geenick Posted June 26, 2007 Report Share Posted June 26, 2007 I've got an 89 Cutlass Supreme International 3.1. It's died a few times intermittently while my girlfriend was driving it. No sputtering or warning, the engine just quits. After it dies, it will either start back up fine, or there have been times it won't start at all for hours. I haven't been able to isolate something you can do to make it start. I had a fuel filter handy, so I installed that. I did a fuel pressure test, and that came out fine. I've been able to do a fuel pressure test in a situation where the car is running fine, and also when it wouldn't start. Both times, the pressure was about 41 lbs, and it would drop 5 lbs when the car started. A couple of times that the car wouldn't start, you could hear a purring or pulsating noise near the plenum, and then it would stop as you could hear a relay under the hood click. It would pulsate / click, pulsate / click, over and over. A couple of times that sound stopped, and the car would immeaditely start and run fine. It seemed like the IAC valve was making the noise, so I replaced that. It seemed to be fine for a couple days until it started dying again. The pulsating and relay click loop has continued in situations when the car won't run. The only code I've been able to get from the computer is a MAP sensor code. The engine light has not come on when the car died any of the times, that I've seen. I heard that if you can get the car to run, you should tap lightly on the MAP sensor to see if it dies, or unplug it altogether, to see if having it plugged in helps. It seemed worse with the MAP sensor unplugged. The MAP sensor code may have been generated when I was checking the vacuum junction on the throttle body. I have thought about installing a new MAP sensor (at $39.99), but I don't want to start throwing parts at the problem. A mechanic I know mentioned that he had a similar car that was dying due to an injector shorting out, but I'm not sure how to tell if that's what's happening here... Any ideas on what I can do next? Are there any good mechanics that know these 3.1L engines very well? I've looked at the car on half a dozen occasions, and I haven't been able to find the problem. Quote Link to comment Share on other sites More sharing options...
Crazy K Posted June 26, 2007 Report Share Posted June 26, 2007 time to test the injectors ohms! Quote Link to comment Share on other sites More sharing options...
DOHCRagtopguy Posted June 27, 2007 Report Share Posted June 27, 2007 Trace your crank sensor wires. One of them may be cracked or exposed and shorting out at random. Or maybe the sensor itself may be on its way out. Quote Link to comment Share on other sites More sharing options...
geenick Posted June 27, 2007 Author Report Share Posted June 27, 2007 I think I found the solution to the problem... I put a new MAP sensor in tonight, and it still wouldn't start. I pulled one of the spark plugs, and the car had good spark. I re-tested the fuel pressure, and that was still fine. It wouldn't start with spark AND gas seeming to be fine! I also noticed the TPS wire connector has a broken tab on it. I re-seated that, but it didn't help. After messing around with it, the relay I mentioned in my last post started clicking every 10 or so seconds again. I took the fuse box cover off and realized it was the Primary Cooling Fan relay. I grabbed it with my needle nose to remove it, and the clicking stopped. I ran right over to the key and the car started PERFECT. I noticed that the primary cooling fan was spinning VERY slow when the car was running. I removed both electric fans, and tested them both. The passenger side fan spun fast when connected to a battery charger on 2 amps. The driver side fan didn't spin at all until you cranked it up to 50 amps! I replaced that fan, and now the car runs fine. I was dumbfounded. I called my uncle (who is a mechanic), and he said that anything like the fan that is shorting out can disable the computer with no code given. Apparently the computer will shut itself down if there is a short circuit, and that was probably causing the car to not start, and to die. I've driven it about an hour since I got it put back together, and it's been fine! I would have never guessed that the fan could make it not run... Quote Link to comment Share on other sites More sharing options...
Crazy K Posted June 27, 2007 Report Share Posted June 27, 2007 WOW! what a find! now I need to figure out why my vert does something similiar! Quote Link to comment Share on other sites More sharing options...
89GP_SE Posted June 27, 2007 Report Share Posted June 27, 2007 GM alternators when put under heavy stress like a fan using an unusual amount of power will often quit, witch in turn will make the car die. Seems all my gm alternators did the same thing, if it wasnt putting out 12.2 amps, if it was any lower, car would die. Quote Link to comment Share on other sites More sharing options...
DOHCRagtopguy Posted June 27, 2007 Report Share Posted June 27, 2007 Good job tracking that down!! That there is some very useful information. Quote Link to comment Share on other sites More sharing options...
slick Posted June 27, 2007 Report Share Posted June 27, 2007 Wow, never heard of that. Makes total sense, but never would have thought of that. Quote Link to comment Share on other sites More sharing options...
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