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Old 01-18-2013, 10:19 AM   #1
dan1587wrx
Scooby Newbie
 
Member#: 132107
Join Date: Nov 2006
Chapter/Region: Tri-State
Location: NJ
Vehicle:
2006 WRX Stage 3
340WHP 340WTQ WRB

Default 2006 WRX Walbro 255 Intermittent Failure Troubleshooting

I have a 2006 WRX with a vf39, ewg, tmic, walbro 255 fuel pump, and supporting mods. The car was protuned a few years ago by Cleo at Precision tuning and made decent power. The car has been running great until recently when it would stall out for no apparent reason.

The car would stall out and not throw any codes. It didn't matter if I was driving at highway speeds or local roads the car randomly stalled out. After it would stall out I would wait a few minutes and restart the car with no issues. Finally a few weeks ago I was driving on the highway when it stalled out and threw CEL P0230, fuel pump primary circuit malfunction. I again waited a few minutes and restarted the car with no problems. I got the car home and began troubleshooting.

After reading through many posts I decided to test the entire system from the cars ECU to the fuel pump controller and finally the pump itself. After ruling out the controller, ecu, wiring and relay to the pump itself I knew it had to be either a bad pump or wiring inside the tank. So I pulled the pump and began testing it. The pump tested within manufacturer specs and I was at a loss because I could not find any problems.

Closer examination of the pump and wiring harness from the bulkhead connector on the tank access panel to the pump revealed that the pump harness had melted around the pump positive connection. I removed the harness and could see the melted plastic connector. This got me worried as there could have been arcing in the fuel tank leading to a fire or explosion. So I had to test the pump and harness and determine what happened.

I then began testing the pump with the bad harness and sure enough I found that the pump would test satisfactorily when given and input voltage from 12V - 14V. I plotted the flow rate vs pressure vs amps and everything was in spec. I then decided to leave my test rig consisting of 2 five gallon nalgene (fuel supply for pump) bottles and a 6 gallon bucket (pump discharge which recirced back to the nalgenes) oscilloscope and power supply on at 13.5V for 1 hour. What I found was that with the bad harness the resistance in the wiring caused the pump to heat up and trip the walbo fuel pump motor over loads. This occurred sometimes in an hour or in 20 minutes with no repeatability.

All in all I changed the harness with a heavier gauge wire with chemical safe insulation and connectors and have not had any issues for 2 weeks now. Sorry for the long winded explanation but I could not find thread that documented any troubleshooting. All the threads just told people to replace the pump or the fuel controller or relay when maybe the harness just needed to be replaced. Hope this is helpful.

Dan
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Old 01-18-2013, 07:09 PM   #2
mechatricity
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Member#: 290592
Join Date: Aug 2011
Chapter/Region: South East
Location: Charlotte, NC
Vehicle:
04 & 06 WRX Wagons
'15 WRX 6MT CWP

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I applaud your thoroughness and the issue is definitely concerning. I can't imagine it could be a completely isolated.... It's particularly poignant because i'm installing a 255 in my 06 tomorrow:P.
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Old 01-21-2013, 09:37 PM   #3
dan1587wrx
Scooby Newbie
 
Member#: 132107
Join Date: Nov 2006
Chapter/Region: Tri-State
Location: NJ
Vehicle:
2006 WRX Stage 3
340WHP 340WTQ WRB

Default

Thank you.

The issues is not isolated and most people just suggest to replace the pump and other parts of the system. I'm a mechanical engineer and like to figure out the cause of issues instead of just replacing parts. If I wanted parts replaced I would go to the dealer.
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