1994 C4 Optispark question
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Instructor
Joined: Sep 2004
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1994 C4 Optispark question
Hi every one I hope Im almost at the end of a long night mire with my vette
I check for voltage at the A and D pins on the plug to the ICM I read very low voltage I took it to advanced auto but they couldnt test it i brought a new one and installed it car still wouldnt start. They let me return it. I also purchased a new coil but that didnt work as well.
Should I now start thinking about replacing the Optispark unit? I know the best is MSD but dont have that kind of money right now because I just put 3k into the before this happened.
Distributor Advanced about $200.00 witn out rotor life time warranty
Ebay $150.00 to $200.00 with rotor any other suggestions on this ??
Thanks everyone
I check for voltage at the A and D pins on the plug to the ICM I read very low voltage I took it to advanced auto but they couldnt test it i brought a new one and installed it car still wouldnt start. They let me return it. I also purchased a new coil but that didnt work as well.
Should I now start thinking about replacing the Optispark unit? I know the best is MSD but dont have that kind of money right now because I just put 3k into the before this happened.
Distributor Advanced about $200.00 witn out rotor life time warranty
Ebay $150.00 to $200.00 with rotor any other suggestions on this ??
Thanks everyone
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
I assume you made this A & D voltage measurement with the coil connected and key on.
Pins A & D should read 12 volts with the key on. That voltage comes thru the coil and fed by the PNK/BLK wire. That wire is the supply and should have 12 volts on it with key on. Check the 10 amp fuse in the panel for the coil to see if it is defective for starters.
Pins A & D should read 12 volts with the key on. That voltage comes thru the coil and fed by the PNK/BLK wire. That wire is the supply and should have 12 volts on it with key on. Check the 10 amp fuse in the panel for the coil to see if it is defective for starters.
Race Director
Joined: Dec 2006
Posts: 10,383
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No offense with this question but have you, in fact, verified that there is no spark? (timing light, spark test tool, exposed wire held near ground, etc)
Are you seeing distributor specific codes?
Did you follow the optispark diagnostic in the second volume of the FSM? (section 6E3-C4-1)
If you rule out buying an MSD on price then I'd get the cheapest one off eBay or elsewhere.
No matter which unit I went with (MSD&AC/Delco included) I'd remove the cap's two screws and re-install them with red loctite which I allowed to set up overnight.
Are you seeing distributor specific codes?
Did you follow the optispark diagnostic in the second volume of the FSM? (section 6E3-C4-1)
If you rule out buying an MSD on price then I'd get the cheapest one off eBay or elsewhere.
No matter which unit I went with (MSD&AC/Delco included) I'd remove the cap's two screws and re-install them with red loctite which I allowed to set up overnight.
Thread Starter
Instructor
Joined: Sep 2004
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These are the codes I got H31 H33 H35 H37 H16 H36 H64 H15
I thought that code H31 and H16 deal with the optispark?
I checked the wires by exposing them to ground to include coil wire
Any suggestions ??
I will take your advise an use the red loctite thanks
I thought that code H31 and H16 deal with the optispark?
I checked the wires by exposing them to ground to include coil wire
Any suggestions ??
I will take your advise an use the red loctite thanks
Race Director
Joined: Dec 2006
Posts: 10,383
Likes: 4
Bummer. I was hoping for the best. It seems the H16 and H31 in combination are indeed fatal.
The loctite bit comes from the pics posted here over the years of new opti's failing in short order due to loose screws.
The loctite bit comes from the pics posted here over the years of new opti's failing in short order due to loose screws.
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
I check for voltage at the A and D pins on the plug to the ICM I read very low voltage I took it to advanced auto but they couldnt test it i brought a new one and installed it car still wouldnt start. They let me return it. I also purchased a new coil but that didnt work as well.
If you missed my above post please read it.
If you made that measurement incorrect and there is really voltage there, then you can go get you opti of choice.
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
I assume you made this A & D voltage measurement with the coil connected and key on.
Pins A & D should read 12 volts with the key on. That voltage comes thru the coil and fed by the PNK/BLK wire. That wire is the supply and should have 12 volts on it with key on. Check the 10 amp fuse in the panel for the coil to see if it is defective for starters.
