sequenced during one full revolution of the crankshaft. Refer to the General specifications section at the front of your service manual.

Service Manual For 6V71, 8V71, 12V71, 16V71 Detroit Diesel Engines

Time Fuel Injector

After the exhaust valve clearance has been adjusted, time the fuel injectors as follows.

Place the governor speed control lever in the idle speed position. If a stop lever is provided, secure it in the stop position.
Rotate the crankshaft, with the starting motor or with engine barring tool J22582, until the exhaust valves are fully depressed on the particular cylinder to be timed.

NOTICE: If a wrench or barring tool is used on the crankshaft bolt at the front of the engine do not turn the crankshaft in a left-hand direction of rotation because the bolt could be loosened.

Place the small end of the injector timing gage in the hole provided in the top of the injector body with the flat of the gage toward the injector follower.
Loosen the injector rocker arm push rod locknut.
Turn the push rod and adjust the injector rocker arm until the extended part of the gage will just pass over the top of the injector follower.
Hold the push rod and tighten the locknut. Check the adjustment and if necessary, readjust the push rod.
Time the remaining injectors in the same manner as outlined above.
If no further engine tune-up is required, install the valve rocker covers, using new gaskets.

Variable Speed Mechanical Governor And Injector Rack Control Adjustment

6V,8V,AND 12V Engines

The single-weight variable speed governor is mounted at the front of the engine and is driven by a blower rotor.

After adjusting the exhaust valves and timing the fuel injectors, adjust the governor and position the injector rack control levers.

Before proceeding with the governor and injector rack adjustments, disconnect any supplementary governing device. After the adjustments are completed, reconnect and adjust the supplementary governing device.

Adjust Governor Gap

With the engine stopped and at normal operating temperature, adjust the governor gap as follows.

Disconnect any linkage attached to the governor levers.
Back out the buffer screw until it extends approximately ⅝” from the lock nut.
Clean and remove the governor cover and valve rocker covers. Discard the gaskets.
Place the speed control lever in the maximum speed position.
Insert a 0.006” feeler gage between the spring plunger and the plunger guide. If required, loosen the locknut and turn the adjusting screw until a slight drag is noted on the feeler gage.
Hold the adjusting screw and tighten the locknut. Check the gap again and if necessary, readjust.
Affix a new gasket to the top of the governor housing. Place the governor cover assembly on the governor housing with the pin in the stop control shaft assembly in the slot of the differential lever and the dowel pins in the housing in the dowel pin holes in the cover. Tighten the screws.

Position Injector Rack Control Levers

The position of the injector rack control levers must be correctly set in relation to the governor. Their position determines the amount of fuel injected into each cylinder and ensures equal distribution of load.

Properly positioned injector rack control levers, with the engine at full load, will result in the following.

Speed control lever at the maximum speed position.
Stop lever in the run position.
High-speed spring plunger within 0.005” to 0.007” of its seat in the governor control housing.
Injector fuel control racks in the *full-fuel position.

The letters “R” and “L” indicate the injector location in the right or left cylinder bank, viewed from the rear of the engine. The cylinders are numbered starting at the front of the engine on each cylinder bank. Adjusting the No. 1L injector rack control lever first to establish a guide for adjusting the remaining control levers.

Remove the clevis pin from the fuel rod and the right cylinder bank injector control tube lever.
Loosen all of the inner and outer injector rack control lever adjusting screws or adjusting screws and locknuts on both cylinder heads. Be sure all of the injector rack control levers are free on the injector control tubes.
Move the speed control lever to the maximum speed position.
Move the stop lever to the run position and hold it in that position with light finger pressure.
Move the stop lever to the run position and hold it in that position with light finger pressure.

Two Screw Assembly – Turn the inner adjusting screw of the No. 1L injector rack control lever down until a slight movement in the stop lever is noted. Turn down the outer adjusting screw until it bottoms lightly on the injector control tube. Then, alternately tighten both the inner and outer adjusting screws.

One Screw and Locknut Assembly – Tighten the adjusting screw of the No. 1L injector rack control lever until the injector rack clevis is observed to roll up or an increase in effort to turn the screw driver is noted. Tighten the screw driver approximately ⅛ of a turn more and lock securely with the adjusting screw locknut. This will place the No 1L injector rack in the full-fuel position.

