P-1094 code and hard starting

[05Duramaxx]

I have an 05 with 250k miles having similar issues. So far I have
- replaced the CP3
- replaced fuel filter
- replaced most of the rubber lines
- replaced the FPRV to a race plug
- replaced all glow plugs
And replaced the glow plug control module.

still hard starts, runs pretty good but definitely not what it used to be. No tunes or serious upgrades at this time. and injectors are all within tolerances of balance. I run clean fuel and diesel additives often too. Any advice?

 

[2004LB7]

Do you have any scanner, reader, anything to watch engine parameters?

 

[05Duramaxx]

Do you have any scanner, reader, anything to watch engine parameters?

Yes, I’ve got a CYS insight II.

 

[2004LB7]

Give use the info. Any codes? What fuel pressure are you getting? Etc

 

[05Duramaxx]

Give use the info. Any codes? What fuel pressure are you getting? Etc

I’m pulling a P-1094 code and the it starts rough hot or cold... almost better cold actually.
I am getting 5KPSI at idle and once I’ve got it running no problems getting 23KPSI so far even with trailers not heavy but decent loads. What other info might help? I’m no mechanic but I’m slowly getting better at it.

 

[2004LB7]

What pressure is it while cranking before it starts? What RPM does it crank at?

It may also be a good idea to run a return rate test from the pressure relief and CP3 and while you are in there might as well do the injectors too.

If it starts better cold, it may be due to too much return fuel from one or more of the above mentioned items. As the fuel warms up, it thins out. This causes it to "leak" more return fuel and make it difficult to build pressure needed to start

Search this site for return rate test or bottle test to see how others have done it and what are acceptable levels

 

[05Duramaxx]

Is replacing injectors the only way to resolve to much return on them?
I’ll get to looking into some testing. Sounds like I’m in for another over haul.

 

[2004LB7]

Yes. But fuel can return from the CP3 and pressure relief valve too so you need to check those also

 

[05Duramaxx]

If I have a new CP3 would that rule out fuel returning from there? And as for the FPRV what would cause fuel to return from there?

 

[2004LB7]

New CP3 would certainly make the possibility of it being that less. But if you are going to be testing it wouldn't be that much more difficult to test the CP3

The pressure relief valve has been known to get weaker as they pop off and leak more. There are numerous posts on how to shim them so you could always try that but they rarely open up at idle pressure. I would guess it would be one or more injectors