5 ton fuel tank selector valve cleaning/rebuild

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Excuse Me

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Ok, today on my M931 8.3L, I took the two bolts out that held the selector valve and pulled the valve down without removing the lines. I took a 13/16" box end and removed the top of the selector valve. Pulled the cartridge out and polished the shaft that hooks to the handle.

Cleaned things up really good as there was some crustified fuel or installation lube at the threads. Installed new orings and put the valve back together. When I went to put the mounting bolts back in, I could not as the valve would not go up quite far enough. Turned out there is a bolt that holds the seat plate down that was too long and hitting the valve. I removed the bolt and shortened it. Then the valve went right back into the mount how it was supposed to. That bolt may have been part of the issue.

After double checking all the lines, I got fuel to the lift pump using my hand held vacuum pump. Then reattached the line to the lift pump and bled the air out of the reast of the system and it fired off and so far, runs fine.
 

73m819

Rock = older than dirt , GA. MAFIA , Dirty
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Make SURE the FLAT WASHER on top of the canister is in the recess and IS flat, if not the canister WILL suck air though the top O-ring.
 

Csm Davis

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Wouldn't think that'd be wise. That pump is all the way up at the engine and having to suck through a real long straw already. Adding a schrader valve would impede flow drastically.
Okay Drew you are not getting the picture the Schrader valve is to let air in or out of the system like a petcock, not inside the line for fuel flow. Also the only place I have seen them was on the bolt that holds the canister on. I wouldn't change out any of the petcocks for Schrader valves, a Schrader valve doesn't work well in a vacuum system they will let in air, that's what they are designed to do. If the system had positive pressure they would work well but it doesn't. This is true for all of the stock 250 powered trucks not sure about the 8.3 or multifuel trucks as I have heard they have in tank pumps.
 

joesco

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I removed the fuel filter canister for the third time today and found the "square" metal washer was very warped. Then I found an old rotted O-Ring on the bolt behind the new O-Ring so I flattened the metal washer, removed the rotted O-Ring and installed the new O-Ring. I filled the canister with some filtered diesel fuel, installed it and +ZEUS+ started right up. I drove it 1200 feet over to my shop and on the way over, lost power and it stalled again! Dang!

Waited about 5 minutes, said a novena as I was blocking my driveway with this huge 5 ton beast and it started right up again, purring like a new motor. Drove it over to my shop and I let it idle while I getting my wood stove going and then I heard it stall out again. I noticed that the petcock on the filter head was leaking a bit. So, over to the auto part store and I purchased a new petcock, installed it and the truck started right up, purring like a new motor, only to stall and die again once a put a load on it. So now I began to inspect all the fuel lines, did not see any apparent cracks or other defects. So I looked at the end of the vent tube which is attached to the intake and found it completely clogged with a spider nest, dust, dirt and who knows what. I ran I wire up the tube and a bunch of debris came tumbling out of the vent tube. So, now I am thinking I am home free. Started the truck, 1/2 turn it cranked right up only to stall again after about 3-5 minutes. I can only hazard a guess that my fuel filter is filling with fuel and once the engine starts, it runs the filter housing dry and stalls out. So now I guess I have to attack the fuel selector switch. Dang, this is so frustrating. I am almost tempted to bypass the selector switch and run a new line from the filter straight to the passenger side tank!!!
 
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Csm Davis

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Joesco what truck are you working on? 931a0, 931a1, 931a2? Double check that the gasket on the canister is in place and that there's only one on there.
 

joesco

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931 with a swap to SS tires and a cut down deuce bed. Thanks, gasket is good, only one and in place.
 

73m819

Rock = older than dirt , GA. MAFIA , Dirty
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Check for air sucking at the tank fittings as well as the valve and EVERVTHING in between
 

Excuse Me

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I removed the fuel filter canister for the third time today and found the "square" metal washer was very warped. Then I found an old rotted O-Ring on the bolt behind the new O-Ring so I flattened the metal washer, removed the rotted O-Ring and installed the new O-Ring. I filled the canister with some filtered diesel fuel, installed it and +ZEUS+ started right up. I drove it 1200 feet over to my shop and on the way over, lost power and it stalled again! Dang!

