Bill - I called my local salvage yard this morning and just asked if they had any 87-89 Broncos. They did, so I went and looked at it. In fact it had the reservoir so I purchased it and will be swapping it in today. Thanks for your help.

80skeys

 

Just an summary update on my fuel system issues, in case anybody cares.

My rear tank had sprung a leak and in the process of trying to get the gas out in order to patch it or drop it, it became apparent some crossfilling was going on. I could never get the damn thing dry, hence any attempts at patching were futile!

So at Bill's suggestion here, I decided the easiest and cheapest solution was to replace to dual selector reservoir with a single tank one. Nobody at the junkyard knew what I was talking about, so I had to go look under one of their old Broncos myself. Walah - there it was. I bought it for twenty bucks and installed it.

In doing so, the lines to and from the rear tank are left unconnected, which is what I wanted. I also disconnected the return fuel line on the passenger side of the truck going to the rear tank.

The end result is that gasoline is drawn only from the front tank. There must have been a little gas left in the rear tank, and I had to drive around for a few days to let it leak out and dry up. Finally it's no longer leaking and no longer smells of gasoline.

In doing all this troubleshooting, I've concluded that the gasoline system design on these older Fords is flawed and prone to problems. I mean, there's a low pressure pump in each tank whose purpose is to push gas to the reservoir. The dash selector switch activates the pump. The gas goes to the reservoir where it sits as a little reserve so that the high pressure pump has some gas to deliver in case the low one isn't primed. So the high pressure canister pulls gas from the reservoir. Then sends it through the filter. And then finally it gets up to the fuel rail. Whew! SEems like a whole lot of parts to do a simple task.

Well, a lot of people posting on these forums have reported the same issues with crossfilling, tanks not working, unable to select between tanks, unable to get accurate readings, etc...

I hope my description helps, and also Bill ("subford") is 100% expert on this stuff so anyone with problems - definitely should talk to him!

 

Well I have a 1987 F-150 4x4 with the 351 carbureted my front tank only seems to use about 5 gallons or so and the fuel pump starves and eventually the truck acts like it runs out of gas. This is an electric fuel pump that is up by the engine. The rear tank runs just fine no problems so from searching I thought I had an intank pump so I dropped the front tank and come to find out all I have in the tank is the fuel sending unit. So could my problem be the selector valve? Which one do I need?

 

Hi every one! 1997 F350 crew cab 7.3 turbo, 4x4 auto tran, am having problem with diesel transfering from back tank to front tank over night while parked. just replaced the FPR with a new one, the old one had a broken spring in FPR. have not had time to see if this soves my problem. could it be the left rail fuel tank selector switch/valve?

 

I bought an 86 F-150 yesterday. It's a 5.0, auto, EFI, 4x4. It has dual tanks. It's at my parents house right now and I haven't been able to fully inspect it but the previous owner told me the back tank didn't work so he only used the front. Well, it turns out the front is leaking so that's my first project.

I'm wondering if it turns out that the fuel selector valve or dual reservoir turn out to be my problem if this is a replacement? AutoZone.com | | Fuel Tank Selector Valve | FUEL SELECT VALVE 6 PORT

 

No it is not.
This is what you would need if that is your problem:
Ford E

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My 85' E-250 351 carbureted has been giving me some fuel problems. So, what I have gathered from the other posts is it that I don't have low pressure pumps in my tanks, only the high pressure pump that is cam driven, Right? So, I took her out for a test run after a ton of work, and I ran out of gas, even though the front tank was full, It was like the thing switched to the rear tank on its own. The rear tanks used to have gas, but obviously not then. So, I filled both tanks, until they clicked. Both read full on the gauge last night, but today the rear was down to half, and I didnt see any leaked gas on the drive way. I assume that my fuel tank selector valve is shot, but where did the gas go?

 

mysticalcracker,

Sometimes when the pump clicks off the tank is only half full. I know on my 95 I have to find a station that the pad is lower on the passenger side so I can fill it all the way.

You wiring or the selector valve is bad. There is only one wire going to the valve, power on front tank, no power rear tank.

 

Do you have plastic fuel lines at the selector?

Does your selector have both inputs on one side and one outlet on the other side.... or connections on both sides AND on top of the valve.

With the selector in the FRONT the valve will be warm to the touch if it is working. It only is energized (powered) in FRONT position. Test to see if it is getting 12 volts with the switch in FRONT.

