Fuel Tank Selector Switch Changed

[rainman15]

I finally got around to changing my fuel tank selector switch and I installed my new toolbox.  After trying to clean up my old one it still looked like crap against the new paint so I just bought a new one. 

Anyway, I can hear the valve change from tank to tank, and the gauge registers fuel in the other tank now, but when I try to run on the other tank it runs out of gas after about a minute or less.  When I switch back to the left tank it starts right back up and all is fine. I filled both tanks with gas and droveback home.  When I parked in the garage my wife came out to complain about the smell of gas in the house.  I looked under the truck and it is pouring out the rear bottom portion of the right tank, the one I'd previously been unable to use because of the bad switch!

So I know I need another tank for the right side, no big deal, and I guess I can troubleshoot why it isn't picking up gas from the passenger tank while I have the tank dropped.  Does anyone have a guess at why it isn't getting fuel from that right tank?  

[Grim 82]

If the tank is in that bad of shape it's reasonable to guess that the line is completely plugged with debris.

[Captkaos]

My first guess it rust and deposits around the pickup filter.  Basically you are switching to the other tank and it is running the line dry and dying.

[rainman15]

Both logical ideas.  I'll find out tomorrow when I drop the tank.  I'd have done it tonight but I don't have the other tank yet and it is supposed to be around 18 degrees here tonight and extremely windy. Not a good time to be working under the truck. Steve

[rainman15]

I'm trying to stay positive about this but I'm getting frustrated. When I swapped out the old right tank the sending unit was really gunked up from all the trash I didn't know was in the tank.  I spent a lot of time cleaning the sending unit and it was good as new before I installed it in the new tank, and also checked all 3 lines in the sending unit and each was free flowing. I lengthened all the rubber gas lines before I put the new tank in to make the installation easier.

While I had the tank supported by the jack I grounded the ground wire to the frame and checked the gauge and it read dead empty. I disconnected the ground and the needle went to 3 O'clock, reconnected the ground and it went back to empty again. I thought that meant the gauge was working properly.

I go to the gas station and put a few gallons in the new tank and listen for the valve to change over when I press the switch, which it did, and drive off.  The needle went to 3 o'clock again and it ran about 30 seconds and died. My 6 year old was with me so my use of 4 letter words couldn't happen like I wanted, so I'm venting here.

WTH? I've put new tanks in, I hear the valve switching when I hit the new switch and it does, the gauges read like they should when I have the tanks hanging but when I mount them they just do whatever they want. And I still can't get any gas out of that right tank.

Ideas?

[rainman15]

Now I've done it, since it wouldn't run off the other tank I noticed someone else had posted gently tapping the switching valve with a hammer.  I tapped it a few times and now it will idle perfectly, but if I touch the gas pedal it dies, and I can't hear the valve switch from side to side anymore.

I guess I get to find out what difference a new valve will make, unless someone here has a better option.

[Grim 82]

It's possible that all that crud from the tank plugged up the valve, so it's not fully switching, or else it's just seriously restricted. I would just put the new valve in. Mine was about $100, and that bought some peace of mind. Otherwise I guess you could keep tapping on it and see if something gives, or remove it and try to blow some air and brake cleaner through it. I'd also replace your fuel filter.

[Captkaos]

I have to agree with Grim 82, if there was alot of crud in the tank it is probably in your valve now.

[rainman15]

The new valve is in, Autozone had one in stock for $55.  I can switch between tanks again just fine.  If I use the right tank it does the same thing, gauge is at 3 o'clock and after a few seconds the engine dies.  I switch back to the left tank and it starts right back up.  At least I can drive the truck again but I still want this to be fixed correctly so I can use both tanks.  I really need that extra range, especially when towing.

[ccz145a]

if you loosen the line from the non-working tank at the valve, does gas come out or can you get it to flow?

[rainman15]

As the valve is mounted in the truck there are 4 lines on the rear facing portion, 2 small and 2 larger lines. Which of these go to which tank? 

[Grim 82]

There should be a feed (larger-3/8") and a return (smaller) for each side. IIRC the feed lines are above the return lines, so the 2 on the right by the frame rail go to the right tank, and the 2 on the left go up to the steel lines and over to the left tank. I can take a look at mine in a couple of hours if you need, but I'm pretty sure that's how it went.

[Captkaos]

The switch should be marked, sounds like you have one side backwards.

[rainman15]

I've been working on this system for some time now. Everything is new right down to the fuel lines.  My last job was replacing the ground wires for both sending units.  I'm still having the same issues. 

All I need to know is this; is there a ground for the selector valve itself and if so where is it?

[rainman15]

Everything in this system has been replaced now, tanks, ground wires, sending units, all fuel lines, dash switch, and the selector valve. 

Keeping the switch set for "LEFT", I swapped the gas lines for the right tank to the input for the left tank at the valve and drove for a couple of days (400 miles) with no problems.  This proves there is nothing blocking the right side in any way. I swapped the rubber lines back to the way they should normally be routed and drove off the left side tank all day today (60 miles) and it ran fine.  On the way back home I tried to switch back to the right tank and it ran for about 10 minutes then slowly died.

I'm starting to think that for some reason this valve is partially switching to the right tank but no fully making the swap.  After a few minutes of driving the valve is slowly drifting back to the left side enough to stop the flow of fuel and kill the engine. 

I'm stumped!