Hot ignition module after engine stall

[MobBarley]

Hi all, I posted this on MSEFI but thought that someone here might also be able to help me..

I am working on MSII'ing an E30 bmw and trying to get MSII (ver 2.68 ) running for the first time with ignition (direct coil control) and having problems with the VB921 IC intermittently getting hot.

On the first run a VB921 was destroyed due to spark output not being set to inverted, this was replaced and the engine will now start and run. When trying to configure baseline settings (Warmup etc), I have noticed that the VB921 will sometimes get very hot (constantly conducting?) after the engine has stalled. I have been wary of this and cut the ignition as soon as this occurs to try to prevent damage. When the IC has cooled and ignition is reconnected it appears to function normally and does not get hot.

I am running a low dwell setting of 1.8, have disabled battery voltage compensations.

Can anyone provide tips on what could be causing this? I'm going to try updating to the latest firmware today and reconfigure everything.. any advice would be greatly appreciated.. :???:

[JohnMc]

On my car (MS'ed LH 2.4 '93 Volvo) the ignition module does the dwell control, so I don't need MS to do it. So I have it set to fixed dwell, 75% duty cycle.

Also, are you using the stock coil for that ignition system? Maybe some new coil is drawing too much current?

[MobBarley]

Hi John, its stock coil which is functioning correctly (have a couple of them). I have looked into the modules but that is a last resort as I would probably have to go pull one from somewhere and I have just bought a couple of the vb921's. The problem only appears to happen after the engine has stalled (and not every time, maybe 25%?). When the ignition has just been turned on or when engine is running the IC does not get hot at all.

[MobBarley]

also when it gets jammed on after a stall, cycling the ignition stops the problem.

[malloy1]

You may want to list what you have running in your car? Is this a stock setup with MS running it all?

I've heard if the spark inverted is set wrong, it will heat up your ignition modular.

Paul

[the poi]

post about this on msextra? the vb921 is running on so many cars, you should be able to get "confirmed" settings for everything, which would leave your troubleshooting a lot narrower. Off the top of my head, I think running dwell on the 921 is like 6ms, so if you need 1.8 to keep em froom getting hot, something weirds goin on

[MrBill]

i actually burned my vb921 module playing with dwell on my direct coil control and ended up going with a mallory hi-fire so I never had to touch dwell again

[MobBarley]

FYI. updating the firmware fixes the problem!