Trouble shooting help
Pro
Joined: Nov 2009
Posts: 583
Likes: 0
From: Maple Grove Minnesota
I also had spark until the pick up coil went out completely. When I did have spark I couldn’t even drive it you put the gas to it and it bogs and it died on several occasions at will. Just something to eliminate if it checks out good.
Melting Slicks
Joined: Nov 2008
Posts: 2,765
Likes: 5
The pickup coil was defective also like you stated in your car.
Would run for a while and then die out without notice. Loose Ignition spark entirely.
Upon troubleshooting, one of the pickup coil leads became unattached at the coil. Right at the Soldered Joint connection.
When enough heat and vibration from the running engine, the pickup lead connection would seperate.
$28.00 for a NOS GM pickup coil and an hours worth of time with the HEI removed from the car, I had the problem fixed permante.
Never lost ignition spark again in that 403 car.
The owner of the 1989 Corvette may have the same issue also.
Not saying that isnt possible.
But none of us are there in person troubleshooting with him on his 89 Vette.
Only he is. Have to wait to hear back from him and see what he found out is the problem 1st hand himself.
We can only give troubleshooting pointers and tips for now.
Only 100 % Positive of the fix when he gets back to us.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
You can Impedance Test(resistance check) each fuel injector before your Corvette dies out again too.
Dont have to wait for it die out.
Usually when the GM Multec (1989-1996) fuel injectors are defective, the Impedance reading of each wont be different if they are cold or hot after running in the engine.
Good luck troubleshooting.
Let us know what you find wrong.
BR
Dont have to wait for it die out.
Usually when the GM Multec (1989-1996) fuel injectors are defective, the Impedance reading of each wont be different if they are cold or hot after running in the engine.
Good luck troubleshooting.
Let us know what you find wrong.
BR
A reasonable test for the spark system is to bring a grounded wire close to an unplugged spark plug boot while someone cranks the engine for a few revs. The spark should be snappy and at least 1/2 inch long. Weak spark can prevent an engine from starting.
Last edited by jfb; Jan 1, 2011 at 05:13 PM.
Melting Slicks
Joined: Nov 2008
Posts: 2,765
Likes: 5
Impedance is NOT the same thing as resistance! An ohmeter cannot detect a turn to turn short in a coil, but an impedance bridge which measures coil inductance and coil Q can easily find a turn to turn short. A turn to turn short will prevent all the injectors from working properly on that bank of cylinders. I found a defective injector coil on my 87 one time with an impedance bridge, the injector coil had half the inductance and half the Q as the other injectors, but my ohmeter showed the same resistance as all the other injectors.
A reasonable test for the spark system is to bring a grounded wire close to an unplugged spark plug boot while someone cranks the engine for a few revs. The spark should be snappy and at least 1/2 inch long. Weak spark can prevent an engine from starting.
A reasonable test for the spark system is to bring a grounded wire close to an unplugged spark plug boot while someone cranks the engine for a few revs. The spark should be snappy and at least 1/2 inch long. Weak spark can prevent an engine from starting.
Not many people a have impedance bridge to check a copper wound coils inductance with.
Surely not most Corvette owners at home.
Q factor.
Mutual inductance.
I do remember each from college electronics tech classes 20 years ago.
Melting Slicks
Joined: Nov 2008
Posts: 2,765
Likes: 5
Impedance is NOT the same thing as resistance! An ohmeter cannot detect a turn to turn short in a coil, but an impedance bridge which measures coil inductance and coil Q can easily find a turn to turn short. A turn to turn short will prevent all the injectors from working properly on that bank of cylinders. I found a defective injector coil on my 87 one time with an impedance bridge, the injector coil had half the inductance and half the Q as the other injectors, but my ohmeter showed the same resistance as all the other injectors.
A reasonable test for the spark system is to bring a grounded wire close to an unplugged spark plug boot while someone cranks the engine for a few revs. The spark should be snappy and at least 1/2 inch long. Weak spark can prevent an engine from starting.
A reasonable test for the spark system is to bring a grounded wire close to an unplugged spark plug boot while someone cranks the engine for a few revs. The spark should be snappy and at least 1/2 inch long. Weak spark can prevent an engine from starting.
Do recall that too.
Melting Slicks
Joined: Aug 2008
Posts: 2,082
Likes: 50
From: Palmdale CA
Another test you might consider is the (throttle position sensor) this could have a dead spot, or eratic feed back voltage, this a primary sensor that the ECM relies on in order to adjust the fuel schedule properly.
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Thread Starter
Racer
Joined: Jan 2010
Posts: 347
Likes: 12
From: Deltona FL
PROBLEM SOLVED........
I did a OHM check on the injectors and 1 is bad, disconnected it and car fired right up and back to normal... So a call to JON @ fic is in order...
Thanks for all the help guys!!!!!
I did a OHM check on the injectors and 1 is bad, disconnected it and car fired right up and back to normal... So a call to JON @ fic is in order...
Thanks for all the help guys!!!!!
Intermediate
Joined: Mar 2009
Posts: 29
Likes: 0
I'm having a similar problem with my 91. I've done the fuel pressure test. 38 to 42 psi not matter how the motor is running. I check the injectors awhile back when I was having problems with my ACI and they were all fine. It will start and idle alittle rough. You can goose the throttle and it rev's up, roughly but it does. The longer the motor runs the idle gets rougher and it will bog down when you try to rev the motor. Will an injector get worse with heat or as some out here have suggested am I dealing with a cat?
Thread Starter
Racer
Joined: Jan 2010
Posts: 347
Likes: 12
From: Deltona FL
I'm having a similar problem with my 91. I've done the fuel pressure test. 38 to 42 psi not matter how the motor is running. I check the injectors awhile back when I was having problems with my ACI and they were all fine. It will start and idle alittle rough. You can goose the throttle and it rev's up, roughly but it does. The longer the motor runs the idle gets rougher and it will bog down when you try to rev the motor. Will an injector get worse with heat or as some out here have suggested am I dealing with a cat?
