deanorlean

Ok, I am another on the endless list who is replacing an optispark distributor. This one on a 1993 corvette. You'd think there's enough written on this subject to find an answer to my situation without starting a new thread. Not this time.

To begin, the car had a no spark condition. Preliminary tests of coil, ICM, and harness all checked out ok. So I purchased an aftermarket opti distributor. With careful forethought I bench tested it, and out came bright blue spark. Problem solved I thought. So I put the whole shebang back together, added coolant and hit the key - NOTHING! Diagnosis - No spark.

Alright, it doesn't make sense, but let's try it again....Take the opti back off the motor. Do another bench test. Just like before, bench tested with big blue spark. Bolt it back on the motor. Connect the harness, coil/ICM, #1 plug/wire and test before going any further. Guess what? Same as before - Nothing. No spark! Next step, desperately check remote possibilities. Verify camshaft is rotating distributor shaft - of course it is. Tighten all grounds and retest harness - check. Well, then let's point the blame then at my newly purchased aftermarket optispark. Beware of their reliability so many people say. So I return it claiming defective part.

Fast forward a week. I just received a new optispark, and am going thru the pre-install ritual again. Bench test confirmed. Bolt it to motor and plug in with #1 plug/wire and whatcha think is happening? NO SPARK! How can this thing send spark when I spin it mocked up sitting on top of the motor, but once I bolt it to the motor I get nothing? I'm looking for some help with this one if anyone can offer.

shbox

Out of curiosity, what did the original opti do on the bench test? So, to bench test, you are hooking it up to the engine harness, but just not mounting it to the engine? What happens if you run a ground jumper from the metal case of the opti to the block and retest? Don't know what your problem is, but just throwing out things.

deanorlean

I didn't check original opti. I let it go as a core return. The two new optis I purchased were bench tested by setting them upside down on top of the engine, connecting harness, coil wire, #1 wire/plug and spinning the shaft with a cordless drill. I get blue spark with or without ground jumper. Bolted to the motor I get no spark with or without the ground jumper.

ACE1252

Which way was the drill spinning? Forward or Reverse?

I'm not sure how people are doing the "drill" test, but, the correct direction for spinning the opti will be using the REVERSE direction on the drill.

If you are spinning it forward, you are going the wrong direction and spark in that direction does not mean anything as it's not the direction the opti will be turning on the engine.

In order to see what is going on with the hi and lo res signals you need an oscilloscope. For the high voltage side(spark side), you will need other tools to adapt the scope to handle high secondary voltages or get a hold of an ignition oscilloscope.

If the drill is spinning in reverse and is presenting spark, I think we need more details on how the test was performed....ie was it just with key on? I'm not so sure that even with that, if the test is truly a valid test to tell you if the opti is okay or not.....I guess what I'm saying is that I have not seen that testing method listed as a valid way of testing the opti in the factory f-body manual.

They do recommend looking for spark with a ST-125 while cranking the engine.

deanorlean

Just tried another "drill" test to confirm spark in REVERSE rotation. Key in on position, same as previous tests. Now there is no spark in either forward or reverse rotation. Why, I don't know. I did nothing different from my previous tests. Now I'm frustrated. I am shutting the hood for the weekend. Wether the test is considered valid, I don't know. But if the test was producing spark at the spark plug then I tend to think that it confirms the wiring harness, ICM, coil,coil wire, plug wire and plug are all performing their jobs. This should be regardless if the opti shaft is spun in forward or reverse.

David94TA

Could it be that the wiring harness has a break somewhere so that if it is in one position there is continuity but moved the break opens up and disrupts the current?

ACE1252

Bud, you appear to have some kind of intermittent problem given that information. They can be the toughest type to chase down. Right now you can't assume anything is okay because it's not working.

One thing I'm certain of is that you don't know how the optispark system works. The low resolution signal consists of varying length windows for cylinder identification....if you are spinning it in the wrong direction, then you are jacking up the ignition timing of the spark. You need to educate yourself on how it works, what to test, and start testing things with a multimeter and scope. You can swap parts if you have known good spares, but that will not help if you have a wiring issue developing....you have to track that down with a multimeter. It can also get expensive quick if you don't have known good spares and have to purchase parts.

Start by watching this....and are you familiar with how to use a multimeter and oscilloscope? If not, you need to learn how to use them too...

deanorlean

I'm trying to not assume anything. Hence the attempt to spin opti shaft in any direction . I'll try anything regardless of whether I personally think it's legitimate if it may help get this engine running again.

One hypothesis could be that I am not receiving proper voltages to ignition components when key is in start position. That could explain why spark occurred with 'drill' test (key in on position) and not with opti installed test (key in start position).

Unfortunately, now that I cannot generate a spark under any circumstance, I need to back up and begin by checking voltages/grounds across the engine harness again as recommended. Thanks everyone for the input thus far. The potential for an intermittent harness/ground problem will be my next focus.

BALLSS

while this may not be your issue, "my" intermittent fail was due to the brown wire (1 of 4 wires) in the short Opti harness that plugs into top of Opti and runs on PS of intake and plugs into engine harness. The crimp on the opti plug end was not done and that wire caused a intermittent fail on several optis the dealer installed when my car was under warranty. It was by sheer luck when I was just poking/pulling gently on wires while engine was running that when I gently pulled on the brown wire...it came out of the connector. was never crimped. Engine died immediately

so be diligent in checking your wiring & connectors. something like this may be your issue

also if you are buying auto part store clone Optis...those are a crap shoot right out of the box

deanorlean

I am playing the crap shoot with aftermarket optis. First one I bought got returned when I discovered no spark after install. Second opti (another import but different kind from another supplier) is what I'm working with now. I'm trying to believe that I couldn't be working with another bogus optI, especially since I can't even be certain the first one was without a doubt defective. No jumping to conclusions until I dig deeper into this mess.