Spyder 4G64 Spyder GS Fuel Pump Relay Module Bypass

Disclaimer: This documents mods made by me. I make no claims about any mods you make on your car that follows my process.

Hours were spent trying to trace the cause of our performance problems on our 1999 4G64 Spyder GS. The car would run great, switching from open loop to closed loop, until it warmed up. Then it would stumble and die. Since the problem was happening starting at different temperatures, it was not easy to pinpoint. Once, when I went to unplug the OBDII logging cable, I about burned my hand on the Fuel Pump Relay Module, which has a metal case. I knew something was wrong.

In 1999 (and 1993-97 for Galant), Mitsu added a Module to control the Fuel Pump Relay. We have been unable to determine the need for it, but some quick research indicates it was an attempt to vary the voltage to the Fuel Pump Relay in order to throttle the speed of the Fuel Pump.

Here is what the Fuel Pump Relay Module looks like, with the cover removed

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Here is how the fuel circuit is wired in the 1999 4G64

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Complicated. By unplugging the Fuel Pump Relay Module, and making three connections, you can eliminate the need for the Module, and just use the Fuel Pump Relay, like all other DSMs.

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Your Fuel Pump Check Connector will still work. Keep in mind that the Fuel Pump will now run with the key in the "ON" position.

If you are going to upgrade to a GST or GSX ECU, keep in mind that Pin #8 on those ECU's is a switched ground, so you could make your new grounding connection (#4) on Pin #8, and the Fuel Pump would only run when the engine is cranking.

Hopefully this helps save hours of time for someone who is having mystery rough-running, or no-start issues on their 4G64 GS.

 

[Justneedthisfixed]

Where exactly is this module located?

 

[DogWhistle]

Where exactly is this module located?

Under the driver's side console cover. Next to your right knee as you sit in the driver's seat.

 

[steve]

If you are going to upgrade to a GST or GSX ECU, keep in mind that Pin #8 on those ECU's is a switched ground, so you could make your new grounding connection (#4) on Pin #8, and the Fuel Pump would only run when the engine is cranking.

Interesting, this is a variable speed controller for the fuel pump. Did you have a stock fuel pump or something aftermarket?

With the GST/GSX ECU's pin 8 is pulled to ground whenever the ECU thinks the fuel pump should be running so you should connect pin 2 on the Fuel Pump relay to pin 8 on the those ECUs.

Do you know what the voltages are on pin 8 with the 4G64 ECU? Is the ECU or the control module sourcing the control voltage and is it a pulse train switching (PWM) on and off or a varying voltage?

 

[DogWhistle]

Yes, Mitsu did a ‘pulsed’ approach with this relay. I had a stock fuel pump with factory wiring. Since the circuitry in my module was fried, I couldn’t determine if it was the module or ecu that pulsed the voltage. I didn’t measure voltage on Pin 8 on the 4G64 ecu since I wasn’t planning on keeping it installed.

Eliminating this relay gives you a choice to either ground on Pin 8 on a GST or GSX ecu, or to run a wire to ground to the body with the 4G64 ecu. As mentioned, if grounding to the body, the fuel pump will run when the key is in the Run position, even if the engine is not rotating.

 

[NVdsm]

Sorry to bring this back from the dead. Do you have a picture of how this is bypassed? I need to bypass this on my sons car but don’t know how to read the wiring diagram

 

[DogWhistle]

A picture was almost impossible to get to show this accurately because the two black wires you need to work with both have color stripes that aren’t visible from all angles.

For specific help, please DM us and we’ll go from there.

 

[japanbastard92]

Thanks Boss I did it work great now

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[DogWhistle]

Glad we could help. Thanks for adding the pictures.

 

[Kryndon]

So let me get this straight. You connect the Black-Blue wire (Pin 3) to the Black-Red wire (pin 1) on that 5 pin white connector, and ditching the metal relay module completely.

Then you are left with 3 other wires. A thin black ground wire (pin 5) which comes from the main Fuel Pump relay (pass side) and terminates at the white connector. You also have a thick Black-White wire (pin 4) coming from that same relay and terminating at the white connector, which in your case you've shown it just goes to ground.

But is that the specific ground wire you have to either connect to chassis (pump always on) or to the White-Red thin wire that leads directly to the ECU pin 8 (pump only on when cranking/running or told by ECM)?

I just did this on a '99 Spyder with a '97 turbo ECMlink ECU and from the 3 possible configurations, only one allows the pump to even run at all, and it runs all the time (Black-White wire connected to chassis ground). If I connect that to the ECU pin 8 White-Red wire, the pump never runs, not even when told by ECMLink through the Misc tab.

So can you clarify which of the two ground wires coming off that white connector are you referencing?

