LLY: No rail pressure randomly upon start issue

[dirtymax36]

Hey guys, I'm stumped with an LLY at the moment. Its my cab and chassis dump truck that doesn't get drove much. has 173k on it and I bought the truck needing work, AKA it turned over 3 times before it started and built rail. It is now tuned, deleted, and has a lift pump, exhaust and intake. I put 3 injectors in it, and LBZ cp3 and put it back together. Fixed my issue for about a month. Now its doing it again except worse, it'll crank over 10 times and still not start. I put a brand new FPR on it via Lincoln diesel and it still has not changed my issue. Once the truck starts, it runs perfect although.

No codes on the dash, if i unplug the FPR and try to start it there's no change in result.

I monitored rail on my v2 while cranking and its around 200-600psi while cranking. When it spikes to 3k it'll start as it should, but there's no repeating time it will build rail. No pinches fuel lines, fresh filter etc..
Any ideas? Thinking a few injectors must have high return rates or something. Any help is appreciated in advance.

 

[ZeroGravity58]

I'd check the injectors again. Maybe send them all out to get checked.

 

[Muff]

Can u get it to run to check balance rates? Assuming not...the Lbz cp3 was a known good pump?

 

[briencolgan]

So that’s fuel pressure reg? How bout the fuel pressure relief valve. Your symptoms are identical to mine. With turning over times getting longer and longer until a no start issue occurs.

I’d add replace repair the fuel pressure relief valve as a possible issue. I have an LB7. But I would imagine all the Duramax is have some sort of fuel pressure relief valve. I just tightened up the spring in my valve by adding two small nuts. Put it back together in the truck fired up very quickly. Now it’s been months and no issues with hard starts or long starts. It’s a pretty easy repair and pretty easy to verify that it’s the Fuel pressure relief valve causing issue. I just find the valve and Remove the return line off the back of it, then have someone crank it while you watch the back of the valve. If fuel leaks out of that you’ve got a bad valve. Test takes about half hour to get it apart.


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