Duramax Diesels Forum Truck of the Week
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Old 02-05-2009, 07:47 PM
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Red face 03 LB7 Won't start when hot, Not Injectors?

I have a 03 LB7, 128,000 mi, and put into service 10/02, so it is currently still under the injector warranty.

Ever since this past summer it has been progressively harder to start after I drive the truck, then cut it off, and try to start it back up between 10min to 3 hours later. It started with just having to crank for 5-6 sec compared to the normal 1-2 sec when cold, to the point it left me stranded on Superbowl Sunday for 5 hours.

On Sunday I drove for 35 minutes, parked at my girlfriends house, and came back out 30 minutes later, cranked 4 cycles of about 20 seconds each, no start. Let it sit for about 5 minutes, and did exactly the same, no start. Did this one more time before double checking that it had not lost prime (it had not, and pumping the primer does nothing to help it) Tried the same process a few more times over the next hour and half with no results, wound up having to watch the Superbowl on her grandparents 25" tv rather than my room mate's 65" HDTV . After the Superbowl I go to start the truck, and of course it takes maybe 2 seconds tops to crank (since it was cold by this time) with a big puff of white smoke.

There is no fuel in the oil (slight smell, but level hasn't risen and doesn't seem to appear with the paper towel test), Doesn't white smoke at idle or when driving, just after a hard start, Went to the dealer and they commanded the rail pressure to 160 MPa, it made it to 160 MPa, then checked the balance rates, I don't remember them all, but the largest one was 2.7 in park, didn't get to see them in drive. The tech told me he still feels like it is injectors somehow, but the evidence is not there to back it up to get it under warranty, which I understand.

I checked it with my PPE tuner while trying to start multiple times, from what I have heard, rail pressure has to reach 1,400psi to start? The most it will build when it is hot trying to start is ~750 psi, when cold it ramps straight to 1,400+.

The truck was warmed up when the dealer tested it, ~190* by the gauge on the dash, and I had just driven 30 miles to the dealer to have it checked.

I was thinking maybe it has something to do with warm fuel being thinner than cold fuel, and that having something to do with the hard start when warm

The truck is currently put completely stock, no tune, it does this with/without the PPE.

Checked the Vin, and the truck has never had injectors replaced before.

This started this past summer, at approximately 118,000 mi, I have changed fuel filter 3 times since, this filter has about 500 mi on it, the last had about 5000 mi on it and looked perfect when cut open.

I had been running power service diesel kleen in every tank, but haven't for the last few, doesn't seem to make a difference either way, only get fuel at high volume truck stops.

Any Ideas? I appreciate any help.
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Old 02-05-2009, 07:48 PM
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Sorry for writing a novel there, figured it best to put all the background info I could, Thanks!
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Old 02-05-2009, 10:03 PM
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I am going through this as well. Check this thread out, might be something to try.

http://www.duramaxdiesels.com/forum/...ad.php?t=10943
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Old 02-06-2009, 09:10 PM
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Absolutely every detail of your story and symptoms is EXACTLY what I experienced up to and including finally being stranded. Only thing that would crank mine at that point was a little ether (with emphasis on the word "little"). The dealer experience was also identical. The return rate test was going to be too expensive and they were not willing to warranty my injectors so I told them screw it.
Isn't it possible your rail pressure will not build to the 1400 psi because of high return rates? With so much fuel bypassing the injectors, it's essentially waste-gating the fuel rail. With thinner hot fuel, cranking rpm is not enough to overcome the fuel loss. Return rates for sure dude. Time for new injectors.
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Old 02-09-2009, 08:37 AM
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Quote:
Originally Posted by Filadog View Post
Absolutely every detail of your story and symptoms is EXACTLY what I experienced up to and including finally being stranded. Only thing that would crank mine at that point was a little ether (with emphasis on the word "little"). The dealer experience was also identical. The return rate test was going to be too expensive and they were not willing to warranty my injectors so I told them screw it.
Isn't it possible your rail pressure will not build to the 1400 psi because of high return rates? With so much fuel bypassing the injectors, it's essentially waste-gating the fuel rail. With thinner hot fuel, cranking rpm is not enough to overcome the fuel loss. Return rates for sure dude. Time for new injectors.
Exactly my thoughts about thinner hot fuel making it harder to build pressure because of return rates.


