Fuel relay issue - 20V swap

[Army Fork]

So I finally have my 20V'd SR5-GTS swap running, but there is a problem. My setup only works if the fuel pump receives external power, like, say, from a separate battery.

We've found and checked the fuel relay and discovered that as soon as there is power supplied, key on or off, the relay clicks on. The relay therefore gets quite hot, but thankfully is still intact, but we also now have no power to the pump.

We've isolated the engine harness and ECU from the body harness to try and eliminate some variables, but with or without the harness connected (a fully custom harness I may add) the relay clicks on and we have no power to the pump.

Anyone have any experience sorting fuel system issues? The relay appears to work fine and the fuses are all intact as well, we're a little stumped.

[ga_goosh]

have you checked the relay itself? it could click but have no continuity therefore not flipping the internal switch. also are you using an afm? you can jump the relay on the side that has 2 wires. if your pump starts up then i would replace the relay or check your wiring.

[Army Fork]

Well it clicks on which tells me that there is a current through the magnetic side, it seems to operate properly. And we are also using an AFM as this is a Silvertop instead of a Blacktop. The side that has two wires.... But it's a 5 wire plug, do you mean the bottom two wires? Do you mean if I bridge that the pump should kick on?

[HASport AE86]

You probably don't have the "FC" pin of the 20v ECU hooked up. It supplies the ground for the coil of the relay.
If you are using a GTS fuel pump relay (aka circuit open relay) you connect the green/red wire of the relay to the "FC" ecu pin.

On a GTS relay:
Grn/red: to FC ecu pin
Wht/blk: constant ground
blk/red: B+
Blk/wht: starter solenoid signal/blk wht wire on ign switch
Blu/blk: to fuel pump B+


If you are using a standard BOSCH style relay:
Pin 30-Batt B+
Pin 87-Wire going to Fuel Pump B+
Pin 87a- Nothing connected to this pin
Pin 85-Key on power (you can use the blk/org or blk/yel wire of the ignition switch)
Pin 86-Connect to ECU pin "FC" or to a switch that provides a ground or a constant ground if you want the pump to run any time the key is in the RUN position

[Army Fork]

I was perusing the 20V harness diagram and wiring book and that seemed to be the issue. Guess I can just splice it in off the ECU, but I also imagine that there is a plug that this wire would connect through and I'd rather do that, just makes my life easier in the future. Would that be the #7 pin on the C* plug?

For reference, this is the C* plug (pretty sure)

[Army Fork]

So as an update we're still having some issues, it partially arises from a disagreement we're having on whether or not the AFM FC needs to be connected to the ECU and relay. Is this correct, or can we disconnect the AFM side and just run the FC wire from the ECU to the firewall plug?

As a note I've checked both the IGN 7.5 fuse and the EFI 15 fuse and both are fine.

As a note we're also having issues with getting the defrost and tach to work, as well as the blower motor. Unsure if they are related to this issue, but there you go.

[Army Fork]

We've managed to fix the issue with the circuit opening relay, and after some good times testing we had another issue crop up after some further tweaking, the circuit open relay now operates properly only in intermittent bursts. Sometimes the pump works and sometimes the relay just clicks away with the AFM open.

On the AE86 diagram I found a relay that is NOT the circuit opening relay but is the EFI main relay, this relay however is shown as a four-wire input while the actual relay is a five wire. Is this the correct relay? number is 85910-30050