Plug lead issues

[Hil911]

I have a newish set of the Beru leads and I must say that I have slight issues with them. I was wondering if I am alone.

I think that the problem comes with the EXTREMELY tight fit of the ends onto the distributor cap. It takes serious muscle to force the leads right down. But the fittings on the end really aren't up to serious muscle: the lead is held into the cap with one puny screw.

I lifted the cap on the Bosch distributor to check the cam timing. I was pretty gentle about it. When I put everything back together the engine was terminal. The right head was cold (4-6). After the usual emotional traumas I decided that I had to test the leads. Leads 5 and 6 had infinite resistance from the cap to the end.

So I had to pull the leads out of the cap to check them ...

I have pretty strong hands ... I thought ...

Both failures were in the cap end, and applying titanic force cannot have helped the chances of future reliable performance.

Sorry - I guess that I don't expect you guys to say much. I just needed to let it out!

[sc_rufctr]

I put a very small amount of non conductive grease inside the boots of the leads of all my cars. (both ends)
It's white in color and I get it from electrical hobbyists.

This helps a lot with getting the leads on and off.

[Bill Douglas]

You could do a resistance test from inside the distibrutor cap to where the spark plugs join, to check it's all good.

[Hil911]

Yup - that's what I've been doing.

The problem is that the copper strip connector that forces into the distributor cap connector is held into the cap unit with what looks like the end of a copper carpet tack. When you pull on the lead, the head contacts the tack and all is well. But on one of mine, at least, the tack has a bit of play, so that if you push the lead toward the distributor, it is possible for it to make a poor or zero contact.



I'm seriously considering a drop of solder to fill the gap reliably.


This isn't a great image but I hope that you can see what I mean.

[sp_cs]

I've heard of this recently I think it maybe the bosch cap - problem solved with a Beru cap

[gtrp]

I got a beru cap in just over the weekend... I'll try the grease as I can't push the wires down on it enough to make contact. Wtf.


81' Widebody SC

[Hil911]

I had to go back and do my leads again today. The problem is not just the boot: you can see how mangled the connector has got forcing it into the socket of the Bosch cap. This is plug 5 which seems to be the worst!

In fact it is SO tight that it can't make contact: the copper tabs are forced completely straight from the tip to the end of the exit hole. There is no room for the tabs to spring. And the flat plate has started to pull itself off the connecting pin.

[Hil911]

The story continues.

The engine was still missing - blowing out unburnt fuel and backfiring.

But which cylinder?

Suddenly I had a Duh! moment. Use the timing gun. I should be able to see the pulse in any lead. Long story short: no pulse on cylinder 2. It was 5 and 6 with bad connections before!

Tested resistance distributor cap to plug in #2 lead: same as the good ones: about 4.05 KOhm. Obviously loose, so I pulled it out and fixed it.

Ran engine - no pulse! The lead is good and the connections are good but no pulse! Distributor cap is new and good.

Hello ... moved Pertronix sensor closer to rotor. Now a VERY irregular pulse on cylinder 2.

I have new leads in a new cap that don't work AND a Pertronix unit with one magnet in the rotor that is too weak to trigger a pulse. I won't buy a lottery ticket this week.

[Hil911]

OK - the weirdness continues.

I rotated the Pertronix magnetic rotor 1/6th of a turn on the distributor rotor. If it is the problem then the bad cylinder should change. It didn't. So the problem is NOT the Pertronix.

I got an old Beru lead and swapped it onto the plug and the distributor. It also does not pulse properly.

I checked and double checked the distributor cap, which is essentially new. It looks perfect and has zero resistance across it. The segment isn't bent or misplaced.

I don't want to swap out the cap - it'll be a nightmare and I'll end up with broken leads.

Sitting here, I suddenly wonder what the timing gun is telling me? Is it telling me that there is no pulse going to the lead OR is it telling me that there is no pulse going THROUGH the lead to create an inductive response? Maybe I'm at the wrong end. Perhaps the spark cannot jump the plug due to fouling?

[Hil911]

I took out plug 2 and cleaned it. Crappy, but I've seen worse. Resistance was about 4.5 KOhm which surprised me. So I took out number 1 and it was the same.

Cleaned plug one as well and put them back swapped over.

They now both show a reasonably regular firing pattern. There seems to be the very occasional missed beat at idle.

So - a timing gun shows you whether it should be sparking. Missed pulses can come from anywhere in the distributor cap through plug system. A pulse shows that electricity flowed right through the lead where tested.

[Robbbyg]

have to answer this post for two Reasons

First if it helps you i don't know but i was having starting issues and gremlins,
I dont remember where i got this mod but it def helped my starting and rough idling

drill holes in the distributer cap, about 1/8 of an inch in diameter, evenly spaced.
IT mostly helps with relieving cap of any condensation thereby keeping innards dry and better to spark. in case its an issue with yours its worth a shot ,

If you do it, drill slowly as to not crack it, , also dont drill too low either, i cant remember why i drilled it this particular way but there was a good reason and i remember trying different ways,
This was what i ended up with and shes been starting on half a crank ever since

Aaannnnd secondly

This is my 1000th Post WOOHOO !!

[Hil911]

Congrats Robbbyg!

Thanks for the advice.