Fault with rev counter – could it be the electronic ignition?

[Europa73]

Hi all,

Just doing some fault chasing with the new toy!

The car was fitted with a lumenition ignition.

The Rev counter is original and not working – could this be an issue with the electronic ignition?

Do I need to change the wiring configuration to the rev counter with the lumenition in place.

Many thanks,

[BDA]

My motor came with an Allison optical ignition (late '70s vintage). The tach was not happy with it. It caused it to bounce pretty erratically above 3000 rpm or so. One day it quit on me in the left lane of the Interstate so I replaced it with a Pertronix unit. The tach is MUCH happier now. The needle is very stable now. Given the age, I think that my ignition was probably using an incandescent bulb and I suspect that the bulb burnt out. Lumenition is not Allison and yours may be newer and may be using an LED which should be very reliable but given my unsatisfactory experience with my optical ignition, I would shy away from them. Now that my tach works, I am really high on Pertronix! Note that if you decide to switch to Pertronix, you need to use resistor wires or plug connectors.

Somebody here mentioned a mod of some kind for the tach (I think to use with a Pertronix!). I am using the stock ignition wiring (other than the fact that I have added an electronic rev limiter and electronic electric fuel pump shut off (I don't think either of these has any effect on the operation of the tach and the ignition) and I have hooked up the tach exactly like as it was originally. I can't explain why I have no problem with Pertronix and my tach as some have.

You have a couple of options:
1. Search this forum and the lotuseuropa yahoo group (you should join that too) to see if there are any mods that might fix your problem and try it.

3. You could have your tach checked out. Since it sounds like you've never seen it working - it may be busted. The place that checks it out may have suggestions on how to make your tach and Lumenition play nice together.

3. Replace the Lumenition with a Pertronix ignition and see what happens. If it doesn't help, try mods that others have used for Pertronix ignitions. If that doesn't help, try #2 (for Pertronix).

I hope that helps!

[Europa73]

thanks for the advice - much appreciated!

[EuropaTC]

Most of the faults I've heard about with tach & electronic ignition have been of the "needle jumps about" variety rather than "it doesn't work".  Of course that doesn't mean your non-working tach is down to the Lumention but before I'd blame the ignition I'd check out the wiring, power supply & earthing of the tach first. It might just be a dirty contact somewhere.

If all looks ok I would be tempted to re-fit CB points to see if it springs into life. The original instrument in my car packed in and I replaced with a new Lotus one sometime in the 80s I think, so a dead tachometer on standard ignition is quite possible.

[buzzer]

First I'd check if the needle is physically stuck. If its not been used for a while it may just need a tap. Mine didn't work until I gave it a tap. I am running on points purely to make sure everything works as std, then to install the electronic ignition.
On the jumping about, which is a very common issue (not just on the smiths gauges), there are some fixes that work. on my Westfield (VDO instruments) I installed a resistor in series with the pickup to smooth out the signal. But the wiring route for the Lotus rev counter is a bit different. I am sure i have read on the forum somewhere about fixes people have used.

dave

[blasterdad]

Someone on my MG forum had the same problem, (same tach).
Turned out the wires weren't hooked up on the back of it...
I always check the connections first then go from there.

[TCS4605R]

I have a Lumenition system on my 74 TCS and have never had any problems with tach function.  Check the wiring at the tach and distributor.

Tom

[Europa73]

thanks to all -


Will let you know how it goes