Fuel pump wire

[19cturbo]

Im currently wiring a 1JZ into a 1987 mitsubishi starion. My question is which wire from the ECU can i use to power my fuel pump relay? I know on the pin out there are two wires that run to the factory fuel pump relay, but i dont have that. pin D1 and FPC. From what ive read already, you can not use FPC directly because at idle it doesnt supply enough volts to kick the relay on. So anyone doing an odd swap, what wire do you use from the ECU to send signal to kick on the Fuel Pump relay?

This is what im looking at. this matches my ecu

 

[IndigoMKII]

And why can't you use the fpc to kick the relay on?

It's strong enough at idle to kick on my 30a aftermarket relay on my mk3.

 

[19cturbo]

From wha I had read it only put out about 8volts at idle and kicked it up
To 12 above 1600 rpm. I wasn't sure if anyone else ha used this wire to kick on a normal relay. I wasn't sure if 8volts would be enough to kick the relay on. I'll try the fpc wire and see how it goes. Thanks for the reply.

 

[IndigoMKII]

if you did what i did, which is pulled voltage directly from the battery, the voltage going to the relay shouldnt matter.

 

[Radial]

There is a huge difference between JDM 1JZ Soarer/JZX FPC signal vs the US MK3 1JZ.

JDM models sends 5v digital pulses through the FPC-wire to signal the FPC-unit in the trunk. That again "steps up" the voltage on the stock fuelpump as the FPC signal changes form ECU. This signal-wire is a very low-current, signal-wire only... and not compatible with running aftermarket relays at all.

the US-spec 1JZ has a completely different Fuel Pump control system with just simple relays and a resistor to slow down the pump when needed. A far different sytem than the Soarer-stuff uses.

 

[19cturbo]

I never knew there was a US spec 1JZ? the one i have is a soarer unit correct? so i cant simply use the FPC wire to kick the relay? i need a solid signal while cranking then running, i can do without the fuel pump prime, of course that would help, but the starion has no prime from the factory anyway.. Basically all im looking for is a wire from the ecu i can use to send enough signal to kick on my fuel pump.. I have be able to work something out using the Factory main relay in my car. It would be easier to use signal from the ECU though .

 

[19cturbo]

Also i have voltage pulled directly from the battery for my fuel pump relay, i just need a signal wire to kick the relay on.



Even if i had a wire to just signal a ground, i could use that instead, i would run power to my relay, and let the ECU close the ground circuit on the relay..

 

[hvyman]

There is no us spec 1jz.

 

[19cturbo]

Thats what i knew haha. anyway, ive done about as much reading as i can, and it doesnt seem there is a way to get a signal wire to my fuel pump from the 1JZ ecu. looks like im going to have to try something different. unless anyone else has an idea?

 

[hvyman]

Can use the ign switch. You will have the fuel pump run with the key on tho.

 

[IndigoMKII]

Thats what i knew haha. anyway, ive done about as much reading as i can, and it doesnt seem there is a way to get a signal wire to my fuel pump from the 1JZ ecu. looks like im going to have to try something different. unless anyone else has an idea?

You can always run it to the 'on' position on your key switch if you're just looking for voltage to keep the relay hot.

 

[19cturbo]

You can always run it to the 'on' position on your key switch if you're just looking for voltage to keep the relay hot.

Yeah, i know i can run it that way, but in that case anytime my key is just on the pump is running constantly.. Its not a huge deal, but id rather keep it more of the way it was from the factory. I understand when swapping you cant always do that. What i may do is wire it through the "on" position of the key switch then through a toggle, and just always leave the toggle on, but would have the option to kill the pump if i just wanted to leave the key on for other purposes..

 

[Radial]

I was under the impression that there is a enormous "market" with 1JZ's in the US, for the reason that many supras came with 1JZ from stock....But further research confirms that only the JZA70 MK3 Supra had 1JZ from stock, and thats the JDM-version..... all the MA70's in the US came with 7M's obviously. Withdrawing my statement of "US-spec" 1J's

But yes, your issue with the Soarer ECU and fuel-pump is a well known issue during swaps.
You can use the M-REL output, but it won't stop the fuelpump if you crash etc.
the M-REL turns on when ignition-switch input is activated, and turns off when deactivated (a small 5 sec delay i think)

If you want to utilize the stock FPC signal, you need a circuit like this to get it working with a relay, but then it's a fully functional Fuel Pump circuit:

 

[19cturbo]

someone else said a similar circuit would work. this one looks much simpler and should work the same, just apply 12v to the DI pin as suggested before so the PWM circuit will activate

 

[19cturbo]

Also, doesnt the M-REL pin need to be hooked to the main relay, that keeps the ecu on for a few seconds allowing the IAC to return to "home"position. I know thats not super important as it will do that when i turn the key back on anyway. I dont want the pump to run as soon as i turn the key to on, i want it to run when cranking then dropped back to "on" I dont think i can use the M-REL output for that purpose. my pump will run as soon as my key hits on.

 

[3p141592654]

I wouldn't use the second circuit as it doesn't attempt to filter the PWM signal. Also, the COR will give lower voltage drop in the fuel pump circuit than a transistor. Bear in mind I'm just theorizing, I haven't rigged up either of these.

 

[Radial]

Yea, the 2nd circuit is a no-go. The FPC signal is a square wave signal like this:

If you use a transistor directly on that signal, your fuel-pump will switch on/off just like the signal.... and transistors get REALLY hot with large currents. 10A current through a transistor (normal fuel pump current) is at least 15W of pure heat needing to be cooled down.

The signal needs to be straightened out to one long DC-signal.... that requires the use of the 1st circuit.

Then the Transistor can do its job on the Coil side of a normal automotive relay.... thats like 15mA of current for a normal on/off relay (~90ohm internal coil resistance), and heat from transistor is now close 0,5W instead

 

[19cturbo]

has anyone actually used this? im willing to try it to see if it would work, but why wouldnt the other diagram i posted work to connect the ground? My intentions were to use the ignition switch to control my relay for my pump and let the other circuit i posted control the ground.. but your saying that wont work?