Why Do My Plug Wires Keep Popping Off?

Discussion in 'Classic Mustang Specific Tech' started by eleanor_350, Apr 18, 2005.

  1. Has anyone had trouble with their plug wires popping off the spark plugs by themselves?

    I have a set of 9mm Ford Racing wires on my 351w that keep popping off while the engine is running. Usually, I just find one wire at a time that has come off. But, yesterday I was letting it warm up in the driveway and I raised the hood to find three wires had come loose.

    Could the heat from the headers make them pop off?

    Should I try crimping the plug wire ends so they clamp the plug a little better?
  2. I would not suggest crimping the wires because that might lead to a new set of wires if you mess up. Are you sure you have the right spark plugs and wires? Also do you press them on hard enough so they click into place? Sometimes I don't realize that I have to push really hard to get those suckers on.

  3. I don't know why it happens but it happens to me on occasion as well, to the point where I almost routinely pop the hood and double check each wire is on all the way before I leave. :shrug:
  4. That's a possibility, I guess. This is in a 65, so a few of the plugs are tough to get to. I be sure they are all pushed on really good.

    Whatever the cause, the wire doesn't just come lose. Something is causing the wire to come completely off the plug. I watched one literally "pop" off the plug yesterday while it was idling.
  5. Are the plugs snug and tight in the heads? If they were loose could this cause vibration and exhaust gas escape leading to the plug wires working themselves loose. Are the wires supported close to the plugs in some form of loom? I'm sure this would help.
  6. All I can say is I have to have my plugs well lubed with dialectric grease so that I can even get them off the next time I need to, I'm usually afraid to split the boot they fit so snug. I have never ever seen one pop off before like that but something is not right at all. You are positive you have the right wires or plugs? Do they feel the same as the fit on the other end of the distributor? Adding a wire loom on the tab of your valve cover may aid in keeping them put, but I have a feeling something is not as it should be.
  7. Mine don't fit that tight. The plugs I have are nothing special, just Motorcraft spark plugs from the parts store. I have Ford Racing wires that I bought from Summit (around $40-$50 for the set). I'm pretty sure they're 9mm. I'm running the later model large-diameter distributor cap. I havn't had any trouble with them coming off the dist. cap. Actually, they've been on the car since last July and I'm just now having this trouble with the plugs.
  8. Check to see if your spark plugs, not wires, have come loose. Then use diaelectric grease inside all of the wires. This not only eases installation and removal, but seals the wire to the spark plug. I could be wrong but I think your spark plugs may have worked loose and the compression is blowing the wires off.
  9. i had an f-150 with a 4.6 and it kept popping a single plug wire. turned out to be the spark plug. it either had a crack, didn't seat right or whatnot. once i replaced it everything was fine.
  10. Did someone tell you the old "racers trick" of drilling tiny holes down the center of your plugs??


    Sorry that was lame.