Someone please help...symptoms below:

About 6 months ago, my car would crank healthily, but not start. I replaced the opti, still no start. Replaced coil, no start. Replaced ICM, no start. Eventually, the car started, but to be honest, I'm not completely sure what I did (if anything) to get it to start. Car started and ran fine for the last 6 months.

Just recently, I dropped in another LT1, and now, I'm experiencing the exact same issues. Every once in a while the car will start after long cranking, but it's very inconsistent. With the motor swap, I've installed fresh plugs & wires, re-installed my cc503 & springs from my old engine.

Tried 2 optis (one old and one new): cranks, no start
Tried 2 coils (one old and one new): cranks, no start
Tried 2 ICM's (one old and one new): cranks, no start
Fuel pump primes, and fuel pressure reads (35-40 psi) at the schrader valve (key on and during cranking), and I have plenty of fuel in the tank.
While having someone crank, I've actually lifted the rail off and no fuel is spraying out of the injectors, but I do not think all of them can be clogged to the point of no spray or dripps during cranking.
While cranking, I take the coil wire off the opti end and hold to ground and get no spark or sporadic spark from the coil.
I've unplugged the battery, unplugged pcm, unplugged the pcm bat fuse, and still cranks but no start when hooking all of those back up.
All fuses look good.

PCM tuned by madwolf over a year ago for the cam, vats disabled from pcm. I've even grounded the yellow/black wire from the TDR and that actually PREVENTED my car from even cranking over, so I re-connected that wire back to the TDR and car cranks again but will not start. I haven't tried the resistor/key bypass, but I'm not, nor have I ever gotten, any security lamp, so I don't think it's that.

Small PCM ground wire is connected firmly to oil pan rail and I've also re-located it to the frame and still cranks but no starts. The 3 ground wires to the coil are also in good shape and connected firmly.

When the car does get started, it idles fine (5-10 mins) but I haven't been able to road test because it's been on jack stands since the motor swap. It throws the "high res failure" DTC only, and this is with the brand new opti installed. From my understanding, that code shouldn't prevent the car from starting or running, correct?



Everything else being changed or swapped, I think I may need to change my pcm with someone to see if the car fires right up. What do you guys think? Anything I may have missed during my troubleshooting?

 

If you have no injector pulses, more than likely the PCM is shutting them off. It should be scanned to see if that is the case. Yes a hi res failure will not shut off the injectors. A low res code will. So the first question is if you have a hi res code, is your SES on?

Also, if you have a loss of spark, the first place to look is to see if the ignition system has voltage. Start by checking fuses.

 

VATS System?

 

Yes, the High Res failure is causing the SES light. I never had the code before, however. I've checked all relevant fuses (injector fuses, pcm bat, ign, etc.) and all look fine. As far as VATS being the problem...I still am not sure. Like I said, I've grounded the small yellow/black wire on the TDR and that caused the car not to crank, so I switched it back. I haven't tried jumping the yellow and purple wires @ the TDR because, from my understanding, these only allow the car to crank, and the car cranks fine. What would be symptoms of an ignition switch going bad?

 

Now you need to actually probe the coil and ICM to see if they are getting voltage.

 

I'm getting 11.75 dc volts at icm harness terminals a and d. While crankng I get less than .5 ac volts on terminal b. I highly doubt it's the opti since both new and old give the same symptoms. Opti harness is new as well. What is left? Vats disabled at pcm. No security light. Gauge lights do not cut off while cranking but could this be ignition switch related? I still haven't swapped pcms...this is frustrating.

 

Changed ignition switch...same issues. When I got the car to start today, it was missing and would backfire out the exhaust upon moderate acceleration. I will double check my pushrods and valve adjustments and swap to a 3rd opti that I have laying around tomorrow. Only getting dtc 36 (hi res failure).

 

And the moral of the story...always use a gm opti. Swapped and starts and runs like a champ.