After reading the closed thread about the opti-spark I hesitate to scratch any sore spots but I need some advice.

I have an '87 that I just put a 96 LT-1 into. The engine, trans and computer are out of a Caprice Police car. while grafting two wiring harnesses into one that will work, my Brother and I were able to get the thing to run if you sprayed gas into the TB. The injectors are not getting signal but that is something that we can overcome, no big deal.

The problem began when the thing lost all spark, all at once. I have removed the distributor (wow, what a treat!) and heard a rattle inside that turned out to be one of the screws holding the rotor in place had fallen out. There is visible corrosion, normal, I believe, on the rotor and the contacts in the cap.

M first question is: Could the screw have gotten anywhere to cause a short that would have killed the spark, and could it have killed the distributor as well? My father-in-Law, a great oldschool wrench (worked at the Flint engine plant, designed the 400SBC, et. al.) thinks that we can clean the unit up and get it to work.

My concern is that to test the thing I have to re-install it and if it is indeed toast, yard the thing out again. You all know how much fun it is to get to the front of the engine in this car, so hopefully you will understand why I hesitate to risk it with an old distributor.

This leads me to question #2&3: How can I take the distributor apart to check the sensors or whatever are inside (Hall-effect?) and clean it well with electrical cleaner to at least give the thing a fighting chance before I put it back in? And what exactly IS inside the distributor?

Or should I just toss it and buy a new one through Summit? (GM performance part # 1104032)

ANY help or thoughts on this are greatly appreciated.

Please answer either here or email me direct at
my1987vette@verizon.net and put LT-1 in the subject box.

 

My personal opinion is that I wouldn't mess around with the old one. I'd just install a new one and be done with it.

Hope this helps.

Norm.

 

You can install just the distributor and not the water pump, etc to see if it works.

 

Good Idea

 

Disclaimer: I haven't actually worked on one of these things - yet.

I did work in the field of optical encoders some years ago. The opti is an optical encoder. It senses a mechanical (rotary) motion and encodes it into a stream of electrical pulses. The stream is fed to a computer which uses it to adjust the spark timing.

There are three main parts to the typical encoder. They are the base/bearing assembly, the optics, and the electronics. This particular unit also has a rather expensive distributor cap attached to it.

Unless it is impossible to replace the bearings (or it is broken), I don't see why the base/bearing assembly would ever need to be discarded. The optical disk, which is a rather crude one at 360 count, should be okay unless it is bent or broken. The optical pickup and associated electronics are contained in a single module.

I don't see the advantage to buying a brand new unit as opposed to repairing the existing one for half the money. (or much less if the cap is good)

What you want to see in an encoder is a base/bearing assembly that runs true without side play or end play in the shaft. The optical disk which mounts to the shaft must be centered and run with minimum face wobble. If you have that your old unit is as good as a new one.

It should be fairly easy to bench test an opti. The requirements would be a fixture to mount it in with a variable speed motor to drive it, a power source to power it up, and a dual channel oscilloscope to observe the output waveforms. The fixture could be fabricated. An old computer power supply would do for the 12vdc. The scope you'll have to buy or borrow.

I'd like to get my hands on one of these and play with it a little. If anybody who reads this has on old one they want to dispose of PM me. I don't care if it doesn't work as long as it is all there.

 

Do that, there is DIY for the opti.

 

Roger That! I just did this on my LT4 and I can tell you...whatever you do, don't put the same one back in. After replacing mine, I had no spark - long story short, it was the ignition control module! It is MHO that you should replace both in unison now. Or, you could just borrow one from another car (post-'95) to yield diagnosis if you're on a budget.

 

There is an optical pick up and slotted disk under the inner plastic cover that is all. As stated above replace with new you said you had corrosion and it will fail probaby sooner than later. A new opti is not much more than the cap and rotor you need to replace. Trust me this is one part you do not want to "refurb" at home.

 

Thanks guys, just tossing it has seemed like the best way to go.

I found a place in bakersfield, Ca. that has new AC Delco units for $290. Since a cap&rotor are $210 I do not think I can go wrong.

Thanks for the advice!

Joe

 

Joe all you have to do when you get the new unit is to plug it in, turn on the ignition and give the shaft a spin by hand, you should see a good series of sparks from the coil lead and you should hear the injectors firing, if you solved the injector issue. If you see sparks from the coil that means that the PCM is working and is seeing the reference pulses from the opti.