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Fuel pump control module


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Does the fuel pump controller vary the voltage through resistors? Or is the pump somehow pulsewidth modulated?

 

I do not think it would work with the factory controller. To be honest I am not sure. But it is easy enough to hook it up to MAF, TPS or a hobbs switch.

 

Here is a link to them. http://www.fuelab.com/index.php?option=com_virtuemart&page=shop.browse&category_id=1&Itemid=3

 

From instructions:

Pulse-Width Modulation or other means of reducing input power voltage may result in erratic or non-operational condition

 

Something else cool about these:

Fuel Pump may be mounted inside a fuel tank or cell

 

We actually are installing one of these in a Legacy GT as an in tank pump in the next week or so.

Edited by Sarg
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How bout just use the stock ECU PWM output to drive a power mosfet? You really have no reason to run the thing at 100% most of the time (it will DECRESE the life of the pump), just let the ECU do it's thing bit with less total inline resistance fore the pump?

 

Yep that's what I had in mind. I am looking into getting a PCB fabricated with quick-disconnect terminals and proper voltage and current stiffening.

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You could start by hooking it up to the stock wiring and see if the pressure is high enough for your needs, since the supply current from the ECU might be limited. If not, then you can run it with a relay and run it at 100% with current drawn straight from the battery. Fuel pumps can get pretty noisy running at 100% all the time though :lol:

 

The first guy who wanted to adjust the fuel pump duty cycle was actually doing it for noise reduction, but the other way around. He said his pump was very noisy when running at low speed. At 100% it runs quieter. Go figure.

 

Anyway, I can certainly see value in running a heavy duty fuel system with a heavy duty power supply. I've seen pics of setups with three pumps and it never occurred to me until this thread that you'd probably destroy the ECU's fuel pump driver that way. Using the stock fuel pump line to drive a good mosfet (with a good heat sink) seems like a great idea.

 

If anyone has reason to believe that running your pump at 100% all the time would solve a problem, I can get you an EcuFlash ROM definition to make that happen. However you will first have to convince me that you really need it. :)

 

Tons of Impreza people are running Walbro 255s off the stock ECU, I'd be very surprised if that setup was really problematic.

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The first guy who wanted to adjust the fuel pump duty cycle was actually doing it for noise reduction, but the other way around. He said his pump was very noisy when running at low speed. At 100% it runs quieter. Go figure.

 

...

 

Tons of Impreza people are running Walbro 255s off the stock ECU, I'd be very surprised if that setup was really problematic.

 

My friend's setup with dual Walbros sounds like a jet about to take off when only the ignition is on and the pumps running at 100% :lol:

 

For people running E85, they might be teetering on the edge of not having enough fuel pressure with a single pump if they are running higher boost levels. That's why we went with a dual setup pulling power off the battery. The car has a TD06 20G and Bosch 1000cc injectors with E85. My friend used a fancy spread sheet accounting for actual flow rate, IDC, and fuel pressure to realize a single Walbro wouldn't be enough.

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I'm actually surprised the actual FP supply voltage comes from the ECU. I'm normally accustomed to seeing the ECU control a relay that is wired to B+.

 

I guess it's just a Subaru thing.

 

I'm not convinced at all that the ECU directly drives the fuel pump . That doesn't make much sense. There's too much current. I've NEVER seen a sequential fuel injection system which does that. I looked through the '05 LGT service manual and unfortunately the fuel pump control pins on the ECU are not specifically detailed in the pinout. We do have this basic diagram though:

 

http://legacygt.com/forums/attachment.php?attachmentid=89016&stc=1&d=1282328307

 

http://legacygt.com/forums/attachment.php?attachmentid=89018&stc=1&d=1282328557

 

 

In red I have shown where I believe the main power for the fuel pump comes from, which is listed as fuse #11. It's highly likely that the ECU controls a few transistors in the control module which in turn regulate the current to the pump.

 

If any of you have worked on older 90s cars, a lot of them have various types of seperate/external igniter boxes for the ignition system. SR20DET and 13BREW engines have these kind of boxes for their distributorless systems, plus GM and Honda have ignitors for their distributors with electronic spark advance. These modules contain various transistors and other circuits which then control the ignition coils. The ECU doesn't ever directly drive the ignition system, and I highly doubt Subaru is directly driving the fuel pump either.

 

The LGT ECU switches on the fuel pump relay which supplies the main current from the fuse box for the fuel pump. The control module is in-line with this current supply and a chassis ground. Two pins from the ECU may control transistors in the control module which in turn control the power and/or ground to the pump itself.

LGT_fuel_pump.thumb.jpg.fc5d63ad378a1d6bb5799f97775056c9.jpg

LGT_fuel_pump2.jpg.1c54b65906e572f7f9e9574a58e80b26.jpg

Edited by Boostin
On the search for a new DD...
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oh and to those of you who want to run full battery voltage on a Walbro 255: I can tell you from personal experience with that (not on an LGT) that they don't call them "Whinebros" for nothing. They are annoyingly loud. I've got a Cosmo 20B-REW 3 rotor pump on one project car and a 2JZ Supra TT pump on another and they are much quieter than the Walbro was. Those pumps are also made by Denso.
On the search for a new DD...
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You people frighten me :lol:

 

The ECU doesn't directly supply power to the fuel pump.

 

This thread will probably never end, so I might as well ask a very important question:

 

What kind of fuel should I use if I get a Walbro fuel pump?

 

I would go with JP-5, but only if you are going to run dual pumps at 100% all the time.:rolleyes:

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You people frighten me :lol:

 

The ECU doesn't directly supply power to the fuel pump.

