tim95z28

This is for my LT1 road race car. I run it about 8 times per year.

Back in July I was getting ready for an event and the car was hard to start. I kept cranking and it wouldn't start. Waited a few minutes and it fired right up. Went to road atlanta. Ran fine the first session. Then did not want to crank for the next but finally fired and ran ok. Then I went to get gas, and the car temp was sky high going into the gas station...I was thinking blown head gasket. I let it cool down and driving back, the temp crept up, and then shot down, (about 1 mile from the track), I have seen this happen before when I have air in the system. Pulled into the track and at 20 mph the car died. Would not start, and still will not at all.

I have fuel pressure (not measured, but I hear the pump, and when I push on the schrader vale fuel squirts out at pressure)
I don't have spark. I have replaced the opti, ignition control module, Coil. that leaves the coil wire, which looks fine, and the pcm.

I have rung out all of the wires between the pcm and the opti and between the pcm and ignition control module. I have checked all grounds and voltages.

So now, the only thing left I can think of is the PCM. I did check the signals to the ecm, and I did not get the ac voltage while cranking. I did see about 200 mv ac while cranking.

Before I had this problem, I did find that the water temp sensor was grounded out. This could cause damage to the pcm, but I would think that the pcm would work or not. Does the PCM ever fail really?

Am I missing something? Also, please let me know where I can get a new pcm if that is the problem. I could not find one at the local auto parts store. Want to get this car running for a road atlanta event at the end of the month.

Here is a vid with me running with a new ZR1 this summer at vir, with dead tires, for encouragement, help me get her going again!

http://www.timz06.com/vir2008/virzr1lowmed.wmv

Thanks,

Tim

MislMan

I recommend taking a look at the temperature sender and its connector. Engine temp is used by the PCM for a few things. Maybe the sender is faulty or cracked and needs replacement. It may be sending sporadic signals to the PCM that cause a severe overheat reading and the PCM shuts things down. I had a temp sender go bad on my '95 Vette and it would alternately make contact then break contact. The car would intermittantly run poorly, die, buck, cough, etc.

tim95z28

Thanks for the reply. I don't have any of the sensors connected right now. I replaced the OPTI and was just trying to get it to fire, before I put everything back together.

It won't even make a pop now. I have run it before with everything disconnected, so I know it should at least start.

Tim

95Blackhawk

Are you sure you checked all wiring to and from PCM? You are talking 2 batt feeds and 2 ignition feeds. All are checked? 2 grounds and both are checked?

Doubt it is the PCM but there is no harm in getting one from a junkyard as a spare for under $100. I have 5 or 6 myself, most are fried

Injuneer

Hook the sensors back up. Clear the PCM by pulling the "PCM BAT" fuse for 30 seconds. Try and start it. Scan if for codes.

Have you visually verified that the Opti harness connectors (both of them) are not corroded, or damaged?

The pump will prime and develop fuel pressure as soon as the key is turned to "on". However the pump and injectors will shut down until the PCM sees the low resolution pulse from the Opti optical sensor.