`93 Distributor Dampness?

[Gary Bishop]

Re a `93 with 35,000 miles. 40th Anniversary.

A friend called and asked if I had heard of a problem with moisture getting into the Distributor and rust causing a misfire.

The garage wants to change the distributor cap and internals and the water pump at the same time. Apparently the water pump has to come off to get to the distributor.

Any feed back on this problem?

[Tom S.]

Re: `93 Distributor Dampness?

Gary it is called an opti- spark.If you wash the engine or they get wet for some reason they will misfire. On a 93 if the water pump has not been changed I would do it, you are right there.They only made this system for a couple years and it does not like to get wet! Tom

[Tom H.]

Re: `93 Distributor Dampness?

Yep, we change them out in pairs quite often. Not a cheap fix, but should cure the problem for a good long time. Always use extra care when washing the engine to keep water away from the opti spark unit.

[Kieran A.]

Re: `93 Distributor Dampness?

Gary, I remember an article in Corvette Fever magazine where a vent kit was used and retro fitted to the optispark unit to cure the water problem. I think the author/ mechanic was Chris Petris. Maybe you can check their archives as this was a common problem that was eliminated by a new design. Regards,Kieran #11373

[Wayne W.]

Re: `93 Distributor Dampness?

Funny how young engineers make the same mistakes over and over. We learned that was no place for a distributor long ago.

[Joe L.]

Re: `93 Distributor Dampness?

Gary-----

Very common problem on 92-94 Opti-Spark distributors. My advice is as follows:

1) ALWAYS replace the waterpump when the distributor is serviced. It does have to be removed to get at the distributor and you don't want it leaking (I can almost guarantee you that they'll find it leaking, anyway, but even if they don't, replace it);

2) Use a COMPLETE NEW DISTRIBUTOR. Do not replace just the cap and/or other "internals". Use an improved MSD-manufactured unit rather than a GM replacement (how infrequently do I recommend something else over GM?). In this case, the MSD is better than either the GM replacement or a vacuum ventilation-modifed GM replacement. The MSD unit is a direct fit for 92-94 (i.e. pin drive) unit and it's been designed with vacuum ventilation like the 95-97 Opti-Sparks (i.e. the "paddle-drive" units);

3) I would apply an additional bead of silicone between the cap and the body of the new distributor. These MSD units are MUCH better sealed than originals. Nevertheless, I'd still apply silicone RTV as described as a "back-up". You don't want ANY moisture to get inside these distributors. Moisture will cloud the optical sensor and cause great problems.

Are the MSD units expensive? You bet (about $600). However, a new GM distributor for 92-94 is very expensive, too.