LB7: Won't Start After CP3 pump change out

daltongd

New member
Sep 25, 2010
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I went out and ran it again. This time I tried rev'ing it up. It won't go past 2000 and now i reads a code 1781. I also noticed that I sucked a piece of cloth that I had been used to keep the intake clean. It was down in the turbo blades. I pulled it out and who knows what damaged that caused. I started it up again and its doing the same thing. doesn't appear that sucking in the rag did anything.
 

daltongd

New member
Sep 25, 2010
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So today I swapped out the fuel pressure regulator with my old one and its still does the same thing. When I start it I have less and less connected to the engine. Just trying to test it without installing everything. I noticed this time he tack is not working.

So the bottom line here is the fuel pressure regulator is probably not the problem.
 

daltongd

New member
Sep 25, 2010
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My code reader actually has a real data readout and it says I am getting 6200 to 7000 PSI at idle. Thats way more than 30mpa.
 

daltongd

New member
Sep 25, 2010
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Ok more info on my new revelation on my code reader and data read out.

With the key on it and its not running it says 5800 psi desired and 6100 psi actual. When I start he engine the desired value goes up (6200 -7000) and the actual value stays frozen at 6100 PSI

I also noticed that I can hear a sort of high pitch pulsing sound coming from what I believe is the rail pressure sensor. even when the key is turned off I hear the sound for about 2-3 more seconds and then it shut off.

I am starting to thing maybe my rail pressure sensor is bad. Anybody got any comments?
 

Mika

Bastardo Finlandias
Oct 25, 2008
291
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I had once similar problems after engine install. I dont remember now, but I belive it was fuel temp sensors plug that was not connected properly. Or rail pressure. Check both.
 

Mike_S

OOPS!
Nov 18, 2009
803
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40
Idaho
If the reading of the rail pressure does not fluctuate then the sensor is bad or the wiring to the sensor. The pressure should go up when the engine is revved, and should follow the desired pressure closely.
 

sweetdiesel

That's better
Aug 6, 2006
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If the reading of the rail pressure does not fluctuate then the sensor is bad or the wiring to the sensor. The pressure should go up when the engine is revved, and should follow the desired pressure closely.

Maybe not if the regulator is fubared


Is the regulator humming?
 

Mike_S

OOPS!
Nov 18, 2009
803
0
0
40
Idaho
Maybe not if the regulator is fubared


Is the regulator humming?

Yes, however, if I am reading what he says right, the actual value never changes at all, no fluctuations at all. Even with a stuck regulator the actual rail pressure reading will move around a few hundred pounds up and down all the time. If the actual rail pressure reads 6100 and never ever moves at least 50-75 PSI then I say the sensor is retired.
 

daltongd

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Sep 25, 2010
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More rationale for it not being the regulator is that I put in the old regulator and it still did the same thing. So basically (2) regulators have been installed and the problem is still there. I ordered a new pressure sensor so that will be the next thing I change out.
 

Mike_S

OOPS!
Nov 18, 2009
803
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Idaho
Just to clarify, does the actual fuel pressure reading (not the desired pressure) fluctuate at all, or read a constant 6100?
 

daltongd

New member
Sep 25, 2010
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I stays frozen at 6100. Its basically stuck at 6100.

In addition a pulsing humming noise is coming from the sensor area.
 

LBZ

Super Moderator
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Jul 2, 2007
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I stays frozen at 6100. Its basically stuck at 6100.

In addition a pulsing humming noise is coming from the sensor area.

Unplug your rail pressure sensor and see what your code reader says. Just to confirm it's working correctly.

I've run into problems with generic code readers before..........just sayin....
 

daltongd

New member
Sep 25, 2010
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Latest update, I got a new sensor and swapped it out. When I went to plug the electrical connector back in I notices 2 of the 3 wires had ripped out of the connector. So now I have to order a connector with pigtail from the dealer. Another $65.

What I don't know was if the wires were broke before I took the initial sensor out. Maybe my problem all along was the wires had pulled out of the sensor when I removed the wires to pull out the CP3 pump.

The way the wire harness was routed was such that it didn't allow for much movement when the whole main cable bundle is moved out of the way for the CP3 installation.

This whole job has taken 3 weekend all in all and 4 installations of the CP3 pump. What a pain.
 

daltongd

New member
Sep 25, 2010
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Anybody know the wiring schematic for the sensor? I haven't got the pig tail yet so I don't know if it comes with a schematic or not.

The #1 wire looks brown with a black stripe (thats the one that is connected) but the other two wires look to be the same color. They look brown or maybe tan.
 

daltongd

New member
Sep 25, 2010
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Just in case anybody ever has the same problem the wiring schematic for the fuel pressure sensor plug is orange/black pin #1, Yellow is pin #2 and Tan is Pin #3. Yellow and tan look pretty much the same but you can tell the difference.
 

daltongd

New member
Sep 25, 2010
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Well its back together and working just fine. To sum up the problem I had the code so I just assumed it had something to do with the regulator and or pump. I decided to go ahead and replace both since I had 220K mi. I got it all together and it made this god awful sound at idle. After replacing the regulator with my old one and still having the problem I put the new one back in. All in all I changed it out (4) times. Got smart and figured out the sensor was bad. In changing that out I found (2) wires in the plug had broken off.

Advice for the rookies like me: make sure you use a scanner and verify what is what before doing any kind of repair. If you don't have one spend the money and go pay someone to do it for you.

Taking the CP3 pump out is a real pain in the ass. The hardest part is actually the very end where you have to rotate and lift the pump out. You need to bend the one fuel lines out of the way and just kinda start rocking the thing out. It takes a pretty good pull and then it will came out. When I did the regulator swap outs I just rotated the CP3 pump up and then pulled the regulator. It wasn't as bad since I didn't have to actually pull the pump out which requires you to bend the fuel line back out of the way again. You might be able to remove the regulator with the pump installed if you made some kind of special tool. In my case it was easier to just take it all apart.

All in all it cost me about $1000 and (3) weeks of time.
 

onebadduramax

One Bad Duramax
Jul 28, 2009
30
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Latest update, I got a new sensor and swapped it out. When I went to plug the electrical connector back in I notices 2 of the 3 wires had ripped out of the connector. So now I have to order a connector with pigtail from the dealer. Another $65.

What I don't know was if the wires were broke before I took the initial sensor out. Maybe my problem all along was the wires had pulled out of the sensor when I removed the wires to pull out the CP3 pump.

The way the wire harness was routed was such that it didn't allow for much movement when the whole main cable bundle is moved out of the way for the CP3 installation.

This whole job has taken 3 weekend all in all and 4 installations of the CP3 pump. What a pain.

3 wires??? on the FPR???? There should only be 2
The FPRV has 3

I'm confused please explain. I'm running into the same issue thanks