97 Jimmy, 4.3- Crank, but No Start in Rain/Humidity

This has gone on for two years and over two grand. I am slowly going insane. When it starts, it runs GREAT…but if it is moist outside, it is not going to happen…can crank it til the battery dies. I have replaced: spark plugs, fuel pump, MAF Sensor, distributor cap and rotor, stupid poppet fuel injection, battery x 2, and the ignition switch. It used to pull a random misfire code, but now has NO codes. I have been through five garages and four really good at home mechanics. When it is not starting, it has spark at the plugs and good fuel pressure. Last mechanic wanted to do a second fuel pump with the new injection system…I swear I think it is because I am a girl…PLEASE help me. I love my truck, but I am running out of money to throw at it.


Have you replaced the plug wires yet?

This sounds like the classic case of a vehicle with bad plug wire insulation

No codes . . . not even any stored codes?

You might want to take a closer look at the crankshaft position sensor

When it doesn’t start, is the antitheft symbol lit?

Had two guys tell me the plug wires were good…didn’t seem to want to replace them, but I will give it a shot. It doesn’t have that annoying antitheft syststem, tg. It was the year after that they put those in. I’ve read a bit about the crankshaft position sensor and saw there was a bulletin on it. Is there a way to test it and is it something that I can get to on my own? Thanks so much for the suggestions.


I’m disappointed that the guys didn’t replace the plug wires when they replaced the plugs, cap and rotor. That usually goes hand in hand. Not to mention that the plug wires are often so brittle that they break when you do the tune up.

If you get plug wires, go for AC Delco. And replace them one at a time, because the wires aren’t numbered. You’ll have to match the wires by length, as you replace them.

@southshappyphantom…I agree with @db4690. I always advise someone to change out their spark plug wires when the vehicle engine has trouble starting in the rain or even high humidity. Spark plug wires can look serviceable when checking out by sight and feel but that simply does not work when they are bad. Unless the wires are old and brittle, which does not happen to many spark plug wires, it’s nearly impossible to determine a good plug wire by simply looking at it.

“When it is not starting, it has spark at the plugs and good fuel pressure.”

How were these things verified? If you know with certainty that there is strong blue spark at all plugs during a no start then plug wires are unlikely to fix it. I’m not telling you not to replace the wires. That’s never a bad ideas.

Anyway…on a DRY day, get a misting bottle of water and a plastic bag. Start the car, pop the hood and start misting things one at a time (the plastic bag is in case you want to cover one thing while you dampen another). Especially don’t miss the crank sensor which you might have to get to though the bottom rather than the top. Keep misting stuff 'till the car responds.

Somewhere on your dash is a security system light. What does it do on those damp no-start days?

+1 cigroller

Well, now it is not getting spark. I took it back to the ‘get a fuel pump’ guy when it rained and wouldn’t start on Monday. At least he isn’t saying fuel pump anymore. He said he opened the distributor cap and it was wet. They dried it out and it still wouldn’t start. After sitting overnight in their garage, started right up and he put it back in my driveway.
I said, why not replace the cap. He says that down here in the Deep South condensation is inevitable and there will always be moisture in the cap. I’d love to hear y’all’s thoughts on that.
He said he copied the key and I should just leave it there next time it’s going to rain. They suspect the cam sensor, which he said is in the coil pack? or ignition control module.
Sooo…can’t an ICM be checked without me missing another day of work cause it rained? And…why can’t he water test it? Am I being unreasonable?
I am going to water test it myself this evening. I will post my findings.
I will do the plug wires first.

@southshappyphantom…get a second opinion. This “get a fuel pump” guy is full of beans. I lived in the deep south for over 10 years and my distributor caps were always dry.

I’m with @missleman. I’ve lived in the south nearly my whole life, and haven’t had a wet distributor problem. Either the cap is defective, or the hood has a problem near the firewall, like missing weatherstrip or gross misalignment. Also, have the plug wires been changed yet?


Install an AC Delco distributor cap, rotor and plug wires

And see what happens

That condensation thing the guy was telling you sounds like a pathetic excuse for his inability or unwillingness to diagnose the problem

When I lived in Germany, where it rains a fair amount, I didn’t always have water inside my distributors

And the rule of thumb was, if the car didn’t start on a damp or wet day, and the plug wires were in any way old or questionable, they got replaced.

Oy. Pop the hood and start misting things. This does not have to remain a mystery.

The week got crazy on me, but I have purchased the wires. It is going to be foggy this weekend, so I will try to replace the wires and start misting in the morning. I will post an update. Thanks SO much for the advice.

I might add this. It’s quite possible and often happens in very humid conditions that condensation can build up inside a distributor cap after the engine has been shut off; even with a new cap.
Engine heat can draw the moisture in. As an analogy, think of a window sweating on a cold damp winter day.

You might try spraying the cap and wires down with WD-40 and see if that helps a bit.

OK, so i did the driver’s side plug wires…the wires on it said Packard and were numbered…maybe the originals lol…I broke few clamps, which I plan to remedy with zip ties. The problem came in when I got to the passenger side…they run under a plastic encased hose, just outside of the engine oil add place and by transmission fluid dipstick thingy (yes, I know these are girl terms, but you get the idea)…there is another stupid wire clip under there!!! I CANNOT get to it. I tried everything. My hands are bloodied.

My question is: can I just cut the old wires and pull them out of there, then zip tie the new ones? or is there some secret to getting to that thing?

Thanks again for bearing with me. I did start the truck up after doing the one side. It seems to be idling better to me…maybe it’s wishful thinking. Thanks again for the advice y’all!

Go ahead and cut the old wires. I had to do that with the first wire change on my Explorer.