Jump to content
LegacyGT.com

FPCM Wiring Upgrade - Relay Staying Switched w/ Key-Off


Recommended Posts

Hey guys followed along on all the post about the fuel pump rewiring. Finally got around to wiring it up. Followed exactly to the diagrams. Car fires right runs for about 1 min then dies. Noticed duty cycle at 100% on fire up and stays at 100% for fuel pump. Not sure what is going on at this point :( any help would be great thanks guys
Link to comment
Share on other sites

  • Replies 98
  • Created
  • Last Reply

Top Posters In This Topic

Hey guys followed along on all the post about the fuel pump rewiring. Finally got around to wiring it up. Followed exactly to the diagrams. Car fires right runs for about 1 min then dies. Noticed duty cycle at 100% on fire up and stays at 100% for fuel pump. Not sure what is going on at this point :( any help would be great thanks guys

 

The reduced percentage is done by the fuel pump control module on the negative leg. It is pulse width modulated.

 

You either have something wired wrong or something in wrong with your module

Link to comment
Share on other sites

Definitely agree to double check all wiring/connections and try changing the module, but the engine could be dying for any number of reasons not necessarily related to the pump wiring. Are you able to do basic querying of the ECU? i.e. Pull a learning view, or monitor/datalog OBD2 data? Do you have the means to check fuel pressure in the engine bay?
Link to comment
Share on other sites

I'm pretty sure I have the wiring correct. Only question I have or want to double check with you guys is 86 wire on the new relay gets tapped into the red/black wire (b+) wire. Then that wire is removed from or cut before it reaches the controller ? According to the wiring print u guys have posted. 87 wire from new relay goes to the pump + side correct ?
Link to comment
Share on other sites

http://legacygt.com/forums/attachment.php?attachmentid=215305&d=1440504392 i have 87 going straight to fp+ and not going threw the controller is that maybe my problem ? i followed this write up http://legacygt.com/forums/showthread.php/upgrading-your-fuel-pump-wiring-4th-gen-213570.html Edited by mikesubie13
Link to comment
Share on other sites

Yes Underdog I can data log the ecu and have a fuel pressure gauge in engine bay. Car had no issues before I touched the wiring. Wanted to upgrade the wiring for full potential of pump. I think I see my mistakes and will correct them and test again. Thanks again for the help
Link to comment
Share on other sites

Think where I am getting confused is to where fp+ goes to ? Off the pump to where cuz turkeylord write up shows it getting un pinned from the fpcm connector and pin 87 going to fp+ wire. Your saying 87 goes back to b+ and into the fpcm ? Correct ?
Link to comment
Share on other sites

In my version you leave the FP+ and FP- wires between the FPCM and pump intact, and add solder in new wires in parallel with the original wiring. Essentially just beefing up those stock wires.

 

Yes, the new relay pin 87 feeds the FPCM B+ terminal. Essentially you take the old B+ (black red wire) and use it to trigger the new relay, which then feeds the B+ on the FPCM. Its all there in my version of the diagram in the OP and your post, #56 in this thread.

Link to comment
Share on other sites

i'm pretty sure FP Duty Cycle is normally 100% at startup for a moderate duration. Once you hit the gas or idle stabilizes it usually drops to 33%. I was watching FPDC for a little while to see if a sound I was hearing was related.
Link to comment
Share on other sites

Thats true Alex but the engine shouldn't die.

 

agreed, was just responding to this quote as to confirm the 100% is normal operations.

 

Hey guys followed along on all the post about the fuel pump rewiring. Finally got around to wiring it up. Followed exactly to the diagrams. Car fires right runs for about 1 min then dies. Noticed duty cycle at 100% on fire up and stays at 100% for fuel pump. Not sure what is going on at this point :( any help would be great thanks guys
Link to comment
Share on other sites

Big thanks to you guys for the help !!!! Found my problem in the middle of reworking to underdogs write up. While plugging back in the fpcm connector come to find out I had some lose pins from de pinning the wires earlier. Fix that and Fire her up good to go boys !! Just need to clean up the wiring tomorrow and do some voltage test to see my gains. Thanks again guys!
Link to comment
Share on other sites

  • 6 months later...

Thanks Underdog. What should the voltage be at the FP- pin with the key at ignition?

 

I will double check all my wiring, but I did ground both the relay and stripped a window in the black FPCM wire and ran that to the chassis ground.

