I have put a new coil and ICM on the car I am getting power to the ICM but not the coil and if I jump power to the coil the car still dose not start has any one come across this problem before I am new the lt1 and have3 no one to help me out can anyone help?

 

no spark?

check the connections from the ICM to the coil. It is not uncommon for those to have worn down to the point where they don't make a good contact.

 

 

On the 92 LT! the coil gets its current from the 10 amp fuse marked coil in the fuse box, through a pink/black wire that is connected to the B terminal of the gray connector on the coil. If there is not 12 volts on this terminal (gray) B then you have a blown coil fuse or open circuit between fuse and coil. Likewise the A and D terminals in the ICM connector should have 12 volts as they get their power from the same fuse. If they all look fine check the coil to ECM connector located on the passenger side of the intake manifold.

Check terminal C in the ICM connector and terminal A in the gray connector on the coil to see that they both go to ground.
The ground for the ICM and coil are on the front of the cylinder head between the coil and water pump, taks this off and clean it too.

You should also disconnect the connection on the opti and test terminals A and B, they should have about 5 volts. Terminal D should test connected to grould.

report your findings and we can go from here.

Jerris

 

Good morning!

I've been battling the same problem over the past few years with my '92 - gone through 2 Opti's (reman - NO GOOD and a Delco - GOOD) , coil, driver, etc.

I had the Vette parked over the winter - just fired it up this weekend, drive it for the day, parked - went back out - no fire just crank.

Went back several hours later when the engine was cold and hoped it would fire but no dice - no fire (this method used to work)!

I used my FSM as a reference and did all the checks Jerris recommends,

I cleaned and checked all connections first - then I did my voltage checks and found all voltages good -

Here's the kicker:

All grounds were good EXCEPT COIL TO GROUND. The white coil wire (terminal A) goes to a solid state device taped to the wiring loom. This item is the TACH FILTER (part 12088559) - I checked the black lead coming out of it and it shows the ground is good to the block. The other white lead goes to the IP (must be tach gauge readout).

Question is:

Am I on the right track on this - seems perfectly logical, but things with this Vette seldom are lately!!

Can this item go bad - never heard of ANYONE having this item go out, but I'm assuming it must have opened (heat related probably) and dropped my coil ground - this intermmitent was NOT caught by the Goodwrench folks two years ago either!!

Eckler's has one at the following link:

http://www.ecklers.com/product.asp?d...B3HJ7JRP0V9NF9

Is this item worth the cost - gotta check GMPartsDirect - who's got the best deal these days aside from the dealership?

 

It sounds like the tach filter is burnt out. Try junping the coil straight to groung to see if that allows the engine to start.
Some people have removed the filter altogether without any adverse effects on the tach reading.
The ground for the coil is on the front of the cylinder head next to it.
On mine with a similar problen the culprit was a wire in the ICM connection that had burnt off inside the jacket that intermittantly seperated. With the car running tru wiggleing these wires to see if you can recreate the problem.
GM does not stock the tach filter so you will have to buy it aftermarket like Ecklers.

 

Thanks Jerris!

Just got off the phone with the dealer - yeah, they used that part from '92 to '94 - there is no substitute for it anywhere.

I'm assuming its some kind of capacitor, correct? I searched and found another post where someone had the circuit diagram for this thing - hate to run without SOMETHING in there - you would think they put it in there for a reason, wouldn't ya?

Thanks for the response - I'll bypass it just to see if she fires for now!

 

the tach filter is a capacitor...

there was a huge thread on JUST this problem last fall by Jet-Jock. I will try and find it...

 

Found the post by Nico on the tach filter components - I figured out the power rating below as I had not heard back from Nico yet.

http://forums.corvetteforum.com/show...ht=tach+filter

If you find the thread by Jet-Jock I'd be glad to go over it as well!

Many thanks! No wonder this forum is the best!!


Well, I did some calculations using my rusty knowledge of electronics -

Nico said we could get away with a couple 5.6K resistors and a 0.1mfd capacitor - using Ohm's Law:

E=I*R 12v=I*5600 therefore I=.002 ampere

P(watts) = I^2*R P=(.002^2)*5600 therefore P (watts) = .025W

I'm going to look for some 1/4W resistors right now!

 

I had a similar no start condition on mine before and it turned out to be a corroded connection between the opti and the main wiring harness. I can't imagine the tach filter would be a problem being that you can bypass it completely and the car runs perfectly.

 

Hello Nathan -

Thanks for the input - where exactly did you find the corrosion? I've checked every connector I can find and mine are all clean - maybe I missed one! I inspected the connector under the passenger side fuel rail as well as the connector that goes into the top of the Opti tonite.

I made up a tach filter per Nico's instructions - made no difference. I then tried to use the ground from the tach filter and jump to the ground terminal on the coil (white wire on the gray connector) - I got a good ground - still no fire.

I didn't have an extra set of hands to go further through the flow chart in the service manual, but will do so tonite. All I know is I have juice to the coil and from there juice to the ignition module, but no high output from the coil - and no codes (except for 12) from the ECM when I jump the diagnostic connector - I'll post tomorrow if I get any further!!

BTW - took the ICM and the coil off after all of the above and brought them into Advance Auto Parts (I called and they told me they could test the ICM) - got there, they say they can't test it - told me to use a VOM and check for opens on the coil; no opinion on the ICM other than that it is a non-returnable part. Offered to order me an ICM for $100 - they don't stock them (go figure!)