LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Car won't start after it rain's or when really humid outside?

Old 03-07-2009, 05:59 PM
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Default Car won't start after it rain's or when really humid outside?

Everytime it rain's hard or is really humid out my car will crank over until the battery is dead but won't fire.

Weird thing is, today I went out during a rain shower and tried to start it, it cranked and cranked so I put the pedel to the floor and it started choking and kicking like it was going to start, I kept it depressed until I got about 1K RPM then let off and gave it gas to get it past 2500-3000 until I felt comfortable that it may keep running, after that I let it settle back down and it ran great.

Thought I'd add that it doesn't idle right when warm either, likes to jump up and down a few hundred rpm's at stop-signs. Also sometimes run's like crap after a long WOT run.

Car's been a headache since I got it but I'm determined to get it running right, I'm just 100% new to EFI so I'm needing a little help.

I'm guessing cracked cap? Car has a freshly installed Walbro 255 with new filter so I'm doubting it has anything to do with FP unless my FPR is bad but I checked it before replacing the pump and it wasn't leaking....guess I could check it again.

Any suggestions or opinions are GREATLY appreciated.

Thanks.

Last edited by NitrousJunkie; 03-08-2009 at 12:28 PM.
Old 03-07-2009, 06:04 PM
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had that problem with a silverado.it was the distributor cap.the moisture/dampness put a halt on it starting.
Old 03-07-2009, 06:23 PM
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Pull the diagnostic codes, some chain parts stores can help you do it. Once you have that info post it here.
Old 03-07-2009, 10:48 PM
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NO SES light so I figured probably no codes but I'll try that tomorrow, I wonder if it will pull codes if its a dry day out? I know OBD1 doesnt show as many codes as 2.

I'm leaning towards Cap which will be getting replaced next week.

If I get any codes I will def post them tomm, hopefully I'll get something.

Thanks.
Old 03-08-2009, 12:06 AM
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First, what year is your car..?
I had a similar problem.. on my 96.. When it did that It ended up being my ICM pigtail.. like it had moisture in it.. I would get out and unplug it, then plug it back in and it would fire right up.. worth a try, and its >>FREE<<... that always intrest me...lol..
Old 03-08-2009, 12:44 AM
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It's a 94, I'll try the ICM pigtail and see if it helps at all.
Old 03-08-2009, 12:55 AM
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btw.. if it does, take a pick and pry the prongs inside the pigtail up for better contact..
Old 03-08-2009, 07:36 AM
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since you said you dont have a filter on it.... maybe your getting debris in your injectors. mine started to act the same way before it finally wouldnt start at all. replaced the fuel pump,opti,icm,coil, blah blah blah and it still wouldnt start. hit it with some starting fluid fired right up. so i changed the injectors and she ran like a champ since then. it was also on a 94 with around 120k on the clock. how much you got on yours?
Old 03-08-2009, 12:31 PM
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lol, I just noticed I put no filter - Fixed it.

We tried starting fluid before the new pump went in because it was acting up then and it didn't help at all, just acts like its flooded.

If you put your foot to the floor and are feeling lucky that day lol, it will start to choke and cough up to about 1K RPM's then choke up to about 2500ish then settle back down, then run great.

When the car run's, it runs hard.
Old 03-08-2009, 03:40 PM
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I would think you are getting moisture in the opti check the cap. also make sure that your water pump is not leaking into your opti.

good luck with your car
Old 03-08-2009, 04:37 PM
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yeah I'm looking for a cap so if anyone has one let me know, the water pump is leaking thats why its getting changed next week and I want to do the cap/rotor while I'm at it.
Old 03-08-2009, 05:35 PM
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Originally Posted by NitrousJunkie
the water pump is leaking thats why its getting changed next week
That is why your car is running the way it is
Old 03-08-2009, 05:46 PM
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Water pump weep hole is right on top of the opti; not the best design but once you get your water pump and opti replaced or dried out you will be fine.
Old 03-08-2009, 07:07 PM
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Having a non-vented opti don't help
Old 03-08-2009, 07:14 PM
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Same thing happened to me years ago.... it was the coil wire. Whenever it got humid... especially after rain... it wouldn't start.


Try the easiest things first.
Old 08-14-2012, 11:38 AM
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I'm having the same problem with my 99 Olds Bravada. It just won't start during high humidity and forget about it during rain. I've had the fuel pump replaced, battery cables replaced and have found Seafoam helps. I however can't afford a bottle every time conditions are unfavorable. I'm about to recheck my d.cap. Fingers crossed.
Old 08-15-2012, 06:28 AM
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Originally Posted by Carmela Ramos
I'm having the same problem with my 99 Olds Bravada. It just won't start during high humidity and forget about it during rain. I've had the fuel pump replaced, battery cables replaced and have found Seafoam helps. I however can't afford a bottle every time conditions are unfavorable. I'm about to recheck my d.cap. Fingers crossed.
Olds Bravada? This is the LT1 forum homey.
Old 01-29-2013, 07:54 PM
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Just to add a bit of info this this thread...

I drove 75 mile down the interstate yesterday, car started fine, etc. Well yesterday morning I went to fire it up and it would roll over and "try" to fire, but no luck. It had just rained the night before also between the time I parked it and the time I tried to start it.

Well, I came back to it later that day and tried some more, eventually after holding it to the floor it fired and caught me so off guard I turned it off in 1 second haha.

Fast forward to the next day, its 65 degrees out, I go to try and start it and it fires up like nothing wrong, I took it down the road and give it a few short runs and all seems fine.... I believe moisture is the culprit but I will not be able to tell yet. So, a heads up to anyone else who thinks this could be wrong with theirs.
Old 02-01-2013, 07:16 PM
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replace your plugs and wires. bad wires will act up with rain/moisture. One of the first things I learned in my tech class. If that doesn't solve your issue, check your opti. It's possible some moisture got into that and is screwing things up, but then it would be a more repetitive issue. My guess is wires. best of luck!
Old 02-01-2013, 07:26 PM
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