No start, no codes, this truck is killing me!

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mojito5000

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Aug 20, 2019
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So last week my truck let me stranded, no start, no codes... I only had my torque app available, so I couldn't do much troubleshooting. After the 60 mile tow, I hooked up the tech2 it showed only around 190psi of fuel pressure while cranking.

Doing a bottle test with the hand pump the fuel was coming out one for one. Something is bypassed. Reading up on the issue, injectors. Ok, not what I wanted to do right now, but damn it, ok. Just finished doing the injectors today, and the same problem. When I was in there, I replaced the fuel pressure relief valve with a good known working one. During the injectors, I also did the cups, lines, and fuel filter.

The reason this is killing me is I bought an engine to replace the one I had in the truck. The replacement engine had a bad CP3, which I didn't find out until I got the engine installed and truck running. Replaced the CP3 with the one from my old engine and things were awesome. The truck ran amazing, put about 1000 miles on her, and didn't have a single issue. 7000ft elevation gain to Crater Lake and man it reminded me why I love Duramax.

On the morning of the stranding, I noticed the engine had a slight miss? It was like a small vibration, but it went away after the engine ran for a few minutes. The oil pressure was good, and it wasn't smoking so I didn't think anything of it.

I pulled the oil fill tube and had the wife crank it over and the pump is turning.

I need some help. The truck has been down for way too long.
 
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mojito5000

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It's making about 60psi of oil pressure when cranking.

A little shot of starting fluid got it to stumble, but not enough to actually fire. No smoke out the pipe, and no smell of diesel either.

Would the injection pump being bad cause it to leak the pressure out the return line?
 
2004LB7

2004LB7

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what I mean is, have you checked the oil level and made sure it is not raising. ie is diesel leaking into the engine and mixing with the oil.

also, try and stay away from either. if you get desperate, use a small amount of gasoline, WD40 or something similar. much safer

bad CP3 can definitely leak fuel in to the return. pull the return on the CP3 and verify how much comes out when cranking. if it is too much it can rob the pumps ability to make pressure
 
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mojito5000

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Ahh, gotcha. I did do the paper-towel oil test and no halo, the oil level is middle of the stick, just as it was when I changed the oil.

I'll pull the return line off the CP3 tomorrow and try that.

Thanks for the help!
 
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mojito5000

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I did the bottle test and the pump was not holding pressure from the hand pump. Got a reman Bosch unit from Oregon Fuel Injection a week ago and the truck back :). Thanks, @2004LB7 for your help! I really appreciate it.
 
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Brimmy

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Aug 11, 2015
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Sorry to piggy back this thread.

I have similar issue happening. Could someone refer me to this bottle test for the CP3 pump ?

My issue currently is "no suction" from CP3 pump; therefore no rail pressure. Will not start. Cranks all day
Just replaced all 8 injectors with reman Bosch. Ran great for the past month. I am still getting diesel into the crankcase.
Went back in & installed all new GM return hard lines and seals.
Valve covers currently off as I want to check for leaks before sealing it back up.
Prime is good & holds quite some time before bleeding back down.
Engine was running fine before replacement of injectors. It was just leaking diesel into the crankcase.
 
2004LB7

2004LB7

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Sounds like a bad CP3. Kinked line or some obstruction in the line. Try disconnecting the fuel line into the CP3 and pump the primer bulb to see if you can get any fuel there
 
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Brimmy

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I thought it may have been air locked. But cracking the line would have took care of that. Just logically trying to figure this out.
 
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Brimmy

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I'll try that line next & check for an obstruction. Will let you know findings tomorrow morning sometime.
Appreciate you taking time & responding.
Just odd to me that the CP3 would die between line replacement.
Time will tell. If it is a bad CP3, any recommendations?
 
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Brimmy

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Looks like the rubber hose from the hard line coming from the filter to the CP3 may kinked and possibly collapsed. I am going to get some clear line and try to see if pump has suction out of a portable fuel container, then proceed from there.
 
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mojito5000

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Brimmy said:
Looks like the rubber hose from the hard line coming from the filter to the CP3 may kinked and possibly collapsed. I am going to get some clear line and try to see if pump has suction out of a portable fuel container, then proceed from there.
Click to expand...
You could get about 5’ of line and use a 5gal diesel container off the side of the truck bypassing the tank for supply. I replaced my soft lines when troubleshooting my bad CP3 in the hopes it was that but no luck.

When my CP3 died, it died silently. I drove the truck about 50 miles with no issues. Stoped it for about 10 minutes, started and ran it for about 5 min, stopped again for about 5 min and when I went to start it again, nothing.

If you have a Tech2 it can help troubleshoot, but it doesn’t tell you it’s the CP3 or a bad injector. My truck had 240k and the pump was original. I was pretty sure my injectors were good and took the gamble on the CP3 and luckily I was right.

Make sure you get a new Bosch or a reman Bosch from a Bosch sponsored shop. It’s a pain to replace. Just take out the intake manifold y pipe (leave the individual intake manifolds on).

Good luck, I hope it’s just a kinked line.
 
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Brimmy

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Update. Appears I had a kinked line. Engine runs; I bypassed and ran a hose to portable fuel supply. Now to change oil and add dye to fuel to check for high pressure leak or return line leak before re-installation of valve covers. If we are free & clear there; we will see if I have solved my fuel in oil issue. I do hope so or will be finding a way to check the front seal of the CP3. We will see what the UV light & dye show me next.
 
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