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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29457
Experience:  GM Grand Master Technician 2007. 14 years experience.
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Chevrolet Duramax: Absolutely will NOT start!

Customer Question

Other than injectors, is there any reason that a 01' Duramax 6.6 LB7, would be putting out more than 40cc of fuel, during the 15 second crank test, from the small fuel line?

Submitted: 1 year ago.
Category: Chevy
Expert:  Gary replied 1 year ago.
I am sorry for the long waitis the engine oil over full at all ?40CC being measured where ? the return ?
Customer: replied 1 year ago.

Oil level is perfect.

Yes, being measured from the return, at the rear of the driver side head.

I should add that prior to changing the injectors the fuel measurement was 130+ cc, per 15 sec crank. Now it is 80cc, per 15 sec crank.

I'd also like to add that the ECM has been swapped out, with a security disabled ECM, with no change to the crank- no start issue.

Expert:  Gary replied 1 year ago.
ok so this has 8 brand new injectors in it ?no codes set at all ?fuel prime did nothing ?
Customer: replied 1 year ago.

Correct.

Expert:  Gary replied 1 year ago.
the only other thing to have that kind of return rate would be the fuel pressure relief valve built into the aluminum junction blockhow much pressure is the rail showing actual and desired when cranking it over ?
Customer: replied 1 year ago.

Actual is 38-51/52 MPa

Desired is 42 MPa

We did a test the rail pressure with the FRP plugged in, as well as unplugged, there was no change. The scanner that is being used is a Modis.

Expert:  Gary replied 1 year ago.
no codes at all ?did it run with the old injectors in it ?
Customer: replied 1 year ago.

No codes at all, at this point. Original code on the truck was the FICM (U1800)

None running upon arrival. Owner stated she was driving down the road and it just died, hasn't started since. She said as far as she knows, there was no hard start or any type of miss/white smoke, prior to it shutting down. She has owned the truck for 8 years, claims this is the 1st problem she has ever had. Has done regular maintenance, as far as oil changes go, but has only done 2 fuel filter changes. We put a new AC-Delco filter on it, replacing the napa filter she was running.

Expert:  Gary replied 1 year ago.
does it still have a U1800 code ?can you communicate with the FICM ?
Customer: replied 1 year ago.

No sir. The code was cleared and didn't return, upon changing the FICM.

To my knowledge the scanner is communicating with the FICM. Could you give some detail as to what type of communication you are looking for?

Expert:  Gary replied 1 year ago.
when the FICM was changed was it programmed to the trucks VIN number ?
Customer: replied 1 year ago.

No sir. It was a used FICM (came off a running truck) & I don't know that we've ever had to program one. Going out a limb here and guessing that only a dealership can do that?

Expert:  Gary replied 1 year ago.
yes the FICM needs to be programmed to the trucks VIN number as it is a computerany shop with programming capabilities can do this for youi just think we need to be 100 % sure that is not our problem next
Customer: replied 1 year ago.

Okay. I will make some calls and see what I can get done. In the mean time, I have ordered the FRP sensor, just to be on the safe side. It will be here later this afternoon. I will let you know what I find out next.

Customer: replied 1 year ago.

Bad news. Per the VIN & build date(01/01) this FICM does not have to be programmed to the truck. Back to square 1. =(

Expert:  Gary replied 1 year ago.
lets see if any other experts have any ideashang on another expert will reply back to you
Customer: replied 1 year ago.

Thank you!! ūüėÜ

Expert:  GM Tech (Cam) replied 1 year ago.
Hello, I'm Cam.
Can I get your first name please?
Ok so 8 new injectors, can you tell me the source of the injectors?
Customer: replied 1 year ago.

Hi Cam! Amanda. Yes sir, 8 brand spankin new Injectors. They are direct from Bosch.

Expert:  GM Tech (Cam) replied 1 year ago.
Ok, so on the top of the injection pump is the return line from the pump. ITs an elbow. Lets take that off the pump, plug the line, put another on the pump and repeat the test. This will eliminate the pump or condemn it. If its still coming from the main return line at the back then one or more of your new injectors are bad.
Customer: replied 1 year ago.

I'd also like to add that we just replaced the black fuel line, with clear line, from the CP3 to the metal return line, on the driver side, which appears to have constant bubbles & squirted a lot of fuel.

Expert:  GM Tech (Cam) replied 1 year ago.
Ok, take that line off and try the return test without the pump contributing to the return flow.
Customer: replied 1 year ago.

Yes sir. Hold please.

Expert:  GM Tech (Cam) replied 1 year ago.
Sure thing.
Customer: replied 1 year ago.

Main return line, from the back, has no fuel coming out of it.

Expert:  GM Tech (Cam) replied 1 year ago.
Ok, so you pulled the return line off the pump and repeated the test to find no fuel being returned from the injectors?
Customer: replied 1 year ago.

Correct. However there is a ton of fuel coming from the CP3 line

Expert:  GM Tech (Cam) replied 1 year ago.
Then your pump is bad as well. During cranking that should not be returning anything or very little. This is odd, I have only changed 1 pump for this issue.
Customer: replied 1 year ago.

Changed the pump, crank no start. Changed the FRP sensor, crank no start. Any more ideas?

Expert:  GM Tech (Cam) replied 1 year ago.
Did you replace the pressure relief valve before?
Customer: replied 1 year ago.

No.

Expert:  GM Tech (Cam) replied 1 year ago.
Has this engine had a programmer or chip installed to boost the power? .
Customer: replied 1 year ago.

It has a Duramaximizer, which we unhooked.

Expert:  GM Tech (Cam) replied 1 year ago.
Ok that would do it. The first action of the chip is to trick the system into running higher pressures by sending false readings of the actual fuel pressure. That then turns the fuel pressure relief valve which normally does not operate into a fuel pressure regulator and causing it to fail. That is the last component in the system that can possibly cause this. You will need to take the hose off that which is on the drivers side fuel rail and see if fuel exits it. If so then it had failed.
Customer: replied 1 year ago.

Just wanted to give an update on this vehicle. Replaced the FRPV, still will not start. Truck has now been transferred to a different shop. Thanks for your help, even though we were unable to determine the issue.

Expert:  GM Tech (Cam) replied 1 year ago.
Did any fuel shoot out when you tried it?
Customer: replied 1 year ago.

No sir.

Expert:  GM Tech (Cam) replied 1 year ago.
Ok, If you should happen to find out what went wrong, please let me know what it was. If I can help you with anything more, please let me know.
Customer: replied 1 year ago.

Will do!! We know the people that own the shop that it is now going to(We were the 2nd shop to work on this truck) so I'll be sure to ask them what they find out with it!! Thanks again!!

Expert:  GM Tech (Cam) replied 1 year ago.
Thanks.