I have a bit of a head-scratcher here. Ever since I completed the last round of modifications on my '06 LGT I have had a small drain on the battery (~.1A). This causes a battery voltage drop of ~.1V/day. In the process of troubleshooting I discovered that pulling the FP relay's 30A fuse resolved the issue.
I can make this problem occur simply by cycling the key to IGN and switching back off. Once I pull the 30A fuse the relay switches off and does not switch back on when the fuse is reinstalled. Once the contact is broken the current draw drops to ~.01A.
I have verified that the wiring between the battery/relay/FPCM is correct. My battery is in my trunk and the wire runs are very short. 12V+ goes from the 30A fuse to Pin 30 on the relay. Pin 87 goes to FP+ at the pump. Pin 85 to chassis ground. Pin 86 to ("B+", red/black) at the FPCM. This has been verified against the instructions here
, and in the DW FPHWK install instructions.
I have used two different standard 40A/12V SPST relays in the process of troubleshooting.
What appears to be happening is, once the connection is made, the current is feeding through the FP wiring and back into the FPCM via the "FP-" where it somehow keeps the "B+" pin hot. Since the FPCM "B+" is the trigger for the relay, it is keeping itself switched.
The FPCM is the original from my car. Entirely possible it has an internal fault, although it seems unlikely. I do have a spare STI FPCM I received as a replacement for a DOA unit I bought off eBay, and I can try it.
I have tried to duplicate the problem with the FPCM removed and it does not occur. The relay still switches with IGN since it is tapped off "B+" which gets power from the factory FP relay; but when the key is turned off the relay contacts open since there is no back-feed through the FPCM keeping B+ hot.
P.S. The car drives fine and if anything is running quite rich (still on break-in map; pulling fuel, but not pegged, in A/F learning A-C).