Cracked Cap? Car won't start when its humid or after it rains.

[NitrousJunkie]

So I went out today, to go to a job interview none the less and my car wouldnt start......again.

I noticed moisture on the back window and the humidity is 78%.
This also happends 99% of the time whenever it rains all night.

Could I have a crack in my cap? Might explain why its been stuttering from time to time.

Any idea's? I'll be replacing the water pump, PS pump, cap/rotor and plugs coming up in the next week so I'm praying to god that will fix it.

I'll be ordering a cable and either running tunercat or LT1edit (Or both) so I can scan it, hoping that might show something.

Funny thing is, I thought about selling the car last night...guess what I'm thinking now? :D

This is my first EFI V8, and its been nothing but a headache and to top it off, nobody I know knows anything about the engine, there all old school carb guy's. (Speaking of that I've been thinking about switching to carb)

So if you have any idea's on what might be causing this, let me know I appreciate it.

Thanks.

[Firebat]

First figure out if its fuel or spark. Check fuel pressure. If thats bad, its probably fuel pump, fpr, clogged injectors. Test the ignition coil, refer to this picture: http://shbox.com/1/coil_testing.jpg

You also may want to look at this link: http://shbox.com/1/4th_gen_tech2.html#opti_test

Or it could be VATS if it starts up for a couple seconds then shuts off.

Could be a blown fuse.

Does the engine crank at all? What happens when you turn the key?

Sputtering from time to time sounds like a bad fuel pump but could be something else. I would recommend changing the fuel filter regardless of what problem you might have. You could have a clogged fuel filter but it won't hurt to change it anyway, preventative maintenance.

I also see that you have a 94, which means its not a vented opti. Opti could be it too, but check the simple stuff first.

[NitrousJunkie]

Has a brand new Walbro 255 and filter, I'll check the pressure again but I'm sure its dead on, it only won't start (cranks and cranks) after a hard rain or when the humidity is really high out.

Otherwise it sputters after WOT at times but only once in a while and its usually when the temp starts rising above 200 (I think) but that could be something completly different than the not starting.

I'll check the ignition coil, its getting a MSD cap/rotor when I change the waterpump next week either way.

Thanks.

Update: Went out today, it was raining, car cranked and cranked so I put my foot to the floor and it began to choke and cough and kept it there until I felt it would run, let off the pedel and it choked up to about 2500-3000 rpm then settled back down..........then ran perfect.

Its acting like it's flooded.

[NitrousJunkie]

Do LT1's have a choke sensor? But that wouldnt explain why it only does it when it rains or the humidity is really high.

I'm lost, really need somebody with extensive LT1 knowledge to chime in, I'd really appreciate it as I am getting extremely frustrated with this.

Shit I'd even paypal someone some money at this point if they could point out exactly what it is, getting desperate.

[enjoi355]

ive never heard of a choke sensor for the lt1... i had a problem pretty much the same as yours some time ago, car would run like crap when/after it rained or lots of humidity, i was sure it was because there was some moisture enttering the opti somehow however mine kinda went away after some time... when you replace the cap and rotor, take the opti completely apart and clean as much of it as you can

[Firebat]

I recommend installing a vented optispark and do whatever it takes to get one installed. I do not know what it takes to do that though.

[Green96Z]

Run your car at night and see if the spark plug wires are arcing. Spray a light mist of water on them and see if they arc then.