MPGuino injector connection - no 0v feed
 

I've built my MPGuino and have got it recognising the difference between stopped (0mph) and moving (some mph).

I just want to double check the connection to the injector system. I have a 1999 Mercedes Benz C-Class (petrol). It uses a HFM or PMS injection system (Siemens I think, or maybe Bosch?).

I have probed the injector wires with a digi-meter in DV volts mode (20v), connected with (+) in the plug and (-) tgoing to a bolt on the head, looking for the 0v one.

I can see there is one hovering just under (12v) which must be the power wire, but the other starts at 0v then rises quickly to around 5v.

Now I assume "injectors is injectors" so to speak, and the 5v wire is the one to tap into. Surely the Bosch fuel system on the car cannot be any different from any other injection system?

Anyone got a clue (coz I don't!)...

It would seem that you found the injector wire to use. Go ahead and try to use the wire that starts off at 0 VDC, then rises to about 5 VDC. That is likely your DVM charging up the capacitor filter on the injector switching circuit.

Cheers - I can confirm that's the correct wire - the car isn't bothered by the connection and the MPGuino now shows some numbers from the injector.

Hopefully will get the vss problem sorted and be in business after some calibration.