bobxyz
Board Member
- Joined
- Aug 29, 2014
- Location
- Boulder CO
Assuming you mean the coil and wb "logic ground"s, that should be fine. Connecting anything that draws high current to the sensor ground wire(s) is bad. So is running the sensor ground to anything other than the MS sensor ground pin.The MicroSquirt ecu has one dedicated sensor ground for the sensors. I tied the sensor grounds for the map, air temp, coolant temp, wb, tps, and coils into that per their wiring diagram.
I'd run the ecu ground wires to the intake manifold. The wb heater ground to the battery is OK.As far as power grounds...the coils go to the intake manifold, ecu and wb to negative battery terminal. My shield ground for the cas wiring is grounded to the intake mani.
Ideally, the cas shield should go to the sensor ground pin/wire close to the MicroSquirt, but it really shouldn't matter since the cas uses hall effect sensors, which are pretty robust. If you were using the factory VR-type CPS sensor, it would be worthwhile to move the shield ground. I'd leave it alone unless you're seeing lost sync problems.
I'm not sure if it matters, but do you have the flat woven ground strap between the back valve cover acorn bolt and the bulkhead?B21 battery ground goes to engine and the chassis at the apron just behind the battery tray.
None of the above would explain your weird Vref and MAP voltages. A few tenths of a volt maybe, but many volts, no. I'm still thinking something is broken or shorted in the wiring.
On other stuff, where is your MAP sensor mounted? It should be good up to 125degC, but might be happier in the passenger compartment.