Can't shut off the engine

[iracer]

Just had a new engine built and installed in one of our formula Mazda's and the engine now won't shut off with the ignition switch or the kill switch. Have to disconnect the msd box or turn off the fuel pump and let it run out of fuel. Any ideas what has caused this?

[Bob L.]

Sounds like alternator is self energized... check against old stuff that did shutoff...make sure same and you hooked up same...

[BeerBudgetRacing]

If the ignition switch isn't shutting off the power to the ignition then something is mis-wired.

Also, if the cutoff switch is not disengaging the alternator, either it's the wrong switch (it should have an alternator cutoff) or it's wired wrong.

[preston27]

The wire going to the alternator from the coil side needs to be in the horizontal position not the vertical. The back of the alternator has two male connectors on the back if the wire from the coil side is in the vertical position the car will not shut off.

[iracer]

Thanks everyone.
The problem was caused by a bad alternator. As soon as I replaced it everything work normally and the engine can now be shut off with the ignition switch.

[Lotus7]

Thanks everyone.
The problem was caused by a bad alternator. As soon as I replaced it everything work normally and the engine can now be shut off with the ignition switch.

Any chance you could take a moment and clarify how the bad alternator caused that? thx

[iracer]

I honestly dont know. I checked the charging and it was 18.75 v instead of the required 14.2v so I replaced the alternator and voila problem solved and now charging at 14.2v.

[Fred Michael]

Did you check the orientation of the plug on the alternator to make sure it was on the horizontal pin before replacing the alternator?

[Lotus7]

Fred Michael: any chance of sample photos and a more detailed explanation? thx

[Numbskull XIV]

The wire going to the alternator from the coil side needs to be in the horizontal position not the vertical. The back of the alternator has two male connectors on the back if the wire from the coil side is in the vertical position the car will not shut off.

Did you check the orientation of the plug on the alternator to make sure it was on the horizontal pin before replacing the alternator?

Fred Michael: any chance of sample photos and a more detailed explanation? thx

Preston and Fred,
You guys are on the right track with this answer but wanted to clarify it a bit more. There are two male connections in the back of the Alternator. Instead of distinguishing them as "horizontal" and "vertical", distinguish them as "Regulated Voltage" and "Unregulated Voltage". When installing the Alternator, you have to measure which one is which and connect the wire to the correct one. "Vertical" DOES NOT = "Unregulated Voltage" and "Horizontal" DOES NOT = "Regulated Voltage". I have replaced some that "Regulated Voltage" = the "Vertical". You just have to measure it before putting it on that wire.


Jon Updegrove
610-509-7321
Jonupdegroveracing@gmail.com