Hard Starting 91 Ciera
eiknl
03-08-2004, 06:09 PM
Wanted to share my adventure so maybe someone else won't have to go through what I did diagnosing a hard start problem.
1991 3.3 mpi Olds Ciera started not starting a couple of months of go after it sat for 15 minutes to an hour after being brought up to operating temperature. No scan codes were being set. When it didn't start seemed to smell a little like excess gas but was getting spark ok. Funny thing is that it would start and run for about 2 seconds and then die. It normally would start after it cooled down which usually wasn't problem if you waited long enough in the winter weather. First part I replaced was the ignition module. Two weeks later it died and wouldn't start on a warm day when I went into a store for a few minutes. Now it wouldn't keep running at all. Replaced the crank position sensor. Started right up after sensor was replaced but I hadn't put accessory belt on yet. Soon as I put belt on and tried to start it now would fire but wouldn't stay running. Pulled wire to alternator and engine started up and I let car warm up. After running 5 minutes plugged alternator back in and car ran okay. Two weeks later car again would not start when warm. Ended up replacing computer, seemed to be better for a while but would occasionally not start when warm. Always started fine on cold mornings. After while problem is getting much worse. It seemed that after it had a problem starting when warm it seemed to remember that it had a problem and didn't want to start very good, even when cold. It would fire up run 2 seconds and die. If you could get the engine started and rev'd up then often everything would be fine for awhile. I checked out book from library that has detailed info on troubleshooting fuel and ignition for this car. I started suspecting fuel injectors and last week when driving down the road it just died. Finally I got a dead condition with no fire. Since suspecting injector problem I was carrying tools and ohm meter and measured the injectors and one injector was reading 1 ohm. Good injectors measure about 12 ohm. Disconnected the bad injector clip and car started up though only now on 5 cylinders but enough to get me home. It seems the injector when warm would short and mess up the pulse to other 2 injectors that were connected in parallel with it. MPI injection is wired such that 3 of the six injectors get pulsed at the same time on every other engine revolution. At cold temp the injector measures okay resistance but at warm temp the injector seemed to short(low resistance). I suspect that when warm injector resistance was too low and injector often would stay in that condition until temperature changed from either running and getting hot or cold temps.
I guess why alternator disconnected sometimes allowed it to start is if low voltage is sensed the computer modifies(lengthens?) the fuel pulse and spark which may explain why alternator disconnected seemed to affect the starting. Anyway injector is now replaced and starts and runs great.
1991 3.3 mpi Olds Ciera started not starting a couple of months of go after it sat for 15 minutes to an hour after being brought up to operating temperature. No scan codes were being set. When it didn't start seemed to smell a little like excess gas but was getting spark ok. Funny thing is that it would start and run for about 2 seconds and then die. It normally would start after it cooled down which usually wasn't problem if you waited long enough in the winter weather. First part I replaced was the ignition module. Two weeks later it died and wouldn't start on a warm day when I went into a store for a few minutes. Now it wouldn't keep running at all. Replaced the crank position sensor. Started right up after sensor was replaced but I hadn't put accessory belt on yet. Soon as I put belt on and tried to start it now would fire but wouldn't stay running. Pulled wire to alternator and engine started up and I let car warm up. After running 5 minutes plugged alternator back in and car ran okay. Two weeks later car again would not start when warm. Ended up replacing computer, seemed to be better for a while but would occasionally not start when warm. Always started fine on cold mornings. After while problem is getting much worse. It seemed that after it had a problem starting when warm it seemed to remember that it had a problem and didn't want to start very good, even when cold. It would fire up run 2 seconds and die. If you could get the engine started and rev'd up then often everything would be fine for awhile. I checked out book from library that has detailed info on troubleshooting fuel and ignition for this car. I started suspecting fuel injectors and last week when driving down the road it just died. Finally I got a dead condition with no fire. Since suspecting injector problem I was carrying tools and ohm meter and measured the injectors and one injector was reading 1 ohm. Good injectors measure about 12 ohm. Disconnected the bad injector clip and car started up though only now on 5 cylinders but enough to get me home. It seems the injector when warm would short and mess up the pulse to other 2 injectors that were connected in parallel with it. MPI injection is wired such that 3 of the six injectors get pulsed at the same time on every other engine revolution. At cold temp the injector measures okay resistance but at warm temp the injector seemed to short(low resistance). I suspect that when warm injector resistance was too low and injector often would stay in that condition until temperature changed from either running and getting hot or cold temps.
I guess why alternator disconnected sometimes allowed it to start is if low voltage is sensed the computer modifies(lengthens?) the fuel pulse and spark which may explain why alternator disconnected seemed to affect the starting. Anyway injector is now replaced and starts and runs great.
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