03 lb7 crank no start - Chevy and GMC Duramax Diesel Forum
01-04.5 LB7 Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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post #1 of 3 (permalink) Old 09-07-2011, 08:37 PM Thread Starter
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Join Date: Mar 2011
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03 lb7 crank no start

i was on my way to work this morning at 70mph and my truck just shut off. I coasted to the side of the road and tried the key again, no its a crank no start condition. I had recintly baught a ppe tuner and its been fine for the past three weeks its been installed, tons of power and great mpg, but I belive its adding to the problem. I called ppe about the problem and they told me that if I was cranking the engine and there was no stumble and no bounceing of the tach then the problem was in the crank sendsor. This guy seems to be to cocky in his diagnosis for me. The hand primer is hard enough for me to asume it has a good prime so I'm thinking ecm. The only thing that is bothering me is the cranking engine speed. Its cranking between 125-175 rpms, this seems a little slow. Please let me know if you have any insite or possible previous experience. thanks
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post #2 of 3 (permalink) Old 09-08-2011, 08:40 PM
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My 03 along with my buddies 03 when we put a program on the truck our fuel gauge dosent read corretly and both run out at anywhere from 1/8th of a tank and 1/4 tank. By saying the hand primer was hard enough, were you talking about priming the fuel?
Have you try to scan for codes or set back to stock?

2003 LB7 CCSB Lifted 9x,xxx Miles,, 22x10.5 Novakanes ,Charcoal Matte Gray Vinyl wrap,Suncoast 1056, Gmax, SoFloDiesel 6" Custom stacks, PPE BIV, EFI Live Tuned by Rob, Merchant Motor Mounts, Eaton Tru Trac, Profab Horn, Airdog, Wetzel Wheel, Rare Parts T-rods, T-Case Brace, Pump Rub, Congnito Braces, 4" Custom welded intake,CTS Monitor,Autometer Boost/Pyro,Soflo Diesel Trac Bars, Totaled 1/16/15

2007.5 LMM CCSB 26x16 ,37" M/t's, 12" Cognito,Dual Fox Shocks/Resi,Soflo Diesel 8" Custom dss cats,Soflo Diesel Trac Bar ,AEM, EFI by Soflodiesel
1954 Dodge Job-rated with 12valve swap, 22's,5x16,s366,Suncoast,Dual Ram intake, fullcuts,4kgsk,60lb Vs,studded,Little Spray
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post #3 of 3 (permalink) Old 09-10-2011, 01:48 PM Thread Starter
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i figured the problem out. I had a u1800 code for the ficm power supply. the 25amp fuse was blown due to a short to ground in the wire harness. I ended up finding the issue to be under the harness on the drivers side of the engine where is goes over the valve cover. I had to use my multimeter to determine that it was shorted to ground, (also the blown fuse was a slight indication). I had good continuity to the ficm and shitty continuity to ground, but continuity non the less. I pulled out portions of the harness and found the pink 12 ga wire had rubbed through on a 3/8 piece of steel tubeing. I fixed the wire and cleared the codes. the trucks been fine for the past 3 days. moral of the story is the ppe tuner wasnt the issue like i had originaly thought and everybody should probably start checking there trucks for this failure before they end up on a flatbed like me haha. it harness has very little protection on it , and the harness was run that way from the factory so i'm assuming its going to be common as these trucks get older
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