No Start condensation problem in a 3.2 after rain - is there a fix?

[mthomas58]

Post on subject by John Walker:

rough run on a 3.2 after a rain storm is generally condensation in the distributor cap. seems to affect 3.2s more than the rest.
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Porsche 911 Service | Parts | Performance | John Walker's Workshop, Seattle, WA 206 789 6800
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I have this problem frequently. After a rain - if engine is hot, condensation builds in the engine compartment and dizzy cap and engine won't start. I now keep a wet engine starter kit in the car (WD 40 screwdriver to remove cap and paper towels). This does the trick every time but a major PITA - especially if its raining. Heavy rain on a cold engine - never a problem.

Has anyone come up with a fix for this problem? If the cap were sealed (perhaps a large O-Ring at the mating surface of the dizzy and cap) would that work or might condensation still build of from temp changes and not be able to vent?

[Tippy]

From my understanding, the environment inside a cap/dizzy is important if I'm not mistaking. Not sure about sealing cap with o-ring and using a vent, but putting a boot around the cap may work.

The fox body Mustangs from the 80's used them.

[wwest]

Spark not HOT enough or slow risetime..?

Also be sure the cap doesn't have a virtually invisible crack.

Metal braid wrapped HV wires can result in slow risetime.

And make sure you're using the correct rotor, a tad too short and...

[rusnak]

Wd 40 leaves a residue. I would replace the cap.

[Lorenfb]

"rough run on a 3.2 after a rain storm is generally condensation in the distributor cap. seems to affect 3.2s more than the rest."

Correct. It is because of the design of the distributor cap with an internal metal shield that
causes the problem. Moisture/condensation in the cap causes a high voltage breakdown
between the center contact and the shield. On my 3.2, I've used H.V. clear sealer spray to prevent
moisture from entering.

Or remove the shield from the cap!

[stlrj]

Originally Posted by mthomas58

Has anyone come up with a fix for this problem? If the cap were sealed (perhaps a large O-Ring at the mating surface of the dizzy and cap) would that work or might condensation still build of from temp changes and not be able to vent?

Most of the water seeps into the distributor where the cap mates with the distributor due to capillary action. I use RTV Gasket Maker, 3.5 Oz Ultra Gray # 82194 by Permatex which helps. The terminal boots at the cap and plug connectors are also notorious for wicking moisture and causing shorts and they need to be sealed as well.

Extreme wet performance test and with plugs gapped at 0.060":


Any questions?


Joe

[Lorenfb]

"Most of the water seeps into the distributor where the cap mates with the distributor due to capillary action."

Not really!

[Tippy]

Loren, if you were to seal the cap, don't you need ventilation of some kind?

[Lorenfb]

"if you were to seal the cap, don't you need ventilation of some kind?"

The cap doesn't to begin with. The void between the shield and the cap is the problem.

[stlrj]

Originally Posted by Lorenfb

"if you were to seal the cap, don't you need ventilation of some kind?"

The cap doesn't to begin with. The void between the shield and the cap is the problem.

I'm not using a shield in my experiment (too many voids to deal with), so the void is as I mentioned: between the cap and dizzy. In either case, any void needs attention due to capillary action.

Surface Tension


Cheers,

Joe