NOTICE: Overtightening of the injector control lever adjusting screws during installation or adjustment can result in damage to the injector control tube. The recommended torque of the adjusting screws is 24-36 lb-in (3-4 N*m).

The above step should result in placing the governor linkage and control tube assembly in the same position that they will attain while the engine is running at full load.

5) To be sure of the proper rack adjustment, hold the stop lever in the run position and press down on the injector rack with a screwdriver or finger tip and note the “rotating” movement of the injector control rack when the stop lever is in the run position. Hold the stop lever in the run position and using a screwdriver, press downward on the injector control rack. The rack should tilt downward and, when the pressure of the screwdriver is released, the control rack should “spring” back upward.

If the rack does not return to its original position, it is too loose. To correct this condition with the Two Screw Assembly , back off the outer adjusting screw slightly and tighten the inner adjusting screw slightly. To correct this condition with the One Screw and Locknut Assembly loosen the locknut and turn the adjusting screw clockwise a slight amount and retighten the locknut.

The setting is too tight if, when moving the stop lever from the stop position to the run position, the injector rack becomes tight before the stop lever reaches the end of its travel. This will result in a step-up in effort required to move the stop lever to the end of its travel. To correct this condition with the Two Screw Assembly, back off the inner adjusting screw slightly and tighten the outer adjusting screw slightly. To correct this condition with the One Screw and Locknut Assembly, loosen the locknut and turn the adjusting screw counterclockwise a slight amount and retighten the locknut.

Remove the clevis pin from the fuel rod and the left back injector control tube lever.
Insert the clevis pin in the fuel rod and the right cylinder bank injector control tube lever and position the No 1R. Injector rack control lever as previously outlined in Step 4.
Insert the clevis pin in the fuel rod and the left bank injector control tube lever. Repeat the check on the No. 1L and No. 1R injector rack control levers as outlined in Step 5. Carefully observe and eliminate any deflection which occurs at the bend in the fuel rod where it enters the cylinder head.
To adjust the remaining injector rack control levers, remove the clevis pins from the fuel rods and the injector control tube levers, hold the injector control racks in the *full-fuel position by means of the lever on the end of the control tube and proceed as follows:

Two Screw Assembly:

Turn down the inner adjusting screw of the No. 2L injector rack control lever until the screw bottoms (injector control rack in the full-fuel position).
Turn down the outer adjusting screw of the injector rack control lever until it bottoms on the injector control tube.
While still holding the control tube lever in the full-fuel position, adjust the inner and outer adjusting screws to obtain the same condition as outlined in Step 5. Tighten the screws.

NOTICE: Over Tightening of the injector rack control tube lever adjusting screws during installation or adjustment can result in damage to the injector control tube, The recommended torque of the adjusting screws is 24-36 lb-in (3-4N*m)

One Screw and Locknut Assembly

Turn down the inner adjusting screw of the No. 2L injector rack control lever until the screw bottoms (injector control rack in the full-fuel position)
Turn down the outer adjusting screw of the injector rack control lever until it bottoms on the injector control tube.
While still holding the control tube lever in the full-fuel position, adjust the inner and outer adjusting screws to obtain the same condition as outlined in Step 5. Tighten the screws.

NOTICE: Overtightening the injector rack control tube lever adjusting screws during installation or adjustment can result in damage to the injector control tube. THe recommended torque of the adjusting screws is 24-36 lb-in (3-4 N*m).

One Screw and Locknut Assembly

Tighten the adjusting screw of the No. 2L injector rack control lever until the injector rack clevis is observed to roll up or an increase in effort to turn the screwdriver is noted. Securely lock the adjusting screw nut.

NOTICE: Overtightening of the injector rack control tube lever adjusting screws during installation or adjustment can result in damage to the injector control tube. The recommended torque of the adjusting screws is 24-36 lb-in (3-4N*m).

