The BGB lists the resistor as 0.73 ohms (i.e. less than 1 ohm). Just wanted to be sure you knew how low the resistance value was. Most of my HF multimeters are not accurate enough to reliable check this (I have better meters).

 

It showed 0 on my cheap harbor freight’s meter.

 

Guys
Since I bought the car, the fuel pump never work. It’s being wired directly thru an aftermarket relay.
I would like to revive the OEM fuel pump system for safety, in case of an accident.
I checked Resistor pack with multimeter and it reads 0 ohm. The Relay passed the test. BGB recommendation is to replacement of the resistor.
Any body has one for sale? I don’t want to post a thread and get all the scammers.

I think you are confused about how the systems work.

The ECU controls the fuel pump for safety but has a secondary speed system that the ECU also controls but does not relate to safety.

 

I read some where on this forum, In an event of accident when the motor shut off but the key is in IGN position, the FPR and Resistor will cut off fuel.
They way I have the aftermarket relay set up, the only way to turn off the fuel flow is to physically turn the key to off. We assuming that the fuel line is ruptured I accident.

 

The ECU will have an "FP" line which is used to ground (close) the Circuilt Opening Relay (COR) to allow power to flow to the fuel pump. The COR also has a 2nd terminal / coil that also closes it when the car is cranking.

The "Fuel Pump Relay" is for controlling high/low power mode of the fuel pump. In low (normal) mode, power flows through the resistor, thereby limiting power at the pump. In high mode the Fuel Pump Relay switches and power flows directly the pump, bypassing the resistor. The ECU determines when high mode is needed - presumably high boost and/or high rpm.

Some folks eliminate the FPR and the resistor and just run their pump in high power mode all the time.

 

So, it’s safe to eliminate the the FPR/Resistor?

 

The OEM system is super confusing in how it's all named. The "fuel pump relay" should be called the "fuel pump SPEED relay". That's all it does, switch the pump from low (running through the resistor) to high. The actual fuel pump on / off relay is the "Circuit Opening Relay".

 

Personally I think keeping the resistor is a better idea, it will reduce wear on the pump not having it run full speed all the time. That being said, my first SW didn't have it and ran just fine.

 

It's not there to reduce wear on the pump. It's to stop extra fuel and electrical load when not needed.
As an example some 2GR run this system while others do not. Fuel pumps are very reliable items from DENSO. Mine is still running in the NA 32+ years later and it runs full speed.

 

And to reduce pump noise at idle when you are most likely to be able to hear it. Especially in a car like the MR2 where it's right under your elbow.

Actually, does it even reduce electrical load? Since it's a resistor dropping the voltage, the extra power is just getting dumped into the resistor as heat.

 

Well now that you put it into words like that, electrical load does not change. I've not been able to hear the pump in my car but it's been awhile since I had a stock muffler on it so that's probably why.

@mtang65 so what is it that we are trying to fix on your car? Can you show us the setup with the aftermarket relay and where it is wired in to make it work?

 

Do not confuse the safety function with the high output function. The fuel pump resistor and its associated relay switch the fuel pump between normal and high output mode. It has nothing to do with safety. The Circuit Opening Relay is controlled by the ECU and turns off the fuel pump if the engine stops turning for any reason.

If your aftermarket relay is not getting power from the Circuit Opening Relay, you have bypassed the safety function.

 

OMG! I got it. It’s so simple. I will run power from C.O.relay to my Aftermarket relay. Thank you!

 

Actually, does it even reduce electrical load? Since it's a resistor dropping the voltage, the extra power is just getting dumped into the resistor as heat.

Yes it does. I = E/R. Increase R (by adding a resistor in-line with the pump) and you decrease current. E (voltage drop across both loads) remains the same.

 

Ok. So next we look at the OEM fuel pump relay. By default if the ECU is not doing any controlling of the relay it should send power from pin 5 to pin 2. Then to the resistor. If the ECU grounds the FPR pin power should go from pin 5 to pin 3.

Check continuity from the FPR pin 3 to the fuel pump. Do the same from the resistor pin 2 to the fuel pump.

