rbattle

My truck has lost fuel pressure while running because the FASS will not run when the truck is on. I reseated the fuse in the wiring harness for the FASS and that made it run if I just bump the starter, but still no pressure with the truck running. I got a p1689 code while I was screwing around with it, but it is gone and hasn't come back. Anybody know why my FASS would not be running?
R

Rauschbo

The FASS should run continuously when the truck is on, but yours isn't running at all?!? -0- FP reading? Did you check the wiring harness connection to the pump? I can't think of any interruptor circuit in the line, and your hot wire / ground must be good (pump runs with a key-bump)...

rbattle

When I bump the starter the FASS runs, when the truck cranks, it does not run at all. I disconnected the batteries last night and replaced them this morning....no help. As far as I can tell, the only problem with the truck is the FASS not running when the truck is running....might cheat and add a switch to override the relay and make the FASS come on for the time being. I am a busy college student and cannot be bothered with this right now, this weekend will be a better time.
R

RCW

Just a quick thought. Some people install the FASS with the OEM lift pump in place and use the power from the OEM lift pump circuit. If the OEM lift pump bypass sticks it will open the circuit and keep the FASS from operating.

Personally, I trash the OEM lift pump and simply go with the FASS. Your original FASS instructions should have everything you need to install without the OEM lift pump if that is the issue.

Rauschbo

I'm not sure I understand the last post - ? The lift pump can be let in place - physically, sure; The pump is disconnected, and the wiring that went to the OEM plugs into the FASS ...

Unless you mean that the LP may still be wired up as well as the FASS?

When you turn the key, the pump will run for a few seconds, and if you then bump the key to Start - VERY briefly, so that the truck will not start - the pump should run for another 20 seconds or so - does your pump do this? You mentioned that you lost pressure - what is your FP pressure reading?

farmer dave

The FASS plugs into the oem wiring but the oem pump is not connected. Some people run them together saying it helps, but that is not in the FASS intructions. I would start by giving FASS a call and see if they can help any. There is a warranty on the pumps and something may be bad with it. If it isn't the pump at least they should have some kind of idea were to look for problems and how to fix it.

rbattle

Well this story gets stranger. I did some testing, and thought it was the relay for the fass from the factory harness to turn on the fass system. As I was just directly jumpering the connections I noticed that if I turned the truck on, I now had low pressure with the system with a new relay. So I replaced the fuel filter, and now I have full pressure again. I guess the relay went bad, and the filter clogged at the same time? Has anybody had to replace their filter at 5,000 miles? Well, at least it is fixed for the time being.....
R