no spark on 1 or 5 when running

[mattszcar]

so when the car is running and i unplug num.1 spark plug wire . Thecar actually runs a little smoother because the num. 5 spark plug starts firing. The same thing happens when all are connected and i unplug num 5.The car starts running smoother because the num. 1 spark plug starts firing.. so basically when all wires are connected 1 and 5 arent getting spark UNLESS you pull one or the other.. all other spark plugs are firing normally. Please help i am moving duty stations in 2 days i need to figure this thing out..

[EuroDat]

Are you sure its not firing? Have you checked for spark by holding a spark plug against the engine to see if its sparking correctly? A timing light could also check for spark pulses.

It could be cross firing. 1 and 5 are next to each other in the distributer cap. Tha cap may be cracked and have carbon tracking between the two. Cracks can be hard to see. That could cause 1 and 5 to fire at the same time and when you do your test its giving confusing results.

If you have a multi meter, you may be able to detect carbon tracking by removing the HT leads from the cap and measuring the resistance between all the poles. See if 1 to 5 is different from the others. Note the position of the leads before you remove them. Its easy to switch them and mess the firing order up.

If it looks old, investing in a new distributor cap at this point probably be a good move, wouldn't hurt.

Chas

[mattszcar]

Thank for the idea Im going to change the cap today just to see. So Yes as I was going thru the process of elimination I pulled 1 and 5 laid them on the engine and sure enough I was getting spark. When i realized that both number 1 and number 5 disconnected made the car run better. While the engine was running I pulled 1, the car ran better then i pulled 5, and it ran worse with both of them disconnected. So, when i went to put 1 back on as i was getting close to the spark plug i could here and see it sparking. I thought that was odd so I left 1 off again and put 5 back on and the same thing happened with 1 disconnected i could here and see it sparking as i put the wire on the plug. End conclusion is 1 and 5 won't spark when the engine is running if both are connected. But they will spark if one or the other is disconnected... Its like there grounded out when both are connected at the same time. This is the confusing part for me. The cap i not even a year old as i got the got last winter and it hadnt been running for some time the first thing I did was replace the cap the rotor and the wires and spark plugs.