14 replies to this topic

[Scorp]

Hello i'm having an issue with my minis tacho going crazy (up/down/everywhere) when the car revs over around 4000rpm under load. If I try to drive fast on the motorway at about 70-75 the engine will start juddering and the tacho is going crazy. Any ideas what this might be? Failing coil/bad engine timings??

 

Thanks

[Stevie W]

Hi Scorp,

 

It does sound ingition related as you state. Are you running points/condenser or electronic ignition? 

Either way, the fact that your tacho is bouncing wildly, does suggest the iginition is misbehaving.

I had the same problem as you at the same engine speed, and that turned out to be the coil, Where it was mounted in it's bracket, the body of the coil had been damaged and was causing a short and therefore erratic ignition.

So check everything ignition related...

 

Cheers, Steve.

[KernowCooper]

Tacho indicates low tension ignition problems so check the coil wiring and points and condenser if your not on electronic, could be a internal tacho fault if the others checks prove to be ok just disconnect the tacho feed off the coil to test

[cal844]

Try tightening the coil connectors a little

[Scorp]

Thank you for the replies - its running electronic ignition

 

I will go and check the coil wiring now I may have a spare coil if i am lucky

[Stevie W]

Electronic ignition will give you wild tacho readings if the ignition amplifier output (that drives the low tension side of the coil) is on it's way out..

 

Cheers, Steve.

[cal844]

Electronic ignition will give you wild tacho readings if the ignition amplifier output (that drives the low tension side of the coil) is on it's way out..

 

Cheers, Steve.

Start with the free things first( if swapping a coil remember to first check the resistance!)

[Scorp]

Update: I've swapped the to a different coil and it made no difference.

 

When I put my foot to the floor in 2nd, it will get to nearly 4000rpm and the engine will misfire (tacho also going crazy) and eventually the engine started popping with smoke coming out the back!

 

So the 2 issues are backfiring and crazy tacho at high rpm

 

Getting a little nervous now as L2B is 2 weeks away.

 

All help appreciated!

 

Scorp

[dklawson]

As suggested earlier by others, the ignition module may be failing.  The misfire is probably causing the backfiring you are hearing.

 

You said you swapped coils and it made no difference. Are you running a factory electronic ignition or an aftermarket kit?  The aftermarket kits can be made to work with just about any coil when wired properly.  The factory electronic ignition requires the GCL143 coil (or equivalent) and cannot use standard or ballast coils.  Early failure of the factory ignition module can happen when the wrong coil is used.

 

If you are using an aftermarket electronic ignition, temporarily refit the points and condenser.  If the problem goes away you have reason to believe failure of the aftermarket ignition module.

[Scorp]

Hello dklawson,

 

The mini is a 1995 spi which has been converted to carbs. its running an "A+ electronic distributor kit" and a non ballast lucas coil - i will check which coil it is. 

.

Edited by Scorp, 30 April 2015 - 10:40 PM.

[dklawson]

its running an "A+ electronic distributor kit" .

 

That suggests a complete "non-factory" distributor with ignition module installed.  Is that correct?  If the distributor is based on a model that can use points, I would still consider fitting them  temporarily to troubleshoot this problem.

[Scorp]

When I advanced the timings the problem became a bit better but not fixed. Does this mean anything? Thanks

[dklawson]

Which problem got better the general running of the engine or the tach bouncing?  If the tach is still bouncing you have an issue with the low-tension side of the ignition system.

[Scorp]

It can rev higher before the tach starts bouncing. Unfortunately I don't have any points and condensers so I guess I will just try my luck and swap as many parts over as possible and then take the hit on purchasing a new module. 

[dklawson]

You still have not confirmed if this is a factory or aftermarket ignition.  It sounds like you have a generic aftermarket distributor but I'd like to know for sure.  Here's the deal.

 

With the factory electronic ignition you need to use the factory electronic ignition coil.  Fail to do so and the ignition module will eventually fail.  When addressing that situation you need to replace both the module and the coil once problems have surfaced.

 

Many aftermarket electronic ignitions (and aftermarket distributors) use a Hall Effect sensor mounted on the breaker plate of an otherwise "standard" distributor.  If you know the distributor type you can buy points and condenser to fit and run the distributor that way as a test.  Points and condensers as a test are much less expensive than replacing electronic modules and coils.