Lift Pump Issues

[BDCarrillo]

This is driving me nuts... Got the fuel filter light today and popped in a new filter at lunch. Burped the air, had good flow at the schrader valve. Drove home and got the light again. Checked flow at the schrader valve, NADA. Just a poot of air. Truck runs 10-20 seconds and dies.

Lift pump is new (1000 miles Bosch unit, replaced a trashed Spectre/Carter with only 6000), fuel filter is new, no drainbacks/leaks, or pressure.

Pushed 5 psi when checked a few days ago... All lines pressure and vac tested recently, no issues and new rubber on hard-line to pump, and up to filter head. I'm kinda stumped and leaning toward a bad pump (again)

Anyone have any off the wall ideas why she'd run fine yesterday and shart the bed today?

 

[cpdenton]

Did the light come on under throttle?

Was the 5 psi at idle?

If so, it sounds like it's just not pushing enough pressure when the fuel consumption is high.

 

[BDCarrillo]

5 psi at idle (before today), light just off idle, no load. Return to idle and light fades after a few seconds. Sounds like a volume issue, right? Lines were blown out, no showerheads, new pickup tubes, new pump, new filter, full tank. Arggggg

Clear line on the pressure regulator down to the first injector, no fuel in the line

 

[IDIoit]

i will never run a lift pump again on these engines.
my holley red pusher pump does well, but it seemed like the holley black pump regulated to 7 psi was better.


do an e-pump!

 

[icanfixall]

From what you have posted. Your telling us there is not enough flow volume to make the engine happy. Sounds like you have a line restriction. Could be the rubber line from frame to lift pump or the fuel change over valve. If the tank suctions are open lines you may have sucked up some broken pieces of the old shower heads and its blocking the flow thru the valve or lines.

 

[gandalf]

It does sound like fuel starvation, doesn't it? Is the problem common to both tanks? Does it act the same when sucking fuel from both the front and the rear tank?

5PSI should be plenty, but if the PSI actually drops when you push on the go peddle, then you would have the symptoms you've described.

Is it possible that you might have a partially blocked line? A partially plugged FSV? a partially plugged shower head or replacement drop hose? A replacement drop hose in a tank which is actually suctioning against the bottom of the tank? Any of thses might allow enough fuel through at idle, but "tighten" up with greater demand and greater suction.


Just a thought.

 

[tbrumm]

The only other thing I could think of if the short end of fuel hose from the hard line on the frame to the lift pump has too severe of a bend or loop in and restricting flow. Maybe it was fine when you put in the lift pump but has since kinked a bit more from vibration or whatever. Or, as Gary said, maybe the FSV has some showerhead bits in it. The showerheads in my tanks had disintegrated into tiny black beads of plastic.

 

[BDCarrillo]

Ah those wonderful showerhead bits... I'll drain and blast out the fuel lines and FSV when I get a chance. I'm hoping that debris in the line is the only issue.

I'd like to go E-pump, but haven't found a good WMO friendly pump yet.

 

[IDIoit]

Ah those wonderful showerhead bits... I'll drain and blast out the fuel lines and FSV when I get a chance. I'm hoping that debris in the line is the only issue.

I'd like to go E-pump, but haven't found a good WMO friendly pump yet.

or a mechanical lift pump either, for that matter

 

[BDCarrillo]

Ha! I don't get why a good gear pump is so hard to find... Or outrageously expensive

 

[BDCarrillo]

Found the issue... Had an anti-drainback one way valve on the pump outlet back when I was chasing air intrusion. It decided to turn itself into a no-way valve or straight up stoppage.

Part of the internal diaphragm had a little sliver for fuel to pass by. Gutted the valve and it's back in business.

 

[fsmyth]

That's one of the problems(?) with the Stanadyne pumps. These things will crank and
run on so little fuel, the errors get hard to trace
The little pumps I use:
http://www.ebay.com/itm/361233010873?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT
have been fine so far pumping anything that will burn.
First time I have ever run across a cheap pump that works.

Should have added - ran out of fuel in the front tank in the field. Selector refused to switch to back tank.
So I dumped in 5 gals. of hydraulic oil that I was using to service an Allison. Truck ran the best it has ever
run. Somewhere around 20W, IIRC - mixed with the 1/4 tank I couldn't use because of bad pickup. Wish I
could afford to run it full time
The pump works fine on WMO w/10-15% RUG.

 

[BDCarrillo]

I appreciate the heads up on the pump!