Fuel Issues. Truck is down.

[Black_Cloud]

Hey guys, I'm having some fuel issues and wondering if you can help narrow it down.

I first noticed a loss of power anything above half throttle. It would completely fall on its face. Same feeling it gave me when my lift pump went out a couple months ago so that was the first thing I checked. Pump was running, but it did sound louder than usual. Changed the filter on the AD, no help.

Changed the engine fuel filter, took it for a test drive, no difference and the lift pump still sounded sick. Took the fuse out of the lift pump for giggles, truck died a mile down the road. Now this has me puzzled because last time my pump was toast, the truck still ran fine.

Finally got the truck started and drove home. Weird part is, the primer bulb on top of the filter is super soft, no tension whatsoever. What gives??

Do I have a cracked filter housing, and the lift pump was just concealing the issue? Do I have both a bad pump and a cracked housing, or is the sick sounding pump due to air getting into the system?

I'm stumped. Ideas are appreciated. Thanks.

 

[custom8726]

Primer is soft when its running or when its off? If the primer doesn't build up solid while its off I would start by rebuilding or replacing the filter head. Do you have any way to data log the truck? What air dog pump do you have? I know my old 150 was flow through so the truck ran fine even with the pump off.

 

[Black_Cloud]

Primer is soft when its running or when its off? If the primer doesn't build up solid while its off I would start by rebuilding or replacing the filter head. Do you have any way to data log the truck? What air dog pump do you have? I know my old 150 was flow through so the truck ran fine even with the pump off.

Primer was soft while it's running. I could be mistaken but, it should build pressure while running right? Primer would build pressure when it was off, but not as much as it usually does, it would never get 100% stiff.

Unfortunately I have no way of logging the truck, I'm really wishing there was a way.

I have the 150 as well. And that's what has me stumped, because a couple months back I had the pump motor go bad and the truck ran fine (gutless, but fine). So I'm not sure why this go around the truck doesn't want to run without the pump?

 

[roxyfever]

Seems like its loosing prime or getting air in the system somewhere

 

[Black_Cloud]

Seems like its loosing prime or getting air in the system somewhere

I think you may be right. Took power away from the lift pump, and the truck will not hold an Idle whatsoever. Dies within minutes.

Good clue for air getting into the system? Filter head cracked?

 

[Awenta]

I'd look back behind the pump. Anything leaking ahead of the pump would probably get wet with the pump running. And the pump would run fine.

Check the draw straw. The pump is sucking air up from somewhere. Run a line from the pump to a clean container of fuel and see if it fixes the problem.

Sent from my SM-N910V using Tapatalk

 

[Black_Cloud]

I'd look back behind the pump. Anything leaking ahead of the pump would probably get wet with the pump running. And the pump would run fine.

Check the draw straw. The pump is sucking air up from somewhere. Run a line from the pump to a clean container of fuel and see if it fixes the problem.

Sent from my SM-N910V using Tapatalk

10-4. Great idea to run a test hose to it. I'll give that a shot.

 

[juddski88]

There's a chance you are bleeding off pressure to the return system too. A lot of times I see it in cp3s, even low mile lbz+ pumps. You can isolate system segments and test with a mityvac