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Fuel pump control module


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Aww shucks, thanks guys. :)

 

I had some time tonight, so I thought I'd go get a real life measurement.

 

My alternator puts out a steady 13.7V measured at the battery.

 

During a 4th gear pull I'm getting 13.0V at the fuel pump. And again that's with the stock FPCM, the STi module would be higher.

 

Sorry so potato, but this wasn't an easy pic to snap :lol:

http://i.imgur.com/rSresvSl.jpg

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  • 2 weeks later...

Anyone have a spare FPCM terminal laying around? Thinking about wiring mine with a switch to go back to the stock harness +12 in case I ever have an issue with the 20A fuse while on the road. Would be easier than tearing apart 1/2 the car on the side of the road. Not that I ever expect to have suce a problem, but you never know...

 

Oh, and I did order a 200A circuit breaker for the 1/0 lead. Hopefully it will look more OEM than the big chrome Stinger ANL fuse holder I'm using now.

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Anyone have a spare FPCM terminal laying around? Thinking about wiring mine with a switch to go back to the stock harness +12 in case I ever have an issue with the 20A fuse while on the road. Would be easier than tearing apart 1/2 the car on the side of the road. Not that I ever expect to have suce a problem, but you never know...

 

Oh, and I did order a 200A circuit breaker for the 1/0 lead. Hopefully it will look more OEM than the big chrome Stinger ANL fuse holder I'm using now.

 

I may have one in my massive pile of Subaru $hit. I will look and PM you.

 

Shawn

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I did it the lazy way... AKA hardwired

12Ga ( I believe) soldered to the back of the bulkhead connector on fuel pump assembly, 12+ from battery, signal from the FPCM Bat+, and grounded on the right side of the center console, allowing for a switched ground leg to be able to turn off the pump while sitting with the key in "ON"

 

1232675_641643839952_1794865403_n.jpg?oh=026f563e653bf4aee6210a7941e0486d&oe=524F18E3

 

1353605_641643086462_974015134_o.jpg?oh=e58056791bd255e1aebf2c37b4ac3cec&oe=524F45A6

 

960869_630443695132_2063956483_n.jpg?oh=4756d4f0f4fe0eab82579f24a8cb9c02&oe=524EB446

Edited by bettner12
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Here is a nice plot of the before and after on a relayed direct current to the pump. 11.2v to 13.6 when 100% duty. Then after got my e85 tune.

 

http://i341.photobucket.com/albums/o381/sphen22/IMG_20130926_193319_038_zps8de40042.jpg

 

 

http://i341.photobucket.com/albums/o381/sphen22/IMG_20130926_193253_981_zps9fea94b7.jpg

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We checked another 2005 legacy GT wagon tonight and it too would only go to 11.75 volts to the pump out of the fuel pump module/unit at 100% pump duty cycle.

 

Did any of the vehicles have the ground mod upgrade? Or has anyone tested the voltage at the pump with a ground mod on their LGT?

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Did any of the vehicles have the ground mod upgrade? Or has anyone tested the voltage at the pump with a ground mod on their LGT?

 

I'm amazed that the first quote you use from this whole thread is an early one during the verification stage of this problem

 

Are you talking about the grounding kits people use under the hood?

 

How would this affect the neg PWM signal coming from the FPCM to the fuel pump?

 

The voltage drop is because of the voltage feed wire to the module being too small, and the wires from the PWM module both neg and pos being too small.

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  • 3 weeks later...

This may be a stretch, but thought I'd also post here:

 

P0171 code 3 times in 3 days.

 

Only @ 27-2900rpm cruising freeway speeds and very light throttle. Afr gauge will pop up to 15 from the cruising 14's.

 

Who wants a guess why I don't have fuel at light throttle??

 

ID 1000 complete top feed conversion, w their fuel line kit, oe fpr and dw 300 pump in Modded basket and has been run this way since last February. It doesn't run lean @ wot, just very light throttle.

 

Additional info: temps just dropped dramatically from 90's daytime to 60's max (but tune was done in the 60's anyways) and at idle my volts gauge drops to 12's or even 11's when in gear, at idle at a stoplight and HID's and factory radio are on....

 

Other than testing for vac/air leaks, looking for where to look next.

Edited by doccrowley
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This may be a stretch, but thought I'd also post here:

 

P0171 code 3 times in 3 days.

 

Only @ 27-2900rpm cruising freeway speeds and very light throttle. Afr gauge will pop up to 15 from the cruising 14's.

 

Who wants a guess why I don't have fuel at light throttle??

 

ID 1000 complete top feed conversion, w their fuel line kit, oe fpr and dw 300 pump in Modded basket and has been run this way since last February. It doesn't run lean @ wot, just very light throttle.

 

Additional info: temps just dropped dramatically from 90's daytime to 60's max (but tune was done in the 60's anyways) and at idle my volts gauge drops to 12's or even 11's when in gear, at idle at a stoplight and HID's and factory radio are on....

 

Other than testing for vac/air leaks, looking for where to look next.