 

That’s the next question I was gonna ask, how to test for continuity. I will do that next.
BTW, your mention pin 5, I only see 4 pins in the plug.

 

No the engine doesn't need to be running and the you can have the key in the off position.

 

Sadly, there’s no continuity between the relay or resistor to the FP at all. There’s a broken or rusted wire somewhere in the wire loom.
looks like I’m gonna run a new wire from pin 3 to the fuel pump.

 

I forgot to mention, the chassis is an NA.

 

Ok, solved! I ran a good size gauge wire from FP relay pin 3 directly to FP. I tested it, if the engine shut off, the FP is cut off and there is no power when key is turned to IGN. This is a peace of mind knowing fuel will shut off in an event of a fuel line ruptured.
unfortunately my chassis is an NA with 3sgte swapped so the OEM FPR and FP resistor pack set will not get power to the FP with the factory wires.

 

Ok. So NA chassis but does I have a 3SGTE body harness? As that is the only way you will have any wiring for he FPR relay and resistor. If it's the NA chassis wiring then it goes directly from the circuit opening relay to the fuel pump.

 

No, I used the NA body harness. Hence, there’s no continuity from FPR to FP.
At any rate, I was able to wired a new lead from pin 3 to the FP.
thanks for you help.

 

Interesting. How do you have the relay and resistor plugged in if it's the NA body harness?

Glad you have it working properly.

 

Aren’t those plugs incorporated into the 3sgte engine harness? I don’t remember exactly when I was doing the swap.

 

I don't think that is going to work as Toyota intended. You will only have a slow pump speed meaning that at boost and on start up you won't have enough fuel pressure to run safely.

Unless I'm missing something.
Can you show me where you have the relay and resistor spliced into the NA body harness. It's a bit more complex than just a simple splice based on what you have shown.

 

The FP relay and Resistor are plugged into the round female connector and on small plug from the resistor pack with 2 pins. I did not spliced them into the NA harness. All the Connectors are there and I just plug and play. According to the diagram Pin 2 from the resistor is spliced (E2) with pin 3 from the FP relay. From what I understand is that when the engine is cranking, pin 3 from relay is activated for full speed run til some time later it switches to the resistor for low speed run and switch back and forth. For some reason there is no continuity from FP relay Pin 3 or Resistor pin 2 to FP connector under ashtray. I went ahead and run a new wire from engine bay to FP and spliced the new wire in engine into Resistor pin 2 just before the Splice point (E2). So, the only way to get power to the FP is via new wire.
If you look at the diagram, E2 is where Toyota spliced the wires, unless there’s some sort of Diode being used there to control the flow of electricity.
I hope my explanation make any sense. Remember, I’m working with a 1991 NA and you’re used to 93 plus. The diagram you posted is a slight diff than the one I’m working with.

 

So the BM1 connector just wasn't connected when swapping in the turbo body harness? For sure the NA chassis have this connector.
When installing a Supra pump in an NA chassis, I have run an additional #14 wire from the fuel pump resistor and relay (which I added), to the fuel pump (F4) connector. I don't feel comfortable with the OEM wiring carrying the current drawn by the Supra pump at full 12v mode.

 

So the BM1 connector just wasn't connected when swapping in the turbo body harness? For sure the NA chassis have this connector.
When installing a Supra pump in an NA chassis, I have run an additional #14 wire from the fuel pump resistor and relay (which I added), to the fuel pump (F4) connector. I don't feel comfortable with the OEM wiring carrying the current drawn by the Supra pump at full 12v mode.

I noticed the factory wire for FP seems a bit small to me. However I’m running with turbo fuel pump so I think it’s ok.
as for the BM1 connector, it wasn’t plugged in during swap. I was a newbie’s at engine swapping. The NA chassis doesn’t have the BM1 connector but I must have transferred all harnesses from the Turbo donor car into the rolling shell NA body the previous owner stripped clean for respray inside and out.

 

Just heads up since you’re already at the BM1 connector
91-92 6 pin bm1 connector is different from 93+ 10 pin
This may give you a better idea of what to look for.

 

Wow, this information would’ve help. Luckily, I found it.