2nd Gen Non-Engine/Transmission FASS not building pressure any longer.

[KChavanu]

I tried to find my receipt for the FASS to see how long it has been on the truck. No luck. I'm guessing it has to be close to 10 years though.

I've noticed increasingly inconsistent fuel pressures probably for the last 6 months. Never a no-pressure situation, though. No drivability problems, until a couple of weeks ago during a cold snap. I had to move the truck out of the garage and it took a lot more cranking to get it fired up than usual. When I went to move it back into the garage, it refused to start, period. Cranked but no sign of lighting off, and essentially no fuel pressure. As an aside, the batteries were replaced at that time. They were 8 years old and just that little extra cranking showed they were needing replacement.

When you bump the key it won't produce over about 3psi according to the gauge, and the pump sounds like it is not under load. I assume it has lost its prime.

If you crack the line at the injector pump and bump the key, it will dribble for a few seconds, and then it is like the pump gets traction and takes off, producing 15+psi. Then the pump signal times out. When you bump it again with the system sealed, it again fails to produce more than ~3psi and fails to start. So, if it is a lost-prime situation, it immediately loses prime.

The only thing I've don so far was replace the filter and water separator. They were due to be changed, but it made no difference.

Any suggestions?

 

[samsonite01]

Test pump before replace. Pop the line off stick it in a bucket give the pump 12v seperatly from the truck. If pump is good mabey you got some air in there. I had problems with that freakin canister every time i touched it.

 

[KChavanu]

Well, I found the "FASS Technical Guide" over at geno's garage.

It fails the "5 Gallon Bucket Test", as I under stand it. Never starts because it doesn't hold a prime.

In the end it talks about putting the output and input hoses into the bucket and "If fuel flows out of the fuel bucket and back into the fuel bucket without any air bubbles, the fuel pump is operating normally.

I have the pump removed, and with all 3 hoses submerged into the bucket, running it on the bench, there are lots of tiny air bubbles in the fuel coming out of the output hose, even after letting it run for minutes.

If you put your finger over the output hose, after a couple of seconds, the checkball pops and you get really, really foamy fuel coming out of the return line in pulses. Otherwise, with the output freely flowing, you just get big air bubbles at a pretty slow but constant rate coming out of the submerged return line.

If you put your finger over the weep hole on the bottom of the silver-colored block that the motor is attached to it almost seems like you can feel a little vacuum, and if you keep it covered for a few minutes, the air in the output fuel is greatly reduced.

The entire pump was wet when I removed it from the truck, and the grime was mostly washed off under the weep hole. So, I am assuming that the seal is bad and that it must be exposed to the suction side of the pump.

(I did find the receipt. It is 8 months past the 6yr warranty.)

I guess it is time to contact FASS and see what they suggest before I go ripping into it and begin the search for seals, etc.

Has anyone tore one apart to replace seals? Will FASS supply parts, or did you source them from an industrial supply house, or somewhere else?

 

[KChavanu]

FWIW, they told me they will not sell any parts or a seal kit. They did tell me my unit was still under warranty, so I sent it in. Upon return, the invoice said that a motor bearing was bad so they replaced the motor and seals. Sent it back the day after receiving it.
Back to a solid 15psi, and quieter too.