C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

1994 C4 Optispark question

Thread Tools
 
Search this Thread
 
Old Jun 18, 2009 | 06:12 PM
  #21  
aminnich's Avatar
aminnich
Le Mans Master
 
Joined: Jan 2006
Posts: 6,564
Likes: 6
From: Woodstock Georgia
Default

Let's back up a little. What was the initial problem that had you check codes and the electrical components? Did you read codes while it was still running? Are you getting codes now? What brand opti did you put on? Is it trying to start at all? Any smoke or gas smell? Spark at the plugs?
Reply
Old Jun 18, 2009 | 09:23 PM
  #22  
MikeC4's Avatar
MikeC4
Melting Slicks
 
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
Default

Originally Posted by donkeydawn11
alright I used my truck to jump the car still no start I check for the voltage again i got the following 12 volts at A and D ICM at connector while disconnected This time I put the meter on AC and measured the B connector on the ICM unconnected nothing I switched to voltage and still read nothing

that was B connector to ground
It looks like your voltage to primary side of coil is fine. However, I am not sure what you are trying to say here:
"measured the B connector on the ICM unconnected nothing I switched to voltage and still read nothing"

Anyway.....
I think you are saying that the ICM connector was off, you put the meter on VAC, then put the red probe on connector B and the black probe on Ground. You do need to have someone turn over the engine while you are watching the meter. You also need to make sure that the VAC range on your meter is greater than 5V. This is not a static measurement like the coil voltage at term. A and D(only need ignition set to on position for the coil Voltage measurement.)

I would also suggest trying the following:
1) disconnect the negative Battery terminal.
2) Disconnect and re-connect the 4 large connectors on your ECM

The above is very easy to do, and this is good practice when you think you may have a open or resistive connection between the male and female pins.


Last edited by MikeC4; Jun 18, 2009 at 09:25 PM.
Reply
Old Jun 18, 2009 | 09:42 PM
  #23  
lt1396corvette's Avatar
lt1396corvette
Racer
 
Joined: Aug 2008
Posts: 457
Likes: 2
Default

Check in the car on the passenger side fuse panel and see it the crank fuse is blown,or any other fuse that might prevent it from turning over.as a matter of fact go through all the fuses there to make sure there good only takes a few minutes.
Reply
Old Jun 18, 2009 | 11:03 PM
  #24  
pcolt94's Avatar
pcolt94
Le Mans Master
15 Year Member
 
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
Default

Originally Posted by lt1396corvette
Check in the car on the passenger side fuse panel and see it the crank fuse is blown,or any other fuse that might prevent it from turning over.as a matter of fact go through all the fuses there to make sure there good only takes a few minutes.
One of the things that is working is that it does turn over. There is no spark and we are trying to figure out why. We are not sure if there is (AC) drive from the PCM to the ICM to pin B. The coil has 12 volts on it as normal and the opti has been changed. There may be a poor connection or a bad PCM. This is the current status.

***NOTE***

MikeC4 has a MAJOR point here. We including me assumed the engine was turning over when you measured pin “B” for the AC voltage measurement. As Mike said,

You do need to have someone turn over the engine while you are watching the meter.


With out doing this you will measure no voltage as it will be the correct reading for that situation. But we need to know what the AC voltage is when the engine is cranking.

Last edited by pcolt94; Jun 19, 2009 at 08:42 AM.
Reply
Old Jun 19, 2009 | 12:25 PM
  #25  
donkeydawn11's Avatar
donkeydawn11
Thread Starter
Instructor
 
Joined: Sep 2004
Posts: 166
Likes: 1
Default replaced opti still no start

Yes I did have someone cranking the car over as I performed the voltage checks

i didnt try disconnecting the battery and pcm i will take another look at the car on Saturday and give you all more results thanks for taking the time on this I will post up some photo of the voltage readings on Saturday or Sunday just so I dont leave anything out

Thannnks again all

Last edited by donkeydawn11; Jun 19, 2009 at 12:33 PM.
Reply
Old Jul 11, 2009 | 10:34 AM
  #26  
donkeydawn11's Avatar
donkeydawn11
Thread Starter
Instructor
 
Joined: Sep 2004
Posts: 166
Likes: 1
Default Found Problem

Ok Im back hope all is well let me update up

i purchased an opti from Advanced and took it along with my old rotor and cap to Dealer and had a Mechanic put it on because I didnt know how far to tighten the screws. I put it back on the car and it still wouldnt start. I took more voltage readings and found no readings from opti unit so I took it off and opened it up and found the rotor broken in small peices. Dont know it it was because the mech tightened the screw to much ?

I went on JEGS and ordered a completly new for $295 I put it in the car still wouldnt start I was living it.

I then by accident touched the b wire on the connector at eht opti and heard the fuel pump turn on. at this point I still didnt have spark at the coil. I then checked I think the b wire it was white going into the ICM while plugged in I took my Bulb tester and put it in the rear of the wire and the car started. I was in haven. even though it cut rught off. In which I believe it was because of the b wire bad connection on the opti. Im going to order new connectors hoping that this will be the end of a long problem

I would like to thank you for your guidence along with the others on this site. You all made this possible giveg me the knowledge to keep trying

Thank you again I will let you know when Im finnally dirving. Ecuse me for any misspelled words in this post but I dont have on my glasses.

A word to all with this type problem as i was taking voltage readings mostly all of them were ok I only found this problem by wiggling a wire at the connector.
Reply




All times are GMT -4. The time now is 05:08 AM.

story-0
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter

Slideshow: From C1 to C8 we compare every Corvette generation by the numbers.

By Joe Kucinski | 2026-05-12 16:54:12


VIEW MORE
story-1
8 Coolest Corvette Pace Cars (and Replicas) of All Time

Slideshow: Some Corvette pace cars became collectible legends, while others perfectly captured the look and attitude of their era.

By Verdad Gallardo | 2026-05-11 09:50:51


VIEW MORE
story-2
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)

Slideshow: Ranking the top 10 Corvette engines by torque output.

By Joe Kucinski | 2026-05-05 11:58:09


VIEW MORE
story-3
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!

Slideshow: A Corvette pace car nearly matching IndyCar speeds sounds exaggerated, until you look at the numbers.

By Verdad Gallardo | 2026-05-04 20:03:36


VIEW MORE
story-4
Top 10 Corvettes Coming to Mecum Indy 2026!

Among a rather large group of them.

By Brett Foote | 2026-05-04 13:56:44


VIEW MORE
story-5
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!

Slideshow: the top 10 things Corvette owners want in the C9 Corvette

By Michael S. Palmer | 2026-04-30 12:41:15


VIEW MORE
story-6
10 Revolutionary 'Corvette Firsts' Most People Don't Know

Slideshow: 10 Important Corvette 'firsts' that every fan should know.

By Joe Kucinski | 2026-04-29 17:02:16


VIEW MORE
story-7
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2

Slideshow: Should you buy a 2020-2026 Corvette or wait for 2027?

By Michael S. Palmer | 2026-04-22 10:08:58


VIEW MORE
story-8
2027 Corvette vs The World: Every C8 vs Its Closest Competitor

Slideshow: 2027 Corvette lineup vs the world.

By Joe Kucinski | 2026-04-24 16:12:42


VIEW MORE
story-9
10 Most Common Corvette Problems of the Last 20 Years!

Slideshow: 10 major Corvette problems from the last 20 years.

By Joe Kucinski | 2026-04-14 16:37:05


VIEW MORE