Megasquirt MS3PRO PNP M30B35, crank signal loss after 4000 Rpm

Hello everyone! I need help. Is there someone with some experience in runing megasquirt ECU's?

Recently I pulled the trigger on a MS3PRO PNP for my '88 E34 535i M30B35 engine for the confort of not having to build an entire harness frpm scratch.

I'm having this strange issue of losing compleetly the crank sensor signal above 4000 RPM. I comtacted AMPEFI and they suggested to check the shunt resistor inside the ECU to be 10 Kohms and that seems ok since it measures 9.89 Kohms or swap the sensor, but the sensor is fairly new, I changed it recently for a brand new Hella one. There is to say that on the OEM ecu, I didn't have this issue.

Unfortunately, there is no way to have some kind of live support from AMPEFI, this I'm finding the hard way. The only way is trough email, and, I only get one reply a day, some days none. Iou can immagine how fast that's going on and how frustrating can it get sometimes...

I'll attach a photo of the log at the moment of the signal loss, just in case.

Thank you, hope that soemone can help me figure this out. Best regards!

Try adding a 1k resistor inline on the VR+ wire, if the sync loss moves up in RPM then you know your going in the right direction

I have had to do this on my M30's using MS2 hardware

Thank you! I'll try that. I measured the resistance on the OEM ECU CKP terminals and it's 65 Kohms compared to 10 Kohms on the megasquirt. I don-t know if that's relevant or not. I'll try rerouting the CKP wires away from the main harness using shielded wire. hope to solve the problem.

I was wondering, wouldn't it be better to use a hall sensor insterad of the OEM VR one?

VR is more noise resistant, and heat tolerant than most hall sensors. I prefer it unless the OEM has selected a Hall effect for their trigger wheel.

Solved!

I added a 10 Kohm resistor in parallel with the CKP+ and everything is working. I added another one on the CKP- just because I had it. Thanks a lot, everyone!