Jim

 

I'm having multiple fuel problems but am trying to repair them one at a time. Here's where things are.

The front tank was leaking so I dropped the tank last weekend. There was a small pin hole in teh side of the tank where I knew it was leaking from but the disturbing part was there were multiple, much larger holes rusted through on the TOP of the tank!

(Slight side note: my truck has A LOT of rust in the muffler area. the frame, rear passenger side shock bracket but especially the gas tank crossmember beam. Mine is rusted through so bad the bracket that connects the bottom of the frame to the crossmember is virtually rusted all the way through. One of the straps was ok but the other is very questionable and I think I should replace it. The rust in this area is so bad it totally dissengrated the heat shield. the only evidence of heatshielding in this area is the bolts and some rusted out pieces of the shield still stuck underneath the bolt. I'm in the process of trying to find a replacement gas crossmember beam but they are connected with rivets and i don't know how to get one out at a junkyard without some type of power tool. i guess i'll have to talk to them and see what they can do for me).

anyway, after I lowered the tank I discovered the fuel sending unit top was super rusty. especially the sending unit fittings coming out connecting to the plastic hose lines. as you can imagine the rusted fittings broke right off trying to get the lines off so I have ordered a new sending unit.

Before I started this process I noticed a leak coming from the front passenger corner of my rear tank. I can't tell if it's leaking there or dripping from there because of the skid plate and spare in the way. The disturbing part is I've never put fuel in the tank and the previous owner told me he didn't use the back tank. This has me believing the dual selector reservoir was malfunctioning and directing fuel into both the engine as it should and also directing some to the rear tank and thus notifying me of the leak. I've never tried switching to the rear tank to see if it would run or not.

While at the junkyard I picked up a dual reservoir valve out of an 87. It looks exactly the same as the one on my 86 on the outside at least and assume it will work. however, before i go through the trouble of putting this in is there a way i can test it to see if it works? from what i read in this thread it's the diaphragm that causes the problems. is there a way to open it up and see if it's ok? (there was still fuel in it and the lines when I disconnected it on Saturday).

This going to be one giant PITA project considering the selector is in the frame practically hidden behind the transfer case. and of course one of the bolts for the valve bracket is stripped to make it even easier!!!

 

An 1986 has a filter inside the selector valve and the 1987 does not.
So if you use the 86 valve you will have to install a filter on the frame.

You test the valve with not over 5 PSI air pressure, any more than that can rupture the diaphragm.

The valve should lock in either the front or back position when you put air on where the supply of each tank goes.

There is a center shaft with detent to lock it to a source tank.

With the valve locked to front or back position you should be able to blow are back through the valve from the engine side and the air should only go to the tank line tubes that is selected. If return air goes to the wrong tube the it is bad and you will have a cross flow problem.

Also click on Ford E in my post number 81 above for more information.

 

thanks sub. to clarify what you're saying, i could take the hardware out of the 87 and put it in the 86 but I'd have to replace the filter which would essentially make it an "86 style valve"? OR, I could do a direct swap of the entire 86 valve to the 87 and thus not have a filter and essentially run it "87 style". Since there is already a filter on the rail a little further up I see no reason for two filters and all the extra swap work. do you?

as far as testing the valve... how do test it with 5 PSI? i remember reading something about this in the haynes or chiltons on how to test it but I do not have any air tools if that's what's needed.

 

The 87 does not have some of the valves that the 86 has and do not think the filter from the 86 will fit a 87 valve.
But the tank source and return valves should be the same along with the center shaft and diaphragm.
I just back the regulator on my air tank down to about 5 PSI when I test them. Then used a air gun with a hose stuck on it and the valve.

If you already have the filter on the frame then no you should not need to add another.
I think the filter in the valve in 86 was just to filter the gas before it got to the high pressure pump but I thunk Ford changed their mind in 87 and said it did not need it.

The 1986 type valve:


Your fuel system:


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thanks for the diagram. my father lent me a mighty vac for when I do my brakes. testing it out i see that 5 PSI is virtually nothing so i'll have to be very careful. anyway, i'll hook it up to the 87 valve i pulled and give it a test. if it passes it's simply disconnect the old one (86) lines and 2 bolts and put in the 87 that is tested and good to go right? the lack of filter and/or valve differences between the 87 and 86 won't matter for complete unit swaps, correct?

 

Right

Correct.



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