I replaced my spark plugs and wiring not long ago, and I noticed that one of the spark plug wires felt a bit loose. Apparently the little metal tip that screws onto the end of the plug had vibrated loose. I screwed it down, and a few days later it's loose again. I am worried the thing is going to come off completely.

I bought the plugs and wires from my Volvo dealer for my 740 Turbo so they are the right ones for a b230ft engine.

How do I keep the little tips from comming unscrewed ?
Or
Which spark plugs have tips that are secured ,i.e. don't unscrew ?


By the way, this is not the spark end, the other end.

I had the same with some bosch plugs. Remove the plugs and tighten the thingy with a pair of pliers. I think NKG's come as one unit.

That's highly unusual, but you might try a little Loctite on the threads. Not too much so you don't spoil conductivity.

All the plugs I have used have screw on tips. If you only tightened them finger-tight try using a pair of pliers to nip them up a bit firmer. I haven't found them to come loose that way. Don't tighten them too much though or you could damage the conductor down the centre of the plug and crack the ceramic shell.

I don't think they would come off completely since that would require the plug lead to turn round a number of times as well. Obviously it would not be willing to do that as it is attached at the other end!

Good luck

OK I will try to put them down a bit tighter, and see what happens. I did not think they could unscrew because of the wires having to turn, but it looks like they are spinning inside the wire without the wire having to turn. I have never run into this before. It's kind of odd. It did it on 3 of them.

I think it is odd in the first place that your wires require the screw-on cap at all. In all my years of owning Volvos I have never seen that -- the wire always click onto the threaded post.

On our #2 snowmobile at the Ski Patrol this weekend, one machine would not stay running. My inspection revealed one of the two plugs had its cap stuck inside the plug wire boot. And the threaded post of the plug itself was stripped smooth!

Vibration maybe did it?
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1989 740Ti 1986 240DL 1984 244GL

Be sure that the plug leads are gripping the plug tops firmly.
You should feel them lock on as you push them down onto the plugs.

If they don't fit on firmly tighten them up a bit by clenching the metal ends within the lead boots with a pair of pliers. You will need to do this through the boots in most cases.

The boot must be off the spark plug when you crimp it. Just a clarification.
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-- Bruce / '82 244 (315k miles!), '86 745, '87 760Ti, '94 854