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'Blade plug caps
andrew.carwithen - 2/4/07 at 04:53 PM

I'm in process of wiring in engine and while replacing HT leads with longer ones, thought I'd check coils primary and secondary resistances to make sure coils are ok.
Primaries (LT side) were fine but secondaries (HT side) were not (opencircuit.)
On further investigation, looks like the plug caps themselves are U/S (with caps removed and connecting multimeter direct to ends of HT leads, resistance range falls within specs but caps are open circuit when meter connected across them direct.) Is this a common problem (i.e. are they that fragile?) and are there alternative aftermarket plug caps that anyone can recommend? (Which are SVA friendly?)

Cheers,
Andy.

Nick Skidmore - 2/4/07 at 05:16 PM

I used an NGK jet ski plug cap (quite long and waterproof) that you can get from M+P and then a soft rubber dirt cap from Magnecor.

The dirt caps are VW Beetle / Porsche type when you ring Magnecor.

ReMan - 2/4/07 at 08:31 PM

How much open circuit? All four??
Are you sure they dont have a resistance perhaps 10k ohms?
Again the secondaries should be about 10-20k ohms, are you sure your meter has'nt got a low battery?

andrew.carwithen - 2/4/07 at 10:02 PM

quote:
Originally posted by ReMan
How much open circuit? All four??
Are you sure they dont have a resistance perhaps 10k ohms?
Again the secondaries should be about 10-20k ohms, are you sure your meter has'nt got a low battery?


I thought that it may have been a duff meter battery, but was still the same after replacing with a new one. I think its 2 out of the four caps that are U/S.
I'm hoping to be able to turn over/start the engine in a few days time and so will check for spark then before condemning the caps.

Andy.

ReMan - 2/4/07 at 10:07 PM

I thought they were quite robust actually.
A problem I had originally with mine not starting was that the HT lead was not pushed into the cap far enough to reach the spike. You're not measuring fom the coil end of the HT lead to the plug clip are you?

andrew.carwithen - 2/4/07 at 10:35 PM

quote:
Originally posted by ReMan
I thought they were quite robust actually.
A problem I had originally with mine not starting was that the HT lead was not pushed into the cap far enough to reach the spike...


I connected one probe of the ohmmeter to one plug cap and the other probe to the other cap of same coil. When I got an open circuit reading, I thought, perhaps it was because one or both HT leads hadn't made contact with the caps.
So I removed one cap and pushed that probe direct into the HT lead. Got a reading of 20K. However, to ascertain whether it was down to a poor contact or duff cap, I used the ohmmeter to measure the resistance of the cap and it was effectively reading 'open circuit' on the highest range of my meter. (I don't have a 'megger' to find the true resistance of the cap, but it is well outside the accepted specs.)

Andy.