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04 C4500 with Duramax diesel

Hsolay

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Hi guys we have a 04 Chevy C4500 diesel and it died on the road and had to be towed back to our shop it’s 3 days where we’ve tried 4 different scanners and it’s coming up no codes but it won’t start can someone help me I’ve changed the filter primed it check fuel from the bleeder near the alternator and there’s fuel when we prime it but we crank it it doesn’t have fuel coming from the same bleeder. Am I missing something could it be the injector module?
 

Rockabillyrat

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Duramax doesn't have a lift pump. So it wont push fuel when your cranking it. The bleeder your talking about is a service port. I think gm uses it for filling the system at the factory. Techs use it for testing the supply side of fuel system.

Two questions. Are you opening the 13mm bleeder screw on the filter housing when pumping the primer? And do you have a scanner to watch live data. If so check your rail pressure while cranking it. If its not making rail pressure you need to start testing the high pressure side of the system.
 

Hsolay

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Thank you Rockabillyrat as far as lift pump got it, the service port found that out when we tried priming while holding down the center stem. Yes we’ve bled from the filter to the service port to make sure fuel it was going through and we have a scanner the said accepted fuel pressure range and we cranked the motor over but it didn’t do much for us cause we really don’t have much to go by since we don’t have a wiring schematic or service manual. So we’re on the thread hoping we can have a start and anything helps so we will try the high pressure side today.
 

Hsolay

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I think I narrowed it down to the injector module I have high pressure from the pump, I have ready from the cam and crank sensor but the injectors don’t open to make it start ohm the wires and I have continuity from injector to icu. So I think I narrowed it enough.
 

Rockabillyrat

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How much rail pressure are you making while cranking it? Duramax needs a minimum of 1500psi to start.
 

Hsolay

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We put the diagnostic scanner on it and the scanner read desired fuel rail pressure 5945 psi and when we cranked it the actual fuel rail pressure was 22,053 ild figure it was enough to at least get it started also we cranked the engine to build pressure and crack open one of the injector line and it sprayed out pretty good. So I know it is building pressure but it seems like the injectors aren’t opening up to send fuel to the cylinders. So it got me thinking it’s the icu, icm do you have any suggestions.
 

MrMarty51

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I suggest You be very very careful when opening lines and cranking the engine. Diesel fuel under high pressure is very unforgiving and dangerous too. A lot of people have lost fingers, hands and even lives from liquids under extreme pressure.
other than that, I am of no help when it comes to the newer stuff, heck, I can barely keep the old stuff running. LOLOLOL
 

Rockabillyrat

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Most of the time if its an injector driver module it will set a code of some sorts. If your not getting any codes in any module that can cause a no start issue. The next step will be to check you injector return rate. Remove the return lines from both banks along with the FICM fuse. Then crank it over for 15 seconds. Anything more that 12ml per bank is too much and some if not all of the injectors will need replaced
 

Hsolay

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Really sorry guys but I’m using a Chevy programmed diagnostic I haven’t been getting any code it just pops up no codes present. So Rockabilly rat I’ll check the return flow today and see what I get. But even with a couple of bad injectors wouldn’t it even try to at least start or cough cause I’m not getting nothing.
 

THEFERMANATOR

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Really sorry guys but I’m using a Chevy programmed diagnostic I haven’t been getting any code it just pops up no codes present. So Rockabilly rat I’ll check the return flow today and see what I get. But even with a couple of bad injectors wouldn’t it even try to at least start or cough cause I’m not getting nothing.
If you have 2 shorted injector coils, it could prevent it from starting. The FICM control s the injectors in batches of 4 so that when is being opened, the other driver can be charging. If 1 injector in a group goes out, gets unplugged, shorted, whatever, the FICM shuts down that group to prevent circuit damage since you're dealing in fairly high AC voltage. So if you have a problem in each group, the FICM won't do anything.

And I don't remember the exact code, but it says replace FICM under the diag for it.
 

Hsolay

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Thanks Thefermanator for the feed back is there a way to test each injector circuit so I can at least try and troubleshoot it and see if the control circuit is good or bad instead of turning my ficm in to have it rebuilt or do they have a plug and play ficm
 
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