Engine/Transmission (1998.5 - 2002) Your Thoughts, FASS wiring

[PSpychalski]

Installing FASS on frame rail. Now for the wiring. Use existing lift pump power as relay contact (PINS 85/86). Run fused hotwire though relay (PINS 30/87) to FASS pump. Get the same result as exiting wiring. ECM turns relay on for 3 seconds for start. Once started ECM powers relay not lift pump. Your thought guys?

 

[Sticks]

Sounds like the same wiring setup for the OEM in tank replacement. If it works, run with it.

 

[PSpychalski]

Pretty close Sticks. OEM uses power from fuse box to contact relay. Power to lift pump is still from ECM. Being there is no fuse protection between pump and ECM, moving power around a little bit. Same but different.

 

[dillrepair]

so my fass is back on the frame rail. is it better to wire it up this way with a relay attacted to the ecm harness? right now its just got wires extended back from the stock harness to the pump on the frame rail. if so what relay should i get and do i hook up the power wires directly to the battery or some other way? i would use a fuse of course.

 

[PSpychalski]

went from ECM harness to power a relay. Relay is connected direct to Battery with fuse to power FASS. Direct from ECM to Fass will throw codes and Check Engine light. you can use the same style relays that are in your power junction box, that way you don't have to have different relays on hand. I always carry a couple of relays with me in the glove box.
I "think" Geno's has a schematic.

 

[dillrepair]

so next question is... can i daisy chain pumps? i have a fass ddrp and a brand new stock pump.

 

[Sticks]

Daisy chain or running in series, yes. You will want your lower output pump first in line from the tank.

By Stock Pump, I presume you mean block mounted carter? You'd be better off using the in tank pump, then your FASS. I have yet to see a Carter block pump perform well and last that was not fed by something else, so in this case, maybe the FASS first in line, then the stock pump.

 

[Sticks]

so my fass is back on the frame rail. is it better to wire it up this way with a relay attacted to the ecm harness? right now its just got wires extended back from the stock harness to the pump on the frame rail. if so what relay should i get and do i hook up the power wires directly to the battery or some other way? i would use a fuse of course.

You are still going to have to run an independent power wire down to the FASS. There is a wire in the factory harness available for the fuel pump if in tank, but it will not handle the amp load of the FASS.

 

[dillrepair]

i'm 99% sure this one doesn't have an in tank lift pump... i'm assuming i'd know by now but i could be wrong. i originally removed the stock block mounted pump and replaced it with the ddrp on the block then later relocated the ddrp to the frame rail back by the tank. over the course of the last year and a half i ended up having to replace my fass under warranty and had a new carter pump in its place during the interim. so i spose i could just put the carter back on the block in series and connected behind a relay with the fass. you think the pressure gain would be worth it? i suppose the redundancy would be there too.. right now i'm running 15-16 at idle and around 9-10 when i give it hard pedal.

 

[PSpychalski]

Numbers look good for pressure. My concern with a series pump is bypass. Should 1 of the pumps fail, you would need a bypass to draw fuel past the FASS or push fuel past the Carter. The FASS would probably "PUSH" past the Carter with reduced pressure, don't think the Carter could pull fuel through the FASS. I have DDRP with a spare in the back. Don't know if series pumping gives any benefit.

 

[Sticks]

Both the carter and the in tank pump (I know, not applicable here) free flow, not sure about the FASS. One way to test is to try to siphon through it.

 

[dillrepair]

wow, the relay works quite well for me. even with only the ddrp. no longer am i going down to 10psi on hard pedal... stays at 12-13, furthermore while cruising at 60 pressures stay at 15. anyone who gets a ddrp for a 24v should do the relay.