 

[DogWhistle]

Maybe we can help clarify a couple things. Pin #8 on the ECU only triggers the fuel pump ground on a turbo ECU, not the 4G64 Black Box ECU. And then Pin #8 will only be grounded when the engine is rotating (or when commanded via ECMLink).

When keeping the 4G64 Black Box ECU, you will have to opt for the grounding where the fuel pump runs whenever the key in in the ON position.

The black wire (Pin #5) from the fuel pump module is ground, the black-white wire (pin 4) returning from the pump needs to be grounded. In our diagram, we are not using the White-Red wire (Pin #2) since Pin #8 on a 4G64 ECU is not a ground. You can cap the wire and save it if you ever go to a turbo ECU and want to return to only running the pump when the ignition is on.

We have installed a hidden kill switch which interrupts this new grounding connection that allows us to work on the car with the ignition on if needed without running the fuel pump.

 

[Kryndon]

Maybe we can help clarify a couple things. Pin #8 on the ECU only triggers the fuel pump ground on a turbo ECU, not the 4G64 Black Box ECU. And then Pin #8 will only be grounded when the engine is rotating (or when commanded via ECMLink).

When keeping the 4G64 Black Box ECU, you will have to opt for the grounding where the fuel pump runs whenever the key in in the ON position.

The black wire (Pin #5) from the fuel pump module is ground, the black-white wire (pin 4) returning from the pump needs to be grounded. In our diagram, we are not using the White-Red wire (Pin #2) since Pin #8 on a 4G64 ECU is not a ground. You can cap the wire and save it if you ever go to a turbo ECU and want to return to only running the pump when the ignition is on.

We have installed a hidden kill switch which interrupts this new grounding connection that allows us to work on the car with the ignition on if needed without running the fuel pump.

That's the thing. The car is a 99 4G64 Spyder GS onto which I installed an EPROM ECMlink ECU. And in this case, the factory wiring still has the White-Red wire leading to ECU pin 8. However, connecting that wire to neither the thin black nor the thicker black-white wire from the pump allows me to trigger the pump through ECMlink or make it prime after key-on for 2-3 secs.

That's what bugs me. Following your diagrams exactly with nothing else being touched, the pump either runs all the time or doesn't run at all.

 

[DogWhistle]

That's the thing. The car is a 99 4G64 spyder onto which I installed an EPROM ECMlink ECU. And in this case, the factory wiring still has the White-Red wire leading to pin 8. However, connecting that wire to neither the thin black nor the thicker black-white wire from the pump allows me to trigger the pump through ECMlink or make it prime after key-on for 2-3 secs.

That's what bugs me. Following your diagrams exactly with nothing else being touched, the pump either runs all the time or doesn't run at all.

You should verify with an ohm meter that Pin #8 on the new ECU does indeed go to ground when the engine is running/turning over.

 

[Hristo]

You should verify with an ohm meter that Pin #8 on the new ECU does indeed go to ground when the engine is running/turning over.

Can you post a step by step tutorial (for newbies like me) and if possible add pictures. My car is a 1999 Spyder but I swapped the ECU with a 1997 with ECMLink. The fuel module delete is somewhat done but the fuel pump runs as soon as the key is on ON position, I want it to run when the engine is cranking. The car also has a fuel pump rewire where a cable runs directly to the battery with a relay. Thanks!

 

[DogWhistle]

Can you post a step by step tutorial (for newbies like me) and if possible add pictures. My car is a 1999 Spyder but I swapped the ECU with a 1997 with ECMLink. The fuel module delete is somewhat done but the fuel pump runs as soon as the key is on ON position, I want it to run when the engine is cranking. The car also has a fuel pump rewire where a cable runs directly to the battery with a relay. Thanks!

Congratulations on doing the fuel pump rewire and eliminating the fuel module and having the pump run.

Your unused White-Red wire should run to Pin #8 on the ECU harness. Now that you have swapped the ECU for a turbo model, use your VOM meter to check to see if this wire does indeed go to ground while the engine is cranking and running.

If it does, then disconnect the Black-White wire from ground, and connect it to the White-Red wire and you should be good to go.

 

[Hristo]

Congratulations on doing the fuel pump rewire and eliminating the fuel module and having the pump run.

Your unused White-Red wire should run to Pin #8 on the ECU harness. Now that you have swapped the ECU for a turbo model, use your VOM meter to check to see if this wire does indeed go to ground while the engine is cranking and running.

If it does, then disconnect the Black-White wire from ground, and connect it to the White-Red wire and you should be good to go.

These are my current connections: Black-Red is paired with Black-Blue. Black-White is grounded directly to the chassis. At the fuel pump Black-Blue goes to a relay and the Black-White is grounded again directly to the chassis.

With these connections the fuel pump is on as soon as the key is on ON position . So if I want the pump to start only when the engine is cranking I have to pair the White-Red with Black-White in the front, but do I have to disconnect the Black-White ground at the back that is next to the fuel pump?

