I think for one last mod I'm going to wire a small toggle switch in the trunk somewhere, probably up by the amps where it will be hidden and out of the way. This will be used to trigger the relay from the DG/YE wire so the pumps stay on full time instead of just priming. This will be used for setting and or checking base pressure with the engine off.
SOLUTION:
OK when I first wired up my pumps return style my thought process was to remove the FPDM from the equation as it's no longer needed. Instead I took the DG/YE wire (pin 9) as everyone suggested and used it to power my relay. The downside of course is the pumps run continuously when the key is on regardless of engine running.
The signal wire from the ECC is the WH/R at the FPDM side (pin 1). It provides the correct times for the pumps to be on such as prime and then off when motor is off. It alone however is to weak to drive a relay.
So the solution is as simple as using the FPDM output that would normally drive a fuel pump to drive your relay. Use pin 10 & pin 3 to wire your relay. This way the ECC still tells the FPDM when the pumps should be turned on and the FPDM in turn activates your relay.
Pin 10 = BN/PK (normally fuel pump positive)
Pin 3 = RD/BK (normally fuel pump negative)
Note: you must use pin 3 to ground the relay coil (trigger) and not chassis ground or it does not work.
There you go guys!!
Malcolm
You guys don't think you will need a modified fpdm because of the amount of amps the pumps required to stay running full time and cause the fpdm to go into thermal shutdown. Just like swaping in gt pumps don't know might be wrong. Can some one verify this
Help me understand this more. Are your referring to the pats module or fpdm?
Pin 1 is a duty cycle signal, that's why it wont work. When the engine is running, the ECU sends a duty cycle signal between roughly 5-50%. The FPDM then doubles that signal for fuel pump duty cycle. When you have key on engine off, the ECU sends a duty cycle signal of 75%. That basically tells the FPDM not to run the pumps.
Running pin 10 and ground didn't work cause the FPDM actually modulates ground, not hot.
As you mentioned, you can have an FPDM basically activate a relay to run the pumps. However, I would make sure that you can set a tune that basically makes the FPDM run at 100% fuel pump duty cycle when the engine is running to insure the relay says on when it should. If the tune is not right and tried to reduce fuel pump duty cycle enough, it could keep the relay from energizing and turn off.
In this case, the FPDM would only be used to energize a relay; that's very little current. It is similar to running a wiring upgrade where the stock FPDM power wire is only energizing a relay to manage power from a new power wire from the battery.
Malcolm, do you have the large wire upgrade for the main power? If so, are you using it to supply 2 separate relays for the pumps, or just 1? At some point when you have time, can you throw a sketch on here with a diagram of how you have everything hooked up? I don't have the Lethal return "kit", I only have the Fore hat/pumps. For the existing wiring, I have the upgraded supply with a single relay wired into the stock FPDM with a BAP, so I have to convert everything to this new setup (without the BAP, of course). I'm assuming that I will also need one more relay too, since I believe most people use separate relays to drive each pump - correct?
At some point when you have time, can you throw a sketch on here with a diagram of how you have everything hooked up?
here ya go. hope this helps ya some!Anyone have some pics?
i just wanted to see if anyone has had success in having there tune setup for wiring this way? i followed this thread to a T and my pumps did infact act normal, priming when key on and car ran great under normal driving. well today i had my tuner set the tune straight and the car would not run worth a crap? it would hardly idle and barely run and couldnt set base pressure. i had instructions from justin@vmp to give my tuner on how to edit the tables to keep the fpdm at ful power but didnt work. car actually ran better before the tune edit?? i double checked the wiring and all was correct. i ended up wiring per instructions from lethal and all is ok. i am having some issues though however on where to set the base pressure at, but ima start another thread for this to keep down the congestion here. thanks anyway but this didnt work for me