Morning,

I'm confused about the fuel pump wiring and megasquirt. I have a brand new loom from premier that is ready to be installed.

The predicament I have is... The loom has a fuel pump feed, and so does the megasquirt, so which one do I use?

Thanks in advance,

Chris

You need to switch the fuel pump relay from the Megasguirt.

If the premier loom wire is from switched fused feed, use that as the power feed to the pump relay.

You cannot drive pump direcly from megasquirt due to the current req.

Megasquirt provides a switched earth for a fuel pump relay, so you provide power to one side of the coil, MS earths other side-but only connects to earth when it detects engine turning 300rpm or higher.

Use the relay contacts to interrupt the fuel pump wiring in the loom. If you wire the fuel pump without the relay arrangement as soon as you turn the key the fuel pump runs and continues until you turn off, so if you stall or engine fails the pump just keeps running.

Using MS to control it means it only runs when the engine does.

MS will also run the pump for 2-3 seconds when ignition is turned on to prime the fuel system for start up. Like others have said, MS will provide a switched ground for the coil of your fuel pump relay.

What I did is install a small jumper wire from the main positive on the fuel pump relay over to one side of the relay coil, then the other side of the coil goes the MS fuel pump wire.

I use my original pump/wiring to feed the swirl pot and the squirt/relay board sorts the high pressure system