trigger issues

[Markysparky1973]

I'm putting a ms1 v3 on my vw camper I've got a trigger wheel 36/1 incorporated with crank pulley the VR sensor has two wires and a screen I have tested the set up on my scope and appears to work OK but engine will not fire unless pickup is touching teeth anyone have any ideas the VR sensor is a gm part off a corsa one wire red other is yellow

[Matt Cramer]

Try adjusting the VR trim pots.

[Markysparky1973]

Been trying that tonight have got it going but need to fine tune I have a scope any ideas what pin to check it on other than direct on VR output

[Matt Cramer]

Can you post an MSQ and a tooth log of the issue?

[DaveEFI]

Been trying that tonight have got it going but need to fine tune I have a scope any ideas what pin to check it on other than direct on VR output

I tend to fit a bare wire jumper between VR out and Tsel on the components side of the PCB. Same between Tach Sel and VR in. Makes it easy to attach a scope probe.

Regardless of the input level, you should see an approx 5v peak to peak square wave at VRout/Tsel.

Generally with a VR sensor, R52 can be left on the default fully anti clockwise position. R56 - close to the edge of the board - needs to be about 6-8 turns clockwise.

It's very easy to see the results of altering R56 with the scope attached to VR out. You'll often get no signal at all with R56 fully anti-clock, and it will suddenly appear as you turn it clockwise. Keep turning to get the best looking square wave. If you can, check at high revs too. If it works ok at low revs, but gives problems at high, turn R56 clockwise a half turn at a time and check.

[Markysparky1973]

OK Dave thank you for your help with that will try tonight