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Hi everyone, I rebuilt a stock ls6 a few months ago, sealed it, and put it in my 78 transam. Plummed new fuel lines etc and I purchased a custom harness from brp hotrods (came with computer (04 4.8 truck computer) and base tune) i went to crank it and it doesn't want to light off. I have all sensors hooked up, crank sensor, cam sensor, lat, lac, tps.. etc. They are all brand new and purchased through summit.
Fuel is getting to the rails, and I have good compression, and what looks to be a descent spark. I used a spark tester from auto zone and I could see a spark but it was intermittent. After around 5 rotations of the engine, it will blow a puff of air through throttle body.
I also noticed that before, when I would crank it, it would fire plugs once but not after. That was yesterday but today it seemed to be firing more than once
it's almost like coils are firing backwards, even though there is no possible way to reverse harness as it carries all it's injectors and accessories with it. Possible incorrectly manufactured harness?
my biggest fear is that the reluctor wheel is damaged and not reading correctly. Hopefully not.
I just checked injector pulse as well, it looked good. I gave it a shot and it popped through intake. I'm gonna go ahead and guess cam timing is off. Any other suggestions before I pull everything apart?
I tried to crank it up again. It tries to light off but isn't close enough. It will back fire through exhaust and intake which I find weird. Does this conclude that timing is off a tooth or so?
Still doing sone research (on ls1tech of course!) and I'm starting to believe it's an ignition issue. I doubt I screwed up cam timing as I've done it many times, I'm sure it was correct.
popping through intake intake and exhaust leads me to believe my custom harness might have been defective as far as coil plugs etc. I'm going to throw my diagnostics tool on there and check all the parameters.
if anyone has any suggestions at all or ideas on how to confirm that coil harness is reversed, please let me know. I can't just swap them unless I find an extension, which I will use to fire it up and then rework the harness my self.
I got a code, reading p0366, which has something to do with crank sensor. Do I need to go through the relearn procedure? My next step is to remove sensor and check condition of reluctor.
while cranking, it pretty much sounds exactly like a firing order issue like on the older distributor motors.
Did you have any crank work done? Best to find someone with a scan tool that can read the crank sensor as its cranking. Could take a shot and change it too. Also pull the crank sensor out and watch the reluctor wheel as its turning, See if its running out etc.
Did you have any crank work done? Best to find someone with a scan tool that can read the crank sensor as its cranking. Could take a shot and change it too. Also pull the crank sensor out and watch the reluctor wheel as its turning, See if its running out etc.
no crank work done, it was in great shape. I have a nice diagnostics computer, I'll hook that up tomorrow and check. What's spec for max run out? 20 thousandths?
no crank work done, it was in great shape. I have a nice diagnostics computer, I'll hook that up tomorrow and check. What's spec for max run out? 20 thousandths?
I got into contact with Andy at swap specialties and performance, he seens to be extreemly knowledgeable and is helping me diagnose the issue. I will report back as soon as I get it worked out
Very good news! It was the crank position sensor!! It was a new unit from summit but I had an old spare one and it fired right up! 50 psi idle oil pressure!!
Oh happy day, moekluse! Gotta be a load off the brain! Congrats man!
you have no idea! I checked everything twice, but I didn't think I'd have an issue with a new sensor! I checked it by turning the engine over and checking to see if the tach was picking anything up. Sure enough it wasn't. It was after I replaced the sensor! Can't wait unroll I get drive shaft made to take it for it's first drive! Thank you everyone!
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New engine cranking issue 
