dampness and 89' GM 5.0L won't start

[formulabird428]

Kind of an interesting problem...

Whenever it's damp out, my 89' GM 5.0L will not start. It will crank and 1 or 2 cylinders may fire. But, the majority will not fire and it just won't start.

Last year this happened, and I put a heater pointing at the throttle body/distributor and it started up perfect after being warmed up for about 2 hours.

Today, I just cranked on it every 10 minutes for about 1 hour...and then it finally fired (running really rough) and eventually evened out and was fine. As it was running, I noticed that the plugs at the distributor cap were arcing with the moisture on top of the wires. Maybe this is the problem? Current transferred to the outside of the wires instead of down to the plug?

Anyone ever have this problem? Would a generous helping of dielectric grease help out?

My other thought is that the cylinders are soaked inside with moisture/water and the is putting the plug out...similar to a very bad wet foul. You could see the block, valve covers, and all the wiring just dripping with water.

[marquisman]

have you done a tune up? rotor/ cap, plug wires and spark plugs should be replaced. if your wires are old or your dissy cap is cracked, the dampness alows the high electrical current to jump everywhere which means the spark plugs wont fire. when its damp out and in pitch dark, while cranking over the engine, you will be able to see the arc from the coil jumping to its closest ground.

[formulabird428]

That's the odd thing. They were all replaced within the last 3 months.

I could see the plugs arcing today...but it was to themselves (on top of the distributor cap).

[marquisman]

the cap and wires? what brand of stuff you got on there?

[sly]

the connector to the engine computer, between the brake booster and fender, good and tight? Connector to the TFI (ignition) module on the distributor goof and tight? wire harnesses along the driver side fender all secured? Sounds like a loose wire somewhere (cracky insulation causing resistive shorts/voltage drops).

[GM_Guy]

That's the odd thing. They were all replaced within the last 3 months.

I could see the plugs arcing today...but it was to themselves (on top of the distributor cap).

Sounds to me like you will be replacing all of it again. Including the plugs.

With regards to plugs: check their packaging for signs of being dropped. If any packaging shows damage, get another package. Porcelain has a tendency to crack when dropped, and that = more arcing. When you install them, make sure you don't cock the plug in the socket. If you do, it cracks, throw that plug away. If you need to force the socket over the plug when you remove it, and you hear a pop or crackle, guess what, it cracked, throw that plug away.

Alex.

[formulabird428]

the cap and wires? what brand of stuff you got on there?

I do have the cheap stuff for cap and wires. But this problem was existing last year well before I put the new "cheap" stuff on. I replaced the old stuff because I thought they were the problem. Maybe "quality-old" stuff = "cheap-new" stuff...

the connector to the engine computer, between the brake booster and fender, good and tight? Connector to the TFI (ignition) module on the distributor goof and tight? wire harnesses along the driver side fender all secured? Sounds like a loose wire somewhere (cracky insulation causing resistive shorts/voltage drops).

I'll check the connections.

Sounds to me like you will be replacing all of it again. Including the plugs.

With regards to plugs: check their packaging for signs of being dropped. If any packaging shows damage, get another package. Porcelain has a tendency to crack when dropped, and that = more arcing. When you install them, make sure you don't cock the plug in the socket. If you do, it cracks, throw that plug away. If you need to force the socket over the plug when you remove it, and you hear a pop or crackle, guess what, it cracked, throw that plug away.

Alex.

Looks like I will be, unless I find the connections are bad.

[gadget73]

Every time I've had dampness problems with one of these its been bad wires or a cracked distributor cap. Might want to unplug the TFI module and make sure that isn't damp in the plug.