What did you wind up doing?
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Old 02-13-2009, 07:17 AM
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Bump...anyone have a clue?
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Old 02-14-2009, 10:59 AM
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I had the very same issue 2 months ago with my 01 work truck. I hauled it to the dealer and refused to pick it up until they did something with it---they changed injectors and all is good again--except now my front tranny seal is leaking and Its parked once again, But its def. your injectors. Leave it at the stealer and tell them to prove YOU wrong!
I took mine in 2 weeks before my 7 years since the waranty effective date, picked it up 2 weeks after the date (1 month later) and I made sure I told them I was aware of my warranty date--That got his attention more than anything--"I better get this filed ASAP!" Apparently GM doesnt care when the vehicle comes in or leaves, its whatever the service tech files the dates at...........
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Old 02-16-2009, 08:14 PM
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Bump, still looking, dealer won't do injectors, since GM will not reimburse them for warranty work as the injectors test PERFECT according to balance rates, and fuel rail pressure.

Tried pressurizing the fuel tank (using the valvestem through a non vented cap trick) when I filled it it with air, I heard air escaping above the tank, but it was really muffled rather than a hiss, which makes me think it sounded like it was escaping through a vent above the tank, rather than a pin hole somewhere. Truck still does not seem to loose prime, as I have tried that each time to see if it helps, each time I loosen the bleed screw, one pump produces fuel out the bleeder screw every time, straight fuel, no air bubbles, which leads me to believe its not a losing prime problem. Again fuel filter has less than 3k miles on it.


I'm about to just leave it at the dealer, tell them I don't want it back till it runs, and just spend my girl's ring money on it since I have no clue anymore. If I was positive it was injectors, and there was no way the dealer would cover it (like they say right now), I could just do them myself, but I'm not so sure its injectors since it tests fine.
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Old 02-16-2009, 08:18 PM
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is the fuel cooler wet at all? just throwing ideas around even though you pressurized the tank.
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Old 02-16-2009, 08:23 PM
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Can you try another dealer?
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Old 02-16-2009, 08:36 PM
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Quote:
Originally Posted by 05' Ditry Duramax View Post
is the fuel cooler wet at all? just throwing ideas around even though you pressurized the tank.
Nope, dry as a bone, as are all of the lines visible, quick connects, rubber hoses around filter, filter itself, bleeder screw, priming pump, etc. Like I said I think it rules out any leaks, because it appears to have no problem holding prime. That, and once it starts it runs perfect, except a huge cloud of white smoke right at startup (but nothing after that), rather than starting then cutting back off like happens after changing a filter and not getting the system fully primed.
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Originally Posted by MaxFarmer View Post
Can you try another dealer?
Tried a couple already, I really hate to keep wasting money for them to show me that it easily reaches 160MPa rail pressure when commanded, and biggest balance rate was like 2.5 or something in park, (far from the +/-4 that deems a bad injector) therefore no reason to continue on to the return rate test and waste even more of my money. I'm probably going to try a different dealer over spring break when I can have a week to come in and check on the truck, and talk to the tech.

Last edited by GCncsuHD; 02-16-2009 at 08:39 PM.
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Old 02-25-2009, 07:35 PM
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Well the truck is now parked on campus at my school, in a spot that will be illegally parked as of 6AM tomorrow, therefore a nice $50 ticket will be waiting on me in the morning. I went to class at 6, came out at 8:30, truck would not start, cycled 8 times, 20 second cranks each time, no good. Reprimed the truck, nothing, still had good prime. Entire parking lot smelled like diesel fuel. Left with a friend to get a couple beers and some food, came back at 10:30. Truck has been sitting over 4 and a half hours, still no start.

Does anyone have ANY clue? Please help, thanks.
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Old 02-25-2009, 07:41 PM
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here are a couple vids from about a month ago of it trying to crank, first one after sitting for about 3 hours, second one after sitting for about 3 hours in freezing cold, when its cold it cranks much easier.

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Old 02-25-2009, 07:57 PM
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i think im having injector issues mine is going to the stealer monday it hayzes blue smoke after it runs for awhile at idle and the rpm surge about 100 or 200 then idles rough .Not real sure if this works but the owner at one of the performance shops here told me if evrything checks out ok but still want new injectors before the warranty is out put fuel in the crank case and they have no choice but to replace them since the evidence is there in the oil even if they cant figure out how it got there
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Old 02-25-2009, 07:58 PM
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Quote:
Originally Posted by smokn03duramax View Post
i think im having injector issues mine is going to the stealer monday it hayzes blue smoke after it runs for awhile at idle and the rpm surge about 100 or 200 then idles rough .Not real sure if this works but the owner at one of the performance shops here told me if evrything checks out ok but still want new injectors before the warranty is out put fuel in the crank case and they have no choice but to replace them since the evidence is there in the oil even if they cant figure out how it got there
Oil in the crankcase won't do a damn thing except contaminate the oil if the return rates don't check out to qualify for injector replacement.
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