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[DogWhistle]

These are my current connections: Black-Red is paired with Black-Blue. Black-White is grounded directly to the chassis. At the fuel pump Black-Blue goes to a relay and the Black-White is grounded again directly to the chassis.

With these connections the fuel pump is on as soon as the key is on ON position . So if I want the pump to start only when the engine is cranking I have to pair the White-Red with Black-White in the front, but do I have to disconnect the Black-White ground at the back that is next to the fuel pump?

Nothing about eliminating the fuel module involves changing any wiring at the pump. You have your pump rewired using a relay for the battery power switched by the 12v fuel pump feed. When we did our fuel pump rewire, we left the fuel pump ground traveling in the harness up to the front fuel module.

With your locally-grounded fuel pump, anytime power is applied to the 12v fuel pump feed, you will activate the pump with no way to shut it off other than cutting the power (turning the ignition off), so yes, you want to disconnect the local ground at the pump and reconnect it to the ground wire (black-white) in the harness.

Up front, the white-red would get connected to the black ground wire and then would only ground when the turbo ECU determines the engine is rotating. If you are using a black box ECU, Pin #8 on the ECU, which is where the white-red travels to, does not provide a ground when the engine is cranking or running. In this case, you will have to ground the black wire directly to the chassis, or, install a switch that will interrupt the ground connection on the black wire.

 

[Hristo]

Nothing about eliminating the fuel module involves changing any wiring at the pump. You have your pump rewired using a relay for the battery power switched by the 12v fuel pump feed. When we did our fuel pump rewire, we left the fuel pump ground traveling in the harness up to the front fuel module.

With your locally-grounded fuel pump, anytime power is applied to the 12v fuel pump feed, you will activate the pump with no way to shut it off other than cutting the power (turning the ignition off), so yes, you want to disconnect the local ground at the pump and reconnect it to the ground wire (black-white) in the harness.

Up front, the white-red would get connected to the black ground wire and then would only ground when the turbo ECU determines the engine is rotating. If you are using a black box ECU, Pin #8 on the ECU, which is where the white-red travels to, does not provide a ground when the engine is cranking or running. In this case, you will have to ground the black wire directly to the chassis, or, install a switch that will interrupt the ground connection on the black wire.

Tried connecting the red-white wire and the black ground together no success there, the pump doesn't work at all. Everything else is how it should be don't know what to try next.

 

[DogWhistle]

We’ll say the same thing we said to @Kryndon above: Use a multimeter to verify that Pin #8 on the ECU is indeed going to ground when the engine is turning over.

 

[Hristo]

We’ll say the same thing we said to @Kryndon above: Use a multimeter to verify that Pin #8 on the ECU is indeed going to ground when the engine is turning over.

Hey bro sorry for opening this thread again can you DM me if possible ? I have some questions

 

[99eclipsegs-2t]

Hey bro sorry for opening this thread again can you DM me if possible ? I have some questions

Would you mind taking pics and documenting your progress on this topic? I too am interested in this procedure as I hope to add boost to my Spyder GS as well!

 

[DogWhistle]

Hey bro sorry for opening this thread again can you DM me if possible ? I have some questions

Go ahead and ask away here on the thread. That way everybody in the futire reading this will benefit from whatever information we uncover.

would you mind taking pics and documenting your progress on this topic? I too am interested in this procedure as I hope to add boost to my Spyder gs as well!

I don’t know how you’d top the pictures above that @japanbastard92 took. Just take it one wire at a time. Follow along with @Hristo and ask questions as you get them.

 

[Hristo]

Go ahead and ask away here on the thread. That way everybody in the futire reading this will benefit from whatever information we uncover.

I tried everything and I just can't make the fuel pump to work only when I start the car. It either turns on directly when I turn the key to ON or doesn't work at all.

Connecting the red and white wire (pin 8) with the thin black wire doesn't make any difference. When I disconnect the thick black wire (ground) the pump doesn't start at all.

 

[DogWhistle]

I tried everything and I just can't make the fuel pump to work only when I start the car. It either turns on directly when I turn the key to ON or doesn't work at all.

Connecting the red and white wire (pin 8) with the thin black wire doesn't make any difference. When I disconnect the thick black wire (ground) the pump doesn't start at all.

The answer hasn’t changed: You have to use a volt meter to check to make sure your Pin #8 on your ECU goes to ground when the engine is cranking and running.

No electric pump will run without a good ground connection.

 

[99eclipsegs-2t]

I don’t know how you’d top the pictures above that @japanbastard92 took. Just take it one wire at a time. Follow along with @Hristo and ask questions as you get them.

If this plug was rotated a bit, it would better illustrate what is going on in regards to the jumpers installed onto the plug and how it can be replicated.

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