Verify the injector rack adjustment of No. 1L as outlined in Step 5. If No. 1L does not “spring” back upward, turn the number 2L adjusting screw counter clockwise slightly until the No. 1L injector rack returns to its *full-fuel position and secure the adjusting screw locknut. Verify proper injector rack adjustment for both No. 1L and No. 2L injectors. Turn clockwise or counterclockwise the No. 2L injector rack adjusting screw until both No. 1L and No. 2L injector racks are in the Full-fuel position when the locknut is securely tightened.
Adjust the remaining injectors using the procedures outlined in step “b” always verifying proper injector rack adjustment.

Once the No. 1L and the No. 1R injector rack control levers are adjusted, do not try to alter their settings. All adjustments are made on the remaining control racks.

10) When all of the injector rack control levers are adjusted, recheck their settings. With the control tube lever in the full-fuel position, check each control rack as in Step 5. All of the control racks must have the same “spring” condition with the control tube lever in the full-fuel position.

11) Insert the clevis pins in the fuel rods and the injector control tube levers.

CAUTION: Before starting an engine after an engine speed control adjustment or after removal of the engine governor cover and lever assembly, the technician must determine that the injector racks return to the no-fuel position when the governor stop lever is placed in the stop position. Engine overspeed will result if the injector raks cannot be positioned at the no-fuel with the governor stop lever. An overspeeding engine can result in engine damage which could result in engine damage which could cause personal injury.

12) Use new gaskets to reinstall the valve rocker covers.

Adjust Maximum No Load Speed

All governors are properly adjusted before leaving the factory. However, if the governor has been reconditioned or replaced, and to ensure the engine speed will not exceed the recommended no load speed as given on the engine option plate, set the maximum no-load speed as outlined below.

Start the engine and, after it reaches normal operating temperature determine sthe maximum no-load speed of the engine with an accurate hand tachometer. Then stop the engine sand make the following adjustments, if required.

Disconnect the booster spring and the governor stop lever spring.
Remove the variable speed spring housing and the spring retainer located inside the housing from the governor housing.
Refer to Table 1 and determine the stops or shims required for the desired full-load speed. The speed will increase approximately 1rpm for each 0.001” in shims added.

Variable Speed Governor Adjustment
*Full Load Speed	Stops	Shims
1200-1750	2	Up to .325” in shims maximum
1750-2100	1	Up to .325” in shims maximum
2100-2300	0	Up to .325” in shims maximum
No load speed is 125-200 rpm above full-load speed depending on engine application

Table 1

Install the variable speed spring retainer and housing and tighten the two bolts.
Connect the booster spring. Start the engine and recheck the maximum no-load speed.
If required add or remove shims to obtain the desired full-load speed. If the maximum no-load speed is raised or lowered more than 50 rpm by installation or removal of shims, recheck governor gap. If readjustment of the governor gap is required, the position of the injector racks must be rechecked.

Governor stops are used to limit the compression of the governor spring, which determines the maximum speed of the engine.

Adjust Idle Speed

With the maximum no-load speed properly adjusted, adjust the idle speed as follows:

Place the speed control lever in the idle position and the stop lever in the run position.
With the engine running at normal operating temperature, back off the buffer screw to avoid contact with the differential lever.
Loosen the locknut and turn the idle speed adjusting screw until the engine is operating at approximately 15 rpm below the recommended idle speed. The recommended idle speed is 500 rpm, but may vary with special applications.
Hold the idle speed adjusting screw and tighten the locknut.

Adjust Buffer Screw

With the engine running at normal operating temperature, turn the buffer screw so that it contacts the differential lever as lightly as possible and still eliminates engine roll. Do not raise the engine idle speed more than 15 rpm with the buffer screw.
Hold the buffer screw and tighten the lock nut.

Adjust Booster Spring

With the idle speed adjusted, adjust the booster spring as follows:

Move the speed control lever to the idle speed position.
Refer to and loosen the booster spring retaining nut on the speed control lever. Loosen the locknuts on the eyebolt at the opposite end of the booster spring.
Move the bolt in the slot of the speed control lever until the center of the bolt is on or slightly over center (toward the idle speed position) of an imaginary line through the bolt, lever shaft, and eyebolt. Hold the bolt and tighten the locknut.
Start the engine and move the speed control lever to the maximum speed position and release it. The speed control lever should return to the idle position. If it does not, reduce the tension on the booster spring. If it does not, reduce the tension on the booster spring. If it does continue to increase the spring tension until the point is reached that it will not return to idle. Then, reduce the tension until it does return to idle and tighten the locknut on the eyebolt. This setting will result in the minimum force required to operate the speed control lever.
Connect the linkage to the governor levers.

