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

I have been running a microsquirt on a Mazda Miata race car since last fall. I am using a 36-1 Ford crank wheel with an Escort VR cam sensor. I am running the version 2.883j code. This has been working fine until this summer. Now the car will start and run fine when it is cool but after a track session if you shut the car off and try to restart it in 5 to 20 minutes, it will crank fine but the engine will not start and the tach doesn't move. Let the car sit for an hour or 2 and it will start again.

I think this must be in the VR sensor input circuit since both tach and coil outputs fail and return at the same time. Anyone have another idea?

I plan to replace the VR sensor and recheck the wiring but I have never seen a VR sensor that is temp sensitive. Could this problem be related to the VR overdriving problem that some people have reported? If so, have I fried the microsquirt? If it is the overdriving problem and the microsquirt is OK, would the series resistors fix the problem?

Marty

VR pickups ARE temp sensitive. They lose amplitude at higher temperatures as well as lower RPMS. So a hot VR pickup trying to pick up a cranking signal is going to be the most likely failure scenario if the amplitude is a bit low. This would therefore be underdriving the input, not overdriving it.

If you have a resistor in series with your VR input, you might want to reduce that resistance a bit. If you don't have a resistor there, you may want to try adjusting the clearance between sensor and wheel a bit to see if that helps.

Didn't know VR was temp sensitive! The sensor is right next to the lower radiator hose so that might compound the problem. I don't have a resistor in the VR line but it is a fair distance from the wheel (> .060"). I'll move the sensor closer to the wheel and see if that helps.

Thanks,
Marty