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

I am having issues with the MS grounding the pump. I am running MS 2 v3.0 w/tuner studio. MS is a new assembled unit from DIY. works normal with the stim hooked up. with MS plugged into engine harness and laptop fuel pump primes but no rpm signal at cranking. all sensors work, double checked wiring (OK) MS gets 12v but just seems like it is not grounding. I have 12v at FP relay. and 12v at Main relay during ign. on and cranking any info would be very helpful in getting this engine to run. thanks

The pump runs at switch on to prime the system. It then needs a tach signal to run after this. So if you're not seeing a tach signal at cranking, no pump.

I agree, but the pump will prime with the laptop plugged in when you key on the ign. if I unplug the laptop, no prime but power to MS power to main relay power to fuel pump relay in but no power out of relay and relay works fine it seems the MS isnt providing ground is it something in the MS.

Does this problem also happen on the Stim?

no when I plug in the stim pump circuit works fine I just dont get 12v at pin 30 on FP relay 12v at pin 37 at MS could it be internal? testing wiring again so far everything is per 3.0 wiring diagraham.

The MS supplies ground, not power. If it's not getting power, check the wiring.

scarpa - I'm not an expert but the two issues I have had with my fuel pump have been bad grounds. Not on the MS side but on the sensors and engine side harness.

My fuel pump was not coming on at all... it was a missing ground on my TPS.

Now my fuel pump comes when I start the car but it does not prime...