96 LT4 wont start suddenly...help....
Thread Starter
Pro
Joined: Feb 2002
Posts: 744
Likes: 1
From: Houston Tx
96 LT4 wont start suddenly...help....
See my sig for mods....H/C LT4 . Entire top end has about 750 miles on it including coil wire, coil, opti, wires , plugs , injectors etc....
Car has been in garage without running much for the past couple of weeks (had a new baby boy!) soo....battery was about shot. It was old anyway so decided on new battery (DieHard Gold). Put the battery in , cranked up the car and drove it about an hour (felt great, had not had time for it much in a while). Parked it and didnt have time to drive it again unfortunately for about another 6 weeks.
Come out to start it and it turns over and over but no spark. Check fuel pressure via gauge on fuel rail and have plenty of pressure(~40+ psi) Checked spark via gauge on wire, upon cranking no light and therefore no spark, sooo....
With the opti being virtually new, coil and coil wire the same ???? Car is showing NO CODES after plugging in the code reader.
I am thinking maybe the ICM or ignition control module (right by the coil) not sure if it was changed when coil was. Then trying to figure out how far electric juice is going (to coil , then opti or whether there may be a computer problem or something)
Any and all suggestions and comments welcomed ...... what is the best place to start and proceed? Thanks in advance.
Car has been in garage without running much for the past couple of weeks (had a new baby boy!) soo....battery was about shot. It was old anyway so decided on new battery (DieHard Gold). Put the battery in , cranked up the car and drove it about an hour (felt great, had not had time for it much in a while). Parked it and didnt have time to drive it again unfortunately for about another 6 weeks.
Come out to start it and it turns over and over but no spark. Check fuel pressure via gauge on fuel rail and have plenty of pressure(~40+ psi) Checked spark via gauge on wire, upon cranking no light and therefore no spark, sooo....
With the opti being virtually new, coil and coil wire the same ???? Car is showing NO CODES after plugging in the code reader.
I am thinking maybe the ICM or ignition control module (right by the coil) not sure if it was changed when coil was. Then trying to figure out how far electric juice is going (to coil , then opti or whether there may be a computer problem or something)
Any and all suggestions and comments welcomed ...... what is the best place to start and proceed? Thanks in advance.
Safety Car
Joined: Apr 2004
Posts: 4,532
Likes: 7
From: Lahaina Hi
I would crank the engine over .
Remove one spark plug and see if it is full of fuel.
Wet then go to the moduel at the coil.
When you look at the coil, see if there are carbon tracks to the left and right on the coil,coil may be grounding out on square metal bracket.
If it is a Jeg's coil throw it in the trash.
I speak from experance on that one.
You disconected the cags so that could be a problem.
You also said the battery went dead?
check the wires to the alt at the intake and see if they are grounding on intake.
Does the alarm work?
Check the ECM fuse in the pass side panel.
Do some checks and let us know.
Remove one spark plug and see if it is full of fuel.
Wet then go to the moduel at the coil.
When you look at the coil, see if there are carbon tracks to the left and right on the coil,coil may be grounding out on square metal bracket.
If it is a Jeg's coil throw it in the trash.
I speak from experance on that one.
You disconected the cags so that could be a problem.
You also said the battery went dead?
check the wires to the alt at the intake and see if they are grounding on intake.
Does the alarm work?
Check the ECM fuse in the pass side panel.
Do some checks and let us know.
Drifting
Joined: Nov 2002
Posts: 1,593
Likes: 0
From: Mobile AL
St. Jude Donor '05
Where did you check the spark? At the plug or out of the coil? If you checked at the plug, check the output of the coil. If there's nothing there, at least you probably eliminated the distributor cap/rotor as the problem. If there's no spark out of the coil, as stated previously, check the wiring harness between the distrlbutor and the coil. You really need a shop manual that will guide you through checks to make. The coil and spark plug wires need to be properly seated to function. They seat once, then push again and it will pop into place. If they were not seated properly, one or more may have popped out after your initial run.
Thread Starter
Pro
Joined: Feb 2002
Posts: 744
Likes: 1
From: Houston Tx
Thanks for the responses , especially REDC4 and Silverbeast.....
Remember the coil and its wire are new , also remember the car started and ran fine just after replacing the battery....only after parking and sitting for several weeks did it not want to start.
