What does the fuel pump driver/control module actually do?

[zimflux]

What does the fuel pump driver/control module actually do?

Can it fail and therefore not keep LPFP psi up at key on? Unsure if I'm dealing with a defective LPFP or module, low pressure at hpfp schrader valve.

I assume I can test the lpfp by placing 12v to it and measure psi from hpfp schrader valve again?

Thx

[Jayz691]

Easiest way too check fuel pressure is vcds, in live data. Then ya can also check duty cycle(%).
The lpfp don't run constantly, so the controller "controls" how much it runs(duty cycle).
Yes it can fail.


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[zimflux]

Easiest way too check fuel pressure is vcds, in live data. Then ya can also check duty cycle(%).
The lpfp don't run constantly, so the controller "controls" how much it runs(duty cycle).
Yes it can fail.


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Thanks Jay.

We spoke about a fuel problem I had a couple months ago where I ended up replacing my lpfp and fuel filter.

However now my car totally died, only cranks.

I can hear the pump running but I get very low fuel pressure as measured at block 106. See attached. This is with key on and pump running for a moment.

Trying to understand whether it's my lpfp again or is the controller wonky or something else.

I wonder if I should jump the pump so it's running on 12 volts to test if it's the pump or controller.

Appreciate your time and thoughts.Screenshot_20240205-114847.jpg

[Jayz691]

What year is your car again? BPG or BWT?
If BWT, check condition of rubber fuel inlet hose, inside.


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[zimflux]

What year is your car again? BPG or BWT?
If BWT, check condition of rubber fuel inlet hose, inside.


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07. Yes will pull hpfp and replace hose anyway. Is that becoming common?

But if not? Still curious, if I can jumper 12v to override the pump module to produce pressure?


Thx

[Jayz691]

Yes, its becoming more and more common with age/milage. And also with some people removing the hose to check cam follower fairly often. Fyi you can leave the hose attached.
Far as putting direct power to lpfp, not sure how much that will tell you besides the pump works. The pump will pump more/less depending on amperage(I believe). When ya turn the car over, check blocks 230 and 231 for fuel pressures, see what your getting on both sides, etc. 106 don't give much info..

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[zimflux]

Yes, its becoming more and more common with age/milage. And also with some people removing the hose to check cam follower fairly often. Fyi you can leave the hose attached.
Far as putting direct power to lpfp, not sure how much that will tell you besides the pump works. The pump will pump more/less depending on amperage(I believe). When ya turn the car over, check blocks 230 and 231 for fuel pressures, see what your getting on both sides, etc. 106 don't give much info..

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Thanks, Jay

Leave this hose attached? How would you check both ends?

The idea I had by powering the pump directly with 12 volts is to bypass the fuel module. My pump primes with the key on but I'm not getting the pressure that I should be getting. This is why I originally asked about what the fuel module does and after further research I understand it modulates voltage to the pump.

The pump is brand new (months old) and the module was replaced a couple years ago as well so instead of just throwing parts at it I'm trying to figure out which part it isn't. Assuming no blockages in the line, my thought is applying 12 volts directly to the pump and test at the schrader valve will eliminate the fuel control module. Agreed?


Thanks for your help

[Jayz691]

I meant you dont have too remove the hose when doing a cam follower. You'll need to remove it to check it. If its damaged, itll be one the pump side.
You can try with direct power, see what ya get.

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[canadianA4B7]

Thanks, Jay

Leave this hose attached? How would you check both ends?

The idea I had by powering the pump directly with 12 volts is to bypass the fuel module. My pump primes with the key on but I'm not getting the pressure that I should be getting. This is why I originally asked about what the fuel module does and after further research I understand it modulates voltage to the pump.

The pump is brand new (months old) and the module was replaced a couple years ago as well so instead of just throwing parts at it I'm trying to figure out which part it isn't. Assuming no blockages in the line, my thought is applying 12 volts directly to the pump and test at the schrader valve will eliminate the fuel control module. Agreed?


Thanks for your help

Pull the feed line from the fire wall off the HPFP, put that into a container and go turn your key. You should then see the prime cycle fuel in the container. If the parts you’ve mentioned work you’ll see fuel. 1 part not mentioned is the fuel filter. Common spot that will reduce fuel flow to the hpfp even if the pump and module are good.

Module seems to be more PWM than just a voltage adjuster. It’s using a few signals to calculate an output through ecu. To test you wud likely need an oscilloscope to correctly see everything it does from input signal to output signal.