The Cummins ISB is a sophisticated inline six cylinder engine that utilizes electronic controlled injectors. The ISB is usually used to power heavy duty trucks, including some for highway use, such as some models of the Dodge Ram. At Diesel Pro, we carry a large assortment of parts for this engine. We have low prices, and let you choose from multiple shipping options, so you can get the parts you want, when you want, at a price that is perfect for your budget.

If you are unsure which type of engine you have, check the dataplate. This model will start with a ISB followed by the displacement of the engine.


General Specifications

• Total system oil capacity: 17 quarts (19 quarts for deep sump)

• Normal engine idle: 700 to 1000 RPM

• Cooling capacity is 9.5 quarts

Troubleshooting and General Information

Listed below are some conditions that users of engines may experience over time, along with possible causes and solutions.

Oil pressure is high (normal for the Cummins ISB is 65 psi):
• Cold weather can cause the oil pressure to reach 100 to 120 psi. Wait for engine to warm and check/replace the gauge.

Oil pressure below 65 psi:
• Oil is high enough to reach connecting rods, resulting in aerated oil. Drain the oil and refill.
• Clogged oil filter. Replace the filter element.
• Oil suction tube or gasket is cracked or damaged, (low pressure usually only when the engine is first starting.) Check and replace tube and gaskets.
• Oil pump or bearing is worn (pressure drops over period of weeks or months.) Replace pump.
• Expansion plug is not in place (causes sudden pressure drop.) Replace the plug.

Thin and dark oil (fuel in oil):
• Fuel injection pump shaft seal is leaking. Replace pump or seal.
• If accompanied by white smoke see section below.

Milky or light oil (coolant in oil):
• A leak or crack in the oil cooler element, expansion plugs or cylinder head gasket. Check and replace as needed.

Coolant has oil in it:
• Oil cooler element may have a rupture. Check and replace.

Engine loses power when going uphill:
• Low oil level or bad suction tube. Fill oil and check tube.

Low power and smoke seen:
• Turbocharger may have a bad bearing. Check and replace turbocharger.

White smoke seen when the engine if first stated (such as in the morning):
• Leaking injector or bad o-rings. Check and replace as necessary.

Loud Turbocharger:
• Leak in air intake or exhaust. Check hoseclamps and replace.
• Foreign material. Check inlet and clean.

'Clattering' noise coming from engine:
• Main bearings could be loose. Check and replace if damaged.

Loud single knocking sound when pulling a load:
• Lose main bearing. Check and replace if damaged.
• Thin or low oil. Drain oil and replace.

Loud single knocking sound when idle or pulling a load:
• Worn crankshaft thrust bearings. Replace if necessary.

Double knocking sound heard during idle:
• Loose piston pin. Tighten or replace.


Cylinder block specifications and when to replace components

This will highlight certain sections of the Cummins ISB cylinder block and detail when they should be replaced when they show signs of pitting, corrosion or scratches:
• The connecting rod bearings.
• Crankshaft main bearings and journals.
• Camshaft (pitting less than 2 mm is ok).
• Camshaft gear
• Top of cylinder block (where it meets the head)
• Cylinder bores, also check for glazing (cross hatched appearance)
• Crankshaft flange (especially if the crankshaft seal has worn a groove)

Connecting rod specifications
• Standard, min 0.0770 inches, max 0.0775 inches
• 0.010 inch, min 0.0819 inches, max 0.0824 inches
• 0.020 inch, min 0.0868 inches, max 0.0873 inches
• 0.030inch, min 0.0917 inches, max 0.0922 inches
• 0.040 inch, min 0.0967 inches, max 0.0972 inches

Crankshaft end play:
• Minimum 0.004 inch, maximum 0.017 inches.

Valve Lobes:
• Diameter, intake, max 1.8859 inch, min 1.8324 inch
• Diameter, exhaust, max 1.8254 inch, min 1.7719 inch

Camshaft thrust plate thickness :
• Min 0.368 inch, max 0.378 inch

Camshaft bore with bushing installed :
• Min 2.1293 inch, max 2.1318 inch

Cylinder bore diameter (used):
• Min 4.0161 inch, max 4.0169

Cylinder block flatness :
• Maximum of 0.003 inches end-to-end or 0.002 inches side-to-side.

Main bearing capscrews torque, tightening:
• Tighten to a torque of 37 ft•lb (first step, after all installed go to second step)
• Tighten to a torque of 45 ft•lb (second step)
• Tighten to a torque of 66 ft•lb (third step)
• Turn 90 degrees clockwise (last step)

Vibration damper capscrew:
• Tighten to a torque of 92 ft•lb.

Rear cover capscrews:
• Tighten to 89 in-lb.

Oil pan mounting capscrews:
• 18 ft•lb


Cylinder Head

Be sure to check the following areas of the Cummins ISB cylinder head assembly and replace if they are in the described condition:
• Crossheads or their contact pads show wear or cracks.
• Any cracks around the injector bore to the intake valve seat.
• Combustion deck has any dips or imperfections.
• The cylinder head is not flat (with a feeler gauge, the end-to-end max is 0.012 inch, side-to-side is 0.003 inch.)
• Check the cylinder head capscrews for any pitting that is larger than 3/8 inch by 3/8 inch, or if any part of the fillet is damaged. If the length is more than 5.20 inches then it must be replaced.
• Valve stems are not flat or show excessive wear, or has a diameter of less than 0.274 inch.
• The breather tube has any signs of obstruction or restriction.

Torque and Specifications
• Cylinder head nuts: tighten to 59 ft•lb.
• When tightening the cylinder head capscrews, tighten to 59 ft•lb then 77 ft•lb. When all are tightened to this specification, rotate an additional 90 degrees clockwise.
• Injector protrusion, minimum of 0.150 inch, maximum of 0.171 inch.