I only checked for spark with a cheap plug wire tester light, but it was new and worked on several other cars before I tried it on the Vette (it does have thick Taylor wires though).
I will take a look at the coil for marks, check the ECM fuse ....
The alarm seems to work just fine, why would my CAGS disable be a problem, RED?
Silver....because the car had run just fine I cant imagine any of the harness or wires just came undone but I will check. Also , I have my GM Shop manuals for the car but as of yet have not seen any specific process or order of operations to perform first with a problem like this but I will keep looking.....
Thanks again guys....I will keep trying and let ya know...
Remember the coil and its wire are new , also remember the car started and ran fine just after replacing the battery....only after parking and sitting for several weeks did it not want to start.
I only checked for spark with a cheap plug wire tester light, but it was new and worked on several other cars before I tried it on the Vette (it does have thick Taylor wires though).
I will take a look at the coil for marks, check the ECM fuse ....
The alarm seems to work just fine, why would my CAGS disable be a problem, RED?
Silver....because the car had run just fine I cant imagine any of the harness or wires just came undone but I will check. Also , I have my GM Shop manuals for the car but as of yet have not seen any specific process or order of operations to perform first with a problem like this but I will keep looking.....
Thanks again guys....I will keep trying and let ya know...
Safety Car
Joined: Apr 2004
Posts: 4,532
Likes: 7
From: Lahaina Hi
You have a 96 and it must be close to my system.The 94 I have went dead when I was gone after a month.
I thought it was dead.
Called tow truck and hulled it away.
Chevy called and said nothing wrong with the car?
To this day I have not figured out what happened to it.
I know the alarm on my car was not allowing me to start the engine. I waited about an hour then it would start did this 3 times and hasen't done it for 6 months now.
I did one thing I cut a new key about 6 mths ago .Maybe ? that fixed it.
Never thought about it until now.
I thought it was dead.
Called tow truck and hulled it away.
Chevy called and said nothing wrong with the car?
To this day I have not figured out what happened to it.
I know the alarm on my car was not allowing me to start the engine. I waited about an hour then it would start did this 3 times and hasen't done it for 6 months now.
I did one thing I cut a new key about 6 mths ago .Maybe ? that fixed it.
Never thought about it until now.
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Drifting
Joined: Aug 2004
Posts: 1,400
Likes: 0
From: Oceansaide CA
Originally Posted by REDC4CORVETTE
You have a 96 and it must be close to my system.The 94 I have went dead when I was gone after a month.
I thought it was dead.
Called tow truck and hulled it away.
Chevy called and said nothing wrong with the car?
To this day I have not figured out what happened to it.
I know the alarm on my car was not allowing me to start the engine. I waited about an hour then it would start did this 3 times and hasen't done it for 6 months now.
I did one thing I cut a new key about 6 mths ago .Maybe ? that fixed it.
Never thought about it until now.
I thought it was dead.
Called tow truck and hulled it away.
Chevy called and said nothing wrong with the car?
To this day I have not figured out what happened to it.
I know the alarm on my car was not allowing me to start the engine. I waited about an hour then it would start did this 3 times and hasen't done it for 6 months now.
I did one thing I cut a new key about 6 mths ago .Maybe ? that fixed it.
Never thought about it until now.
Melting Slicks
Joined: Jan 2002
Posts: 3,293
Likes: 79
From: Jackson MI
Here's a test that most people don't know about.
Watch your tachometer as the car is cranking over. If the needle doesn't move then It is Definately Ignigion Related.
You could have lost your opti signal. It may mean a wiring problem and not a bad opti, but then again I've had them go bad after 1.5 months when they've been mostly sitting in my garage. Pull the opti wiring harness and check the leads that are in the opti for corrosion.
You could also have a bad coil or ignition module. I've got an extra ignition module that I could over night to you for $45 + shipping (they run ~$120 new if I recall correctly,double check that). Or you can pick up a new coil from napa for $30.
Good luck with your search.
Watch your tachometer as the car is cranking over. If the needle doesn't move then It is Definately Ignigion Related.
You could have lost your opti signal. It may mean a wiring problem and not a bad opti, but then again I've had them go bad after 1.5 months when they've been mostly sitting in my garage. Pull the opti wiring harness and check the leads that are in the opti for corrosion.
You could also have a bad coil or ignition module. I've got an extra ignition module that I could over night to you for $45 + shipping (they run ~$120 new if I recall correctly,double check that). Or you can pick up a new coil from napa for $30.
