Mechanical fuel switching valve

[fatherdoug]

I'm told that this is the problem on my '89 F-250. Rear tank works, but front tank does not. The pump in the front tank appears to be working.

Is it worth my time to pull the valve and troubleshoot, buy a replacement mechanical valve, or is there a workaround? Since the truck gets 8 mpg on a GOOD day, I almost have to have both tanks since I live so far away from everything.

 

[95F350XL]

Are you sure the pump is good? There should be a low in tank and high on the frame. My 91 has in tank high pressure..... No valve on the frame.

 

[fatherdoug]

I disconnected the line from the tank to the switching valve, and got a good stream of gas out of the line when I turned the ignition to the on position.

The valving mechanism was changed in 1990 to a different style.

 

[95F350XL]

Id say then yes you need a new switching valve

 

[fatherdoug]

What I was wondering is if anybody has done any work on this type of valve, or have done any troubleshooting. I did find one article on the interpest about O-rings slipping out of place and causing pluggage.

 

[Fellro]

I had one with a hole in the bottom ans switched the cover, but don't hear a lot of success fixing them, and the parts aren't readily available. They operate on pressure from each pump to change the orientation of the valve for both supply and return.

 

[fatherdoug]

Just found a NOS Ford switching valve on epay. Will install it after it gets here and report back later. This will also give me a chance to pull the old one and look inside. I'm just curious how that thing really works.

Thank you everyone for the suggestions.

 

[BIGRED911]

Ive just got half a front tank...back tank has been gone a long time.. tank switch is a kill switch/ anti theft switch now.....

 

[fatherdoug]

That works too. But I live so far away from everything, I almost have to have two tanks to go ANYWHERE, and make it back!

 

[fatherdoug]

So, I'm still waiting for the new switching valve to arrive - free shipping, might take awhile. Does anybody know what the pressure rating is on the intank fuel pump, or can someone tell me if bleeding all the pressure off the fuel rail at the schraeder valve will also bleed all the pressure off both sides of the switching valve.

 

[Fellro]

I believe the in tank is a lower pressure of 7 psi, then the front pump bumps it up to 35 or so. This is all off the top of my head, so don't take it as absolute. I would expect that the in tank would retain some pressure while what you bleed off is only after the high pressure pump.

 

[fatherdoug]

Thank you, Roger. I was also thinking the low pressure pump would still have some residual pressure.

 

[fatherdoug]

Update. Received a new FORD mechanical switching valve from an NOS Ebay source and installed today, which solved the problem. The truck now runs on both tanks.

The removal and installation wasn't as big of a pain as I thought it would be.

 

[smokey]

Glad to hear you got it fixed

 

[fatherdoug]

Thank you, Randy.

 

[m78]

Glad to hear it. I've seen a few different style valves for boats with 2 tanks. Wonder if one of them would do in a pinch.

 

[fatherdoug]

Thanks, Mark. I'm going to pull the old one apart just to see how it works. I think it works on pressure differential and check valves, depending on which pump is activated in the tank?????????????

 

[SuperCab]

Cool. Let us know what you find in the old one...

 

[DNFXDLI]

Very cool that you found a genuine FoMoCo part Doug..

 

[fatherdoug]

Cool. Let us know what you find in the old one...

Didn't find anything wrong, other than the Oring for the cup on the bottom was mush(new gas) The diaphragm and the valves were still in excellent shape. There was a glob of shtuff on top of the diaphragm, kinda like varnish, but nothing else. I did notice that the part number was a later version from 1991, so maybe they made some improvements?

Very cool that you found a genuine FoMoCo part Doug..

Yes, it was cool. It was a ford dealer in Mass. They sent one which didn't show up for ten days. I contacted them, and they sent another one, no questions asked, AND they overnighted the second one at their expense. Very pleased!