that could cause a no start situation but then your idle would run like cr#p. if it is spraying fuel before it should you will have a knocking/pinging sound and possibly smoke more. you said it runs fine once you get it started. i dont think thats your issue. you can try it if you want but high returns and leaks on the fuel line/filter housing are much more common then stuck injectors.

basically all that was done was remove the glow plugs and unplug the injectors. i suppose pulling the fuse the the FCIM would be easier then unplugging each injector. the glow plug holes that fuel is cumming out of are the cylinders that have stuck injectors

try cleaning the filter housing, filter, water in filter sensor, and the line going into the housing with something like break cleaner and then pressurize the tank and prime the filter. keep the tank under about 5 or so psi for a few minutes. check if you have any fuel leaks. the blead screw, primer bulb, water in filter sensor and a hairline crack in the filter housing are common ones. also the check valve is in the center of the housing and fits into the center if the fuel filter. you should be able to see it if you remove the filter. fuel that goes out of the filter goes through the check valve and is not supposed to be able to come back out. apply about 10 psi to the output on the housing and see if fuel comes out of the check valve

 

well i tried pressurizing the tank and i cleaned the fuel filter housing and everything. still not start and the fuel rail pressure still stayed between 500-600 while cranking it over. i didnt see any leaks either. i havent checked the check valve yet. what do i do exactly? i needa take the filter off and then put pressure on the the hose where the fuel come out of?

also, is there a lift pump or anything on these trucks that could go bad? or could i put one on and that would help? im just throwing ideas out there cuz the only problem the truck has is that it dont have enough fuel rail pressure. i keep hoping it aint injectors but it seems like it might be.

Also, thanks a million for all your help already. ima newbie to these duramaxs and tryin to learn as fast as i can! hopefully we can figure this out

 

"what do i do exactly? i needa take the filter off and then put pressure on the the hose where the fuel come out of?"

you got it. just make sure there is some fuel in the line so you can see if it is leaking out

"also, is there a lift pump or anything on these trucks that could go bad? or could i put one on and that would help?"

there is no lift pump on a stock truck. only the one pump mounted in the valley of the engine that sucks fuel all the way from the tank. adding a lift pump will help if it is a priming issue but not likely if it is an injector problem. if it was me i would install one anyways. so muck easier to prime it and will help you build more power in the future if you so desire.

" i keep hoping it aint injectors but it seems like it might be."

thats why i am trying to help you eliminate all of the other potentials before diving in needlessly into the injectors. if all else checks out then it is likely time for a new set of injectors.

 

also i just realized that if the truck sits fer like 5-10 minutes without running er anything i can go loosen the screw ontop of the filter housing and there is no pressure there. is that normal?? if i pump it up with the hand pump and loosen it, there is alotta pressure. is there always suppose to be pressure under that screw?

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well i tried checkin the check valve like u said. it did leak a few drops while under pressure even though im not quite sure how much pressure i put to it.

also i tried somethin else. not sure if it was a good idea but it worked. i took like a 2 foot piece of plastic tube and connected it to where the rubber hose that connects to the outlet side of the fuel filter. so basically i think i connected it to the cp3. i then held it up in the air and filled it with diesel and tried starting it. it didnt suck any fuel nor did it start. so i then took my air hose and pressurized it with quite abit of pressure while my dad cranked the motor over and it sucked the fuel down and fired off. i didnt have to give it starting fluid or anything.

so now i dont know what to do. i need input. would one them aftermarket fuel pump fix my problem?? should i replace the fuel filter assembly? or could it still be injectors?

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UPDATE: i put everything back on and pumped the hand pump. now if i crank the motor over for bout five seconds itll fire right up with no starting fluid. so im thinkin its somethin to do with the check valve. do you know if you can buy just a check valve or would i be better off buying the whole fuel filter assembly? i seen them on ebay for like $125. im pretty happy cuz im thinkin it aint the injectors now.

 

well thats good to hear. an aftermarket lift pump may get you by if it is just a leak or check valve.

"or would i be better off buying the whole fuel filter assembly?"

you have to by the whole filter housing.

but i would put the $125 into a lift pump. as long as your filter housing isn't cracked (sometimes very hard to tell) then a rebuild kit (ebay: duramax filter o-ring rebuild kit ~$25) may be all you need

with a lift pump you could always install a check valve before the filter too

 

alrighty, do you know which lift pump i should try buy? dont think i need anything to fancy but i dont know also thanks again for all your help. hopefullly this will fix it!

 

this is what i have:

https://www.dieselbombers.com/5-9l-2...0-ok-pump.html

 

well im starting to get fed up with this truck. i ended up jus buying a new fuel filter housing with filter and evrything. got it all on and finally i think i got all the air out and it would stay running. the one time i shut it off and then cranked it over and it did start. (seemed like it mighta cranked a little longer than it shoulda though) but now it will never start on its own again without starting fluid. i let the truck run for like 30 mintutes hoping that might help but it didnt.

I need suggestions! is the cp3 suppos to have alot of suction?? could it be weak? could there be air in the lines still causing this? would a aftermarket pump fix my problem?

 

i dont remember the exact number but i think the CP3 could pull up to -8 PSI but something like over -4 PSI is a plugged filter or restriction.

i would get it started and take it for a drive. getting the fuel PSI up is the best way to remove the air. if it still has a hard time starting, check the cranking PSI again and let see if we are making progress

 

well i had to start it on starting fluid again. i took it for bout an hour drive and then shut it off and tried starting it up again right after i shut it off. the fuel rail presure while crankin it was like at 500 psi. same as its always been. when its runnin it has great psi. im stumped! im really thinkin that the cp3 aint suckin during crankin? but you guys tell me!