Return style wiring HOW TO allowing OE type fuel pump actuation
- Thread starter MalcolmV8
- Start date
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.
That is an awesome idea, plus it may be useful if something went wrong with the FPDM to bypass that.;-)
This thread has me really excited to finish my own system now. Do you still need 2 separate relays (one for each pump), or are you driving them both with a single HD relay?
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
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 - I'm glad you figured this out!!! I knew there was a way to do this, and my Lethal return system will be here this week. I will do the same thing you did and i'll post some pictures for you guys!!
I was wrong, it's the brown with pink wire on the PATS. I don't have an FPDM on my 97'- but I wired my painless relay in this way to power my weldon 1100-a fuel pump and it primes when I key on just fine.
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?
Correct. There is a setting in the ECC your tuner can change the FPDM from returnless to return in which case the FPDM will keep the pumps or relay in this case on constantly instead of modulating. I actually loaded both my new return and my old returnless tunes on last night and did key on to see how it behaved. In my minimal testing in the garage both worked. However as you said one should get that value changed in the tune.
Yup, that's correct.
Yes I have a fused 8 gauge wire running from the battery to the trunk to supply my pumps. I have a single relay right now and don't really foresee changing that. It will be different for everyone but with my Walbro 400 lph pumps they use 12.57 amps at 40 PSI and 14.92 amps at 70 PSI which is probably more than I'll ever see. That's just barely touching the 30 amp mark combined and I have a 40 amp relay in there. I could split it and run dual 30 amp relays and have redundancy in that if one relay ever failed I'd at least be able to drive the car still out of boost and get home.
Will do tonight.
Thanks! I have a 30A relay in there now with my current setup, so in my case, it would probably be prudent to add a second one. For pumps I have the Walbro return ones (can't remember the number offhand), but they are what everyone used prior to the 400lph hitting the market.
About to get going on my triple pump return style system and as always pics would help to show what you guys did :beer:
Will be doing this today on my tripple fuel pump return i will post pics as I get it together.
anyone ever get any pics of their wiring install for the fpdm on return system? installing my lethal budget return system tomorrow. thanks for the good info in this thread guys!
Anyone have some pics?
i just wanted to say this is an awesome thread! i finished my install of the lethal budget return system this evening and i took a bunch of pics. i will start a new thread and organize them and will update this post with link. i did use this for the wiring and kept my fpdm and i must say it went very smooth, i primed the pumps before putting the tank back up and connecting the feed line and it shot out and stopped. once the tank was reinstalled i primed a few times with the key and it fired right up first try. ran perfect all the way home about a 20 minute drive and didnt trip one code! i kept the frps with my kit and watched everything in my torque app and i didnt boost it but just normal driving and pressure stayed right around 39-40 the whole time and it drove smooth as can be! i'm soo happy its unbelievable how well it drove. thanks for all the info posted here. i have some tips for the devision x hat and will try to get a thread up and organized with pics over the weekend. thanks again guys!
Last edited:
here ya go. hope this helps ya some!
http://www.svtperformance.com/forums/how-230/935519-lethal-budget-return-kit.html#post13060378
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
Setting the base pressure is a piece of cake. Post up in our vendor section if you want to start a new thread and I'll reply with pics and a writeup there.
Jared
Users who are viewing this thread
