Dual Fuel Tank Weirdness

[HomeThtrLA]

I bought a 1988 Club Wagon in January of 2003. It has two fuel tanks and a switch, that looks like it is factory-installed, for going from one tank to the other.

The weird thing is, the second time I filled up and kept track of miles to figure out what the mpg was, I never switched to the second tank; after going LOTS of miles, I finally switched and the other tank was almost empty. It was as though both tanks were supplying fuel the whole time.

It never happened again. For almost two years, I have had to switch from tank to tank, as I figure I would have to.

Then about a month ago, it stalled while using the front tank. I switched to the rear, and it kicked back into full force.

Since then I have found that it will eventually stall if using the front tank. So I only use the back one now. But this left me with about a half tank of gas in the front. I kept trying to use the front to empty it but the gauge hardly went down.

Then one day after I filled up the rear tank to be sure I had gas to switch to, I noticed that the front gauge had increased from about 3/8 to about 5/8.

huh?

Are these tanks interconnected? Do they both pump at the same time, regardless of the switch? Is the switch NOt switching and making both pumps work?

Anybody?

[catback23]

The tanks are supposed to run independant of the other tank and only the tank you chose should be supplying fuel. With age I find these tanks mess up in all sorts of ways. It is possible that the switch is malfunctioning and pumping from both tanks but as far as the front tank going from 3/8 to 5/8 when you filled up, by design that can't happen. What probably happened was the gauge settled down enough to read the actual fuel amount. I suspect a problem with the front tank since you can not run the gauge down to E whether because the gauge is reading wrong or the tank won't suck up gas that low in the tank.

[ModMech]

Your van, with dual tanks, has THREE fuel pumps. One in each fuel tank (pre-pumps), and a single main high pressure pump on the inner frame below the driver's seat. Oh, this ASSUMES it is a van, and NOT a 460 powered "commercial cutaway" with a box on it, they are carburated, and have only the in-tank pumps.

The selector chooses which pump, and which sender are used and activates a selector valve that will return fuel to the selected tank only.

Given that the vehicle is over 15 years old, it could very well be that the tank is not properly grounded, so the front gause does not work perfectly accurately. Also, if the front "pre-pump" fails, you will be able to get about 1/2 tank of fuel out of it, but it is VERY hard on the main pump to do so.

[chucke150]

I know this is an old post but someone may benefit from this. I had the exact same problem.
Ford did a recall on the fuel tank selector switch. Take it to a dealer and he will replace it free. I had it done to my 89 E-150. It works great now.

Also if your having problems w/ fuel tank level guage not working or working for a short while after you fill up from an empty tank you may have a leaking float bulb inside the tank. I had to replace both of mine!

[Jack Russell]

I sent you a PM

Have truck, same modle and year, duel tanks switch over valve not working. Ford recall is news to me. would like any information on recall you can give.

Thanks
JR

[sprint11s]

Originally Posted by Jack Russell

I sent you a PM

Have truck, same modle and year, duel tanks switch over valve not working. Ford recall is news to me. would like any information on recall you can give.

Thanks
JR

I'm currently having the same problem with my 1988 F-150 4x4, it has 2 new tanks, new rear sending unit and pump(2 yrs. ago). The front tank has a new pump and selector switch(2 weeks ago) and will only take fuel from the rear tank with switch set on front tank but will read the fuel level in the front tank! Any suggestions?

[Den.]

Originally Posted by sprint11s

I'm currently having the same problem with my 1988 F-150 4x4, it has 2 new tanks, new rear sending unit and pump(2 yrs. ago). The front tank has a new pump and selector switch(2 weeks ago) and will only take fuel from the rear tank with switch set on front tank but will read the fuel level in the front tank! Any suggestions?

Hmm. I don't know anout sprint11s's problem but I DO know that the selector switch is a common problem. Usually it is caused by the switch basically jammimg in the middle of the two settings. This is probably why it is the first thing thought of when the problem is looked at.

I recently had a friend stranded here from Florida because of this in his motorhome. Needless to say he went through HELL before it was diagnosed and fixed. Unfortunately he also had some serious wiring issues in which the previous owner had tried to patch up the problem with shortcuts.

Shortcuts which cost this friend over $3000CDN (including towing each time it broke down again!) before it was resolved. Turned out to be a loose wire....

[warren222000]

I am having the same problem with my '88 Clubwagon. When I switch to the rear tank, the gauge reads full, but it still sucks gas from the front tank. I have the rear tank off right now, and was about to replace the fuel pump, but when I tested the wires going into the sending unit, only one pair of wires was getting electricity. This leads me to believe the sending unit is getting juice, and registering fuel level on the gauge, but the pump is not. Would it be dangerous to connect 12V to the pump to test it? Or how could I test the switch?

[forde350]

Originally Posted by warren222000

I am having the same problem with my '88 Clubwagon. When I switch to the rear tank, the gauge reads full, but it still sucks gas from the front tank. I have the rear tank off right now, and was about to replace the fuel pump, but when I tested the wires going into the sending unit, only one pair of wires was getting electricity. This leads me to believe the sending unit is getting juice, and registering fuel level on the gauge, but the pump is not. Would it be dangerous to connect 12V to the pump to test it? Or how could I test the switch?

you can test any switch with a continuity test thru it if you have an ohm meter,with the power to the switch off, the meter in the "R" or ohm mode,first test the meter by touching the lead ends together,the needle should register all the way over the scale,now we know yor meter is working,then place one tip(lead end)to bare wire terminal connection on one side of switch and other tip (doesnt matter which tip where)to other terminal connection,now when switch is in off position if switch is good you get no reading or movement of needle.....put switch in on position (this is circuit complete)you should get full swing of needle as you did when touching tip to tip.......further in both switch positions with tips on terminals jiggle switch button(toggle) to see if needle reading holds stable, you should get no intermittant bouncing of needle in either position......switch is good if it you see what I have described........otherwise.....not good. The real questions here: are you getting power to the valve that is supposed to move to redirect flow from one tank to other and if you have power at valve is it actually changing position to allow tank switchover??you can check pump activity by listening down filler tube with a short piece of hose for the winning noise you will hear when pump is running....when the tank switch is thrown.

[Lowell 1935]

I have 87 E350 club wagon It has a mechanical fuel pump and a 4 barrel carb.
The rear tank ran out and when I switched to front it did not restart.
The fuel selector valve is no longer available. The after market switch requires replacing wiring and hoses because nothing fits. Is there an easy way to check the mechanical fuel pump before I do all that work. I have been fixing my own cars since 1950, but it is getting harder now that I am 80 years old.

Lowell 1935