Variable Speed Mechanical Governor And Injector Rack Control Adjustment

16V Engines

The governor on the 16V engine is mounted on and driven from the front end of the rear blower.

After adjusting the exhaust valves and timing the fuel injectors, adjust the governor and injector rack control levers.

If the engine or governor has been overhauled or the injector control linkage has been disturbed, the control link levers in the governor housing and auxiliary control link housing must be aligned before proceeding with the engine tune-up. Position the control link levers as follows:

Disconnect linkage to the governor speed control.
Remove the covers from the governor housing and auxiliary control link housing.
Disconnect the adjustable link from the lever in the auxiliary control link housing.
Remove the connecting pin from the auxiliary governor control link lever.
Install gage J21779 so it extends through the lever and fuel rod and into the gage hole in the bottom of the housing. With the gage in place, the auxiliary control link lever will be in the mid-travel position.
Remove the connecting pin from the control link lever in the governor housing and install gage J 21780. Install the gage so the pin extends through the connecting link, control lever and fuel rod and the governor housing dowel pin extends into the small hole in the gage. Then, install a governor cover bolt to lock the gage in place.

With the gage J21780 in place, the governor control link lever will be in the mid-travel position and parallel to the auxiliary control link lever.

Adjust the length of the adjustable connecting link to retain the lever positions obtained in Steps 5 and 6 and install the link.
Remove gages J21779 and J21780 and reinstall the control link lever connecting pins.
Install the governor housing and auxiliary control link housing covers.

Proceed with the governor and injector rack control adjustment.

Adjust Governor Gap

With engine stopped and at normal operating temperature, adjust the governor gap as follows:

Clean and remove the governor cover and the valve rocker covers. Discard the gaskets.
Back out the buffer screw until it extends approximately ⅝” from the locknut.
Place the speed control lever in the maximum speed position.
Insert a 0.006” feeler gage between the spring plunger and the plunger guide. If required, loosen the locknut and turn the adjusting screw until a slight drag is noted on the feeler gage.
Hold the adjusting screw and tighten the locknut. Check the gap and readjust if necessary.
Affix a new gasket to the top of the governor housing. Place the governor cover assembly on the governor housing with the pin in the stop control shaft assembly in the slot of the differential lever and the dowel pins in the housing in the dowel pin holes in the cover. Tighten the screws.

Position Injector Rack Control Levers

The position of the injector control rack levers must be correctly set in relation to the governor. Their position determines the amount of fuel injected into each cylinder and ensures equal distribution of the load.

Properly positioned injector rack control levers, with the engine at full load, will result in the following:

Speed control lever at the maximum speed position.
Stop lever in the run position.
High-speed spring plunger within 0.005” to 0.007” of its seat the governor control housing.
Injector fuel control racks in the full-fuel position.

The letters “R” and “L” indicate the injector location on the right or left cylinder bank, viewed from the rear of the engine. Cylinders are number starting at the front of the engine on each cylinder bank. Adjust the No.4R injector control lever first to establish a guide for adjusting the remaining right bank injector control levers.

Remove the clevis pins which attach to the right rear bank and bank both left-bank fuel rods to the injector control tube levers.
Loosen all of the inner and outer injector rack control lever adjusting screws or adjusting screws and locknuts on both cylinder banks. Be sure all of the levers are free on the injector control tubes.
Move the speed control lever to the maximum speed position.
Move the stop lever to the run position and hold it in that position with light finger pressure.

Two Screw Assembly – Turn the inner adjusting screw of the No. 4R injector rack control lever down until a slight movement of the stop lever is noted. Turn down the outer adjusting screw until it bottoms lightly on the control tube. Then, alternately tighten both the inner and outer adjusting screws.

One Screw and Locknut Assembly – Tighten the adjusting screw of the No. 4R injector rack control lever until the injector rack clevis is observed to roll up or an increase in effort to turn the screwdriver is noted. Tighten the screw approximately ⅛ of a turn more and lock securely with adjusting screw locknut. This will place the No. 4R injector rack in the full-fuel position.