Pins A & D should read 12 volts with the key on. That voltage comes thru the coil and fed by the PNK/BLK wire. That wire is the supply and should have 12 volts on it with key on. Check the 10 amp fuse in the panel for the coil to see if it is defective for starters.
...check that 10A fuse which is located in the fuse box in the passenger door jam. This voltage source is what gets kicked up to 40K Volts or so via the coil primary windings. anyway, if you are reading "very low" voltage readings on your volt meter, this may just be "noise" from surrounding induction. There is no Optispark in the world that will work until you first get juice to your coil.Have you also verified that your meter is working properly ? Measure voltage across your battery terminals to test.
Finally, it would be easier if you stuck with one thread on this issue as opposed to starting a new thread every couple of days.
Last edited by MikeC4; Jun 15, 2009 at 01:56 PM.
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Thread Starter
Instructor
Joined: Sep 2004
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new voltage reading on ICM
Mike 4 thanks sorry about the new posted treads.
alright hope I have this right. I tested the following just a second ago.
1st the plug going into the ICM has the letters ABCD I got 12 volts with volt meter probe on D other to ground with key turned the same for A.
I then checked the Coil there are 2 plugs one gray and black both of which have an A and B wire I got 12 volts on the B wire to ground.
I then retested the coil and plug no spark or AC measurement out of plug wire but while cranking I measured the coil with plug off and got 12 volts.
did I do this right ??
alright hope I have this right. I tested the following just a second ago.
1st the plug going into the ICM has the letters ABCD I got 12 volts with volt meter probe on D other to ground with key turned the same for A.
I then checked the Coil there are 2 plugs one gray and black both of which have an A and B wire I got 12 volts on the B wire to ground.
I then retested the coil and plug no spark or AC measurement out of plug wire but while cranking I measured the coil with plug off and got 12 volts.
did I do this right ??
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
Mike 4 thanks sorry about the new posted treads.
alright hope I have this right. I tested the following just a second ago.
1st the plug going into the ICM has the letters ABCD I got 12 volts with volt meter probe on D other to ground with key turned the same for A.
I then checked the Coil there are 2 plugs one gray and black both of which have an A and B wire I got 12 volts on the B wire to ground.
I then retested the coil and plug no spark or AC measurement out of plug wire but while cranking I measured the coil with plug off and got 12 volts.
did I do this right ??
alright hope I have this right. I tested the following just a second ago.
1st the plug going into the ICM has the letters ABCD I got 12 volts with volt meter probe on D other to ground with key turned the same for A.
I then checked the Coil there are 2 plugs one gray and black both of which have an A and B wire I got 12 volts on the B wire to ground.
I then retested the coil and plug no spark or AC measurement out of plug wire but while cranking I measured the coil with plug off and got 12 volts.
did I do this right ??
"If you have good voltage(which you do), switch the meter to ac scale and connect test leads to terminal "B" and to ground. Observe meter while cranking the engine. You should see between 1 and 4 volts ac (those are the pulses that trigger the coil to fire)."
This trigger pulse is what collapses the primiary field which leads to discharging across to the secondary. The secondary is the dangerously HIGH voltage that goes into the Opti and routed to the correct plug. It is the Opti that determines what cylinder to fire(as determined by the LOW resolution pulses read from optical wheel) and the associated timing (as determined by the HIGH resolution pulses read from optical wheel). This information is processed by the PCM and sends out the trigger signal to the ICM. So if the above test fails, and you do not see a fluctuation of voltage between ~1 and ~4 volts, you are most likely looking at a bad Optical sensor or bad PCM. Given the error codes you have, I would first suspect a bad Optispark.
Last edited by MikeC4; Jun 15, 2009 at 06:59 PM.
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If you decide to go with an AC/Delco Opti on ebay, get it from a vendor called thepartsladi. Best prices and service on 'em you'll find there.
Don't be fooled by that cheap, ghetto, Optispark garbage re-manned in China or Mexico claiming to have genuine copper components and all that noise.
You'll be sorry!
Don't be fooled by that cheap, ghetto, Optispark garbage re-manned in China or Mexico claiming to have genuine copper components and all that noise.
