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Discussion Starter · #1 ·
Ok. So here is my story so far, and my take on all the problems occurring with LB7 Duramax engines and the P0093 code. 2 years ago (2001 Sierra 2500HD) had fuel in the crankcase. Injectors replaced by dealer. Truck ran great after replacement. A year ago, while towing my 14000 lb 5th wheel, went into limp mode. Pulled off, shut down, waited a minute, no more problem (SES went out in 3 cycles). 3 to 4 months later, same thing occurs with trailer in tow again. This was in Georgia, on our way to Key West. Only happened the one time on this 3500 mile trip. Reset and everything is fine for another few months. Again in a few months it did it again. A couple months ago, happened a DOZEN times on a trip to VA while pulling the trailer. Now I can not seem to pull the trailer under any kind of real load without it kicking into limp mode. Sometimes, if I baby it, it seems to run pretty well, until a hill, which is now getting to be a real bummer.
This is everything I have now learned about this problem (in a nutshell) (and kick me if I'm wrong). The code P0093 is a Large fuel leak. This code is thrown anytime the fuel rail pressure sensor is sending a pressure to the computer that does not match what the computer thinks the pressure should be under the conditions the computer is reading from the other engine sensors. There seems to be many reasons why this can occur, or why the computer thinks it is occurring, but basically it is due to not enough fuel available for the load.
Now as to the list of things that have been done to try and fix this problem on my truck!
1.Air filter replacement (by me)
2.Fuel filter replacement (by me)
3.Injector and sleeve replacement (by the dealer)
4.Fuel pressure regulator valve replacement (diagnosed by the dealer, done by me) This did fix the loping idle.
5.Fuel rail pressure sensor (told by the dealer that this would be the next thing to do after the FPRV, replaced by me)
6. Next weekend, I'm going to drop the tank and see if the inlet strainer is clogged.
7. Should I replace the injector pump, or install a lift pump?

This is getting to be a real headache, and I'm sure it has been for anyone else experiencing this problem. So far, nothing has helped, I'm just glad the injector replacement was covered by the 7/200K warranty both times.
Has happened now a couple times pulling a small (5x8) work trailer, and I even got it to trip up once with nothing behind, just pedal on the floor. I bought a code scanner after the problem started happening all the time.
I'll post more after I drop the tank.
If anyone has anymore suggestions, please post. Thanks
 

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Read your son's thread - lots of parts being put in that truck - you really need a Tech 2 to run the tests - or a scan tool that can force the engine parameters you need - you should be able to command 160mp and get at least 145 - if you can't and the injectors are good, the FPR and sensor are good, the filter is good and is on tight - there are few things left I think.

1. Restriction in the cooler or a blocked cooler
2. CP3

Really need to run some more tests to make sure though - on the injectors - fuel bypass flow rate and vacum check on the system to see if there is a blockage.
 

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Could be a leak in the filter housing or in the supply lines. Make sure you have at least 1/2 tank of fuel, and pressurize the tank to 5-7 psi. Look for leaks.

I don't know if it will cause that code or limp mode, but check the intercooler tube on the drivers side at the power steering pump for a hole.

Seems like some have solved this by adding a lift pump to help a week CP3.

Did you check the wiring harness and wiring at the sensor?
 

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Search FPRV. Some will say weak lift pump and a lot will say a weak FPRV. Fixing the FPRV is cheaper. My truck does exactly the same thing. As soon as I get all my parts I am doing a head gasket job. At the same time, I will be either shimming the FPRV or getting a new rail depending on how the shim goes. You can not buy a FPRV. You have to buy a whole rail. I will let you know if this fixes the problem.
 

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Sounds like you might need a new CP3. It could be the FPRV and quite often it is. I had the same problem and replaced both, the problem went away, but by not doing one at a time I can't say for sure what was causing the problem.
 

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Discussion Starter · #7 ·
Changed the fuel pressure regulator valve with a new one I got from the dealer, but that didn't fix it.
If its a weak cp3, can I add another pump before the cp3? Has anyone else done this that has had this problem? I've heard its been done and helps with a weak pump.
The dealer diagnosed bad injectors first. After they replaced them, they diagnosed a bad fprv. I guess they will next diagnose a bad cp3.
 

