'95 LT1 Roadmaster wont start... key resistor? also no heat,

[hdironhead78]

I got this car about 8 months ago, I love it, i put about 18,000 on it since I got it. It has 228,000 total, still strong. But, the other day it wouldnt start on me. I changed the plugs, tested my fuel pressure, and it was good. It started for me, and i drove it a few more days, but then it wouldnt start again. While i crank the key, it turns over, but doesnt try to run, when i back off the key it puffs a little bit. No response with starting fluid, at all. A couple guys said the little black key resistor thing might be a problem, but i dont know anything about it. Anybody else know anything? Also, this is kind of a non-important thing, but it doesnt throw any heat. Has a new thermostat, heater core, and antifreeze. air in the system maybe? Mostly I need help figuring out how to start it though. Any ideas, Pictures, specifications, anything will be just great. Thanks, Paul.

[HotZ28]

The LT1 engine uses an “Optispark” distributor mounted to the front of the engine (behind & under the water pump) and it is notorious for failure due to moisture related problems! It is imperative that you never wash the engine while warm. If you do, it will cause condensation inside the Optispark and it will not fire the plugs. (Like moisture in a distributor cap) Also, if the water pump leaks coolant onto the Optispark, the same condition will exist. First thing you need to do is check for spark at the plugs and post the results.
BTW, if it were a security problem (key resistor), the starter would not engage and the engine would not turn over!

[Hoytman]

I'm dealing with the same type problem. replaced a faulty/leaking water pump yesterday & car ran fine afterward but will not start this afternoon. Good spark out of coil but just cranks & does not start. Sometimes upon releasing the key after cranking the engine trys to run backwards. Do these Optispark units fail after a leaky water pump or do I have a moisture problem that I can dry out or repair. Started fine & ran well after water pump install 3 or 4 times & road tested well but that was yesterday & will not start today.

[hdironhead78]

The other day I parked it in my buddies garage. Not heated, but out of the weather. I went over there today with a battery, and pulled a plug, and it did have spark. not a blue spark, but a decent spark nonetheless. And the weird thing that happened was, when i put that plug back in it, the car started and ran. I let it idle for a few minutes, then drove it up the road, and it quit on me again, so i towed it back to the garage. I just wanted to update what is going on with it. Now before, when it was giving me trouble, I dont know if it had spark or not, i never checked. This Optispark distributor youre talking about, i see it on my car, looks like a real dream to change. Does it have a cap and rotor like a generic distributor? or do I have to change the whole thing? Thanks for any help. Paul.

['97ventureowner]

Yes, you can change the cap and rotor on your Optispark system. This system was introduced in the Roadmaster in 1994 and this system is better than the one that preceded it. The newer version is vented to prevent moisture buildup, a common problem in the previous systems. Also the cap and rotor can be replaced as a unit, which couldn't be done on the earlier models.

[HotZ28]

It would be more accurate to say; the newer design was vented, with the intention of reducing condensation problems. The vented optispark, was nothing more than a quick "band-aid" redesign, in an effort to help reduce the number of failures, not as a permanent solution to the problem! Basically, the vented system uses a vacuum, to pull fresh air through the optispark and only works when the engine is running.

So, what do you do when the optispark becomes saturated and the engine will not start? It takes either heat, or high vacuum to evaporate moisture from inside a sealed environment. On some occasions, I have used a vacuum pump attached to the vent vacuum line and let it pull air through the optispark overnight. I also have used a hot air gun directed to at outside of the un-vented & vented units and let it set for several hours. Both methods work temporally, until the next time it is saturated with condensation.

Now, if you want something that far exceeds any OEM design, Here is the answer. I have been using this unit on my LT1 since they were first introduced, over a year ago. No problems yet, in fact, I have tried many times to make it fail while under warranty (washing engine while warm) and have not been able to even get a misfire condition out of it! Keep in mind, many of the OEM units (vented or un-vented) fail shortly after the first time they were exposed to water/coolant.

['97ventureowner]

Here's another modification for the Optispark system I have done some reading on:http://www.delteq.com/. It's a little more pricier at $785 for the Roadmaster.

[HotZ28]

Thanks for posting that link 97Ventureowner! Actually, I have been considering the same setup for my Z28 if the MSD ever fails. BTW, I noticed you could purchase the identical item from paceparts.com for about 135 bucks less than direct from Delteq.