Truck died, no spark... help!

07sierraclassic

07sierraclassic

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Mar 11, 2012
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Buckley, WA
So I was on my way into work Monday my truck flat-out died before I made it a mile from my house. It was the first 70*+ day we have had here, and had the sun roof open and Van Halen rockin so I didn't hear anything. I rolled into the throttle and was floored, doing about 70-75 and then felt a slight vibration and lost engine power. No loud bang, no obscene amounts of smoke of any kind. All my electronics are still working but engine won't fire. It was at operating temp and had plenty of oil pressure when it happened. Has approx. 50lbs of fuel pressure at the rail, but isn't getting spark. Valves move when engine is cranked over so im a little stumped at this point. A lot of what I've found points to either the crank sensor or the cam sensor, but I am not very good with electronics and don't know how to troubleshoot sensors.

Truck had no previous symptoms, as in it didn't feel sluggish and started just fine. It has an LQ4 with roughly 80,000 miles, so, WTF?!?!
 
Check all of your underhood fuses first as they're the easiest. I had a no-start problem with my 04 and it turned out the 40A ignition fuse was blown. It would still crank like it wanted to start, but never did.
 
All the fuses I have checked are good still. Would a sensor just flat-out fail like that tho? It died under WOT and wont start at all, wont even try! I have a hard time believing it just "blew up"... cause my old 5.3 still ran even with low compression...
 
Gonna grab a scan tool and see if I can find any codes. What reluctor wheel is in this engine? It's a 6.0 out of an 05 Denali


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could also be a ground. If your motor swapped... check all grounds find a guide explaining where each is located. If one is missing/loose/corroded it would cause odd problems like this.

Also what bryan said, could be a pinched wire.
Could also be the PCM.

start with fuses, work to grouds, check coil pack plugs at main harness.
 
Took it and had it diagnosed, something broke internally, motor is blown. I have no successfully blown a 5.3 and a 6.0 in this truck and the most surprising thing... Rear end and transmission are still going at 157,xxx


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Now the big question is... LQ9/4L80E swap or trade it in? This truck kind of worries me, first motor lost compression and now this. I feel if I put a new engine in the trans will fail immediately, and the rear end already needs to be rebuilt. The fact that my 4L60E has outlasted not one but TWO small blocks has to mean the third motor will blow it into a million pieces. Have a Detroit true-trac for it, was going to put 4:10s or 4:30s in it, level it, wheels and tires and be done. I have a hard time bringing myself to buy another GM truck since I have been able to destroy 2 of them now, but at the same time don't really want to have a bigger/longer payment....
 
i think yours is a lemon. hell i have 168k on mine, and 50k of that being on 34in much tires, and all i have had to replace are stepper motors, shocks, brakes and a set of wheel bearings, but that was the first for everything but the brakes, and the brakes were probably done at 70k from the previous owner.

dont let one bad apple keep you away from GM.
 
Yeah thinking that I may as well just put an lq9 in, they're so close in price that it doesn't make much sense not too. Wanna do an 80e swap too but can't find any solid info on a 4x4 4L80e swap that worked, only 2wd


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nickleachy is doing one, the transfer case is the same just the imput shaft is different, number of splines iirc from his thread. you would need to move the trans crossmember, and need a new front and rear drive shaft as well as a different tune. remember the gears are different outputs in the 80e too.
 
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