MicroSquirt.com read only forum (Jan.15,2018)

Evening all,
Having a bit of an issue with the fuel pump relay. I have wired to this relay the fuel pump, O2 and EDIS.

When using the MS purple fuel pump wire for the ground the relay clicks continuously when power is applied.

So as an interim measure I have replaced the purple wire with a permanent ground with a strange result. After turning off the ignition after a run the engine keeps running. I've check the power feed and there is 5V still being applied. To shut the engine down I've had to disconnect the pump feed.

Questions:
1. How does the the MS purple pump ground function?
2. Any ideas why there is 5V after the ignition is switched off?

Thanks
Steve

It should ground the fuel pump output for 2 seconds on power-up, and then at any time it senses RPM. Fuel pump power is cut if it loses sync with RPM. Some code variants (usually MS2/Extra) may click the fuel pump off and on if there's a settings error.

Are any devices the MicroSquirt grounds getting powered from a constant 12 volt feed? Some of them can backfeed power into the unit when the key is off.