A while ago I installed a FASS pump and filter assembely on my truck and quickly learned that once your fuel level falls below 1/3 of a tank the FASS pump will suck the Sending unit cup dry and introduce air into the fuel system, not good :( .

There is the option of turning the pump off before that happens since the FASS is a flow thru design and you can let the factory pump pull fuel again. ;)

But since the factory pump would have to suck thru the FASS water/fuel seperator and FASS fuel filter and FASS pump and my Nictane CAT filter and then still the factory fuel filter, I thought that could put undo strain on the factory pump, maybe it would last maybe it wouldn't, but I didn't want to find out after the warranty expired or out in the middle of no where. :mad:

So I have been looking for a way to still retain the FASS pump/filter assemblly and still use the last 1/3 of my fuel tank.

The major problem with the FASS is that it sucks so much fuel out of the cup and then returns it down the filler tube, that you literally run out of fuel while your guage still reads 1/3. -:t

So I have installed my Trippen/Diesel Tech pick up on a spare sending unit I bought but I also installed a return line that will direct fuel back to the cup from the FASS pump (see pictures). :)

I'm not sure how well this will work, one problem might be that the fuel will just splash right back out of the cup since the return line is under some pressure, but I figured it was worth a try.

My next task was installing a seperate fuel pick up tube and return tube into the Supertank I bought that will by-pass the factory Sending unit cup all together.

I installed the pick up tube in about the same place as the Sending unit and the tube is about 3/4 of an inch off the floor of the tank (see pictures), so as long as I don't go down any big hills it should still supply fuel down to decent low fuel level. I still have to double check tomm to see how many gallons are left in the tank on a say 6% or 7% grade before the fuel pick up tube becomes uncovered.
And the extra fuel return line directs fuel towards the back of the tank for those down hills.

The factory sending unit is set more towards the rear of the tank also, so under acceleration the fuel stays around the cup, but on deceleration or any long down hills you have a chance of uncovering the cup on low fuel conditions and stalling the motor. :badidea:

So thats what I have done so far and some time next week i'll install the Supertank and modified sending unit and try the different pick-ups and return lines and see which one if any work better than what I have now.

If any one has any comments or suggestions I'd be happy to hear them. :ro)

Diesel Dragon

.

The sending unit is spring loaded so that when the stock plastic tank expands and contacts the cup remains firmly seated on the bottom of the tank.

The sending unit should have slight pressure on it when you reinstall it so that assures the cup is sitting on the bottom. That is why the factory uses plastic flex hose as it allows the sending unit cup to float up and down under that spring pressure.

You might want to see about using a brass "T" in the plastic return line and restricting it so that you can fill the cup with the return fuel from the aluminum return line from the FASS and then still dump the excess into the cup from above it. I am thinking that will guarantee that the cup remains full.

Let us know how it works, I had my tank out SAT modding mine myself........

BTW...........Lebanon Valley this Saturday ????????

T:cool: NY
.
.
.

I know what you mean about the spring loading, I had to compress the cup about an inch so it would sit on the floor of the tank with still a little pressure and then cut the hoses and tubes to that size.


That's a good idea about tying into the factory return line but the problem is I'm not sure what kind of pressure the factory return line is under. If the FASS return get's tied into that and pushes the fuel backwards towards the engine that wouldn't be good, or if the factory is under more pressure and tries to push back against the FASS that wouldn't be good either.

Maybe a Diesel Tech would know the pressure readings on the return line ?

And it can still be tied together later too after the tank is in since both lines are external too.

Can't make saturday sorry.

When are we going to Janetty's ?

DD

.