Good luck with your search.
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
I've seen two cars in which the wiring pigtail to the opti corrodes mysteriously. It will cause a crank and no start condition because you never get spark. The opti itself is probably fine. It will not go from 0 to dead without moving.
Melting Slicks
Joined: Jan 2002
Posts: 3,293
Likes: 79
From: Jackson MI
Originally Posted by Shriker
Thanks guys....I will check the leads and the harness.....and mind the tach when trying to start.
MN , may need that IM down the road , will let ya know, thanks.
MN , may need that IM down the road , will let ya know, thanks.
I'm always around if you've got questions. Sometimes its nice haveing a desk job
Good luck
Le Mans Master
Joined: Apr 2000
Posts: 5,589
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From: DrunkDefender
CI 1-2-3-4-5-6-7-8 Veteran
CI-IV AutoX Champ
CI-IV Burnout Champ
St. Jude Donor '07-'10
mn_vette is correct about the tach trick. He's also good to deal with. I purchased items from him.
I use a spark tester from snap on, but you can get em at sears. They look like a spark plug with a graound clamp on them. Make sure you get the HEI version though. They're pretty inexspensive but work great to check spark.
I've had a couple of optis that had the corrosion on the wire harness that comes out the pass side top to the test connector on the intake between injectors 4/6. Its allways been water intrusion. Usually from something done, like mods, and the check-valve on the drivers side was installed backwards or the orfice in same line was blocked. Could even be a bad vac hose. Its one of those things that is very easy to overlook and very easy to slip by but it will kill an opti in a matter of weeks. Seen it several times.
The service manuals are great for this stuff. Go with no spark and backtrack from there. It could be, and likely will be something like a signal not getting where its supposed to be. I've had to chase down shorts and broken wires plenty of times and the service manuals help greatly. I've had wires broken inside the insulation before. Now thats tough to find. Keep after it.
I've got a set of 96 gm y-body service manuals if you need any help gimme a pm.
I use a spark tester from snap on, but you can get em at sears. They look like a spark plug with a graound clamp on them. Make sure you get the HEI version though. They're pretty inexspensive but work great to check spark.
I've had a couple of optis that had the corrosion on the wire harness that comes out the pass side top to the test connector on the intake between injectors 4/6. Its allways been water intrusion. Usually from something done, like mods, and the check-valve on the drivers side was installed backwards or the orfice in same line was blocked. Could even be a bad vac hose. Its one of those things that is very easy to overlook and very easy to slip by but it will kill an opti in a matter of weeks. Seen it several times.
The service manuals are great for this stuff. Go with no spark and backtrack from there. It could be, and likely will be something like a signal not getting where its supposed to be. I've had to chase down shorts and broken wires plenty of times and the service manuals help greatly. I've had wires broken inside the insulation before. Now thats tough to find. Keep after it.
I've got a set of 96 gm y-body service manuals if you need any help gimme a pm.
Thread Starter
Pro
Joined: Feb 2002
Posts: 744
Likes: 1
From: Houston Tx
Well, when I crank the car the speedo needle slightly moves down. I am getting no spark through the coil wire going to the opti so I am thinking its either the new coil or the IM next to it - is there any way to test these? I dont think they are too expensive so I might just replace both. Should I go with GM parts?
mn_vette , I may need that module you spoke of earlier.....I will pm you if so. Thanks
mn_vette , I may need that module you spoke of earlier.....I will pm you if so. Thanks
Safety Car
Joined: Apr 2004
Posts: 4,532
Likes: 7
From: Lahaina Hi
Use a GM module I tried NAPA,luckey mine was still ok .
I was just replacing parts ,Ihave 90, and the moduel from NAPA threw a check engine light .
They said Echlin is now made in china.Put old on back in.
I was just replacing parts ,Ihave 90, and the moduel from NAPA threw a check engine light .
They said Echlin is now made in china.Put old on back in.
Thread Starter
Pro
Joined: Feb 2002
Posts: 744
Likes: 1
From: Houston Tx
El Crapito.....the ignition module did not solve the problem. I am going to try a new coil tommorrow. It has a new one but I dont know what kind was put in it when the work was done a year ago (but only ~700 miles- have not been able to drive it much ).
Will keep y'all posted......
).Will keep y'all posted......