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I had same problem, bad injector pump
 

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I get that code a lot as well when towing. It's the CP3 huh??
 

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I do not think they diagnosed a new fprv. They put a new fuel pressure sensor in. They can not get a new FPRV, only a new rail. Give me a part # number so I can get one. I have not found a dealer or any one else on this forum to get me a 2001 fprv.

I'll pay big bucks for just a new fprv.
 

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I do not think they diagnosed a new fprv. They put a new fuel pressure sensor in. They can not get a new FPRV, only a new rail. Give me a part # number so I can get one. I have not found a dealer or any one else on this forum to get me a 2001 fprv.

I'll pay big bucks for just a new fprv.
Yes, they did diagnose a new FPRV and that's exactly what he replaced. The part # on GMPartsDirect is 97728979 I believe. That was found in this thread. I found the same part using the GMPartsDirect online catalog.

He also replaced the fuel rail pressure sensor.
 

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Discussion Starter · #13 ·
So the relief valve is not part of the regulator? Someone know the procedure for shimming this? And just where it is? I thought they were the same thing (2 parts of the same thing), just a difference in nomenclature.
 

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Okay, I already posted a reply but it is not showing up. So if you see a crazy double post by me that is why.


Soapguy,

no they are different.


anyway, if you want more info i would call steve cole at tts about shimming the lb7 fprv. if that dont work try the cp3. fprv can not cost more than a few cents and your time. I would have had mine done by now but engine locked up yesterday and so I have bigger problems.
 

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Discussion Starter · #15 ·
Dropped the tank. Found some gunk around the screen. Cleaned everything out. Still throws P0093 when I pulled the trailer. Gonna try a shim next. Gonna call TTS on Monday. Thanks thesloppy.
 

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Hi guys, I'm in the same boat as you. About 8 months ago my 2001 started to give me a P0093 and go into limp mode. It only does this when I tow my fifth wheel trailer. Here is a little history... when the truck had 105,000 miles on it the injectors went bad and were replaced along with the regulator (On chevy's dime). I currently have 241,000 miles on the truck, but this problem started about 25k miles ago. I have replaced the fuel filter twice since then but still have the problem. My question is what is my next step? Also, I saw this on another forum...

P0093 is a valid code and there are TSB's on it for his vehicle.


01 02 03 04 6.6L LB7 Duramax Diesel Engine DTC P0093 P1093 - kw data fuel MIL stall hard hose restriction start nostart no #PIP3314 - (Feb 2, 2005)
01 02 03 04 6.6L LB7 Duramax Diesel Engine DTC P0093 P1093
.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in the PI.

Condition/Concern:
01 02 03 04 6.6L LB7 Duramax diesel engine hard start, no start, stall or DTC P0093, P1093

Recommendation/Instructions:
Now that you have completed the published diagnostics for an engine hard start, no start, stall or DTC P0093, P1093 with no trouble found, check for a kink in the (foam covered) injection pump inlet hose. The kink can cause a restriction of fuel flow and result in the concern of hard start, no start, stall or DTC P0093, P1093. Note: The normal procedure of measuring the fuel vacuum reading will not indicate this inlet hose restriction, as the gage fitting is located upstream of the injection pump inlet hose. Also Note: The technician may indicate that it requires fuel prime to start or keep the engine running. This may be an indication that the injection pump inlet hose has a restriction.

.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Models:
(01 02 03 04 6.6 LB7 C2 C3 K2 K3 Chevrolet Silverado, GMC Sierra GMT800)
 

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Discussion Starter · #19 ·
Hey guys, I did it last night. Shimmed my FPRV. Took the trailer out this afternoon. Didn't work. Still got P0093. Still bummed. Gonna have to try the dealer again to diagnose it, I don't have access to a tech2. Gonna set up a link with a couple pictures of how to shim LB7 FPRV. More when I get more.
'the soapguy'
 

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Mine did the exact same thing 2 years ago pulling a 5th wheel. The dealer diagnosed and changed the rubber hoses coming out of the fuel filter. They said the hoses were colapsing internally. I have not had the problem since and I tow alot. Might be worth a try.

Dexter
 
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