Since I put a new motor in a 1990 corvette I have had this problem of it just shutting off. The engines will just die. It does not matter if you are driving, parked, closed loop, open loop it will just die. If you wait awhile it will start up run fine until it shuts off again. It only set off a code one time (code 53) so I put a new alternator in it. Well it still does it but does not set off any codes. I hooked my scanner to it. Once when it died I caught that the voltage only read in at 4.0-5.7 volts. The car would not run until the volts were back around 12 volts again. But again never set off any codes. Does anybody out there know what might be causing this to happen. Thanks for any help in advance,
Darren


[Modified by Biggmon1, 3:02 AM 5/6/2002]

 

This sounds like an intermittent connection from the battery to the spark module or the ECM or the fuel pump all of which will shut the engine down. Your scanner clue of 4-5 volts is significant and I am unable to learn from what circuit the ECM reports system voltage. My 87 manual says that code 53 is an overvoltage and sets when ignition input pin on the ECM is greater than 17.1 volts for 2 seconds. Overvoltage can only be due to a defective voltage regulator in the alternator and I doubt that both alternators you used had the same problem. I would inspect the fuses and fuse clips for bright clean and good spring tension on the LCD, Cluster, ECM/IGN, INJ1, and FP fuse. If your 90 won't start for a while after it quits, then I would carry a voltmeter with you and start checking the voltage on both sides of the above fuses to find out if a poor connection is the cause of low voltage. I am most suspicious of the power to the ign sw and from the ign sw to the distributor (pink wire) and I would include the pink wire when measuring volts to find the problem. If the ign sw (run position) is intermittent, then the power to the distributor will cut off and the engine will stop. Also, it would help to know what other circuits are affected: does the radio, headlights, stop lights, interior and dash lights still work? I believe the 90's may have the block of connections next to the battery where most of the fusible links connect and the tightness of the nuts on these terminals should be checked (be careful, 12v on these all the time).
Good luck.

 

Check your battery grounds

 

Hi, alot of times when the alternator dies, the battery goes south as well. This is due to the increased load on the battery when the alternator is going wacky. Either have the battery tested or get it replaced. Good luck.

 

Thx for everyones help. I checked everything everyone told me about. When my scanner reads 4.8-5.7 volts it still does not set off a code. It also does not effect the lights, radio, heater ect. The scanner will read 4.8-5.7 volts and I will have 12.4 volts at the battery, back of the alternator, the starter and the bat wire into the dist. but yet the engine still will not run. It was at 4.8 volts today for the longest it has ever done it and after I was done looking at it it still was at 4.8-5.7 volts and never started again. Also I dont know if this makes a difference the car sat approximately 3 1/2 years before putting in a new motor. Could the ECM be bad from sitting, it ran fine before. Anymore ideas????
Thx Darren


[Modified by Biggmon1, 3:06 AM 5/6/2002]

 

Unplug one of your injectors and connect a 12v lamp or an analog voltmeter and see if the injector is being pulsed while cranking (and when it won't start). If no pulses, then the ECM went to the big electronic parts counter in the sky.
If you do have pulses, then you need to check for fuel pressure to see if the fuel pump runs for 2 seconds when you begin to crank. If no fuel pressure, then either the ECM is not turning on the fuel pump, or the fuel pump relay is defective. If the pink wire to the distributor has 12 v on it , then I would expect spark. Did you determine if you have spark? Let us know if you have spark and fuel pressure.