Intermittent no start condition.....

[40BelowSummer]

Hey, just thought Id run this past the forum since Ive been thinking about it. Every once in a while my SHO will crank but won't start.

• Cam sensor replaced
• Tach is present during no start condition
• No codes present
• Fuel pressure is there (new FPR/Injectors/Fuel Pump)
• Will push start everytime this happens, but won't fire during cranking

The problem is intermittent. For example, I will drive to the store and return to the car shortly and the car will start fine but sometimes it won't and I will have to push start it. (did it twice yesterday) The car seems to start everytime if it has been sitting for a while though. Seems to run fine otherwise.

Any ideas?

 

[kylix.rd]

Maybe the Crank Position Sensor? Had the same thing happen on my '89 when the water pump started weeping down over the sensor and killed it. Would start fine when cold, but would fail intermittently when warm. Could also sometimes push start it and it would fire over. Did this for a week or two when it finally just died completely (Ironically it died on my way from picking up a new set of plugs in preparation for doing the 60k service, timing belt, water pump replacement and CPS).

 

[40BelowSummer]

Just drove the car today for the first time in 4 months and the problem is still present. I drove the car on a 15-hour trip and everytime I stopped to get gas I had to push-start it. If it sits for a while (not sure how long, probably an hour or more) it will start up just fine.

I now have a code 528 and here is what I found that to indicate:

Clutch pedal

For the 92 SHO, DTC 528 indicates that the PCM detected that pin 30 CES (Clutch Engagement Switch) was high (not grounded) during a cranking episode.

In normal operation, the CES is closed and pin 30 is grounded (low) whenever the clutch pedal is pressed. Do not depress the clutch pedal while running KOEO PCM Quick Test.

You can pull the connector from the PCM and measure between pins 30 and 46 with an ohmmeter. Should be an open circuit. Press the clutch pedal and it should go to a closed circuit. Check the pin 20 side for possible shorts to power or ground. If all checks are normal, the PCM is likely defective.

Primary use of the CES signal is to 1) Disengage the cruise and 2) Signal the PCM to control idle speed and for dashpot control.

I wanted to see if this might cause the problem I am seeing before I resort to replacing the CPS. (no codes for the CPS, but I replace the CID sensor)

Why would the car not fire when cranking, yet push start everytime this happens??

Any help/info would be great.

 

[NotSoSlowSHO]

The only correlation I can make between no start when stopped and start when moving is the VSS. Unplug it and see what happens.

When you have the no-start condition, does depressing the throttle help at all?

 

[40BelowSummer]

When you have the no-start condition, does depressing the throttle help at all?

No, that was the first thing I instinctively tried. I'll look into the VSS, that never crossed my mind. But, would the VSS really keep it from starting?

 

[NotSoSlowSHO]

It would certainly make for a more difficult start. As the AIB valve would remain closed. And it is the only sensor I know about on the MTX SHO besides the cruise control equipment that responds or has anything to do with motion.

But if depressing the throttle a bit doesnt help... then I dunno

 

[aggiesho]

woah im having the same or slightly different problem. itll just crank over but wont fire and pressing the gas doesnt help. another time it would fire up and die and pressing the gas wouldnt help. i was leaning towards the cps but a lil while ago i went out and it wouldnt start but i didnt hear the fuel pump come on, so i let it sit for a few mins then it fired right up. has done this 3 times in the past 3 weeks only on cooler nights. any suggestions?

 

[40BelowSummer]

woah im having the same or slightly different problem. itll just crank over but wont fire and pressing the gas doesnt help. another time it would fire up and die and pressing the gas wouldnt help. i was leaning towards the cps but a lil while ago i went out and it wouldnt start but i didnt hear the fuel pump come on, so i let it sit for a few mins then it fired right up. has done this 3 times in the past 3 weeks only on cooler nights. any suggestions?

Next time it doesn't start and you can't hear the fuel pump, check and see if you have fuel pressure at the rails or not. Start with that.

 

[TimboSHO]

Any ideas?

Give the car to me? J/K, but you have one heck of a sweet ride there.
The problem you have with it is quite perplexing as well, nothing really comes to mind. It always fires right up on the first push start? How many times do you try cranking it before you push it? If it were a CPS, it wouldn't fire when push starting either..... very odd...

 

[40BelowSummer]

It always fires right up on the first push start? How many times do you try cranking it before you push it? If it were a CPS, it wouldn't fire when push starting either..... very odd...

Yes, it fires right up everytime when push-starting. I've done this many times now. I have tried cranking it plenty when I do try, before resorting to push-starting it. Are you sure that when the CPS is out, it would not fire when push-starting?

It has to be something. Because, bottom line, it will start right up everytime after it has been sitting a while (like overnight). But won't start right up after it has recently been running, yet will push start everytime this happens. It isn't throwing a code and seems to run fine otherwise. But something is amiss.

 

[expy916]

I know this thread is old, but did you ever figure the problem out?

 

[sperold]

Go back and look for a water pump leak, it has all the classic symptoms. After it sits for awhile, the crank position sensor dries out a bit and works better than when it is wet. Eventually it will quit when you are driving along, but you haven't graduated to that yet.

 

[okcoolthnx]

Also having this problem. The CPS and CID was changed 30k ago, so could it really be that again? Starts great cold, hard time warm. Sometimes no start at all warm.