Fuel Tank Selector Valve

Discussion in 'General IH Tech' started by Bud Seymour, Aug 10, 2019.


  1. Bud Seymour

    Bud Seymour Farmall Cub

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    Can a fuel tank selector valve go bad? A few days ago, after filling up both tanks, I took my Scout for a ride. As I was driving, I switched tanks. After shortly switching the tanks, my engine sputtered to a stop and appeared to have run out of gas. Since I just filled both tanks, I thought my fuel pump had stopped working. I replaced the fuel pump. When I started the engine, it would turnover but not start. When I disconnected the fuel line at the pump there was no gas in the line. I removed the gas line connector at the selector valve and no gas. Turning the valve to both tanks and still no gas. I cleaned the tanks a few back.

    Any advice is appreciated.
     
  2. patrick r

    patrick r Binder Driver

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    There’s not much to go bad with them, although there is at least one o-ring in it. I replaced them in one but doubt it would cause your problem. maybe it’s plugged. Take it apart and see, put in new o-rings and reinstall.


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  3. George Womack

    George Womack Y-Block King

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    Are you seeing gas in the lines TO the selector valve?
     
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  4. Bud Seymour

    Bud Seymour Farmall Cub

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    That’s what I thought. I thought, if it’s plugged, only one tank would be blocked, not both tanks at the same time. I have to drain my tanks and then I’ll take it apart to see what was causing the fuel to stop flowing. Thanks.
     
  5. Bud Seymour

    Bud Seymour Farmall Cub

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    I’ve only worked my way back up to the valve. I plan to drain the tanks tomorrow. Once drained, I’ll check for flow of fuel to the valve. It’s just hard to imagine that somehow fuel from both tanks become blocked at the same time. I’ve used compressed air in the valve to see if I could move any blockage but no luck.
     
  6. Dana Strong

    Dana Strong Dreams of Cub Cadets

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    If you have a leak in/at the valve, so that air is drawn in when the pump is running, rather than fuel being pulled from the tanks, it will give your results. I'd first open the valve to see if a problem with the "O" ring(s) is obvious. If the tubing from the tanks is full and because the valve is lower than the stock tanks of an 80/800, siphoning can occur when a leak does, and it it can also cause fuel to leak from the valve, engine running or not. If the lines are full, you can either plug them or carefully blow the fuel back into the tank so you can work on the valve w/o such siphoning.
     
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  7. mallen

    mallen High Wheeler

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    Anything can go bad. To start, get a 1 gallon gas can, take a piece of fuel hose, connect one end to the fuel pump, put the other end in the gas can. Dont reuse the piece that is there or have the fuel filter in line. You want all of that out of the picture. Spray some starter fluid into the intake. Try to start it. It should try to start and possibly stop because the float bowl is empty. Try a couple more times. You should be able to get it to start and run. If it does, then the problem is in the stuff you disconnected and bypassed with the fuel can and hose. If not, then its in the stuff you didnt.
     
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  8. pwschuh

    pwschuh Farmall Cub

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    I agree there's likely no need to drain tanks just to fix this. Pull the lines off the selector switch that are coming from the tanks and see if there is fuel in them. As has been mentioned, the switch needs to be sealed up tight so the pump can draw a vacuum. If the lines have fuel in them , take the switch apart, put in new (fuel safe) O rings and use a new gasket for the cover.
     
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  9. Bud Seymour

    Bud Seymour Farmall Cub

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    Air leak...forgot to check for that. I’ll hv to ck the O-ring and any other potential leak points from the carburetor back through the valve. Thanks.
     
  10. 1975IH200

    1975IH200 High Wheeler

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    Scout 80 / 800 Fuel Selector Valve assembly.........
    Scout Fuel Valve.jpg
     
  11. Bud Seymour

    Bud Seymour Farmall Cub

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    Went with your advice and tested the pump by itself with a gas can. The pump worked great and the 152 turned over and started without a hiccup, so now on to check the rest of the fuel line.
     
  12. Bud Seymour

    Bud Seymour Farmall Cub

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    Before tearing the valve apart and wanting to see if the valve could hold any pressure without leaking air, I pulled the two fuel lines coming from the two tanks at the selector valve and plugged the two input ports. I used compressed air to blow out the fuel lines back to the tanks. Using a Mityvac, I added 35 psi to the line leading from the fuel pump back to the valve and the pressure remained constant for both sides. I didn’t detect any loss of pressure so the O-ring must still be good. So, all appears to be good with the valve.
     
  13. Jeff Jamison

    Jeff Jamison Lives in an IH Dealership

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    Things will hold pressure,where they wont hold a vacuum,and your fuelpump pulls a vacuum.Next hook your lines back to the fuelpump and move the gas can and hose to one of the tank ports on the valve,now see if it runs.
     
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  14. Dana Strong

    Dana Strong Dreams of Cub Cadets

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    Very true, and still easy to do.
     
  15. Jeff Ismail

    Jeff Ismail High Wheeler

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    Not to discredit what has already been mentioned but to me it sounds like you lost the siphon from the tank. When I can't get a fuel system to prime, and know the fuel pump is good and that there are no obstructions in the line, I'll take the gas cap off, stuff a rag in the opening and then carefully blow air in the tank to pressurize the fuel system. Doing this will force fuel out the tank and into the lines. Don't go crazy here as the fuel tank and system isn't designed for 100 psi air so try and regulate it down to 10-15 psi. And again do this carefully and let the air out slowly from the tank or you might get a face full of gas.
     
  16. Dana Strong

    Dana Strong Dreams of Cub Cadets

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    I thought of this, but originally he said he'd just filled both tanks, so shouldn't have needed much vacuum to get the fuel 'over the hill', so to speak. Have you ever had a new pump with which the valves didn't seal perfectly so wouldn't produce a vacuum until wetted by gas? I haven't, but have only worked with/replaced a relatively few. That would have been equivalent to loosing the prime and your method would have quickly solved that problem. To amplify your warning, the tank should only get at most a few ounces of pressure buildup.
    Having already successfully tested the new pump with a fuel can beyond the pump, I'd expect he could now just rehook the two tank lines to the valve and run the engine just fine.
    I like to do whatever tests are necessary before replacing parts, so I know where the original problem is.
     
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  17. Bud Seymour

    Bud Seymour Farmall Cub

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    I was able to get the fuel system back up and running. Thanks for everyone’s input. The last things I did to get gas flow from the tank to the selector valve was use compressed air on both lines (still no gas flow) and, finally using the Mytivac again, using a vacuum to create a flow of gas from the tank to the valve. Took it on a drive and no problems. If there aren’t any more surprises, I still might be able to make it to Nationals this weekend.
     
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  18. patrick r

    patrick r Binder Driver

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    I’m glad you got it running. Now it makes me wonder what the cause was. Not something you should really need to do. I didn’t think a diaphragm pump could cavitate and would just pump the air out, pulling the fuel with it. I have run one tank dry many times, switch tanks, hold the pedal to the floor and keep driving.


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  19. mallen

    mallen High Wheeler

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    Carry a long length of tubing and a 5 gallon gas can or two. If it happens again and you cant figure it out, you can at least do the gas can on the front floor boards thing.

    I wonder if something could have lodged in the outlet of the tube. Personally,I like to have one of those little billet alumiumum fuel filters with the sintered brass filter element BEFORE the switch, one for each tank. It keeps anything from sticking in the valve and especially fouling the seats up. I like to have another just before the carburetor. (especially considering how bad my fuel tanks are.)
     
    Last edited: Aug 14, 2019
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