You'll be sorry!
Last edited by onedef92; Jun 16, 2009 at 12:00 PM.
Thread Starter
Instructor
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new Opti no start
Ok put in new Opti still no start. I looked at the old one and even though it didnt correct the problem it look wet inside and the opti was covered with some rust debris.
I will go though the checks again to check voltage at the coil and will post them in a few mins as soon as I get over this frustration
Question it the opti isnt realigned properly will it also give a no start the car turns over but wont start same as before?? Will be right back going out to check for spark
I will go though the checks again to check voltage at the coil and will post them in a few mins as soon as I get over this frustration
Question it the opti isnt realigned properly will it also give a no start the car turns over but wont start same as before?? Will be right back going out to check for spark
Le Mans Master
Joined: Jan 2006
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From: Woodstock Georgia
Instructor
Joined: Jul 2006
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From: Erie PA
Yes- loctite screws
No matter which unit I went with (MSD&AC/Delco included) I'd remove the cap's two screws and re-install them with red loctite which I allowed to set up overnight.[/QUOTE]
Great tip, 2 years ago I bought a MSD opti. This past spring the car would stall or have a no start condition. Turns out my 2 year old opti rotor screws came loose causing the rotor to flop around. When I took the cap off of the opti I found a bunch of plastic shavings. I sent the opti back to MSD a month ago for repairs and now without my vette till I get the thing back, good luck
Great tip, 2 years ago I bought a MSD opti. This past spring the car would stall or have a no start condition. Turns out my 2 year old opti rotor screws came loose causing the rotor to flop around. When I took the cap off of the opti I found a bunch of plastic shavings. I sent the opti back to MSD a month ago for repairs and now without my vette till I get the thing back, good luck
Thread Starter
Instructor
Joined: Sep 2004
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im working on only .5 volts at B on the connector to ICM as a pulse when the car is being turned over
Im working on off a battery jumper at this point if that makes any difference of why the car wont start
Im working on off a battery jumper at this point if that makes any difference of why the car wont start
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
Ok put in new Opti still no start. I looked at the old one and even though it didnt correct the problem it look wet inside and the opti was covered with some rust debris.
I will go though the checks again to check voltage at the coil and will post them in a few mins as soon as I get over this frustration
Question it the opti isnt realigned properly will it also give a no start the car turns over but wont start same as before?? Will be right back going out to check for spark
I will go though the checks again to check voltage at the coil and will post them in a few mins as soon as I get over this frustration
Question it the opti isnt realigned properly will it also give a no start the car turns over but wont start same as before?? Will be right back going out to check for spark
With that said, it can also be forced on incorrectly.
Le Mans Master
Joined: Jan 2006
Posts: 5,620
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From: Orlando FL
0.5 volts at B is not correct and is not enough to drive the ICM correctly. Make sure you are measuring on the AC scale and have a good ground. Might try another meter just for the heck of it. However if there is no higher output there than what you have, the problem is a PCM or opti related. Not including bad connections or other things that can cause problems other than an actual part.
Make sure PCM is getting 12 volts DC turn on from ignition switch. And there should be I think 12 volts DC on pin C of the opti connector (wire 631). I think wires 430 and 433 (A&B) might float at 5 volts DC but not sure, not done it in a while.
Other than having a spare PMC to try, a few checks are going to be necessary to see if there is a input or output problem to or from the PCM.
Even if the opti shaft was not aligned correctly you would still produce the correct AC voltage at pin “B”. (Of course it won’t start because the timing would be way off).
Make sure PCM is getting 12 volts DC turn on from ignition switch. And there should be I think 12 volts DC on pin C of the opti connector (wire 631). I think wires 430 and 433 (A&B) might float at 5 volts DC but not sure, not done it in a while.
Other than having a spare PMC to try, a few checks are going to be necessary to see if there is a input or output problem to or from the PCM.
Even if the opti shaft was not aligned correctly you would still produce the correct AC voltage at pin “B”. (Of course it won’t start because the timing would be way off).
Last edited by pcolt94; Jun 18, 2009 at 08:34 PM.
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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
that was B connector to ground