I spent the day Thursday meticulously installing a new fass system on my truck. I did the pump only and used a different filter bracket than the fass. I used all Parker store push lock fittings, copper line for the pressure gauge. I installed everything hit the key, it primed right up and held a solid 45psi. I went to work yesterday (my job requires me to drive this truck all day long) and when a got out of the grocery store last night I hit the key, got my pressure, then it just started dropping like it had no fuel. I could hear the pump running, but no pressure. I check under the truck and no leaks. I finally got it to run, but still no pressure. Took it to my friends house and we double checked EVERYTHING.

We pulled the line from the suction tube and stuck it in a can of fuel- nothing.
Blew air back into tank through the suction line, it was not blocked
Checked the return line spring in pump, looked new

Here's the kicker- we installed another new pump and same results

I finally got pressure by blowing air into the tank, it picked up prime and off it went. I'm going to drive around today and see what happens, also I'm going to switch back to my other pump.

What gives?? For the life of me I can't figure out what would cause this. I do have a full tank of fuel and this pump worked all day long. After my install I had appx 7 gallons of fuel in the tank, and now its full. Return line is clear.

Open to any and all suggestions. Thanks guys!

 

Is the suction line you are using rated for suction. If not, it could be collapsing on itself while the pump is running, even if you don't see it. Just a thought.

 

Its the line that came with the fass system, I would assume so.

 

u got trash in the tank sounds like

 

Glad to see you made it here Paul......I am wondering if you had air in the filters. When I change my filters I have to leave the fuel filter cracked open and turn on the pump until fuel come out of the filter and then tighten it back up and she's good to go. Another thing is if the tank is low that stupid and you stop short that fuel runs away from that damn draw straw and you'll lose pressure. It will come back up but the draw straws SUCK. I want to put a Hellman Sump in my tank to fix it.

 

I vote air in the filters, Crack them open and It'll prime back. The new high flow modules will work for all these trucks, but you'll have to run the return line to a draw straw in the module instead of in the filler hose!

 

Will that stop the problem of the draw straw sucking air at a 1/4 tank and under?

 

Sure will!

 

I assume that is the new Draw Straw I correct? DO you have them in stock? I am sick of that pressure drop around a 1/4 tank that I get with the FASS suction tube. PM me a price if you would. Sorry for jacking your post Paul....

 

I'll PM ya a price when I get to the shop. I'm at a buddies house right now.