1989 Pontiac Firebird Car won't start when at running tempe

Tiny
JOEMARSH
  • MEMBER
  • 1989 PONTIAC FIREBIRD
Electrical problem
1989 Pontiac Firebird V8 Two Wheel Drive Automatic

The car starts and runs great when it is cold. Once it warms up to operating temperature it will not start. There are no error codes posted. The problem appears to be that the injectors are turned off. There is fuel rail presure and good spark. We have eliminated the TDM by replacing it with an alternate class 2 signal source. We can get the car to start when using starting fluid but it runs poorly like it is in a limp home mode. Are there any other temperature sensitive sensors that would shut off the injectors?
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Tuesday, May 18th, 2010 AT 3:14 PM

12 Replies

Tiny
LEGITIMATE007
  • EXPERT
Your problem should be the engine coolant temp sensor(ect).
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Tuesday, May 18th, 2010 AT 4:27 PM
Tiny
LEGITIMATE007
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Does the vehicle shut off by itself?
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Tuesday, May 18th, 2010 AT 4:28 PM
Tiny
JOEMARSH
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No the car runs okay until you shut it off. Then you can't start it with out starting fluid. Once you get it started with starting fluid it runs really poor. If you let it cool completely down then it will start and run good.
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Tuesday, May 18th, 2010 AT 4:45 PM
Tiny
LEGITIMATE007
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Ok, I would check/change engine coolant temperature sensor, then the crank sensor. You should be all set. Anything else, just reply when you need to
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Tuesday, May 18th, 2010 AT 4:49 PM
Tiny
JOEMARSH
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Does the temp guage and engine coolant sensor use the same sensor? The temp guage works fine.
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Wednesday, May 19th, 2010 AT 5:30 PM
Tiny
LEGITIMATE007
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It works ok once you get it started and run it. But once you shut it off, after being hot, it causes an open circuit or a false signal to the ecm. Causing the no start until it cools off again and creates a closed circuit, same thing with the crank sensor. This is why I say it has to be one of the two or even both.
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-1
Wednesday, May 19th, 2010 AT 8:19 PM
Tiny
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Well I have some up dates. There seems to be 2 coolant temp sensors. One in the front of the engine and one on the right cyclinder head. The one in the front measured 3500 ohms cold and when we brought the car to operating temp it measured 345 ohms. This seems to be okay. The sensor on the cyclinder head cold measured 1 megohms and at temp measured 4 megohms. This seemed high to us so we replaced it with a 7000 ohm resistor to see if it would start. No go still no fuel. It will start with starting fluid and run poorly. We also checked the oxygen sensor cold.2v hot.7v seems okay. Also checked the Mass air flow
by applying power and blowing across it. Signal
went from.05V to.072V so we could see a change.
The IAT power open circuit measured 5V and in circuit went to.9V. We have already changed the computer.
We are out of ideas ! !
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Wednesday, May 19th, 2010 AT 10:49 PM
Tiny
LEGITIMATE007
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Have you checked the cam sensor?
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Friday, May 21st, 2010 AT 12:36 PM
Tiny
JOEMARSH
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Do you know where the Cam sensor is located? I don't think the 5.0L 89 Firebird has a crank sensor. There isn't one in the front of the engine. Where else would it be?

Thanks, We will keep fighting it.
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Friday, May 21st, 2010 AT 11:10 PM
Tiny
LEGITIMATE007
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Check by the crank pulley. If this car has a distributor it may be on or attached to it
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Saturday, May 22nd, 2010 AT 8:02 AM
Tiny
JOEMARSH
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Well we finally got this fixed. We replaced the temp coolant sensor with a 3500 ohm resistor making the computer stay in open loop mode and we still had the problem. So we started to look for things that fail at temp that the computer doesn't have diagnostics for. It turned out to be the fuel injectors themselves. This is a known problem with Rochester Multec fuel injectors in GM cars in the late 80's and early 90's. At temp the coil
impedence on some injectors would get as low as 1.5 ohms. Should be around 12 ohms and no less than 10 ohms. Tough problem since cold the injector impedence measured okay and most injector impedences fail by increased impedence. I hope this is helpful to someone else. We put a new set of injectors in and the car runs fine.
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Monday, May 31st, 2010 AT 8:37 PM
Tiny
LEGITIMATE007
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Awesome, wow, I will put this in my archives. Thanx
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Tuesday, June 1st, 2010 AT 8:25 AM

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