Fass HD Runs but low pressure

[stibuilder]

About 3 months ago the my fuel pressure gauge that usually reads 10/9 psi jumped up to 21 and then started doing weird stuff bouncing all over the place. I chocked it up as a bad sending unit (Autometer) the other day I changed both the filter and water separator, along with the sending unit and no change. Gauge reads max 6psi and then after driving it goes to 0 if I get on the throttle.
I added a mechanical gauge today and when my digital reads 6 they both read 6 but when the digital reads 0 the mechanical reads 2/3 roughly. Both are in the FASS filter replacement bowl.

Its a pretty old unit SN 27305, should I buy a new pump or just a motor or a whole new unit?

 

[snowman22]

Sounds like a good time as any to see how FASS stands behind their product. I know they have a warranty card that says it must be turned in for warranty in the future, but you never know until you try.

 

[stibuilder]

Talked to tech support they think its the return spring, advised I pull the fitting and stretch the spring out 1/4" and see If that helps any.

 

[stibuilder]

Got a new spring and ball from FASS, and the new spring is 1/4" shorter than the spring I stretched, and it made the fuel pressure worse. Now it never shows positive pressure, on the stretched spring it showed 5-7 at times and then would go to 0. Should I try and rebuild the pump or just buy a new setup?

 

[stibuilder]

Well its not the Pump, we replaced the pump motor today and same thing no pressure
We went on to build a new feel line to make sure the old line wasnt sucking air. Still no pressure. Wondering if there is some issue in the oem filter housing? My hunch now after we took one of the return springs in the FASS system and i stretched it out pretty far and it made 5psi for a bit then went to 0. Truck wont make any fuel pressure with just the pump running an the engine off. To make sure we put a physical gauge on and the same results.

Is it possible the factory filter head is just returning the fuel? Pressure is being measured from the FASS filter delete bowl things.

 

[zakkb787]

Bypass the filter head. If you have a Fass you don’t really need it.

 

[DMAXDFloridian]

Trash it and go with Kennedy!

 

[DetailsUnlimited]

I may be way off but check the voltage to the pump.

 

[nmband13]

I recently worked on a customers truck which had a poor GROUND for the pump. Power was good but the ground was bad and was causing issues.

 

[stibuilder]

Pump runs great, power wise its 13.3 at idle

 

[2004LB7]

Is that to the pump? Because I think the posts are referring to the "from the pump" wiring. If you have voltage om the negative wire then you have a bad ground connection

 

[WVRigrat05]

Is it reading no pressure with the truck running?

 

[nmband13]

Is that to the pump? Because I think the posts are referring to the "from the pump" wiring. If you have voltage om the negative wire then you have a bad ground connection

^ this

 

[stibuilder]

Pump is running great, after replacing the filter head with a new one and running pressure sensor off the bleed screw we got the same thing no pressure unless I pumped the priming plunger. Now today we just so happened to crack the fuel tank fill cap and noticed a seriously high amount of fuel being returned to the tank. Is there something we are missing?

 

[NC-smokinlmm]

Collapsed fuel line...

 

[stibuilder]

Collapsed fuel line...

Interesting thought, most of the line on the Kodiak runs in the frame and is metal line ill look around for the soft line and try and see, the truck is driving fine drove it today.

 

[NC-smokinlmm]

They have 2 piece soft lines so the inner line can collapse and it look visually fine. The lines on my LMM did this, I ran all new fuel lines and truck was much happier...

 

[JoshH]

When you installed the FASS filter delete bowl, did you remove the check ball?

 

[stibuilder]

When you installed the FASS filter delete bowl, did you remove the check ball?

Yes, and when i put the new filter head in with the oem filter I didn't change anything. I installed it as is, and just put in an adapter at the air bleed screw to go to the sending unit.

 

[JoshH]

Are you sure you aren’t hooking up the hoses backward?