NOTICE: Overtightening of the injector rack control lever adjusting screws during installation or adjustment can result in damage to the injector control tube. The recommended torque of the adjusting screws 24-36 lbs-in (3-4N*m).

The above step should result in placing the governor linkage and control tube assembly in the same position that they will attain while the engine is running at full load.

To be sure of the proper rack adjustment, hold the stop lever in the run position and press down on the injector rack with a screwdriver or finger tip and note the “rotating” movement of the injector control rack when the stop lever is in the run position. Hold the stop lever in the run position, using a screwdriver, press downward on the injector control rack. The rack should tilt downward and, when the pressure of the screwdriver is released, the control rack should “spring” back upward.

If the rack does not return to its original position, it is too loose. To correct this condition with the Two Screw Assembly, back off the outer adjusting screw slightly and tighten the inner adjusting screw slightly. To correct this condition with the One Screw and Locknut Assembly, loosen the locknut and turn the adjusting screw clockwise a slight amount and retighten the locknut.

The setting is too tight if, when moving the stop lever from the stop to the run position, the injector rack becomes tight before the stop lever reaches the end of its travel. This will result in a step-up in effort required to move the stop lever to the end of its travel. To correct this condition with the Two Screw Assembly, back off the inner adjusting screw slightly and tighten the outer adjusting screw slightly. To correct this condition with the One Screw and Locknut Assembly, loosen the locknut and turn the adjusting screw counterclockwise a slight amount and retighten the locknut.

Remove the fuel rod-to-control tube lever clevis pin from the right front bank fuel rod and install it on the right rear bank fuel rod and adjust the No 5R injector rack as outlined in Steps 4 and 5.
Repeat Step 6 for adjustment of the No. 4L and injector racks. When the settings are correct No. 4R , 5R, 4L, and 5L injector racks will be snug on the ball end of the control levers when the injectors are in the full-fuel position.
With the fuel rod disconnected from the injector control tube lever, adjust the remaining injector rack control levers on the right front bank. Hold the No. 4R injecto rack in the full-fuel position by means of the control tube lever and proceed as follows:

Two Screw Assembly

Turn the inner adjusting screw of the No. 3R injector rack control lever until the injector rack has moved into the full-fuel position. Turn the outer adjusting screw down until it bottoms lightly on the injector control tube. Then, alternately tighten both the inner and outer adjusting screws.

Recheck the No. 4R injector rack to be sure that it has remained snug on the ball end of the injector rack control lever. If the rack of the No. 4R injector becomes loose, back off the inner adjusting screw slightly on the No. 3R injector rack control lever and tighten the outer adjusting screw.

One Screw and Locknut Assembly

Tighten the adjusting screw of the No. 3R injector rack control lever until the injector rack clevis is observed to roll up or an increase in effort to turn the screwdriver is noted. Securely lock the adjusting screw locknut.

Verify the injector rack adjustment of No. 4R as outlined in Step 5. If No. 4R does not “spring” back upward, turn the No 3R adjusting screw counterclockwise slightly until the No. 4R injector rack returns to its full-fuel position and secure the adjusting screw locknut. Verify proper injector rack adjustments for both No. 4R and No. 3R injectors. Turn clockwise or counterclockwise the No. 3R injector rack adjusting screw until both No. 4R and No. 3R injector racks are in full-fuel position when the locknut is securely tightened.
Adjust the remaining injectors using the procedures outlines in step “B” always verifying proper injector rack adjustment.

9) Recheck the No. 4R injector rack to be sure it has remained snug on the ball end of the injector rack control lever. If the rack of the No. 4R injector has become loose, loosen the locknut on the No 3R and turn the adjusting screw counterclockwise a slight amount and retighten the locknut.

When the settings are correct both injector racks must respond in the same manner on the ball ends of the control levers when the injector control tube lever is held in the full-fuel position.

10) Position the remaining injector rack control levers on the right front cylinder bank as outlined in Step 8 and 9.

11) Adjust the remaining injector rack control levers on the right rear, left front and left rear cylinder banks in the same manner as outlined in Steps 8,9, and 10.

