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Actually I thought the switch read "AUX" and "MAIN" but this manual calls them "FRONT" and "REAR".
I think we discussed in the other thread that Ford changed the wording on the switch at some point, so earlier seventies trucks read differently from the later ones. Sounds like the manual is just reflecting that.
So i went out and crawled under my truck.
Traced gasline from tank selection valve to back tank.
tank switch on dash in the main position.
Took off line and got lots of gas , so in my truck the rear tank is the main.
Traced gasline from tank selection valve to back tank. tank switch on dash in the main position.
Took off line and got lots of gas , so in my truck the rear tank is the main.
This is your '78 F350 Vinford? Two or Four-wheel drive? Not a Camper Special by any chance, is it?
Just wondering about the Camper Specials since they're oddballs with their narrow frames and odd spare tire mounting and whatnot.
Not sure taking the fuel line off and looking for gas is a definitive check though. Unless you're the original owner and remember every time you might have changed the fuel lines over the years, they could have been either accidentally or purposefully swapped by a PO.
Or are you talking about gas coming out of the valve from the front toward the engine?
If the tank side of the valve, either the active, or inactive tanks can still siphon fuel out the feed line at a pretty good volume when you open it up. Fuel should stay in the line most of the time unless the tank is almost empty, and once started, you can dump a tone of fuel out just from gravity.
Just looked at my original owners manual and apparently they changed their minds again in '79 and went back to "Front" and "Rear" designations again.
Must have formed a focus group to study the reason they were getting so many complaints about not understanding what they meant!
But even though they don't specify anything about Main or Aux, they're still using the front tank as the primary (valve default position) and the rear as the secondary (valve energized) positions.
Boy, they just weren't trying to make it easy on us!
I think I'm gonna have to get me one of them factory type switches after all. Kind of put it off all those years I could actually find them in the junkyards because I didn't want to go to the trouble of swapping the control panel.
But now I'm just going to have to bite the bullet and make my truck complete.
My first truck was a 1978 F100 2wd ,300 six with a 3 speed standard transmission . It had only one gas tank and it was mounted aft of the rear axle.
Thanks for that Rob! Finally someone with a single tank after mid-'77.
Was it a standard cab, Super or Crew cab? Or perhaps most telling, is it a long bed, or short? Assuming short with the F100 designation?
Did short-beds even have the dual tanks available? I used to think they did, but in searching I don't see any shorts with dual doors. Short wheelbase that is. There are short boxes with super and crew cabs that have dual tanks, but otherwise don't see any.
And search I did! Finally got my head out of my butt and simply googled "images 1979 ford pickup" and up popped a bazillion images, many of which are single tank trucks.
So far though, all single tank images are short beds. And as far as I can see (so far, but I'm still scrolling) all long beds in the pics have dual tank doors.
If so, this is perfectly consistent with what the owner's manuals are stating. You can legitimately have a rear mounted "main" tank if that's all that is available for your truck, and a front mounted "main" tank if they simply decided to call it that and no other reason. As the book says, "if dual tanks available" then they can call them whatever they want. They just say front and rear in '79, but do still call it the "aux tank switch" to backhandedly indicate that the tank that needs it is the aux tank. In this case the rear. If so they're just changing the naming because they can and not for any other, more logical reasons.
Confusing! Can't wait to hear confirmation from others that have long beds and/or long wheelbase trucks (longer than 133"?) and single tanks.
Anybody with a long bed, standard wheelbase truck with a single tank can put this to bed pretty quick I'd say.
Well I was just about to post up that I'm now in the rear-tank-as-main camp. But then I came across this gem:
Seems even Ford didn't know, as most of the single tank long wheelbase trucks had rear tanks only.
Apparently of the known universe, everyone that decided to take a picture of their Ford truck did it either from the passenger side, so poorly exposed you could not see doors, customized beds with no doors at all, or parked in front of telephone poles that blocked the front locations!
But I did finally find several long wheelbase trucks with single tanks that were in the rear. One was from the UK, so it could be forgiven for being unusual maybe, but the rest seemed to be from the US and had rear tanks.
New paint and customized beds? Bed changes due to damage?
Dunno, but the bottom line seems to fall into the Saturday Night Live category.
"It's a floor wax, AND a dessert topping!"
Ok, last post for the night (yay!) but the more I look at that red truck, the less I'm sure it's a long bed. Hard for me to tell at this angle, but isn't that a short box?
Well that's an interesting one then. The Ford book calls the aft tank the aux in that other thread. But it's not without precedent that a factory book can be wrong either. Not often, and even less on important stuff, but it could be wrong.
Then again, were your trucks new when you bought them? If not it's conceivable (if not very likely) that the lines could have been swapped too. I can even see someone doing it on purpose because they liked the old way that they'd gotten used to.
I think it's still going to come down to someone with a '78 or '79 truck having only one tank from the factory, and which one it is. If it's got only one tank, then that's the "main" tank no matter what.
So anyone have one of those thar trucks?
Maybe we need to start another thread with that question in the title.
Paul
I'm going to assume you're responding to me even though you did not "quote" my post.
You say it's not very likely that a PO switched the lines to the solenoid valve. Now think about how unlikely it would be for TWO previous owners to do the same thing to both of my trucks. It's almost impossible. The rear tank is the "main" tank and the side front tank is the "aux" tank.
As an aside to the main question here, there is an available switch for the dual fuel tanks. It's not the frame-mounted solenoid valve in front of the rear tank that controls fuel flow, it's the dash switch.
As an aside to the main question here, there is an available switch for the dual fuel tanks. It's not the frame-mounted solenoid valve in front of the rear tank that controls fuel flow, it's the dash switch.
See post #2. This switch (D5TZ-9A050-A) was also used on 1980/86 F100/350 with single fuel system.
I did see post #2. I then showed where the switch was available. You did not.
P.S. Please excuse my ignorance but why would a truck with a "single fuel system", whatever the hell that is, need a switch to go from one tank to the other?
11-15-2018, 07:43 PM