 

This thread will probably never end, so I might as well ask a very important question:

 

What kind of gas should I use if I get a Walbro fuel pump?

 

Wow, awesome.

 

Thanks for the diagram, Boostin. I agree with your interpretation.

 

So today we learned that Franz' project could be implemented as a replacement for the "fuel pump control unit" rather than as an add-on, and that Rao can't be helpful without being a douchebag about it.

 

Carry on.

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That is not what I leaerned from this :lol:

 

I've heard bad things about using gas in your car.:rolleyes:

 

Dude, please be constructive and not condecending when posting in my threads or I will disrespect you in the same way. Thank you.

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  • 1 year later...

Older thread but have an interesting one related to this.....

 

Went to Cobb tuning back in 2009 and my car at 350whp 373wtq with an AVO380 AVO fuel pump and DW 850 injectors was at 100% duty cycle for some reason.

 

Just went to Cobb this week, I had changed regulator and orings in the tank but still had my 2-3 year old AVO pump in but now have Id1000's.

 

While at the beginning of tuning right when we got to 360whp 415wtq, still in the rich stages of the tune I was at 97% duty cycle on the ID1000's.

 

AFR's were in the 12.7 range when they should have been in the 10.5 range at the beginning of the tune.

 

 

I changed my pump to the Aeromotive Stealth in the parking lot and the AFR's dropped by a point immediately but I was still at 97% duty cycle on the injectors.

 

Through some trouble shooting and tearing of my interior apart to get to the fuel pump relay and the fuel pump control module/unit we found part of the problem.

 

My stock wiring harness was dropping almost 2 volts from the fuel pump relay to the fuel pump module at the back left of the car. It was causing the fuel pump to never get above about 11.7 volts coming out of the fuel pump module/unit.

 

We bypassed the wiring from the relay to the module and then were able to get 12.7 volts out of the module to the pump and the duty cycle of the injectors dropped to 80-85 % when the pump was at 100%

 

If we bypassed the fuel pump control module/unit altogether and had 14v battery/alt voltage it would drop the duty cycle of the injectors even more.

 

We are doing some more testing to find if the fuel pump module/unit is defective or not but it was interesting to see how the pump changed the AFR's as well as how I had a 2 volt drop in my wiring harness.

 

In my case the fuel pump control module/unit never allowed the pump to go above 11.75 volts on stock wiring and with external wiring it went to 12.7.

 

Stay tuned......

Edited by Scooby2.5
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Yes, I may have been on to something! Great info, I'm going to check the voltage on mine for the hell of it. I will say when I start the car the pump is at 100% and it whines pretty loud until the controller steps down the voltage.

 

Did you do a voltage drop across the power feed from the control unit and at the FP module? It may go through an intermedate connector somewhere and you could have high resistance. Subscribed!

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When you start your car for the first 4-7 seconds the pump goes to 100% duty cycle.

 

You can monitor this with your AP by selecting fuel pump duty cycle.

 

We monitored ours with the AP and then stuck a volt meter at the pump.

 

The connector on the pump has a flip top on it so you can leave it plugged in and still get a meter on it but you need some sharp thin lead wires. Its a green/yellow and green/red wires.

 

I have a BS degree in electronics so this has been a bit fun messing with. Although I want my car back :)

 

We measured the voltage first across the fuel pump relay and no drop at all. Then measured the difference at the exit of the relay and then at the input of the fuel pump module.

 

It was about 12.7v at the relay but closer to 11 at the fuel pump module. Somewhere there is an almost 2V drop across the wiring between the relay and the fuel pump module.

 

Lastly I may be purchasing a fuel pump control module from an impreza and seeing if we can hook it up to see if it works.

 

My goal is to have a control module that allows for more voltage to the pump. I do NOT want to bypass it on a daily driver

 

Here is a link to one I am trying to purchase:

 

http://forums.nasioc.com/forums/showthread.php?t=2085811

 

Here is a link to the 08 up STI

 

http://opposedforces.com/parts/impreza/us_g12/type_19/engine_electronic/relay_and_sensor_engine/

 

Here is a couple links to the older ones:

http://opposedforces.com/parts/impreza/us_g11/type_5/engine_electronic/relay_and_sensor_engine/illustration_1/

 

http://opposedforces.com/parts/impreza/us_g11/type_5/engine_electronic/relay_and_sensor_engine/illustration_2/

Edited by Scooby2.5
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Hey unclemat thats what we did see post 42:

 

My stock wiring harness was dropping almost 2 volts from the fuel pump relay to the fuel pump module at the back left of the car. It was causing the fuel pump to never get above about 11.7 volts coming out of the fuel pump module/unit.

 

We bypassed the wiring from the relay to the module and then were able to get 12.7 volts out of the module to the pump and the duty cycle of the injectors dropped to 80-85 % when the pump was at 100%

If we bypassed the fuel pump control module/unit altogether and had 14v battery/alt voltage it would drop the duty cycle of the injectors even more.

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Ah, damn, I see.

 

Cool, I am very curious about it. Careful about the nasioc part. 08+ STI hatch indeed has 22648AA140. Earlier years had a different part number.

 

Interestingly on 08+ the part number seems to depend on wagon vs sedan. Maybe there is a difference in mounting bracket or something like that.

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Ill keep everyone posted on what happens with this. It is an interesting one.

 

There is a 08 WRX with my exact same setup that was tuned by Tim Bailey at Cobb surgeline that put 380/440 to the wheels and did not have this problem with DW 850's.

 

He may be able to check his pump voltage for me this week.

Edited by Scooby2.5
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