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Discussion Starter · #1 ·
This is a bucket truck that died while I was using it. The fuel gauge doesnt work, so I thought it just ran out of fuel. Ended up having about 15 gallons in it when i drained the tank.
I can prime the truck and I can get it to start sometimes and it will run for 3 seconds and die UNLESS I give it throttle and keep it above idle.
It will run all day long above idle. When I let it go back to idle it will immediately die and wont restart.

I've replaced the filter and filter head with a new head and GM filter. Replaced the short rubber lines to filter and out of filter.

I ran a hose from the filter to a jug of diesel and I get the same result of running for 3 seconds and dies unless I give it throttle and keep it above idle.

Wanting some opinions on what it could be and what to try next.
 

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Welcome to DieselPlace

Have you checked for any codes?
 

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Discussion Starter · #3 ·
Only codes are for glow plugs and glow plug controller. The truck has had those codes since I bought it.
 

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Discussion Starter · #4 ·
I took off the return quick connect fitting at the rear of the driver side of engine and when I pump the primer on the filter I get fuel starting to run out the return line as I'm pumping
 

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I took off the return quick connect fitting at the rear of the driver side of engine and when I pump the primer on the filter I get fuel starting to run out the return line as I'm pumping
When you pump up the primer button let it sit at a minimum for a few hours and recheck. If the primer is soft when you recheck you have an air intrusion/leak in the fuel system.
 

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2007 Klassic CCSB 2500HD. Six-gun w/speedloader, iDash, and EFILive.
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Any idea the mileage or hours on the motor? I'm no expert, but if you're returning fuel when you try to prime, You've got issues. So I'd suggest you go at it like this:

Problem: won't idle, hard start.

Symptoms: returns fuel when priming. Will run at high idle but not low idle.

Causal factor: lack of fuel.

Could be:
-A dying CP3
-A dying fuel pressure relief(release, safety) valve. (FPRV)
-(unlikely) a dying pressure regulator (would surge at idle, backfire like stuff)

You need to figure out where the bypassing is occurring. I'm not the engineer that built the thing, so we have to go hick from here. Three places fuel can get into the bypass return line that you removed four really: injector return lines (2), if the cp3, and the FPRV. I would go right to the FPRV first.

So, the relief valve is pretty easy to get at. Right by the glow-plug control module. The one you keep getting codes from oddly. I would think this is most likely the problem. There's a U shaped rubber line that connects the driver's side fuel rail (where the FPRV is) up to a return junction where they all meet up prior to heading to the tank.

Pull the bottom of the rubber U off of the nipple on the driver's side fuel rail and plug the hose.
Put another piece of tubing on the nipple where you just removed the U, and run it to a milk jug or clear jar or something where you can see if fuel comes out.

Pump the primer until fuel leaks out either the QD you have off, or into the jar/jug. If it's the jar/jug where it comes out, your FPRV is shot, and stuck open. If not, you'll need to keep using the same methodology on the other 3 lines that can feed into that return junction.

Lemme know. Oh, and MY advice is worth exactly how much you paid for it.





https://youtu.be/GOJtQfCTsLM
 

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2007 Klassic CCSB 2500HD. Six-gun w/speedloader, iDash, and EFILive.
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Yeah, probably. You can pull that return line and check it too. If you have EFILive or a TECH2, you can command it to make pressure and see what it'll do.

I've also read you can add in optilube or 2 stroke oil to try and unstick a stuck valve. I think that CP3, maybe 3.2 may have a zero-fuel return circuit. Could be a stuck valve. Might be worth trying since pulling the pump is SUCH a pain. You can also remove the wire from the pressure regulator and it will default to max pressure. If I were going to try and see if I could unstick a valve, I'd probably do just that and let it run a while. Easiest is to put it on something to see if it's making commanded fuel pressure. Kinda seems like it wants to but it's got an open bypass circuit.

There is a bypass test for the CP3. Sorta

Ferm says signs of a failing cp3?

Sounds to me like you'll have to pull it regardless of the cause. But I'm also just about the dumbest person on here, so hopefully someone smarter will step up.



A video on how to rebuild a CP3, in Mandarin

Exploded diagram

Stroker Pump how-to
 

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Discussion Starter · #12 ·
Put in a cheap lift pump and it fixed it.
Probably a band aid fix on a problem but it runs and drives now.
 

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2007 Klassic CCSB 2500HD. Six-gun w/speedloader, iDash, and EFILive.
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Nice. That'll work. Nice thing about a bypass system like that. As long as you keep head pressure on it and the CP3 is making pressure, you're good. Makes me thing the gearotor (low pressure) part of the CP3 is what's causing bypass. But it's a bucket truck. Probably not going to get the chance to leave you stranded on the side of the interstate in the middle of nowhere LOL.
 

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2007 Klassic CCSB 2500HD. Six-gun w/speedloader, iDash, and EFILive.
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I wouldn't put it of too long. They're better than the CP4 about contaminating the whole injection system when they die, but they can. Then you get to buy new injectors, pipes, rails, etc.
 

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Discussion Starter · #15 ·
Yes, I eventually will replace the inj pump since I'm almost positive the pump is the problem.

I'm just happy it's running so I could retract the bucket boom. The truck quit with the boom halfway in the air. The PTO wont engage unless the truck is at idle.
 
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