Fuel System Troubleshooting and final resolution (IT WAS THE SOCK)

[98G]

RESOLVED! IT WAS THE SOCK! I drove It 7mi each way to the fuel station and filled it, after cleaning the tank.

I've been driving this truck since 2017. Never a hiccup until now.

I suspect there was life in the tank. The fuel had not been sitting , but was nearly opaque green. (My understanding is that algae is red in diesel)

I'll be driving it ~60miles round trip tomorrow and adding biocide.

If anyone wants to recommend a biocide...

Now that the problem has been resolved, i see no compelling reason to alter it from stock.

 

[98G]

Do not try this... put a can of CLEAN fuel in the passenger foot well, run a hose to the mech. pump, carefully tied up so as to not get into the tire. If the truck runs good your problem is south of the pump, if not bad lift pump or injection pump. In my opinion the filter housing needs to be removed and thoroughly cleaned, "crud" accumulates in the bottom causing problems later. Removing the fuel sender and putting an eye ball in the tank might be in order if the truck runs with the "good" fuel. My 2 cents.

You told me so. If i had done this, I would not have replaced the lift pump.

 

[98G]

I have had similar issues with both gas and diesel engines over the years and it almost always is the pick up sock. As the engine runs and return fuel agitates the fuel in the tank, crap from the bottom gets sucked up to the screen. Eventually enough gets on it to restrict flow to the point of stalling. When the engine stalls and the pump stops creating suction the junk falls off and you can start the process again. If you have an old fuel system vacuum gauge you can plumb it into the suction side of the lift pump and tape it to the windshield, drive the truck if vacuum drops during power loss there is a restriction before the gauge or the previously mentioned clogged vent. If the vacuum goes up there is a restriction after the lift pump. If there is no change you're looking at a high pressure side problem.
Hope this helps

Your first post, and your diagnosis was spot on.

Thanks for the input and welcome to the site!

 

[marchplumber]

 

[Mullaney]

Your first post, and your diagnosis was spot on.

Thanks for the input and welcome to the site!

.
Well, I have been watching the goings on in this thread. I have seen lots of trips logged on this site with this truck - and I never would have figured a clogged sock would have been the problem. LOTS of miles have passed under this vehicle...

Congratulations on finding the fix!

 

[Mogman]

The sock was suggested in post 18, and the OP said in post #20 "Filter and housing were terrible. Makes me suspicious of the fuel tank"
Which would have been the natural progression of troubleshooting as all that crap had to come from somewhere.
Unfortunately it took 4 more pages and a lift pump to get to the tank.

 

[98G]

The sock was suggested in post 18, and the OP said in post #20 "Filter and housing were terrible. Makes me suspicious of the fuel tank"
Which would have been the natural progression of troubleshooting as all that crap had to come from somewhere.
Unfortunately it took 4 more pages and a lift pump to get to the tank.

Agreed.

I was biased in favor of the lift pump due to a similar experience with an M936A2 that was the lift pump.

And a buddy's M923 where we dropped the tank and thoroughly cleaned it, and the dirty tank was not the culprit.

Again, thanks everyone who contributed.

 

[TNDRIVER]

RESOLVED! IT WAS THE SOCK! I drove It 7mi each way to the fuel station and filled it, after cleaning the tank.

I've been driving this truck since 2017. Never a hiccup until now.

I suspect there was life in the tank. The fuel had not been sitting , but was nearly opaque green. (My understanding is that algae is red in diesel)

I'll be driving it ~60miles round trip tomorrow and adding biocide.

If anyone wants to recommend a biocide...

Now that the problem has been resolved, i see no compelling reason to alter it from stock.

Power Service BIO KLEEN, a little goes a long way. I mix it with anti gel and diesel in a 2.5 gal jug and splash it before a trip to the pump. Don't ask how much, I have to break out the calculator or have my kid (math major) do the math. My suspicion is the translucent nature of the tank promotes biological growth in the fuel. Also thanks for the follow up. It seems some forget that part after rectifying a problem and it helps the rest of the community. Be safe.

 

[TOBASH]

Hummer H1 uses an aftermarket fuel filter assembly on his expedition off road rig.

Eric only has about 300,000 miles on it. After-all, it’s just a filter.

You need to also check the usual culprits. Fuel lift pump, fuel line directional valves, clogged sock, water in fuel.

Hey Mogman:

Sock was mentioned in Post #2.

[EDIT - Just to be clear, I’m teasing Mogman. I’m not trying to insult the OP.]

 

[ikoinu]

RESOLVED! IT WAS THE SOCK! I drove It 7mi each way to the fuel station and filled it, after cleaning the tank.

I've been driving this truck since 2017. Never a hiccup until now.

I suspect there was life in the tank. The fuel had not been sitting , but was nearly opaque green. (My understanding is that algae is red in diesel)

I'll be driving it ~60miles round trip tomorrow and adding biocide.

If anyone wants to recommend a biocide...

Now that the problem has been resolved, i see no compelling reason to alter it from stock.

Congratulations on finding the culprit! Must be quite the relief to have the truck running again.
I've gone through most of the usual suspects on mine, sock was not bad but switched it anyway.
Injector bleeding time...

 

[Mogman]

Ok I had to laugh when I read the edit of the title.
It was not the sock, it was a grossly contaminated fuel tank, and you are along way from a final resolution just by removing the sock.

 

[ikoinu]

Ok I had to laugh when I read the edit of the title.
It was not the sock, it was a grossly contaminated fuel tank, and you are along way from a final resolution just by removing the sock.

Good clarification.
That was the first order of business when I dropped mine. The tank wasn't the original bull nose one, but had been upgraded to the 25 gallon so was significantly newer (and cleaner) than the 1988 original.

 

[98G]

Ok I had to laugh when I read the edit of the title.
It was not the sock, it was a grossly contaminated fuel tank, and you are along way from a final resolution just by removing the sock.

I didn't remove the sock. I see no compelling reason to alter the fuel system from stock at this point.

I cleaned the tank and the sock, dumped the contaminated fuel, and applied biocide to prevent recurrence.

I plan to proactively open and reinspect the tank to see if there's any indication of regrowth, before it gets to the point of another clog.

Your input was of immense value.

 

[TNDRIVER]

I didn't remove the sock. I see no compelling reason to alter the fuel system from stock at this point.

I cleaned the tank and the sock, dumped the contaminated fuel, and applied biocide to prevent recurrence.

I plan to proactively open and reinspect the tank to see if there's any indication of regrowth, before it gets to the point of another clog.

Your input was of immense value.

Rumor has it that "dead" slim in the tank looks like coffee grounds on the bottom of the tank. Something to look for. You should be able to easily see the bottom of the tank with clean highway diesel (non dyed on highway fuel) .