Got a bit of a weird fuel thing to me anyway at least it SEAMS to be a fuel thing.

I opened the test/condensate drain on the fuel filter canister.
Nothing came out.
Started the truck it started right up no issues, and was running perfectly then just stopped.
I never got anything out of that drain the entire time.
Took the drain line completely off, again Nothing there.
Took the hard line off at the pump outlet.
Cranked and nothing. just a dribble if anything I was not able to WATCH this while cranking.
I removed the inlet line to the filter canister and reattached the line at the pump Cranked. Nothing.
I decided to go ahead and change the filter while I was in there so I pulled the drain line, then pulled the INLET line and fuel started running out the bottom.
OK so it HAD been full of fuel???
Went on with my filter change while I was there anyway.

got that all buttoned back up, Checked voltage at the shutoff solenoid and it is good.
Checked that it was clicking while energized and it was. Checked continuity through the solenoid, something like 43 Ohms. to ground.
and as I say it was clicking when energized.

Cranked it 20 seconds. Nothing.

Acted like it wanted to start one time but mostly nothing.

Thoughts?

I tend to think the lift pump died.
But shutdown was not a taper off it just DIED.
as I say it was running at the time. no bad noises nothing like that.
Just suddenly not running.

Cranked the batteries dead or nearly so, and nothing.

First...Make sure you have fuel in the tank. Like dump in five gallons sure.

Remove the fuel supply line to the lift pump and check that fuel can freely reach the pump. light suction on the line should draw fuel easily.

If still no fuel it could be a loose or cracked fuel supply line, a stuck check valve, or a clogged fuel inlet filter sock in the tank.

If you have fuel flow to the lift pump but none pumps out then you know for sure its the lift pump

Air in line? Cracking an injector and try to start.

Yes Tank is half full, was running just fine and started just before this.

Just trying to make sure I understand what you are saying.

Engine off, no fuel from filter drain (normal)

Engine running, no fuel from filter drain (not normal)

You opened up filter housing and replaced filter, it had fuel in it.


Sounds like fuel delivery issue before the filter. That pretty much just leaves:
Bad lift pump
Blocked check valve
Fuel pickup in tank issue
fuel line before lift pump letting air in somehow, or has blockage.

You can disconnect fuel line at lift pump, and gently pressurize tank and see what happens.
If fuel comes out, then probably bad lift pump.
If no fuel, then either check valve stuck or plugged, or issue in tank.


The injection pump will suck fuel through a bad lift pump. When mine went out I only noticed the engine didn't have as much top end power, but still seemed to run normally at low speeds.

Coug said:

Just trying to make sure I understand what you are saying.

Engine off, no fuel from filter drain (normal)

Engine running, no fuel from filter drain (not normal)

You opened up filter housing and replaced filter, it had fuel in it.


Sounds like fuel delivery issue before the filter. That pretty much just leaves:
Bad lift pump
Blocked check valve
Fuel pickup in tank issue
fuel line before lift pump letting air in somehow, or has blockage.

You can disconnect fuel line at lift pump, and gently pressurize tank and see what happens.
If fuel comes out, then probably bad lift pump.
If no fuel, then either check valve stuck or plugged, or issue in tank.


The injection pump will suck fuel through a bad lift pump. When mine went out I only noticed the engine didn't have as much top end power, but still seemed to run normally at low speeds.

Click to expand...

Correct.

Engine OFF no fuel from drain.
Engine ON no fuel from drain and engine died... (was actually running just fine until opening the drain...
Disconnected line out from pump no fuel present when cranking
Reconected that
disconnected line at filter no fuel when cranking.
Reconnected that and disconnected drain hose. no fuel draining.
disconnected filter inlet and fuel freely drained from canister.
swapped filter since I already was this far in and only one hose and 4 bolts left.
Strainer packaged with replacement filter was broken so reused the original strainer that was in good shape.
reconnected all and still no fuel present.

As you say it must have broken the seal and no more fluid column....

Opening the drain with it running was how I determined that my lift pump had failed.
Injection pump will suck air in through the drain, and you won't get it started again without fixing the issue.
Lift pump is relatively inexpensive and not that difficult to replace, other than being careful about the push rod position during reassembly.

Coug said:

Opening the drain with it running was how I determined that my lift pump had failed.
Injection pump will suck air in through the drain, and you won't get it started again without fixing the issue.
Lift pump is relatively inexpensive and not that difficult to replace, other than being careful about the push rod position during reassembly.

Click to expand...

Well acquainted with fuel pumps of the type (small block chevy) unfortunate they didn't include the bolt hole to put a longer bolt in to hold the pump push rod... would be so much easier.

