Diesel Injection of Pittsburgh’s Engine Symptom Troubleshooting Guide
By Gary Hoffman
Proper troubleshooting will not only make the job easier but it will save you a lot of money. You would be surprised how many expensive parts are replaced just because someone thinks it might be the problem.
Please do not call us and ask us how to fix your engine if you do not use our products!
I’m sure you understand why I make the above statement. Unfortunately, it is not possible to fix your Cummins engine over the telephone. We have three full time employees taking phone calls everyday, all day and if we don’t sell you parts we cannot stay here to help you with your high performance needs.
The below symptom list is for the Cummins NTC and N-14 mechanical engines only. Although, some may apply to other engines in some situations.
1. My truck is smoking white/blue smoke:
A: Valve and injector adjustments are not correct. Also verify the accessory drive gear alignments are correct prior to setting the overhead.
B: Bad injector or injectors.
C: Camshaft injector lobe or lobes flaking.
D: Incorrect injection timing.
E: Worn rocker boxes, injector links or push rods.
F: Bad fuel.
G: Water temperature not holding at proper operating temperature.
H: STC/MVT system malfunctioning or lube system sucking air (STC
only).
Comments on above symptom:
A common miss diagnosis is blaming this on the fuel pump. This is not a fuel pump issue.
Nor is this an oil consumption related problem. You very rarely see oil smoke from the exhaust of a diesel engine.
2. I’m pumping oil out the exhaust.
A: This is most likely diesel fuel and may be normal under some situations. The earlier Big Cam engine (BC-II through BC-IV) had low compression pistons and will do this in colder weather if idled for extended periods. Improper operating temps will aggravate it also. If this is not a “normal” situation, use the above white smoke symptom list. This is usually a related problem.
B: If the oil is showing up in the exhaust pipe after the turbo and is not in front of the turbo or in the exhaust manifold, this is a turbo problem. (Turbo removal is required to determine this)
3. My BC-IV low flow cooling system is overheating:
A: Please refer to the troubleshooting and repair manual mentioned above. This is a complicated system and diagnostics are extensive to determine the proper repair.
B: Engines making over 450HP will overheat on a hot day under a long pull. The only way to eliminate the problem is to convert it to a high flow system.
4. I have low power. What is wrong:
A: Low fuel pressure.
B: Fuel restriction.
C: Low manifold pressure.
D: Exhaust or air intake restriction. (rare)
E: Valve and injectors not set properly.
F: Wrong parts in engine. IE: pump, injectors, turbo, cam, pistons etc.
G: Any of the problems described under question 1.
5. I have an 840 (or 838) CPL engine. I installed different parts and now it smokes or has no power or both.
A: You cannot intermix parts between these two CPL #’s and other engines. This is a very common issue. Severe engine damage will result. If you want more power from this engine, please call and we will supply you with custom parts to achieve your horsepower needs.
6. How do I remove my STC system:
A: First question I ask is: why would you want to do this? You are taking a step backwards in technology. If you are having injector problems, and want to remove this system for that reason (most common), you need to find out why you are having those problems. Don’t blame it on the system. The STC engine is a good engine and will run a long time if properly maintained and has proper repair procedures performed on it. Most problems on this engine stem from improper repair procedures, improper troubleshooting/diagnosis and lack of knowledge towards the STC system itself.
7. My engine won’t come back to idle fast enough and/or has an idle surge problem:
A: Restricted main return line to the tank.
B: Throttle leakage not set properly.
C: Bad main body of fuel pump or pump throttle shaft fit problem
D: Cut injector o-ring or o-rings.
E: Bad injector.
8. My manifold pressure is low and I have high exhaust heat:
A: Manifold pressure leak.
B: Exhaust restriction.
C: Wrong turbo or turbo problem.
9. Why would my engine use oil when it only has a few hundred thousand miles on it?
A: Improper break in procedure.
B: Engine has been overheated.
C: Aftermarket non-Cummins cylinder kits used to rebuild.
D: Air intake system allowing dirt to pass into engine. (Damages rings, liners and valve guides.)
E: Excessive lugging.
F: Bad STC valve allowing oil into the fuel system. (If equipped)
G: Using starting fluid to start the engine. (Breaks the rings)
H: Oil leaking past the compressor or turbine seals of the turbo.
10. I have high blow-by.
A: This statement comes from people seeing oil dripping from the road draft/engine breather tube after they park the truck. It is normal to have a few drops of oil come from the tube under this condition. The only way to determine if you really have high blow-by is to run a manometer test. But, if you do not have an oil consumption problem you probably do not have high blow-by.
11. I have fuel in my oil.
A: Bad injector barrel to plunger fit.
B: Cut injector o-rings
C: Bad front seals in fuel pump.
D: Cracked cylinder head.
E: Bad camshaft.
