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Discussion Starter #1
I keep losing prime when my 03 sits for very long. I replace the vent cap on the top of the prime pump because the previous owner had stuck some other type of bolt in there. I figured that's where my leak was. But I'm still losing prime. If my truck sits for very long I have to reprime it so it will start. Once it starts it does just fine. I have heard that the check ball inside the prime housing can get stuck. Is this very common and if so is there a way to get inside and clean it? A new part is 600.00 bucks. Don't really want to go that route if I don't have too.
 

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Are you sure the threads are still in good shape at the vent screw ?

Maybe they got damaged before with the other screw in there, it is a bit of a oddball thread size and now even with the correct screw it's still leaking a little.

Also how about the fuel filter is it nice and tight and installed correctly ?
Some have had leaks around the o-ring causing loss of prime.
 

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Discussion Starter #3
the thread screw has an o-ring that should seal anyways, it screws in nice and tight. as for the fuel filter i put a new one on and i'm pretty sure it is on correctly i tightened it pretty tight with the new o-ring in place. have you heard anything about the check ball sticking?
 

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First, as stated I would check the bleed screw, put a new one on order just screw online from Diesel Injection service, second put on new fuel filter - put a little lite oil or grease on "O" ring and put on slowly to make sure it doesn't move and has proper seat. Many a person has put on the fuel filter, including myself and found it has come out of the groove. There maybe an old "O" ring from the previous filter that stuck on when it was removed.
 

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Maxtorque--Did by any chance you tighten the filter with a wrench? A few weeks ago someone here did that and put a small hole in the filter.Also--is your bottom water trap on tight and sealed?
 

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I have heard of a someone having a primer plunger seal go bad and it was sucking in there, but I think the only fix for that is a new filter head which like you said is big buck's.

Other than that maybe do a check of the fuel lines from the tank up to the engine and see if theres any built up grit on any fittings which might indicate a leak.

You mention after sitting a long time it loses prime, what exactly are you considering a long time ?

.
 

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I had the same symptoms.

New injectors.
 

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Before I plunked down $600 on a new priming pump I would opt for the JK lift pump and harness and improve on stock and save $300.
 

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Discussion Starter #9
It is getting to where if it sits for about a half hour it loses prime. Blacksilver what exactly did your truck do? And btw there is no fuel loss around the filter. I cleaned it up really well and have driven for about two days now and there is no fuel residue anywhere around the filter.

If my injectors are bad would the engine fire right up and run fine as soon as I primed it? Sorry for all the Q&A I know gas motors prety well but am fairly new to the whole diesel scene. If the injectors are bad are they covered under the factory 200K warranty, mine being an 03 and all.
 

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Does it not want to start when it's cold in the mornings too or is it just when the engine is warm that it takes a while to start ?
 

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It is not the ball check valve. There are two disk checks in the head but both would have to fail to loose prime. Has it done this since you bought the truck? Later! Frank
 

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It is getting to where if it sits for about a half hour it loses prime.
I had problems starting my 04 a few weeks ago. I had it towed to the dealer. They primed it and it started and ran fine. They let it sit for about 30 minutes and it wouldn't start (lost prime). The dealer replaced the Fuel Manager and so far it has been running/starting fine.

FWIW, the dealer was able to deterine that the Fuel Manager was bad by installing clear fuel lines and looking for air bubbles on the outlet side of the fuel manager.
 

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Discussion Starter #13
That sounds pretty close to the same thing that happens to mine. It does it hot or cold and yes it has done this since the day I bought it. Left me stranded for two in an ice storm the first time. I was a little T.O.d.

I talked to the dealership I bought it at. I think they are going to try and fix it for me. I sure don't want to have to put out alot of money right after buying it. Are the 03s warrantied for the faulty injectors?
 

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Discussion Starter #14
BTW about what temp should my engine and tranny be running. It was about 90 degrees today and my Ally was running 200 and the engine was running at 205. That was running empty with the A/C on. Is this about right?
 

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About right. Mine runs just a little cooler on both counts but you're OK.
 

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Mine is at the dealer right now with some of the same starting problems. Starts hard, worse when warm. Didn't start the other day so I primed it and it started. Dealer saying they found a leak in the fuel filter housing. They want $1,200 to replace the housing. I called Chevy and they said they were going to help with the cost of the repair. I was told they need to make sure this is the problem and then they will let me know how much help they can do.
 

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hold the phone....?

I have heard of a someone having a primer plunger seal go bad and it was sucking in there, but I think the only fix for that is a new filter head which like you said is big buck's.

From Chevy's Duramax warranty page on what's covered up to 5 yrs/100000 miles....


The engine parts listed next continue to be covered, subject to a $100.00 deductible, for 5 years or 100,000 miles, which ever comes first.

*Cylinder block and heads and all internal parts, intake and exhaust manifolds, timing gears, timing gear chain or belt and cover, flywheel, harmonic balancer, valve covers, oil pan, oil pump, water pump, fuel pump, engine mounts, seals and gaskets

*Diesel Fuel Metering System: injection pump, nozzles, high pressure lines
and high pressure sealing devices

*Glow Plug Control System: control/glow plug assembly, glow plugs, cold advance relay, and ECM

*Fuel injection control module, integral oil cooler, transmission adapter plate, left and right common fuel rails, fuel filter assembly, fuel temperature sensor and function block


Am I reading this wrong, or wouldn't the filter head be part of the fuel filter assembly? Why would they skip this and cover virtually everything else around it?
 

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o3 injectors arent necessarily bad, but they are covered to 200k as per a tsb, so don't sweat it.

read the above post as to what is coveed under warranty, and takethat to your dealership and ask questions.
 

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I Have 01 Gmc With Loss Of Prime Problem In Winter. It Starts Immediately, Runs 20-30 Seconds And Dies. I Re-prime And I'm Good To Go. My Driveway Is On A Hill And I Always Parked Facing Up....i Tried Backing Up, And Viola! No Loss Of Prime. I Must Have A Check Valve Someware That Isn't Working Right.
 

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o3 injectors arent necessarily bad, but they are covered to 200k as per a tsb, so don't sweat it.

read the above post as to what is coveed under warranty, and takethat to your dealership and ask questions.
Hey,

Is that on a case by case basis, or are they all covered?
 
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