Well, replaced the Mechanical Lift pump Old pump was very "soft" new pump was not so SOFT. BUT same thing no fuel flow through pump. I can use my manual transfer pump and pull fuel from tank (full) to line at filter but lift pump doesn't do a darned thing. I'm going to try an electric pump before the mechanical tomorrow just to test it almost started once but didn't run long...

Describe your method of holding the fuel pump drive rod up during the lift pump install.

A buddy just replaced his bad lift pump and still no worky... made him remove the lift pump and lo and behold broken pump rod!

grease... checked it multiple times during install...it isnt broken... I'll go electric this afternoon and get it running and figure out the rest later.

What have you done with the check valves?

98G said:

What have you done with the check valves?

Click to expand...

" I can use my manual transfer pump and pull fuel from tank (full) to line at filter"
It is a little plastic hand pump if it can pull fuel through the check valve the valve is not clogged or stuck.
and if drainback is a perceived issue and people remove them, then it doesn't matter if they work or not as long as they flow.

KKroger said:

" I can use my manual transfer pump and pull fuel from tank (full) to line at filter"
It is a little plastic hand pump if it can pull fuel through the check valve the valve is not clogged or stuck.
and if drainback is a perceived issue and people remove them, then it doesn't matter if they work or not as long as they flow.

Click to expand...

Agreed.

I went through a similar issue last year with my M998.

I was absolutely convinced it was the lift pump and so I replaced it, along with the fuel filter. That didn't fix it.

Mine was the sock on the pickup in the tank. I don't think the sock is your issue. If it were, it'd run for a while before it sucked up enough detritus to clog.

In your position, I'd be tempted to top off the tank and try again. I'd also be tempted to put an electric fuel pump in place of the supply side check valve and try that, merely as a diagnostic measure.

I watch with interest to see how yours turns out.

Little note to the pick-up filter / sock... There is a bypassing valve on the end of the sock. (normal Hmmwv part) If filter screen / material is full of crap and pump is a sucking (tech term) one could have just bypassed the filter element, drawing in tank junk. I read somewhere it was better than totally plugged up. See the picture.

Another Hum-dinger design, CAMO

98G said:

Agreed.

I went through a similar issue last year with my M998.

I was absolutely convinced it was the lift pump and so I replaced it, along with the fuel filter. That didn't fix it.

Mine was the sock on the pickup in the tank. I don't think the sock is your issue. If it were, it'd run for a while before it sucked up enough detritus to clog.

In your position, I'd be tempted to top off the tank and try again. I'd also be tempted to put an electric fuel pump in place of the supply side check valve and try that, merely as a diagnostic measure.

I watch with interest to see how yours turns out.

Click to expand...

planning to do an electric pump this evening.... see what happens

OK, Cheap Arsed 12V inline electric pump ($22 shipped next day arrival amazon) runs like a champ better than ever since I had it. used to falter on hills, no more will do 60 over the top of a long hill that used to bog it down to 35... So $99 mechanical lift pump didn't work... at all... Electric pump works great. I'll put a mechanical back on it when time permits and also another inline 24VDC Carter pump... as soon as it gets here. Right now it is a ME Switch... not automagic... I have a box of 24V Relays that I could wire in... But she runs better than ever.

KKroger said:

Well acquainted with fuel pumps of the type (small block chevy) unfortunate they didn't include the bolt hole to put a longer bolt in to hold the pump push rod... would be so much easier.

Click to expand...

I keep meaning to look and see if there is a reason they did not include the ability to "jam" the pump rod like the SB and BB chevys.

Milcommoguy said:

Little note to the pick-up filter / sock... There is a bypassing valve on the end of the sock. (normal Hmmwv part) If filter screen / material is full of crap and pump is a sucking (tech term) one could have just bypassed the filter element, drawing in tank junk. I read somewhere it was better than totally plugged up. See the picture.

Another Hum-dinger design, CAMO

View attachment 948414

Click to expand...

Keeps the truck running until the filter on the firewall clogs.

Designed by geniouses, for idiots to operate....

KKroger said:

OK, Cheap Arsed 12V inline electric pump ($22 shipped next day arrival amazon) runs like a champ better than ever since I had it. used to falter on hills, no more will do 60 over the top of a long hill that used to bog it down to 35... So $99 mechanical lift pump didn't work... at all... Electric pump works great. I'll put a mechanical back on it when time permits and also another inline 24VDC Carter pump... as soon as it gets here. Right now it is a ME Switch... not automagic... I have a box of 24V Relays that I could wire in... But she runs better than ever.

Click to expand...

So do you think you missed the pump rod? Why isn't the replacement mechanical lift pump working?