 

Wow with your setup If I I would get the wiring kit from DW and follow this thread and rewire your fuel pump direct from the battery. Then rewire from the neg on the FPCM to the pump.

 

Aftermarket pumps are flow rated at about 13.5-13.7 volts

 

Also if you measure less than 13 volts at the battery with the car running you have a really weak alternator.

I'd do the diode trick and if you don't want to do that replace the alternator. Maybe even do both.

 

I'm not sure why you are having partial throttle problems but it can't hurt to fix the voltage to the pump. Especially running 1000's

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^ i wonder if his pump doesn't like the 33% duty cycle..

 

just to test just ground the pump directly to ground to bypass the fpcm and see if it still does it.

 

just need to lift the rear seat .

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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Did anyone consider running a thicker wire from the factory fuel pump relay to the FCM (and then from FCM to the pump)? Essentially replacing the wiring only and avoiding the extra relay? One less thing to malfunction (and the generic relays are often of dubious quality).
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Wow with your setup If I I would get the wiring kit from DW and follow this thread and rewire your fuel pump direct from the battery. Then rewire from the neg on the FPCM to the pump.

 

Aftermarket pumps are flow rated at about 13.5-13.7 volts

 

Also if you measure less than 13 volts at the battery with the car running you have a really weak alternator.

I'd do the diode trick and if you don't want to do that replace the alternator. Maybe even do both.

 

I'm not sure why you are having partial throttle problems but it can't hurt to fix the voltage to the pump. Especially running 1000's

 

L C Tables?

 

http://www.romraider.com/forum/viewtopic.php?f=15&t=8015

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This may be a stretch, but thought I'd also post here:

 

P0171 code 3 times in 3 days.

 

Only @ 27-2900rpm cruising freeway speeds and very light throttle. Afr gauge will pop up to 15 from the cruising 14's.

 

Who wants a guess why I don't have fuel at light throttle??

 

ID 1000 complete top feed conversion, w their fuel line kit, oe fpr and dw 300 pump in Modded basket and has been run this way since last February. It doesn't run lean @ wot, just very light throttle.

 

Additional info: temps just dropped dramatically from 90's daytime to 60's max (but tune was done in the 60's anyways) and at idle my volts gauge drops to 12's or even 11's when in gear, at idle at a stoplight and HID's and factory radio are on....

 

Other than testing for vac/air leaks, looking for where to look next.

 

A weak or dying alternator will give you lots of issues. When my alternator was dying, I saw weird AFR issues at idle and cruising, as well as a bunch of misfires at idle. I would consider replacing the alternator first and then see where you are at. A DW 300 pump, running at 33% duty cycle, with low voltage, is probably not real happy.

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Did anyone consider running a thicker wire from the factory fuel pump relay to the FCM (and then from FCM to the pump)? Essentially replacing the wiring only and avoiding the extra relay? One less thing to malfunction (and the generic relays are often of dubious quality).

 

do it and tell us how hard it was ..

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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do it and tell us how hard it was ..

 

Are you suggesting is a dumb idea?

 

Might be, I realized the stock fuel pump relay is in the passenger side kickpanel, so not a convenient location to run a wire from.

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its a good idea.. but the wiring to the relay needs to be updated... and it may pass through others relays that are to small also.

 

so its a shit load of work .. might as well sell the car and buy a sti.

 

and dont worrie to much about the relay failing ... they tend to act up before failing, and if they do completely fail you can cut it open and mash the contacts together to get home!

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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I am only seeing 13.2 volts at 100% FP duty cycle, with 12g wiring, STI FPCM, and the pump wired directly to battery power.

 

The factory FPCM power wire powers both the FPCM and the relay. Direct power to FP from the battery. 12g wire for both the + and - to and from the FP and FPCM. I am seeing 13.5 volts at 100% FP duty cycle.

 

I am seeing about 13.6-13.8 volts at the pump (100% fp duty cycle) while retaining the factory modulation of the fuel pump.

 

13.8 volts - Upgraded wiring, battery power to pump, DW 65c
13.2, 13.5, 13.6-13.8, 13.8? Any changes between these measurements Shawn? :confused:
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^ well its hard to say .. you should be also including voltage level measured at the battery at the exact same time. as just after startup, the voltage will be higher and it tapers down after that. with or without the diode mod.

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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I thought about actually measuring the drop, as in positive test lead on the batt, negative test lead on the test point. Then do the same thing with the negative side to ground. Might need some longer test leads :D

 

Then again the drop should be negligible along the 1/0, I could just test from there...

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if you have tgv delets to bad those sensor inputs cant handle 12v ? or can they ? you could run a wire back and it would be in the datalog.

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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Found it.....

 

Good news is that if you bypass the stock wiring harness that seems to drop 1.7-2 volts the STI/Impreza module outputs 13.5 volts to the pump.

 

If you bypass the wiring harness on the legacy module we would get 12.5 volts.

 

So it looks as though the STI/Impreza module does output a bit more voltage on max than the legacy module does if the voltage into the module is correct or more.

 

Edited by Scooby2.5
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