Waited about 5 minutes, said a novena as I was blocking my driveway with this huge 5 ton beast and it started right up again, purring like a new motor. Drove it over to my shop and I let it idle while I getting my wood stove going and then I heard it stall out again. I noticed that the petcock on the filter head was leaking a bit. So, over to the auto part store and I purchased a new petcock, installed it and the truck started right up, purring like a new motor, only to stall and die again once a put a load on it. So now I began to inspect all the fuel lines, did not see any apparent cracks or other defects. So I looked at the end of the vent tube which is attached to the intake and found it completely clogged with a spider nest, dust, dirt and who knows what. I ran I wire up the tube and a bunch of debris came tumbling out of the vent tube. So, now I am thinking I am home free. Started the truck, 1/2 turn it cranked right up only to stall again after about 3-5 minutes. I can only hazard a guess that my fuel filter is filling with fuel and once the engine starts, it runs the filter housing dry and stalls out. So now I guess I have to attack the fuel selector switch. Dang, this is so frustrating. I am almost tempted to bypass the selector switch and run a new line from the filter straight to the passenger side tank!!!
I missed what engine you have. ??
On the 8.3, go up to the secondary fuel filter and there is a line with a banjo bolt that faces the firewall. 10mm box end wrench I think. Put a rag over it and crack the line while pumping on the lift pump primer. There is a spot just beyond that banjo bolt that traps air.

The bleed screw on the filter faces you when you are sitting on the drivers side wheel. It only removes a air that is not trapped above the filter. Cracking the line banjo bolt seems to bleed the air that is trapped for some reason, and can not get out to the bleed screw.

I started mine again today. Less than a turn with the starter and it was running. So my air leak seems to be fixed. But it took new orings in the selector and removing the trapped air above the secondary filter to get it running.
 

joesco

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Thanks, I have an NHC 250. Hopefully once the storm blows through today, I will replace the o-rings in the selector valve and my issues will be solved. This is wearing me down!!
 

dezert ratt

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The rubber lines can also have cracks and pinholes that you cannot see. I had to bench test my lines with air and soapy water and found lots of tiny holes in all the lines to and from the selector valve.
 

crasheej

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The bottom line is if you go to the trouble to rebuild the valve replace the hoses. You'll be glad you did.
 

Warthog

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Rebuilding a selector valve on a M818. Found the #9 and #25 o-rings at Ace Hardware.

The 1/2 suction hoses need to be replaced but I will replace all the hoses. Where is a good place to find the Parker Push-Loc hose? All the hose places where closed today.
 
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VULCANGUNNER

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A few pictures of my M931A0 fuel selector valve rebuild.....Fuel selector valve - dirty1.jpgFuel selector valve - Clean3.jpgFuel selector valve - Clean1.jpgFuel selector valve - Clean2.jpg23mm 5-ton wrench.jpg

23mm 6-point wrench I made myself to remove the extremely tight big fuel lines from the valve (worked like a charm on a previously-beat fitting)

** All bead blasting was done with pipe plugs in place & the inside valve parts removed **
 
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Warthog

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Went to my local hose supplier and $19 later I had 6 new lines in hand. Took it home and cleaned and polished the housing and valve stem. Now to reinstall, change the filter and bleed the system.

photo 1.jpgphoto 2.jpgphoto.jpg
 
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Warthog

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Install went fine. Replaced the fuel filter, gasket and bolt o-ring. Filled the can with a gallon of fresh diesel. After about thirty or so pumps of the primer and a few cranks, she fired off. The truck hasn't ran in three years.

Now to fix the split in the air drain line and replace the transfer case. The joys of helping a fellow SS member. ;-)
 
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