I have a 93 LT1 coupe, I am in NH. Seems like the past few times we have had rain this fall, the car wont start. It cranks fine and will even let out a sputter here and there, but it just wont start. The next day after the weather clears, it fires right up like nothing happened. I am guessing that I have a condensation issue. It has been cold at night, then the warmer moisture laden air comes in and must be condensing somewhere. Always seems to happen when I am in a hurry to get somewhere so I just jump in the truck and off I go, next day its working so I havent been able to troubleshoot. Has anyone else had this problem? Where would I start? Is the coil susceptible to moisture? Thanks.

 

This definitely sounds ignition-related. How old are your spark plugs and your plug and coil wires? If you don't know or have never ever changed them, this might a good time. If you do, be sure to coat the spark plug threads with anti-seize and run a glob of dielectric grease all the way around the inside rim of both ends of each and every wire boot. You could have voltage short-circuiting at the coil wire connector on the distributor to some place on the block or water pump that's in close proximity, thus preventing it from ever reaching your ignition coil. If it's dark outside the next time it happens, and you can have someone crank the engine for you, you can check for arcing at both ends of the coil wire. It's best if there's no ambient light whatsoever when you do it, and even then, you'll have to look very closely. The coil wire connector on the ignition coil is somewhat easier to put eyes on than the coil wire connector on the distributor. If you have one of those little telescoping swivel mirrors, that might help as well. Any arcing is a sure sign of a problem. That's the first thing to fix if you notice any. Either way though, I'd stick a glob of dielectric grease all the way around the inside rim of both ends of your coil wire, whether you notice any arcing or not. When you put the coil back in, make sure you get the boots back on the connectors all the way. You'll usually feel the boot snap into place when it gets to where it's supposed to be.

There's a very remote possibility that it could have something to do with your fuel pump as well, but if you can hear that low humming sound coming from the back end of the car for 2 or 3 seconds as soon as you turn on the ignition (the fuel pump priming), I'd rule that out until all other ignition-related avenues have been exhausted.

 

If you believe it to be possible coil issues or would like to start there I would test that. You can always quickly pull a plug and test for spark. Spark tester for a few bucks is handy here. Im guessing fuel and air are fine, due to it running day after. You are electrical of some sort. It can be the seal on the optispark allowing moisture to get in and wet the contacts. Or it could be the coil as stated. Coil is easier start there first.

 

Ahh, yes, you're right. GM, in their infinite wisdom, didn't vent the Opti-suck until '94. They stuck a negatively-pressured distributor underneath the water pump, right below the G-D weep hole. Idiots!

When it happens again, I would check for trouble codes. The only thing the Opti-suck was fairly good at is throwing codes.. It don't matter if the SES light is on or not. I've read plenty of codes without seeing the SES light..

 

I'd suggest getting a water dispersant spray like LPS and take apart every connection and spray the inside of them then reassemble.
I had problems with a Spitfire but that resolved them for me.

May not solve your problems but it sure won't hurt.

 

I have an 86 C4 that dosnt like to start. i did get it to start by turning the dist back but it runs like crap. When i advance it till it runs good the dam thing wont start. HELP!!

 

Hey guys, thanks for the inputs. I replaced the plugs/wires when I got it almost 2 years ago, the MSD's that were in there were arcing all over the place. I havent really had an opportunity to troubleshoot yet. The last time we had the right conditions for it to act up, I actually had time to look into it and would you know it, it started right up. So I guess another symptom is that it only does it when I am in a hurry to get somewhere! Even though I couldnt really troublshoot becuase everything was working, I did re-apply a liberal amount of di-electric grease to all but the drivers side connection on the opti (PIA to get at). Not sure if I will get another opportunity to figure this out before it goes away for the winter.

 

This does sound like a no spark problem. Of course I would check for fuel pressure and at least make sure you here the 2 second prime of the fuel pump.

This sounds like a ICM problem if it is a no spark situation. A bad ICM can be affected by temperature an take on a personality of its own by not working when it wants to. It's easy to replace and not that expensive compared to an opti.

This is not a classic opti problem and would not go for it due to labor effort and expense. You can check you injector drive pulses which is driven by the opti's low resolution pulse. If it is there and there is no spark, that would sound like the opti is working.

You can also check the AC voltage (as engine cranks, pin B) (1-4 volts A/C) drive to the ICM. If it is there, then the opti and ECM are working and the problem would be the ICM.

On the 93 with a ECM, many weird problems can occur. I would keep this on the bottom of my list as temperature can affect a ECM more so that moisture.

 

I had the same type of problem with my 1994 Corvette. I solved my problem after some investigative work. In my case, when it rained, water was able to bypass a sealed area and drain onto a fuse block behind my battery. It is this fuse block that serves many if not all or the necessary systems needed to start the car. I cleaned all of the fuse connections, which were fairly corroded,, and made a rubber boot to cover it. I corrected the failed seal above this area, so that water didn't pour onto this fuse block. The seal in question stops the water from the windshield area from entering the engine compartment area. The caulking along that seam had gotten old and failed. After my repairs, my car starts great all the time,, despite the current weather conditions. Best of luck to you all!!!