Cam followers, push valves and tappets

The following items are related to the Cummins ISB Cam followers and push valves. The following parts should be monitored and replaced when they reach the described condition.
• The push rod is not straight, which can be tested by rolling it on a flat surface.
• The tappet stem, socket or face have excessive wear, such as deep scratches or cracks. A small amount of pitting is normal, but if it is larger than 2 mm, or it has multiple pits, then it should be replaced.
• The crankcase breather has obstructions.


Fuel System

This section outlines the role of certain parts in the Cummins ISB fuel system, and when they should be replaced.
• The fuel heater is controlled by a strip on the head of the filter. It should turn on at 34 degrees F and turn off at 65 degrees F.
• The fuel heater should have 12 DC volts powering it.
• When running the engine at a high idle, the fuel supply pressure should be a minimum of 10 psi. If it is below this then the fuel filter may be plugged.
• If the fuel lines, fittings or washers show obvious signs of damage then they need to be replaced.
• Leaks seen around the fuel lift pump or fuel line fittings. Replace any malfunctioning or damaged parts.
• Burs or debris is seen around the banjo fittings.
• Check for plugged fuel inlet screens (this can be done with a lift pump pressure test, outlined below.)


Injectors and related systems

This is a general guide for problems that can come from the Cummins ISB fuel injectors and related areas. Use the following as a guide to check and replace components as needed.
• If you suspect air in the fuel system, disconnect the return banjo fitting attached to the fuel drain line. Run the pump, allowing the air to be bled out. After a couple minutes, if air continues to bubble out then there is a leak. Check the area between the fuel filter and the suction tube inlet for the fuel tank. If the outlet fitting is at the top of the tank, then there would have to be a tube that runs to the bottom of the tank. Check this juncture, tube and surrounding welded areas for any cracks or pin holes.
• If you see air in the stem, check to make sure an injector is not stuck open. To diagnose this, open the injector supply lines on the pump end, using two wrenches (one for holding the delivery valve one to loosen the line) and crank the engine. If combustion gases is blowing back through the line then the injector is stuck open. If it continues, you should consider replacing the injector.
• Also check the high pressure fuel lines, by loosening the fitting that connect with the cylinder head and craning the engine. Tighten back to a value of 30 ft•lb. Vent one at a time until the engine runs smoothly.
• Replace any fuel lines or fuel drain lines if they are bent or have obstructions that you cannot remove.
• Replace any banjo fittings with burrs or debris.
• Replace injectors if they are damaged or have overheated, which will cause the needle or nozzle to turn a dark yellow, dark tan or blue color.

Torque and Specifications • Tighten the fuel drain line and their clamp capscrews to a torque of 18 ft•lb.
• Filter head retaining screws, tighten to 18 ft•lb.
• High pressure fuel line, tighten to 30 ft•lb.
• Fuel supply lines and banjo capscrews, tighten to 212 in-lb.
• Injector retaining nut, tighten to 35 ft•lb.
• Injector hold-down, tighten to 89 in-lb.


Lubricating oil pump

The following outline when you should service the Cummins ISB oil pump, or related areas:
• Gears have chips, excessive wear or signs of cracking.
• The drive has damage or excessive wear.
• The torque for the pump's installation bolts is 18 ft•lb.
• Any of the suction tubes show signs of cracks.
If you found any metal particles, then these are the possible sources.
• Chromium – Check piston rings.
• Copper – Check bearings and bushings.
• Iron- Check cylinder liners.
• Aluminum – Check piston for wear or scuffing.


Cooling system

When inspecting the Cummins ISB cooling system, check the following components and replace if they match the description :
• The drive belt shows any tears, cuts, cracks or signs or hardening.
• The thermostat is leaking. This can be tested by running a hose from the thermostat housing to a dry container and tighten it with a hose clamp. Operate the engine for one minute, and if it has more than 3.3 fl oz or 100cc of fluid, then the thermostat is leaking and needs to be replaced.
• Any hoses or clamps show signs of being loose or damaged.
• The fan pulley has any cracks near the bolt holes.
• The radiator core or gasket shows leaks, or the fins that are bent to the point of restricting most of the air flow.
• The water pump housing has cracks or damage.

General information and specifications
• The coolant capacity for the ISB 9.0 is 2.38 gallons.
• A 50 percent mixture of water and propylene glycol-based or ethylene glycol mixture is best.


Common areas for leaks in the air system

For this engine, the following areas should be checked when you suspect an air leak. This can be helped by coating the areas with a soap and water mix and watching for bubbles. Air leaks generally are accompanied by a high pitched whistling or whining noise.
• Air inlet piping hoses.
• Sealing surfaces and outlet connection on the turbocharger.
• Intake manifold.


Installing a new turbocharger

To remove and install a new turbocharger on your ISB Cummins engine, follow this general guide. As a reminder, any serious repairs should be done by an experienced Diesel mechanic.

• Step One- Remove the lines going in to the turbo. This includes the intake and exhaust pipes, oil supply line and oil drain line. Pull the drain line out of the boss. Remove the v-band clamp along with the elbow and o-ring.
• Step Two- Clean the gasket material and all deposits from the surfaces.
• Step Three- Apply a high-temperature antisieze compound to the turbocharger mounting studs along with a new gasket. Tighten to a torque of 33 ft•lb.
• Step Four- Install the discharge elbow, v-band clamp followed by the o-ring seal. Tighten clamp to 71 in-lb.
• Step Five- Install and tighten the oil drain line, tighten to 18 ft•lb.

When you should replace the turbocharger:
• The exhaust manifold gasket surfaces, mounting studs or mounting flange has cracks.
• If you experience oil or debris in the charge air system then the charge air system should be replaced.