Cannot stop engine once running

dh154 · Post by **dh154** » Mon Mar 27, 2006 5:42 am

Hello all, I would really appreciate some help in tracking down a problem with my brothers ford capri. I have installed an MS-1 ecu with MSnS-E code (version 024s9) and everything works very well apart from the fact that I can't turn the engine off once it is running.

I have used a voltmeter to measure the voltage at the ignition feed (which activates the main relay / fuel pump relay). When the engine is not running, this terminal goes between 0v to 12v. However, if the engine is running and the key is turned back to the 'off' position, the terminal gives 3v, which is enough to keep the relays switched on, hence the engine keeps running.

I thought that this may be caused by a faulty alternator, so I removed the fan belt (to avoid damage to the rectifier inside the alternator) and then tried the engine. It works perfectly with no alternator (it switches off immediately) so I went and bought another alternator. I have just tried the new alternator (and refitted fan belt) and the problem is still there.

What could cause this 3v input to the ignition circuit? The Capri is a 1980's model so relatively new compared with my 1969 Hillman Imp which I have also converted successfully so perhaps there is something in the loom which my Imp doesn't have?

I would appreciate any advice,
David

EstateAgent · Post by **EstateAgent** » Mon Mar 27, 2006 5:57 am

Assuming its powered off the same circuit as the coil.

Then perhaps the ignition switch or relay is worn? Or a stray strand of wire is bridging somewhere?

The alternator should be wired direct to the battery, make sure the alternator or engine block is well grounded as should the battery - poor grounding of the block does some weird things! The alternator shouldn't affect the ignition circuit faulty or not though - usually the charge/battery warning light is wired via the lighting circuit on most Fords i've seen.

dh154 · Post by **dh154** » Mon Mar 27, 2006 6:54 am

Thanks for those tips EstateAgent, thankfully it now seems that i have solved the problem. It seemed that current was being leaked back into the ignition circuitry from the alternator (only when running). The only link between the ignition supply and the alternator is the charge warning light. Therefore, I have put a diode in series with the warning light which stops the small feedback current from entering the ignition side of the wiring loom.
Hope this helps someone else in the same position in the future... I can only assume that my Hillman Imp has an different make of alternator (Lucas instead of Bosch) which already has this diode built in.
Cheers,
David

dh154 · Post by **dh154** » Mon Mar 27, 2006 7:01 am

I have just realised why my Imp does not have this problem: I replaced the warning lights on the dashboard with LED's, so they will prevent the feedback from the alternator.

I just wonder why is this problem is seemingly uncommon? I made the loom as suggested in the Megasquirt documentation. Very strange!

David

hudsonhawk · Post by **hudsonhawk** » Mon Mar 27, 2006 7:28 am

Not uncommon at all. I had the exact same problem on my Jeep the first tiem I started it. Once I realized what was happening I did the exact same fix you did.

bleoh · Post by **bleoh** » Mon Mar 27, 2006 8:37 am

Same here with my old jeep. My powermaster alt can be run as a one wire self exciting alt, so I am running it that way now.

dh154 · Post by **dh154** » Mon Mar 27, 2006 9:43 am

Interesting, thanks for letting me know! I assumed the problem was uncommon because I couldn't find any threads on this topic by searching the forum. Looks like another successful MS conversion now!

Post by **jsmcortina** » Mon Mar 27, 2006 11:46 am

I got around to installing a diode in series with my charge light and BINGO! My engine shuts off on the key now too.

The same issue and solution can be found on MSD's site.

James