Truck Tractors are not QUITE Identical to Cargo Trucks

[98G]

So today on the side of the road I learned that the switch to the left of the steering wheel on M931A2s changes where the fuel gauge reads, but NOT where the fuel feeds from. That function is performed by a nice little lever to the left rear of the driver's seat.

Extreme caution should be used before operating that nice little lever, because the o-rings are prone to cracking and then sucking air into the fuel system. Against the advice of those more knowledgeable than myself I rolled the dice , turned the valve, and got lucky on that aspect. Mine didn't crack and all I had to do was re-prime the fuel system and go.

A sincere thank you to everyone I texted for support. I was just certain I had sucked crap out of the right tank and clogged a fuel filter. I was all set to begin changing fuel filters on the side of the road.

 

[Warthog]

Been there. Done that. Those orings will give you fits.

 

[gimpyrobb]

Glad you got the info you needed! I didn't know the switch on the dash was for the sending units either. You have CSMDavis to thank, he is the one I got the info from.

 

[jdknech]

I made the same mistake when I got my m932a1, i ran out of fuel about 20 (up hill) feet from the fuel pump.. I had to walk around the truck stop and ask people for a pull up to the pump.. Made for fun memories lol

 

[jasonjc]

The M818 are the same way.

 

[VPed]

Wreckers too.

 

[ke5eua]

Check my build thread, I ditched the tank selector and combined the tank feeds and returns so both tanks run as one. Only downside is you have to fill both together, but the positive side is I don't have to worry about changing the lever ever again.

http://www.steelsoldiers.com/showth...-s-818-Build&p=1614218&viewfull=1#post1614218

 

[patracy]

I did away with that valve on my SEMTT (931). It's all solenoid valves now.

 

[Trailboss]

I thought my dash switch was broke when I switched tanks. Fortunately, my fuel gauge was broke, so I looked into the tanks before I ran out of fuel. When I re-read the TM, I found what I had read and forgot about the floor tank valve.

I now have one truck that will only suck from the right tank, and will die when the lever is put on the left tank. Probably an air leak from the left tank to the bi-way valve that I need to find.

 

[hklvette]

I did away with that valve on my SEMTT (931). It's all solenoid valves now.

I'm curious about this. Any more details?

 

[Powershift]

The valve on my truck works fine, and I switch between tanks with every other fill up. Are they really that prone to failure?

 

[73m819]

So today on the side of the road I learned that the switch to the left of the steering wheel on M931A2s changes where the fuel gauge reads, but NOT where the fuel feeds from. That function is performed by a nice little lever to the left rear of the driver's seat.

Extreme caution should be used before operating that nice little lever, because the o-rings are prone to cracking and then sucking air into the fuel system. Against the advice of those more knowledgeable than myself I rolled the dice , turned the valve, and got lucky on that aspect. Mine didn't crack and all I had to do was re-prime the fuel system and go.

A sincere thank you to everyone I texted for support. I was just certain I had sucked crap out of the right tank and clogged a fuel filter. I was all set to begin changing fuel filters on the side of the road.

VERY SURPRISING what INPORTANT tid bits of INFOMATION can be FOUND in the -10

 

[KsM715]

Just out of curiosity, did you all not notice the tank selector valve on the floor next to the seat and wonder what it was for before you even started your truck for the first time? I know once I was I my M818 for the first time I looked all over the cab just to see what everything was.

 

[98G]

Knowledge is power, absolutely. The TMs are generally the source of MV knowledge.

Thing is, it usually isn't what you don't know that bites you. What bites you is what you think you know that is wrong.

I come out of this with more knowledge than going in. Nobody injured, no equipment damaged. I feel good and I'm having fun.

 

[98G]

Just out of curiosity, did you all not notice the tank selector valve on the floor next to the seat and wonder what it was for before you even started your truck for the first time? I know once I was I my M818 for the first time I looked all over the cab just to see what everything was.

The first time I got I to a 939series truck I did too. This isn't the first of these things I've driven. It's so similar to the cargo and expand expandible van variants and the other differences were accounted for in my mind: "ok, there's the trailer brake and there's the fuel tank selector" while looking at the dash. The valve is unobtrusively located tucked off to the rear left.

 

[Trailboss]

When everything is new, not everything sticks the first time thru. I saw the lever and read the TM, but over time had forgotten all that when I actually needed to use it months later. The next day, I kicked myself in the rear for not remembering.

 

[Warthog]

The valve on my truck works fine, and I switch between tanks with every other fill up. Are they really that prone to failure?

If the lever is not used the grease and o-ring will harden and dry up. It takes years.

If the lever is not used and is left in position it is it usually won't break.

With you using the lever on a regular basis you don't have anything to worry about.

The replacement of the o-rings isn't hard, it is the removal of the step, tool box, fuel hoses and the valve that takes time.

 

[ke5eua]

If the lever is not used the grease and o-ring will harden and dry up. It takes years.

If the lever is not used and is left in position it is it usually won't break.

With you using the lever on a regular basis you don't have anything to worry about.

The replacement of the o-rings isn't hard, it is the removal of the step, tool box, fuel hoses and the valve that takes time.

+1 on the removal that is the hardest. That's why when I finally got the tool box off and the valve out with the little hoses still attached I ditched replacing the o rings and headed to Home Depot and got two tees for a more long term solution.

 

[73m819]

Need to do like the 39 series 5ts, just put a transfer pump in, pump the right tank to the left tank, drew out of the left tank, the fuel gauge switch stays as it is.

 

[mikey]

Just out of curiosity, did you all not notice the tank selector valve on the floor next to the seat and wonder what it was for before you even started your truck for the first time? I know once I was I my M818 for the first time I looked all over the cab just to see what everything was.

I fell for this also when I first got my M931A2. There are two problems with the "looking around" approach. First, if you've ever driven a Ford F250 stake truck from the 80's, which I drove for years, the tank selector is on the dash, so when you see the tank selector on the dash of the 939 it's easy to think that switch changes tanks, not just fuel sending units. Secondly, that actual lever to change tanks is hidden quite well on the side behind the seat.

It IS in the operators manual and running out of fuel and learning the hard way is a lesson learned about reading the TM's.

Mikey