Don't know exactly where to put this , but it is a conversion so here it is . I have a L76/6L80E out of a 08 G8 in a 69 Camaro that cranks over excessively before it starts , but once running , it will sit and idle , take throttle and generally run ok . You can shut it off and immediately , or wait a minute , and try to restart and it does the same thing . I have had it start after 3-5 seconds cranking or 12-15 seconds cranking , no pattern . I don't think that I have had it entirely up to operating temp yet , but it has definitely been beyond stone cold , oil pressure around 40 psi , and voltage 14+ volts .

Now here are the variables , complete DOD delete ( Muscle car pan , no oil pressure relief valve , new standard pressure oil pump , new lifters / pushrods , new valley pan , Texas Speed 224 cam ) Speartech modified original harness and reprogrammed ECM and TCM , usual deleted items with harness rebop (2 O2 sensors deleted , vats removed ....) Longtube MuscleRods headers and a Cold Air Induction setup on the intake side . I have relocated the coils and have lengthened/shortened several different wires within the harness for fitment purposes . There are no codes been thrown that I can read with a general code reader , haven't had a High end diagnostic tool hooked to it yet . Also the car has no exhaust beyond the open headers and the remaining O2 sensors are within 6" of the open ends , so that could be an issue .

So that's my situation , can't say for certain that I do indeed have a problem quite yet because of the open exhaust ,lack of run/learn time and not having the car up to full operating temp for any period of time . Would like to get some opinions on why the car won't start up immediately and if there is an issue here . Thanks and I look forward to hearing the responses .

 

Have you checked fuel pressure? I wouldn't do much troubleshooting beyond that until you've got an exhaust on it and get a proper tune so you don't chase your tail too much.

 

Sounds like you're losing your fuel pressure prime and its having to reprime the system when you start it. Like the other poster said, check your fuel pressure and make sure it holds when shut off.

 

Easy to test. Turn key, let t prime, key off, key on and repeat a few times and then crank it. If it starts right up you're losing pressure probably a bad regulator or something.

 

http://www.summitracing.com/parts/ea...EHSxoC4Ovw_wcB

one of those with a gauge on the fuel rail is a pretty nice way to verify all is good w/respect to fuel psi

 

Fuel pressure is fine ,52-56lb and does not leak down , will maintain after shut down . In testing this , I checked for compression and spark , had good compression but was not firing when initially cranking engine over but did start firing a few seconds later , directly in correlation with the engine turning over and not starting . Now when it did start firing , it did not start immediately like FI usually does , instead it seemed like it was firing but not catching kind of like you had to turn the engine over fast enough to get momentum before it would continue running , if I'm making any sense . What do these engines have to see to start the spark ? Fuel pressure ? Oil pressure ? When you spin the engine over long and fast enough and it does start and run , it seems to run and take throttle and rev up ok .

Is anyone familiar with Speartech's gauges that run off of the CANbus with the GM ecm and tcm ?

 

Anybody ? Going to look into my coil relocation and see if anything jumps out at me , going to go over grounds really good . Again , is the engine supposed to see fuel pressure or oil pressure before it fires ? Anyone know ? Also , would the be a better place to post this than here ? Thanks

 

A weak crank or cam position sensor signal can create a time delay in start up. I don't have a fuel pump check valve in my conversion and my car starts within 4-5 seconds when cranking cold and does not hold residual line pressure when shut off, just be sure your ecm primes the pump/line when you turn the key on everytime.

 

Make sure ECM is powered when key is in crank position. By default GM kills everthing but the starter in 60's cars when in crank position. Maybe when you release the key, the engine is still spinning enough for ECM to then fire the engine.

 

Thanks for the replies , the ecm does turn on and fire the fuel pump and I am getting 60psi at the fuel rail . I am running a Holley fuel rail setup with -6 braided line , a Rick's tank w/internal pump and Corvette filter/regulator setup no check valve , unless there is one internally in the Corvette regulator . I will have to check both the position sensors and see if they are within specs.

The car doesn't have any GM wiring left in it except for the Speartech reworked engine harness , the body harness was completely replaced with a 18 fuse 21 circuit EZ Wiring harness . I have tested the spark plug fire several times by removing the plug , reattaching the plug wire , grounding the plug body and spinning the engine over . It consistently has no fire for 2 or 3 seconds then begins to fire (with a yellow/orange spark) and will continue to spark until I release the key to stop spinning the engine over . The yellow/orange color of the spark does concern me , any comments ?

 

I encountered a similar problem. Turned out to be the cam sensor even though testing indicated that the offender was within spec.

 

IIRC 52-56 is s bit on the low side. 58 psi regulated is what is generally required. But I could be wrong. As i may not be informed for that engine.

 

agree, after fuel pressure and checking the injectors and coils with a noid light
i'd be looking at the cam sensor. heck its possible it needs a case learn.

 

You are correct. It should be at 58psi.

OP which fuel pump are you using?

 

Let me correct that , when running it is 60psi , unless I'm totally off base , it isn't a fuel problem . primes up to 60psi when key turned and maintains while engine running . I reworked the coil mounting method making sure ground was clean , tight and even added ground wire from bracket to known good ground .

I had someone hook up a obdII code reader to the engine and found a P0335 code thrown that my reader didn't catch for some reason . That is a crankshaft position sensor code .......but if that's bad would it even run ? Is that where the tach signal originates ?