no start when hot
Thread Starter
Heel & Toe
Joined: Jan 2007
Posts: 21
Likes: 0
From: Hatboro Pa.
no start when hot
have 89 coupe. does not start after warmed up. wait 10 minutes and then will start. car will begin to miss and get worse to point of almost stalling and will surge at idle. all this begins as soon as closed loop begins at approx 138 degrees. have replaced est, o2 sensor, ign module,coil,cap,plugs,both maf relays, Have also cleaned maf, replaced air check valves. The injectors I thought ohmed out a bit strange. The 4 front cylinders were 8ohms and the 4 back cyl were 16. I thought this was strange but ??. I had this checked out at local garage and they could not find anything wrong with it. They had the car for the past week. I was told they had 2 different corvette mechanics look at the car and everyone is still scratching their heads in complete confusion. I was going to replace the injectors but the problem begins after going to closed loop so it appears to be a sensor/switching problem somewhere. Any help is appreciated. I'm lost and the specialists are too evidently. anyone has any ideas I'm open for information. When it won't start if I spray carb cleaner in the throttle body it fires right up so I think it is a fuel problem??
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Sounds like a injector problem. Since they ohmed different, it is something I would look into. Ohm them again cold, then hot. See if there is a difference since heat will change the resistance values. Also attach a fuel pressure gauge and check the fuel pressure at key on, start up, hot idle, and then key off. I think you will find that the injectors need to be serviced or replaced. If they are the stock injectors then they will need to be replaced.
Is the SES light on?
Is the SES light on?
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Measure the fuel pressure at the shrader valve on the end of the fuel rail. When the engine is warm and doesn't want to start, turn on the ign for longer than 2 seconds to charge the fuel rail and turn the ignition off and watch how long the pressure holds up. If it falls rapidly, you may have leaky injectors when they get warm. What does your exhaust smell like? raw gasoline? if so, you have leaky injectors causing too rich condition to start.
Melting Slicks
Joined: Apr 2002
Posts: 2,118
Likes: 0
From: St. Charles, MO Route 66 Corvette Club
The injectors in years 89 thru 91 have a tendacity to have "shorted turns" of wire in the coils of the injectors. This is due to the fact that gasoline flows around and actually comes in contact with the injector coils to keep them cool. The coating (insulation) on the coil wire breaks down (over time) and some turns of wire "short out" to each other and the resistance of the coil is reduced. As the resistance is reduced, the injector will not deliver the needed fuel to the car cylinders. This causes the engine to run like crap.
Here is a GM service bulletin where they warn you not to use fuel injector cleaner as this accelerates the degrading of the insulation on the injector coil wires:
The resistance spec for the GM Multec injectors is 16.5 +/-.3 ohms when hot or cold. The injectors tend to have more problems when warm.
You will have to remove the stock injectors and replace them. Good luck finding a reasonable priced replacement injectors. Do not replace with GM replacments due to price and to possibility of having the same problem again.
Send me a PM or email if you want more info on this.
Here is a GM service bulletin where they warn you not to use fuel injector cleaner as this accelerates the degrading of the insulation on the injector coil wires:
The resistance spec for the GM Multec injectors is 16.5 +/-.3 ohms when hot or cold. The injectors tend to have more problems when warm.
You will have to remove the stock injectors and replace them. Good luck finding a reasonable priced replacement injectors. Do not replace with GM replacments due to price and to possibility of having the same problem again.
Send me a PM or email if you want more info on this.
Last edited by Sam Lam; Apr 24, 2007 at 11:58 PM.
