How to test troubleshoot Isuzu NPR diesel no start, hard start, won't start without starting fluid

How to test troubleshoot Isuzu NPR diesel no start, hard start, won't start without starting fluid

My 2005 GMC W3500 (same as Isuzu npr) with the 5.2 Liter 4 cylinder turbo diesel engine wouldn’t start without starting fluid, so I immediatly suspected a fuel problem.

After replacing the fuel filter and bleeding the fuel system multiple times, it still didn’t fix the problem.

I came up with a test to test the fuel return, or pressure buildup, of each injector individually.

To perform the test, what you have to do is make a cap for the fuel supply line to the injector from the common rail. Next, cap each fuel supply line from the common rail one by one and attempt to start the engine. If it starts with one of the fuel lines to the injector capped, you know that that injector is allowing fuel to pass and not allowing enough fuel pressure to build in the common rail to start the engine.

My test showed that the injector on cylinder #4 was allowing the fuel to pass and not allow the pressure to build high enough to start it. To be on the safe side, I’m replacing all 4 injectors, but in reality, I could have got away with replacing just the 1 bad injector.

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Comments

Tommy Bryan says:

Can some one tell me what to do no fuel from fuel pump

Darrin Wilson says:

Can someone point me to a video on how to change a fuel injector on an isuzu npr like this one?

noka noka kokey says:

If its computerbox it needs scan and troubleshoot to gain rev and full power

icecoalman smith says:

Great Video

robertaco98 says:

any idea where I can get the radiator fan? please help!!

Inayat Mirza says:

Uncomplicated video

Thomas Smith says:

Just rebuilt a 5.2 I Have times it twice but still wont start cranks just fine. I have fuel going to the injectors. Do you think that the injectors are the problem? If you want to get back to me you can message me at 7123189920 or email me at bigredrepair@gmail.com.

SuddenFashionDOTcom says:

Yes, I have replaced all 4 fuel injectors. It starts up great now, with no ether needed. The engine seems to run good, but unfortunately it doesn't rev up (only about 10% rpm) in Drive or reverse. It will only fully rev up (100% rpm) neutral or park. I know the transmission is good because it ran and drove with the old injectors. So now I don't know what to do. I'm thinking the high pressure fuel pump is the problem.

Edward LaPaugh says:

Did you do the injectors yet? I also have a 2005 npr the other day when changing the fuel filter fuel would not stop siphoning out of the fuel tank i had to put a bucket under while changing the filter
i'm thinking the suction control value is leaking. I never had this problem before. 290,000 miles still running strong.

Michael McClure says:

I hope you don't make it a ether junky.

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