Rev Counter crazy after new HT leads

[Andy Graham]

Finally treated the Chim to some new 10mm HT Leads after I saw a topic here last week about ht leads on ebay.Car is now flying...maybe even quicker than these fast blue ones I've heard so much about Only problem is now the rev counter is bouncing all over the place.Where have I gone wrong??? I did raplace dizzy cap and rotor at the same time, and have tried going back to original coil to dizzy lead,but still got a hyperactive rev counter...any ideas out there??

[greenv8s]

The combination of non-resistive plugs, non-resistive plug extenders and non-resistive leads may have increased the inductive kick from the coil to the extent that it is interfering with the tacho pulse detection. I suggest you fit resistive versions of one of the above components and see if the problem goes away.

[hugepiece]

i've also got this issue, have replaced leads/coil/dizzy cap/rotor arm/ign amplifier - still does it. I assume you have made sure that the king lead is not close to the low tension leads?? I have been told that this could be an alternator issue, that's the next thing on my list to try.

[pete1]

I have had this exact problem,

Changed plugs, dizzy etc. and the rev counter bounced all over the place. Took forever to fix as i un-replaced everything in turn.

I eventually fixed the problem by replacing my brand new expensive King lead with a cheap halfords one that is actually far to long but it works.

Also if you loosen the king lead so it is just sitting on the coil not firmly connected this may fix the problem, not a long term fix i know but usefull for diagnosing that the problem is the king lead.

I am not sure what the root cause is but change the king lead for about £4.00 it is a VFM solution.

hope this helps

Pete

[greenv8s]

The original leads are resistive but for example Magnecor ones aren't. The original plug extenders are resistive, but some of the aftermarket ones aren't. The plugs themselves are not resistive. If you have no resistive components anywhere, then adding any resistance at all can make a big difference.

[Andy Graham]

Thanks for your replies guys....I did try swapping back to the original lead dizzy to coil,but same effect, also tried routing leads differently, still joy. Thanks GreenV8S, will see if i still have old plug extenders floating around the garage from a couple of years ago, might prove a point.Always the same with a TVR...one step forward....two back