Thunder 2jz fuel pump wiring

[dan7773]

Hi everyone, could really do with some help with wiring in the Supra fuel ecu.

Followed all instructions, I was getting the pump to prime for 2 secs when turning the key to On, then all of a sudden nothing, replaced the relay now it stays on permernatley. I had a quick look thru the forum and found some diagrams of how to wire in the relay differently but still get the same results. I’ve used spst 4 pin relays, hella ssr’s, the car is ready to start just this is strange. Had the ecu wired up for low side power hold everything was fine, could test the injectors, fans, coils then all of a sudden lost all coms and couldn’t get back into the ecu. After a few hours and nothing ,decided to wire it up for high side power hold now everything works except fuel pump. Any help would be great as this is driving me mad.

Thanks,

Dan

[ClintBHP]

Sounds Like you have a positive supply issue, check the +14v line, this will both make the laptop lose comms and trigger the fuel pump relay.

The ECU will ground the output when the ECU is not powered so you need to wire BOTH the ECU +14v and the positive side of the relay to Ignition Key switched live.

For the relay to stay on it need both the +14v from the ignition switched live AND a ground from the ECU:

If the ECU +14v is powered off then also the relay should be off so the fuel pump should also be off, if it is running then the ECU alone must have lost power or you have another wiring issue.