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Fleetwood
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95 Fleetwood 6door. 120k miles. This car starts & runs great summer and winter. Just will not start in rainy weather. Even if parked in an open garage,(car is too long to fit so I can't shut the roll up garage door) It will not start until the weather clears up. Last winter after a very wet and deep snow it started while in the garage,(after it stopped snowing) I pulled it out of the garage over 6" of wet snow/slush then shut it off to hook up a trailer, went in to eat lunch and it would not start after sitting over the wet snow for about an hour. Pushed it into the garage and it started right up a few days later.

Yes, you can hear the pump in the tank running, it has good fuel pressure, (new fuel pump, sender, new wiring to new harness from engine compartment to tank, new ground to frame near pump connection) New plugs, wires, distributor.

There was one time while driving in heavy rain (started before it started raining) that the engine stalled for a second or two but recovered and went through the rain just fine for the next 1/2 hour. Most of the time I don't take it out if rain is in the forecast so I don't know if this would normally stall while driving in rain. But it is very consistent. If parked in the open garage during a heavy rain, it will not start or even hint at firing. Once things dry up, it starts in a few seconds -always.

I suspect a corroded ground somewhere but really don't know where to look. I'm tired of paying a mechanic to guess at what this might be. (I've taken it to 2 highly recommended) 'm not afraid to get my hands dirty and am fairly mechanically inclined but not good with electronics. Any help out there with this type of issue? Thanks, Duane
 

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2010 DTS
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:welcome:

How old are the ignition wires? I can recall the same problem a few times back in the dark ages. I always carried a can of Permatex DFL (Dries, Free's, Lubricates) in the trunk. It was WD40's older brother. Spraying the wires always got it to start. Worst case, I would even remove the cap and spray inside. If WD40 does the trick, then it might be time for new wires (and maybe distributor cap).
 

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70 Deville 77 Fleet 78 Seville 92 Deville 03 Deville
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At this point I would start to suspect the ECM. If it isn't too hard to get to I would try bringing it in the house and set it next to some heat on a rainy day and see if that helps the situation. 90% of the time it is usually a spark plug wire problem.
 

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2001 DeVille
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411 Posts
Your engine sensor wiring harness is rubbed through and shorting to ground on the voltage side, a corroded ground would do worse when dry. There's probably some corrosion in the spot that easily absorbs moisture and then becomes a conductor. You need to inspect the under hood wiring harness on the back side where it touches everywhere, pay particular attention to any place it is on a sharp edge or it has been mis-routed (i.e. missing or loose fastener letting it hang, put in a bind or wrong spot during servicing, compressed under another part such as the air cleaner, etc.) Also look at any point where engine or suspension movement can cause contact damage. The opti-spark harness runs all over the engine itself, esp. down the front cover. The MAF sensor is particularly susceptible to high humidity because it pulls air through it at a high rate during engine operation.

What I would do is mix up a spray bottle of brine water and set it for a fine stream then start squirting the harness a little at a time near the likely places I mentioned until it suddenly dies or stumbles, based on your description it will die instantly when you find the short. If you vary from this your results will be not as good. Spraying a garden hose will flood the whole place in seconds and you already know it shorts out when wet. Wiggling the harness may or may not find the spot and if it doesn't it will likely knock some of the conduction corrosion off and delay the find unless you see it. Try the squirt bottle full of a conductor first.

Vernon

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Here's a case history file of the same problem with this engine:

Complaint: hard start damp wheather, stalls after 10 min. Tech Notes: test drove vehical and hooked up mastertech scanner. found code 36 in system history but no check engine light. Fuel and ignition test were done everthing checked out ok. the customer had a new distributer put in at another shop. then sprayed engine compartment with water. When we tapped on the MAF sensor the car died and would not restart. found that by wiggleing the wireing harness to the computer we could get the car to run and shut off. found the wireing harness under the are cleaner rubbed on the wheel tub causeing a short to ground. Fix Notes: see technician notes. SPlice in new wires for computer wireing harness.

BTW, LT1 tune-ups are among the most expensive and Opti-spark distributors are notorious for going out the second you get them wet, so the previous shop(s) can't be judged too harshly. Many times you have to get the tune-up straight before you can go further, people rarely understand this.

Vernon
 

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Fleetwood
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Discussion Starter #7
Vernon, Thank you for the well thought out response and research. I seem to recall someone going through the test sequence for the MAF and determining that it was good but everything was done in a warm shop or not likely with any moisture simulation.

This has been an ongoing problem for the past 2-3 years and only recently made the connection to the rain by chance -but seems consistent.

Thanks for the brine water / spray bottle suggestion. Is the salt to water ratio important? May have to wait for warmer weather here as I don't have access to a heated shop and forecast is for highs only in the mid teens for the next few weeks.

With a new distributor, plugs & wires is it likely that there should be any issues in this area?

Will respond as soon as I have a chance to check it out. Regards, Duane Z
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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My grandfather's '95 Caprice wagon (LT1) had a similar issue in wet weather. He never fixed it, just used WD-40 and a hair dryer to get it started. The problem was with the harness to the distributor IIRC.
 

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2001 DeVille
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411 Posts
Thanks for the brine water / spray bottle suggestion. Is the salt to water ratio important?


With a new distributor, plugs & wires is it likely that there should be any issues in this area?
The ratio isn't critical, I've always just mixed in a bit. Two teaspoons in a regulation size spray bottle should work fine. This makes the water very conductive to electricity so any bare wire you hit will cause an immediate reaction from the running engine.

With the new distributor, plugs, and wires not changing or resolving the issue I would concentrate my efforts elsewhere.

The best test for a bad MAF with no codes is to just unplug it and see if the problem goes away or the poor running engine runs better. In absence of a signal the PCM calibrates fuel needs based on the other sensors and programmed expectations. Of course a code will set for low MAF but it's better to have no signal than a good signal that is completely incorrect. I don't suspect the MAF as much as the wiring on it, but if all else fails give the disconnect test a try.

Vernon

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My grandfather's '95 Caprice wagon (LT1) had a similar issue in wet weather. He never fixed it, just used WD-40 and a hair dryer to get it started. The problem was with the harness to the distributor IIRC.
Yes it's going to be the wiring to something critical to engine operation that doesn't set a code if it flat lines such as ignition signal which the PCM sees as an engine stall. Like your grandfathers the case history I posted was from an LT1 Caprice.
 

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Fleetwood
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Discussion Starter #10
The ratio isn't critical, I've always just mixed in a bit. Two teaspoons in a regulation size spray bottle should work fine. This makes the water very conductive to electricity so any bare wire you hit will cause an immediate reaction from the running engine.

With the new distributor, plugs, and wires not changing or resolving the issue I would concentrate my efforts elsewhere.

The best test for a bad MAF with no codes is to just unplug it and see if the problem goes away or the poor running engine runs better. In absence of a signal the PCM calibrates fuel needs based on the other sensors and programmed expectations. Of course a code will set for low MAF but it's better to have no signal than a good signal that is completely incorrect. I don't suspect the MAF as much as the wiring on it, but if all else fails give the disconnect test a try.

Vernon
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Thanks for all the responses -especially Vernon. Will post back when I've tried some of these things. Duane Z
 
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