Link to comment
Share on other sites

I found one issue. I had the FP+ and FP- wires crossed and since I was still using the original wiring, battery voltage was being applied on both terminals. I re-soldered them and I am now seeing a 11.2v between FP+ and FP- at the fuel pump harness. When I measure the voltage across the FP+ and FP- when the fuel pump is connected there is no voltage drop.

 

The issue remains that the pump isn't priming. I connected FP+ to the pump and then grounded FP- and the pump turned on, so I know the pump is working.

 

Underdog I am using your wiring schematic. After a turn my key the FPCM on the FP- pin goes to .7v and stays there. I have a feeling I blew the FPCM when I put the 12V on the FP- pin.

Edited by need bb
Link to comment
Share on other sites

I ordered a WRX FPCM. Hopefully that fixes the issue FP- not showing 0v during ignition.

 

At this point I know the wiring is correct and the new relay is sending battery voltage to the FPCM. Anything else I should check?

Link to comment
Share on other sites

Sounds like the Module is blown. It should change the reference to ground voltage to proved 33% 66% 100% pump duty cycle.

 

If you have an AP you can check it on startup to see if it is changing but sounds like you found the problem.

 

On startup it goes 100% for a few seconds then drops to 33%.

Link to comment
Share on other sites

Thanks Underdog and Scooby2.5. Put in the WRX FPCM and the fuel pump primed :)

 

I noticed I am running rich by about 3-4% at higher RPMs so it looks like the fuel pump is flowing more fuel.

Link to comment
Share on other sites

  • 1 month later...

Information from AEM E85 pump that Cobb sells. This is the pump I will be going with on my 2013 STI. I was reading the instructions and thought this was more good info that AEM provides......

 

Electrical Requirement

The supply voltage will affect the fuel delivery of the AEM Fuel Pump. The typical electrical system on modern cars is between 13.2 – 14.2 volts. Although the AEM fuel pump will run at lower voltages the flow will be lower. Ensure the voltage is 13.5V at the pump. The current requirement is minimum 10 amps. The correct wire size will be determined by the length of wire, the wire type and the resistance of any terminals, splices or solder joints in the electrical or ground supply. The ground is equally important and the preferred ground is to route the ground wire to a star ground source that is directly attached to the battery negative post. The minimum wire gauge is 12ga. TXL wire. Twelve feet (12’)of TOTAL CIRCUIT length (power & ground) 12 ga. is required and Twenty feet (20’) 10 ga. is required.

Before wiring the pump to the electrical system make sure the polarity is correct. Connecting the pump with reverse polarity will damage the pump and is not covered under warranty. Please note; the connector on the AEM 320-E LPH Fuel Pump has a small insulated wire on it between the positive and negative terminals. It must remain place, do not cut it off.

Link to comment
Share on other sites

  • 3 months later...

A lit bit of a bump but finally testing voltages and installing my kit. I have looked into this about 2 years ago when I installed the pump but decided to not worry about. Now that I am looking into higher HP numbers I wanted to make sure it's good.

 

AccessPort=APort

Before adding wires

V@Pump-13.06

V@FPCM-13.37

V@APort-14.08

@idle OT

After adding wires

V@Pump-13.32

V@FPCM-13.36

V@Aport-14.08

@idle OT

 

This was a quick test and haven't made a solid connection, just wrapped the new wires around a window on the stock wires. Will double check to see what it does with a solid connection.

 

I am curious to what your numbers were before. I have a buddy that has a very stock GT and I will be testing his to see the difference. I have also added grounds in the engine bay and curious to see if that had any effect. My numbers seem to be pretty high of the start.

22449990_623675324526_8573340386252429419_n.thumb.jpg.caa4cc51b804584c5a9d32c3176eac20.jpg

22489781_623675638896_2981965668388163566_n.thumb.jpg.0dbb22fab9fdd2e542f28e3ef37ba854.jpg

22365187_623675434306_4585642764426495524_n.thumb.jpg.298230d787c4c45d3dbdd13f575f530d.jpg

22539870_623675439296_8239165701863403476_n.thumb.jpg.3d832f4d80ea9ebb1aac5fca26a310a1.jpg

22519445_623675319536_3466487180196106120_n.thumb.jpg.a4ba55418c3f10813bc094d9a69a1441.jpg

22491740_623675314546_7151213861473972151_n.thumb.jpg.d7e17a8eabbfbade09bdbd38d29f9225.jpg

Edited by Silinc3r
added photos
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



×
×
  • Create New...

Important Information

Terms of Use