Cummins ISX & QSX Parts+
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From troubleshooting parts to a complete ISX engine overhaul repair kit, find the parts you need by selecting your engine above, or scroll down for more information.
If you are unsure what type of engine you have, check the data plate, which can be found on top of the rocker lever cover. The model number will be towards the center-left side of the plate. Another important number to reference with this engine is the ECM dataplate. This can be found on either the front or the back of the ECM or electronic control module.
General Information on Cummins QSX and Cummins ISX Specs
Important note: Many failures following repairs are due to contamination or dirt entering the system. Be sure to always keep a clean work area and take extra steps to ensure that nothing enters the engine's components.
General Specifications and Recommendations for Cummins ISX and Cummins QSX15 Parts
• Recommended oil is 15W-40 or API CH-4. For cold weather (consistently below -13 degrees F) it is recommended that synthetic oil or API category III oil be used.
• CM870 Dry engine weight (pounds): 2650 (automotive), 3020 (generator), 3360 (industrial)
• CM871 Dry engine weight (pounds): 3093
• Firing order: 1-5-3-6-2-4
• Fuel pump, maximum allowable restriction: 8 in Hg. (clean filter) or 12 in Hg (dirty filter)
• Maximum fuel inlet temperature: 160 degrees F
• Oil pressure, minimum at idle: 15 psi
• Oil pressure maximum: 35 to 40 psi (warm engine) or 150 psi (cold engine)
• Oil capacity, automotive and industrial: 10 to 12 gallons
• Oil capacity, automotive and industrial: 19 to 22 gallons
• Coolant capacity: 25 quarts (without EGR) to 35 quarts (with EGR)
• Maximum coolant pressure: 63 psi (CM871) 38 psi (CM870) or 33 psi (without EGR)
• Maximum temperature, tank top: 225 degrees F (below 565 horsepower) to 230 degrees F (above 565 horsepower)
• For the cooling system, water should have a maximum calcium magnesium (hardness) of 170 ppm. Chloride should not exceed 40 ppm and sulfate should not exceed 100 ppm.
Checking and replacing components
• The fuel filter should be changed every 25,000 miles.
• The valves and injectors should be serviced and adjusted every 5 years or 500,000 miles. For non-highway uses, adjust every 10,000 hours.
Use the following as a guide to diagnosing trouble with your Cummins QSX15 or ISX engine. As a reminder, this is intended as a general guide, and any major repairs should always be done by an experienced Diesel mechanic.
Alternator keeps malfunctioning or having to replace often
If you find you need to replace your Cummins ISX or QSX alternator frequently then these could be the reason:
• The alternator must have enough clearance or the unit can overheat. If it is placed too close to the turbocharger, manifold or other source of heat, then it would need to be positioned so that cool air can enter the front of the unit.
• The alternator may be mounted in a way that it is exposed to salt spray, dust or debris.
Loud air compressor
These are areas to check if your ISX15 or QSX15 is experiencing excessive noise from this area:
• If it is cold, check the lower sections of the air discharge line for ice.
• Look for carbon buildup in the air discharge line.
• Make sure the compressor is properly timed and in good condition. To do this, pin the crankshaft so it does not move. Then remove the support bracket and the mounting capscrews. At this point check the gear, gasket surfaces, and inside of the cylinder head show damage, then the entire unit needs to be replaced. When viewing the open compressor, you will be able to see a mark on the gear. This should be lined up with the notch on the outside, which will be at roughly the three o'clock position. After replacing or timing the unit, put on a new gasket and put Loctite or equivalent on the capscrews and tighten them.
Oil temperature is too high
If your ISX or QSX Cummins engine is experiencing oil that is overheating, then use the following as a guide to find the source of the problem:
• Check the oil switch, gauge and sensors.
• Make sure the oil is at the proper level, drain and replace.
• Check the oil thermostat to make sure it is not malfunctioning.
Oil sludge in the crankcase
This can be the result of the following conditions:
• Wrong fuel grade.
• Oil needs to be changed, or may be contaminated with coolant or fuel.
• Crankcase pressure is too high, causing excessive blowby.
• Damaged injector cup or high pressure connector torque.
• Fuel actuator or timing is malfunctioning.
Low oil pressure
Low oil pressure is usually caused by one of these areas:
• Lubricant is not proper for operating conditions (if operating in cold areas, see the oil section under general specifications above.)
• High pressure relief valve malfunctioning.
&Bull; Oil pressure regulator malfunctioning.
Fuel in oil
Check the following if you suspect your Cummins QSX or ISX contains fuel in the oil:
• Try idling the engine less. Leaving the engine in idle for over ten minutes can cause this.
• If long term idling cannot be avoided, increase the idle speed.
• The position of the fuel tank results in the fuel level being higher than the cylinder head then gasket check valves are needed in the supply and return lines.
• Check for any damage or restrictions in the flow of the fuel drain line.
• Look for injectors that are malfunctioning or are missing the plug balls.
• Check for an o-ring or injector timing plunger that is damaged.
• Cylinder head has a crack or hole.
Fuel in coolant
If you suspect fuel is in your coolant, check the following areas:
• Fuel heater.
• Injectors, particularly the o-rings.
• Cylinder head, especially any signs of cracks.
Engine starts but does not stay on
If your Cummins QSX15 or ISX15 will not stay on after starting, be sure to check the following areas:
• Make sure the idle shutdown or PTO features are not activated.
• Double check that the fuel level is not too low and the right grade.
• Check or replace the battery.
• Check the fuel inlet and system to make sure it does not have air in it. If so, bleed the system and refill.
• Check to make sure the transmission, fan, or other units driven by the engine are not causing excessive resistance.
Engine does not crank at all
The following outlines what to check when the engine will not crank at all:
• If the engine is cranking slowly, the engine may be cold. Warm the engine and battery and retry starting.
• Check or change the battery, being sure to replace it with one that can handle the ISX15 or QSX15's power requirements. For 12 V DC batteries, the minimum cold cranking amperes is 1800 for automotive and 2700 for industrial. For 24 volt DC batteries, the minimum cold cranking amperes is 900 for automotive and power generation and 1350 for industrial uses.
• Look for broken or corroded starting circuit connections.
• Check the starter, especially if it has an interlock device engaged.
&Bull; Disengage any engine driven units to make sure that are not causing too much resistance.
• Look at the ring gear or pinion of the starting motor to make sure it is not cracked or worn.
• Check the crankshaft to make sure it can rotate freely.
• Remove the injectors to see if there is any fluid in the cylinder as you rotate the crankshaft.
Alternator is not charging
This can be caused by the following conditions:
• Batteries are too cold.
• A fuse is blown or a wire is broken.
• The alternator belt is loose.
• The alternator pulley is not tight enough on its shaft.
• Capacity may not be high enough, install a higher capacity alternator.
See parts for the Cummins ISX
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