LT 4 won't start
Thread Starter
Cruising
Joined: May 2011
Posts: 13
Likes: 0
From: PA
LT 4 won't start
I had an issue with my 96 LT-4 today, was running on track for a couple laps, then the engine just seemed to die out, seemed like no fuel at first like when a fuel pump fails, pulled off track and car started right up,,, then went out again and car died, will not start at all now, fuel pump turns on with key and there is fuel pressure at the motor, cranks over good,,, any ideas... optispark, crankshaft sensor??? I read a little in the manual bad fuel injectors could cause a no start condition, car has 120K on it,,, where to start?
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
When it won't start, see if you have spark. See if you have spark from the spark coil. Use a noid light (available at parts store) and see if you have pulses at the injectors. Measure fuel pressure, it should be 35-42 psi and it should hold up for at least 1/2 hr after the ign is turned off.
Le Mans Master
Joined: Dec 2006
Posts: 5,139
Likes: 482
From: H-Town Texas
Fuel and spark are the best places to start your search. I know mine has cut out under wot acceleration when the fuel level was low. That reading can be tricky when you get down to three bars.
Another important thing to look at is oil pressure, If you get below 4# the switch will cut off fuel, I believe.
Have you tried starting it cold? What happened? I have heard of the coil and ICM going out when hot, being located on the front of the passenger side head.
Good luck, I hope it's nothing serious.
Another important thing to look at is oil pressure, If you get below 4# the switch will cut off fuel, I believe.
Have you tried starting it cold? What happened? I have heard of the coil and ICM going out when hot, being located on the front of the passenger side head.
Good luck, I hope it's nothing serious.
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,008
From: Texas
Lots of good advice. Some things to check that will cause a hard or no restart when hot...
- Fuel Pressure Regulator. Pull the vacuum line off and check for fuel. If fuel is present the regulator is bad
- Does it restart when cold and then die when it gets hot? If so, this tends to point towards the ICM.
- Does it pop and try to fire when cranking? This is often a sign that the rotor has come loose inside the opti, essentially throwing the ignition system out of time. I had this happen on mine....at over 100mph, full throttle, exiting a banked corner, in traffic. Really bad time to have the engine die
If I was going to bet, I'd lean towards the ICM or the Opti.
- Fuel Pressure Regulator. Pull the vacuum line off and check for fuel. If fuel is present the regulator is bad
- Does it restart when cold and then die when it gets hot? If so, this tends to point towards the ICM.
- Does it pop and try to fire when cranking? This is often a sign that the rotor has come loose inside the opti, essentially throwing the ignition system out of time. I had this happen on mine....at over 100mph, full throttle, exiting a banked corner, in traffic. Really bad time to have the engine die
If I was going to bet, I'd lean towards the ICM or the Opti.
Thread Starter
Cruising
Joined: May 2011
Posts: 13
Likes: 0
From: PA
thanks to all so far..... we pulled the vacuum line off the fuel pressure regulator and it was dry,,, the car still does not start at all,,, it cranks real fast i guess due to no fuel and spark whether it is due to the pcm telling it to or not,,, pulled the coil wire off the optispark and got no spark, pulled the wire off the coil and got no spark, pulled the factory electrical plugs off the ignition control module - it seems the green wire has power with key on, black with yellow/tan stripe is ground, red wire has power with key on, the yellow wire has nothing,,, is this right? also checked the coil plug - red has power with key on and green wire has nothing,,, is this right? I would assume one wire in each plug should have power when key is turned to start position but we did not see this,,,, I will check the actual fuel pressure tomorrow when I can borrow a friends guage and I'll post the result,,,
Thread Starter
Cruising
Joined: May 2011
Posts: 13
Likes: 0
From: PA
updated
fuel pressure is 47psi, checked terminal c of factory plug to optispark and it has power, checked terminal d and it has continuity,,,, does anyone know if the coil feeds power to the optispark or does the optispark feed power to the coil???
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Next to the spark coil is the spark module which receives a pulse from the optispark and the spark module pulses the spark coil to make a spark. You either have a defective spark coil, spark module, or no pulse from the optispark. I believe some auto parts stores can test your spark module. You need to confirm that your coil, spark module is good and that you are getting pulses from the optispark.
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Thread Starter
Cruising
Joined: May 2011
Posts: 13
Likes: 0
From: PA
we tested the ignition control module, terminals a and d have 11.56V which I consider 12V as the car was not running, we put the battery on trickle charge for now,,, terminal C is ground, and the white wire terminal B has 1 to 4 V dc while cranking.... so I guess it means its working and maybe not getting spark signal from pcm, coil has 12V on power side with key on,,, checking the coil it had about 2200 ohms... is this okay??? I know they said the range should be 5000 to 7000.
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,008
From: Texas
we tested the ignition control module, terminals a and d have 11.56V which I consider 12V as the car was not running, we put the battery on trickle charge for now,,, terminal C is ground, and the white wire terminal B has 1 to 4 V dc while cranking.... so I guess it means its working and maybe not getting spark signal from pcm, coil has 12V on power side with key on,,, checking the coil it had about 2200 ohms... is this okay??? I know they said the range should be 5000 to 7000.
Pull the coil wire off the opti (leave the other end attached to the coil). Ground the loose end, crank the engine and look for a spark. That will tell you if the coil and ICM are working. If there's no spark, at least you know the issue if upstream of the Opti. If there is a spark, the Opti is the likely culprit.
It's pretty unusual for the PCM to fail.
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,008
From: Texas
I'll also mention that several of us that run track days have had the rotor come loose inside the Opti. It'll sometimes exhibit the exact symptoms you've described while other times, once it's dead, it's dead.
Racer
Joined: Apr 2005
Posts: 408
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we tested the ignition control module, terminals a and d have 11.56V which I consider 12V as the car was not running, we put the battery on trickle charge for now,,, terminal C is ground, and the white wire terminal B has 1 to 4 V dc while cranking.... so I guess it means its working and maybe not getting spark signal from pcm, coil has 12V on power side with key on,,, checking the coil it had about 2200 ohms... is this okay??? I know they said the range should be 5000 to 7000.
Put a spare plug wire on the coil, as it can be a pain to get it on and off the opti, and run it to ground to see if the coil is firing.
Racer
Joined: Apr 2005
Posts: 408
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You need to actually pull the ICM off and have it checked under load vs a simple voltage check.
Pull the coil wire off the opti (leave the other end attached to the coil). Ground the loose end, crank the engine and look for a spark. That will tell you if the coil and ICM are working. If there's no spark, at least you know the issue if upstream of the Opti. If there is a spark, the Opti is the likely culprit.
It's pretty unusual for the PCM to fail.
Pull the coil wire off the opti (leave the other end attached to the coil). Ground the loose end, crank the engine and look for a spark. That will tell you if the coil and ICM are working. If there's no spark, at least you know the issue if upstream of the Opti. If there is a spark, the Opti is the likely culprit.
It's pretty unusual for the PCM to fail.
