This one came out of the blue & is an intermittent problem on a 88GTA with 5.7L engine. Occassionaly, the engine won't crank (VATS is circumvented). If you wait 5 minutes, the engine cranks & starts. At first, I thought it might be a heat soak problem, but recently occurred after pulling into the garage, engine cold, and then trying to restart.

Now here's the clincher. When it is in this won't crank mode & you leave the key in the KOEO position, you here alot of solenoid actuations & diaphram actuations. You can feel some of the injector solenoids cycling on & off. Furthermore, since we were resetting timing to pass emmissions (high HC), I decided to clear the codes with the scan tool. I couldn't get past the point of: " is check engine light blinking code 12". It was just blinking continuosly. The shop manual troubleshooting tree suggests a short to ground in circuit 419 or probing circuit 451.
Can anyone offer me any assistance, as to a good starting point. I know this is kinda deep. I hope V-man can respond as well, this is right down his alley.
Thanks, FJK

 

FJK,

It sounds like you're in the diagnostic mode. Electric fans running, too? Whether you have a ground in the diagnostic request line or some CMOS logic problem, try to disconnect the ECM power fuse near the battery, or just disconnect the battery and clear everything. While you're at it, you may want to check the connectors at the ECM if you haven't already done so.

I'm operating on a few presumptions, such as the EPROM is stock, the car hasn't been in a flood or experienced overvoltage, and it wasn't struck by lightning. I'm also operating on NO COFFEE this morning, so excuse me if I miss something.

 

Vader: I'll buy you a coffee if we ever meet. I just got into looking into this & I think a step by step process is required. I think the no crank & this diagnostic mode are not inter-acting because I have demonstrated the car will crank even if this strange diagnostic thing is going on. So, first things first.
With KOEO (key in run position) I'm not getting a steady SES light. The SES is continually blinking with the other symptom occurring as well. I'll disconnect the battery, then go after the ECM connector next (under the right hand dash ??). Car has stock prom, never in a flood. However, the car is parked outside & was out of service while doing the trans job, this problem surfaced after a period of inactivity, suggesting a dampness, humidy, corrosion problem. Stay with me on this one, if you could.
Thanks much, FJK

 

Disconnecting battery for 5 minutes & reboothing did not help. I guess I'll go after the ECM connector next. Since the occurred after the trans R&I, I'm wondering if the harness crossing over the back of the engine on the flywheel housing got hurt. My guess there is a done of ECM leads in that harness. If I have to go there, that will be a bit**.

 

Well, I found it. After playing with the harness that runs across the back of the block.... not it. Then I thought it was were I spliced into the coil for the MSD Boost retard control.... almost. Then I disconnected the MSD boost retard control and rewired the coil to run "as stock", problem fixed!. Vader, if you are out there, care to explain how the MSD boost retard box could cause the symptoms I described. This thing splices in series with the white wire on the black connector to the coil, & in parallel with the pink wire on the black connector to the coil. This MSD box allows the driver to retard timing 0,1,or 2 degrees & senses supercharge boost. This seems like a non-esential device as long as the engine has a knock sensor. After removing the MSD box, I monitored the knock sensor with a scan tool & saw more than 10 degrees retard on heavy accelleration. Today it is about 92 degrees ambient & the scan tool showed 162 F intake air temp. I think the knock sensor can out perform the MSD retard control. Anyone with similar experiences?
FJK