Suburban with trouble starting when wet

[scruff102]

I have a 99 Suburban 1500. I have read many threads on these guys not starting and most have talked about the fuel pump or relay. I don't know if my problem is the same or not. I have trouble starting Bessie when she gets wet from rain or sometimes from a heavy dew. My mechanic has checked a lot of electrical stuff and finds all connections ok. We have replaced the ignition but still fails. Our friendly Chevy dealer is of no help. "Bring it in and we'll look at it." If I could start it, I wouldn't need to bring it in. I have had it towed in twice and, of course, it started for them right away. The other posts talk about the fuel pump, etc. Could this be happening to me but only when wet? Seems electrical to me but I don't know.

[2000CAYukon]

If you do not want to debug it yourself, try to find a mechanic that will drive it home for a few days to reproduce the problem. They will have a fuel pressure gauge and spark test to help determine if the problem is fuel or spark.

Since the fuel pump is in the tank and already wet, I suspect you have an electrical problem with moisture but until it can be reproduced and debugged, I am just guessing.

//2000CAYukon

[pkear]

Call me a shade tree old style mechanic and not knowing a lot about the newer engines it sounds a lot like you are getting moisture somewhere between connections in the ignition system. In the old school we would have dried out the distributer cap and rotor and tried it then then if that worked waterproofed it. Sounds like a similar problem especially if it only happens on a wet dewy morning. What happens when you tow it in is by the time they get around to looking for a problem things have dried out. Now take this for what it is worth since I am not a mechanic and know little about those computer controlled space shuttle engines. Get you some of that dielectric grease and one nice warm dry day when you don't have any problems starting your truck apply a thin coat over every electric connection you can find. You don't have to unplug anything just coat over the connection point. This seals out where the moisture can get in. It is a cheap fix and solves the problem. You might have to reapply every so often but as cheap as it is it sure beats paying a tow bill for them to tell you nothing is wrong with it now even if it does not work.

[krewl1]

I know on my older car I had the same thing. Heavy rain or sometimes light rain car would not start. I had to carry a can of wire drier with me to always get it going till I replaced the cap,rotor and spark plug wires.All the problems went away.

[scruff102]

Thanks guys for answering. I've always thought it was something electrical but it does crank but just seems like it doesn't get enuff gas. Also, if it doesn't start on first try and I keep trying, when it finally starts, it seems like there is a big "clunk" sound instantaneously as it starts. Like ther is something opening or closing at that instant.

[Ryan685]

Probably backfiring out the exhaust. It's loaded up with gas from no spark. As soon as it gets spark, it ignites the unburned gas and POW. Well, what you actually hear is a heavily muffled phart.....

I'll put my money on a bad ground somewhere. Remove ground straps, wire brush them and tighten them back up. Start with the battery and work out. Bad grounds cause all sorts of headaches.

[ckaroff]

I too have a 1999 Surburban and it has the same problem as Scruff102.
Does not start when you are in an area that is moist such as the ocean, or when it rains. Fuel pump has been changed. Also, when car gets
towed, it appears to us that by hoisting the car up on a tow truck seems
to allow the truck to start when it is let down. We thought perhaps something is clogged in the gas tank. Anyway we have tried lots of different things and mechanics and changed lots of part, but nothing seems to work. Has Scruff102 resolved the problem. If so, please let us know what it is.