Is it really just a bad plug wire?

[porschefool]

Hey gang,
I had a sudden "Running like crap" situation with my 79SC.
Figured it had been awhile since I checked the plugs, so I pulled/replaced them. #3 cyl (I think, driver's side/front cyl) plug was wet with gas. Replaced everything, fired it up, and still the same thing. Thinking that was the problem cylinder, I pulled the plug wire from the cap, and it ran the same. Aha...
Did that wire just "go bad"? No other recent work, nothing changed.
Anything else to check for? JW said the wires were getting pretty old, so I'm really hoping that's all.

1. What's an easy wire test? Can I just do a continuity test, or maybe use the old plug touching the block to check for spark?
I'm hesitant to even crank it like that, thinking of unburned fuel giving my non-popoff airbox a nice wakeup call when combustion makes its triumphant return..

Cap/rotor pretty new. 196k.

Thanks for any tips!
Eric

[old man neri]

Originally Posted by porschefool

1. What's an easy wire test? Can I just do a continuity test,

Get a volt meter and check the resistance across the wire. I forget what the spec is though. Move the wire around a bit when you are doing it to make sure it is consistent.

[Eagledriver]

SC plug wires have around 1k to 3k ohm resistance depending on which ends you have. When they go bad the resistance jumps to 10k or more.

-Andy

[jonbot]

What about using another one of the known good plug wires and see if that cylinder starts working again?

[3.2 CAB]

Also, a bad plug wire can show to be "open" with a test meter. There should be continuity, and it should be in the proper resistance range.

[billybek]

The nice thing about testing plug wires is that you have 6 of them to compare the results from.

3 k ohm is what you should be looking for..

[porschefool]

Ahh, screw it. I think those were all on their last leg, so I've got a set coming from our host.
Will post results...
Thanks for all your input.

[911pcars]

Originally Posted by porschefool

Ahh, screw it. I think those were all on their last leg, so I've got a set coming from our host.
Will post results...
Thanks for all your input.

Let's hope it isn't a leaking fuel injector. Once a spark plug is wet, it doesn't like to fire. Don't get in the habit of diagnosing by credit card. It can become expensive.

Sherwood

[porschefool]

Originally Posted by 911pcars

Let's hope it isn't a leaking fuel injector. Once a spark plug is wet, it doesn't like to fire. Don't get in the habit of diagnosing by credit card. It can become expensive.

Sherwood

I hear ya, but this is such a baseline item that I'd like to just address it and eliminate it as the cause. Besides, I haven't spent any money on her for months!
Wires show up today, will report back tonight.

[porschefool]

Solved. It was indeed a leaky injector, dribbling enough at idle to wet the plug and prevent firing.
No big deal, and the new red Clewitt wires are an early Christmas present!
Got to go to Aker's shop here in Seattle for the first time, what a lineup of 356s.
Charged way more than our host for an injector, but I had it 4 hours later, so...