Riddle For The LT1 Guys
Thread Starter
On The Tree
Joined: Mar 2002
Posts: 171
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From: Northern Kentucky
Riddle For The LT1 Guys My 94 Z wont start. I can crank all day and it wont fire. It sounds like the timing is WAY retarded. It sounds like it's trying to fire but it just wont start. I'm looking for suggestions. This originally started as an intermittent no-start issue when it rained. The car wouldn't start, but after it dried out a couple days it would start. When it ran, it ran great. Now it wont start at all. This is killing me cause this car has been dead reliable for the first 103,000 miles.
Here's what I know:
I have fuel. It maintains 42-44 lbs of fuel pressure during cranking and the injectors are firing (I pulled the rails and watched).
I have spark. The spark is very strong at all the plugs.
I have air. No obstructions of air flow.
I have plenty of compression.
What's new:
Optispark
ICM
Spark plugs
Spark plug wires
Ignition relay
Head gaskets
Heads just milled
Intake gaskets
What's tested good:
Opti (reference voltages tested good)
Opti pigtail connector
Coil
Coolant temp sensors (both)
PCM (swapped with another good PCM)
Does anyone have any ideas? It has everything necessary to run but wont. Why would timing be so far retarded?
Here's what I know:
I have fuel. It maintains 42-44 lbs of fuel pressure during cranking and the injectors are firing (I pulled the rails and watched).
I have spark. The spark is very strong at all the plugs.
I have air. No obstructions of air flow.
I have plenty of compression.
What's new:
Optispark
ICM
Spark plugs
Spark plug wires
Ignition relay
Head gaskets
Heads just milled
Intake gaskets
What's tested good:
Opti (reference voltages tested good)
Opti pigtail connector
Coil
Coolant temp sensors (both)
PCM (swapped with another good PCM)
Does anyone have any ideas? It has everything necessary to run but wont. Why would timing be so far retarded?
Last edited by SOM WS9; Apr 30, 2008 at 11:45 PM.
Thread Starter
On The Tree
Joined: Mar 2002
Posts: 171
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From: Northern Kentucky
It cranks great. It occasionally sputters, and it continues to sputter a little AFTER I stop cranking it. I can't figure it out. I have air, fuel, compression, and spark....WTF?
I had the timing cover off and it was lined up perfect, dot to dot. There was no abnormal slack in the chain either.
No SES light either.
I had the timing cover off and it was lined up perfect, dot to dot. There was no abnormal slack in the chain either.
No SES light either.
how did you seat the opti to the block it sounds like the cam dowel is not in the hole of the opti but rather one of those cloves. Mine did the same thing you are describing when i made that mistake. I could have sworn i put it in right also. The best way to check is to remove the opti cap and try to spin the rotor by hand. If it has free play its not seated right if it does not then it is. If it is not in the right hole it will fire but timing will be way off and all over the place because that rotor has so much play in it.
Thread Starter
On The Tree
Joined: Mar 2002
Posts: 171
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From: Northern Kentucky
Opti is a spline drive, it's installed correctly. I checked it twice tonight just to be sure. I've done way more optis than even I care to remember, but after this even I had to double check myself. There wasn't a single mark on the index spline either, so it wasn't installed wrong at any point.
Courtesy of the man himself, shoebox:
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Thread Starter
On The Tree
Joined: Mar 2002
Posts: 171
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From: Northern Kentucky
Already checked it several times man. I've seen a few that were installed wrong and all of them had the same mark on the "key" where it had been forced into the splines. Mine is still 100% clean. I even checked to see if the splined drive shaft for the opti was twisted, and it's fine. This is why I'm completely lost here...
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Verdad Gallardo Already checked it several times man. I've seen a few that were installed wrong and all of them had the same mark on the "key" where it had been forced into the splines. Mine is still 100% clean. I even checked to see if the splined drive shaft for the opti was twisted, and it's fine. This is why I'm completely lost here...
It's a splined shaft on the the '94 cars, but still doesn't take away from your theory since it has been documented of people not aligning the splined shaft correctly. This appears to be about the only thing left that could be the reason for the no start.
Courtesy of the man himself, shoebox:
Courtesy of the man himself, shoebox:
Thread Starter
On The Tree
Joined: Mar 2002
Posts: 171
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From: Northern Kentucky
Valves are adjusted properly, been there twice now too second guessing myself. It started before I even had the heads off. It was orginally an intermittent problem with it not starting when rained. This makes me think it's electrical. When it runs it runs great, but getting it running was the problem. Now it wont start at all. I'll edit the original post to make that clear.
Thread Starter
On The Tree
Joined: Mar 2002
Posts: 171
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From: Northern Kentucky
The 95-up vented optis aren't a spline drive. They have the ol' wonder wheel. They're easier to install wrong than the spline drive optis if you don't know what you're doing.
Thread Starter
On The Tree
Joined: Mar 2002
Posts: 171
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From: Northern Kentucky
hmmm.. I wonder why they are easier to install wrong? As long as you get the cam pin in the right slot.. the slot thats not rounded off but more rectangular. Thats the only way it goes in if I'm thinking correctly.... sorry I hijacked your thread but I know what your going through and I'm trying to find answers too lol
I wish that was my problem, I would have solved it by now.
Anyone else have some input?
Well TPS sensor's will allow fuel pressure an spark, but wont let the injector pulse so if it's pulsing its probably not that. Try disconnecting it though for ***** and giggles since that takes all of 10 seconds, try disconnecting the MAF sensor too. Aside from that, PCM maybe? Something isn't adding up, the motor will fire if it is getting fuel in the cylinders, it might run like **** but after fuel builds up spark will ignite and noise shall happen, haha. Just double check the injectors pulsing.
Just because the opti is new dont rely on it, I installed a brand new one from the GM dealership, did exactly what you are describing, I even pulled the plugs, put my finger over the hole, cranked it over and checked for spark on the compression stroke on several cylinders, looked to be firing exactly at the time it was suppose to, Got stumped, replaced the opti,..............Cranked right up..