12) Install the four fuel rod-to-control tube lever clevis pins and check the adjustment of the injector rack control levers.

13) Use new gaskets and reinstall the valve rocker covers.

Adjust Maximum No-Load

All governors are properly adjusted before leaving the factory. However if the governor has been reconditioned or replaced, and to ensure that the engine speed will not exceed the recommended no load speed as given on the engine options plate, set the maximum no-load speed as outlined below.

Start the engine and, after it reaches normal operating temperature, determine the maximum no load speed of the engine with an accurate hand tachometer. Then stop the engine and make the following adjustments, if required:

Disconnect the booster spring and governor stop lever spring.
Remove the variable speed spring housing and the variable speed spring plunger inside the housing.
Refer to table 2 and determine the stops or shims required for the desired full-load speed. The speed will increase approximately 1rpm for each 0.001” shims added.

Variable Speed Governor Adjustment
*Full Load Speed	Stops	Shims
1200-1750	2	Up to .325” in shims maximum
1750-2100	1	Up to .325” in shims maximum
2100-2300	0	Up to .325” in shims maximum
No load speed is 150 225 rpm above the load speed depending upon engine application

Table 2

Install the variable speed spring plunger and housing and tighten the two bolts.
Connect the booster spring. Start the engine and recheck the maximum no-load speed.
If required add or remove shims to obtain the required full-load speed. If the maximum no-load speed is raised or lowered more than 50 rpm by the installation or removal of shims, recheck the governor gap. If readjustment of the governor is required, the position of the injector racks must be rechecked.

Governor stops are used to limit compression of the governor springs, which determines the maximum speed of the engine.

Adjust Idle Speed

With the maximum no-load speed properly adjusted, adjust the idle speed as follows:

Place the speed control lever in the idle position and the stop lever in the run position.
With the engine running at normal operating temperature, back out the buffer screw to avoid contact with the differential lever.
Loosen the locknut and turn the idle speed adjusting screw until the engine is operating at approximately 15 rpm below the recommended idle speed. The recommended idle speed is 550rpm, but may vary with special engine applications.
Hold the idle speed adjusting screw from turning and tighten the locknut.

Adjust Buffer Screw

With the engine running at normal operating temperature, turn the buffer screw IN so that it contacts the differential lever as lightly as possible and still eliminates engine roll. Do not raise the idle speed more than 15 rpm with the buffer screw.
Hold the buffer screw from turning and tighten the locknut.

Adjust Booster Spring

With the idle speed adjusted, adjust the booster spring as follows:

Move the speed control lever to the idle speed position.
Loosen the nut on the booster spring retaining bolt on the governor speed control lever. Loosen the locknuts on the eyebolt at the opposite end of the booster spring.
Move the bolt in the slot of the speed control lever until the center of the bolt is on or slightly over center (toward the idle speed position) of an imaginary line through the bolt, lever shaft and eyebolt. Hold the bolt from turning and tighten the locknut.
Start the engine and move the speed control lever to the maximum speed position and release it. The speed control lever should return to the idle speed position. If it does not, reduce the spring tension. If the lever does return to the idle position, increase the tension of the spring until the lever will not return to idle the lever will return to idle to tighten the locknut on the eyebolt. This setting will result in a minimum force required to operate the speed control lever.
Connect the linkage to the governor levers.

No patent liability is assumed with respect to the use of information contained in this blog post. While every precaution has been taken in preparation of this blog post, the author assumes no responsibility for errors and omissions. Neither is any liability assumed for damages resulting from the use of the information contained in this blog post.

All instructions, diagrams, videos have been checked for accuracy and ease of application; however success and safety in working with tools depend to a great extent upon individual accuracy, skill, and caution. For this reason, the authors are not able to guarantee the result of any procedure contained in this blog post. Nor can they assume responsibility for any damages to property or injury to persons occasioned from the procedures. Persons engaging in the procedures do so entirely at their own risk.

Please follow and like us:

We Deliver To Your Door In Canada

24 hr Worldwide Shipping

Success!

Detroit Diesel 6V71, 8V71, 12V71, 16V71 Engine Tune Up