Optispark test?

[Bonnewagon]

My daughter's car has a 95' LT-1 with the dreaded Optispark and it is showing a code 36 for no high resolution signal. I've been batting my head off searching forums for info and can't get this answered. Is there a test for the optical sensor? Can I use an ohmeter/voltmeter for some sort of value to see if it's shot, or am I required to just change it? It's allready an MSD unit and it cranks forever before starting. I don't mind changing it (shudder) as long as I can test it and know for sure.

 

[pontiacgp]

a friend of mine had a similar problem with his impala ss....he ended up changing the pigtail connector to the distributor. If I'm not mistaken the got the new connector from GM..

and I have also read where an oil leaking into the distributor it it wasn't sealed properly can cause a code 36 and I have seen a coolant from a defective water pump leak into the distributor

 

[Bonnewagon]

That's what started it all, Steve. Leaking WP and oily distributor. New WP and MSD distributor/wires sort of fixed it until now. I am testing everything I can get at without practically yanking the motor and I get both the dist and PCM as faulty, yet it runs, crappily. I have to plan this out since diving into this will keep the car down for some time and I want to be sure what is actually wrong. The code 36 "should" be the tipoff and condemn the dist, but I had a code 42 stored also, and the manual said if you get both, toss the PCM. So I erased the codes and ran the car and got the code 36 immediatly, but not the code 42. And if it is the PCM, I need to get a new one flashed somewhere with the data for this car's VIN. That's why I am searching for a way to test the optical sensor without yanking the dist. One site said you can use a digital voltmeter to see if spinning the dist shaft causes 5v pulses, but didn't say if you open the harness or probe it while hooked up. Any ideas?

 

[pontiacgp]

I'll check with a couple of shops tomorrow to see if if they have any ideas...

 

[Bonnewagon]

Thank's. Then to add insult to injury, there are tons of repop optisparks out there that are pure junk. Even the MSD gets a bad rap. It seems the GM unit is the best, is the most expensive, and it can fail too. And for all the work involved in changing it, it's a damn shame to have to redo it over a cheap part. I've been scouring the LT-1 and Camaro/Corvette boards and no one has anything good to say about any of the units, even the GM which is supposed to have the good Mitsubishi optical sensor. At least the GM seems to last longer, but as you said, oil, water, old plug wires, allmost anything can kill it.

 

[pontiacgp]

I've been finding the same thing. I don't know why they ever designed something like that in the first place....some neat ideas should go no further than the drawing board. I haven't had a chance to get out of here but I'll see what I can do later.

 

[pontiacgp]

not much luck with the guys I talked to tonite. One guy just replaced one cause it got soak by coolant and he used a GM rebuilt one. I have one more guy to talk to at a speed shop and he's pretty good when it comes to stuff like this

 

[dan2286]

I am pretty sure you need an oscilloscope to test optical sensors. The pulses are way too fast to be noticed by a DVOM.

 

[Bonnewagon]

I think the test I saw was for holding the distributor in your hand and slowly spinning it. There are 180 slits in the disc that get read by the sensor, so, yeah, I can see it being too fast for a meter. My cousin has a scope but he's in Philly, damn.

 

[Blake442]

For all the times I've heard of Opti-spark issues, I still can't believe I haven't had any problems with mine in my '96 Caprice.
Especially since it got soaked with anti-freeze when my waterpump drive seal failed at 40K miles...

I know by '96 they added a vent to prevent moisture build up, as that is a common cause of failure.
Not sure if the '95s were as lucky, but it may be worth looking into before you replace it again.