Engine run-on

[steve_D]

On odd occasions my engine will run-on after the ignition is turned off. This is more likely if the revs are up when you switch off.
The MSD6AL instructions recognise this and explain that the alternator is still charging and the small amount of charge feeds back through the ignition light and keeps the MSD alive.
The fix seems to be either a diode or resistor installed somewhere in the system dependant on your make or model of vehicle.

So, on the Ultima, where and what do you install?
Has anybody already done this?
Thanks
Steve

[Ravensbabe]

Steve,

Did you ever get any answer to this query. I suffer from this problem constantly and would like to find the answer also.

[steve_D]

No not yet.
Have it on my list for this weekend to get stuck into the MSD booklet and start experimenting.
Might mean I have to go out on lots of road tests. Yawn, how boring.
Steve

[ultimasimon]

Mine also does this. The solution I had was just to drop the clutch in gear and stall it after turning off the ignition - not very satisfactory.

You turn up in your beautiful machine then sit there like chitty chitty bang bang having an asthsma attack

Only seems to do it when its had a damned good spanking





which is most times

[steve_D]

There is a technical fix ie fitting the supplied diode. It's just not clear where it is fitted in an Ultima configuration.
I'll work it out, eventually.
Steve

[bigmack]

Hi Steve,
I have the MSD 6AL box but do not have this problem and didn't have to install a diode. I think you pinpointed the trouble to the Ignition Light (which I do not run). I would think the diode needs to go near this light. Just a guess. For some reason I thought there was another culprit that would cause this? Not sure..
Cheers!
-Mack

[US-GTR]

Hi Steve,

Has was an issue on a couple of hot-rods I built. A simple solution, place a (large) switch between alternator and the battery (the large main cable). Some Kill switches have this as an option. When you flip the switch it removes the alternator from the electrical system, therefore removing any chance of it continuing to supply power.

On one `rod I added a relay to the ignition switch that controled the Alt.

My 2 cents.

[steve_D]

US-GTR said:

Hi Steve, Has was an issue on a couple of hot-rods I built. A simple solution, place a (large) switch between alternator and the battery (the large main cable). Some Kill switches have this as an option. When you flip the switch it removes the alternator from the electrical system, therefore removing any chance of it continuing to supply power. On one `rod I added a relay to the ignition switch that controled the Alt. My 2 cents.

Our 'better' kill switches over here have a resistor in the circuit when the switch is turned off. My understanding is that if you just switch out the alternator when the engine is still turning over it can blow the alternator. Something about 'back EMF' whatever that is.
Steve

[BliarOut]

I would fit the diode on a pair of flying leads on the feed side to the ignition light. It can go anywhere in that part of the circuit, wherever access is best. Once you are happy it works, make the solution permanent.

Without wishing to teach your granny to suck eggs. Run on, it's not the old over advanced ignition timing thingumy is it?

[Ravensbabe]

Timing is bang on the button but I will try a little retard to see if it has any effect

[bluesatin]

Strange mine never does that. I even hold the revs high so that the Accusump is charged! Are your engines Knight engines?

>> Edited by bluesatin on Friday 20th August 09:37