Checking Spark Plug Wires
 

Hi All,

All of a sudden after a nasty rain yesterday my 1980 450 SL started running like it was missing.
It was running like that today too.
What is my best way of checking each wire on the car to make sure that is or is not the problem?
Can it be something else?

Thanks
Jack
1980 450 SL
1989 560 SEC (just died, temporarily)

I've used Champion high tention lead testers. Ohm meters work real well too. Go out at night when it is dark, look and listen use a transistor radio or walkie talkie off frequency can pick up the tick tick (electrical leak) too. My expirence with wires have always turned out to be the spark plug cigerette ends. But the distributor rotor and cap will give almost the same miss.

450 sl missing Checking of Spark Plug Wires
 

So,

I should check the continuity of the wires from cap to plug side?
I haven't changed the cap and rotor.

Thanks
Jack

It sounds to me like your plug wire insulation has broken down. You might have continuity from end to end but if the insulation has broken down there will be a short to ground and the engine will miss. The clue here is rain. From my experience, moisture will cause marginal plug wire insulation to breakdown. Open the hood at night and you will be amazed at the light show when the wires are bad.

Spark plug wires
 

Kimo,

I do not see any sparks under the hood at night.

Jack
1980 450 SL

Spark plug wires
 

I decided to just change them after I saw rust under the screws on the cap & wires.

Jack