12. I have fuel in my radiator or visa-versa:
A: Cracked injector tube or cylinder head.
B: Defective fuel heater.
13. My injectors keep failing.
A: Use of non-Cummins aftermarket injectors is the most common reason for this.
B: Improperly set overhead or wrong overhead setting procedure being used.
C: Poor filtration of the diesel fuel.
D: Water in fuel.
E: Algae in diesel fuel.
14. My truck is making a bird chirping type noise on a pull:
A: Broken head bolt.
B: Blown head gasket.
C: Low liner protrusion.
15. I need a new turbo because mine is squealing.
A: This is rarely a turbo problem. Most squealing noises are related to manifold pressure leaks. Pressure test the complete intake system prior to replacing the turbo. Most turbos are replaced unnecessarily. If the wheels in the turbo are not hitting the housing it most likely is not the cause.
16. My engine has water leaking from under the head gaskets:
This is common problem on older engines that have never had block upgrades or upper counterbore work done. The causes are:
A: liner to block fit problem. (no lower press fit)
B: Cracked counterbores
C: Bad deck surface.
D: Bad head surface.
E: Aftermarket head gaskets.
F: Improper head installation.
Note: Using the oversize head gasket has nothing to do with repairing this problem. It is used only to achieve a proper piston to deck height or to drop compression ratio on high compression engines.
17. My Holset turbo has a lot of play in the main shaft and wheels:
A: This is normal. If you can’t push the compressor wheel off to the side, and make the wheels hit the housings, there is nothing wrong.
18. I want to install a larger turbo. What should I do?
This is not a troubleshooting related issue but I feel it is well worth mentioning due to the number of times I hear this question. The fact is, if you install a larger turbo, and do nothing else, you will loose response, power, fuel mileage and basically be taking a step backwards. In order to take advantage of our performance turbos, you need to make other changes. Usually larger injectors and a fuel pump or an electronic fueling box such as our Pittsburgh Power will be required.
19. I have a black smoke problem:
1. Improper overhead settings or accessory drive out of time causing the same.
2. Wrong parts installed in the engine. IE: Injectors, fuel pump, turbo, pistons etc.
3. Cracked injector cup. (this is caused from water in the fuel or improper overhead settings)
4. Incorrect injection timing.
5. Boost leak or anything related to a boost problem.
6. Exhaust restriction.
7. Plugged air filter. (Don't trust looking at it. Replace it or check air restriction)
8. Aftercooler leak causing an intake port to get plugged off.
20. What button should I put in my pump?
We hear this a lot also. There is no way of knowing. The button does not "set" fuel pressure. It adjusts it. You can build ten pumps to the same pressure spec and may end up using ten different button numbers to achieve that. To adjust fuel pressure a fuel pressure gauge is required and reading should be taken while driving. We do not rely on "snap rail" fuel pressure testing.
21. I want to replace my head gaskets as they are leaking. I'm seeing bubbles at the gaskets when the engine idles so they are leaking compression.
Here is the situation. The head gasket is a metal plate with three different sealing areas. One area seals the compression. This is done right at the liner and is actually the only seal that is held by the steel plate. Another area seals coolant. This is done at each individual coolant passage and the steel plate holds the seals in place at the passage way. The last seal area is at the oil feed hole that allows oil to flow to the upper rocker/jake assembly and the steel plate holds this seal in place also. The steel gasket itself only seals the compression area at the liner. Therefore, the outer edges of the gasket plate are not being squeezed by the head. When the engine idles the outer edge of the steel plate vibrates up and down. Now, lets put a little liquid in between the steel plate and the head and block surface. When the plate vibrates it LOOKS like it is blowing bubbles where the liquid is. This is a problem that occurs when there are ANY leaks above the head causing the leaked liquid to get between the head and gasket. Also, a minor leak at the coolant seal area or oil seal area of the head gasket itself, will put a liquid in there that will show bubbling at an idle. Washing the engine etc. will do this also. So, what you are seeing is a churning effect not a compression leak. If you have a compression leak at the compression sealing area of the head gasket, you will hear a chirp on a pull. See #14 above.
22. My pyrometer is running high what could it be?
1. Boost leak in intake system. (pressurizing just the charge air cooler does not guarantee a leaK free system. Block the turbo off where the clean air enters it and put 15 lbs of air in the intake manifold on the drivers side of the engine and check for leaks throughout the system)
2. High exhaust back pressure.
3. Air intake restriction.
4. Over fueling.
5. Incorrect injection timing.
6. Wrong turbocharger for your application.
7. Wrong parts installed in engine. IE: pistons, camshaft etc.
8. Inaccurate pyrometer gauge (this is actually the first thing you need to test to verify you actually have a problem)
This page is a work in progress. I will be updating this page as I run across more Q&A's. Thank you for looking!
Gary Hoffman