Im sure its been asked before ………………………………

1977 F-150
Which tank is the main and whjich is Aux?

Where can I buy a new switch , the one underneath passenger side?

 

1975/79 F100/350 with dual fuel tanks have a fuel tank selector valve and solenoid assy (D5TZ-9189-B) mounted on the cross member.

The selector switch (D5TZ-9A050-A - 5 terminals, marked D5TB-9A050-AA) is located in the heater control panel and switches the tanks and the dash fuel gauge from one tank to the other.

Both parts are obsolete, there are a few switches available NOS, but no one has the valve.

 

Thanks for info , do you happen to know which tank is the main and which is the aux>?

 

I canot hardly believe nobody knows which tank is which?

I used to know but its been awhile , something makes me think the back tank is the main?
Anyone?

 

lol, and answered before, see post 10...Answer

 

lololol that was in 2004...…………………………….

 

 

Just reread that whole other thread , I dont think anyone knows the answer to this for sure.
Wouldn't be that hard to pull a line off , guess thats what ill do

 

I disagree. I think we determined that the designations must have changed. Ok, so that does not make it so, but that does at least make sense to me still. So I still disagree!
I believe that early trucks with in-cab tanks, the main was the in-cab unit and whatever tank was under the bed, whether saddle or rear mount, was the default aux. tank. Makes sense anyway...
But which tank was added? I seem to remember the aux tank being the side saddle tank on those trucks. Which would then change the definition of the side saddle tank depending on which model truck you have. And since the in-cab and non-cab tank setups ran concurrently on different models, that just makes looking back into history harder to decode.
But the official book listings seem to concur, that after the mid-'77 trucks lost the in-cab tanks completely, the rear became the aux tank by simple change of designation by the manufacturer.

Later trucks with the large saddle tank and the small 19gal rear tank seemed to indicate the side tank was the main.
But is there anyone with a stock original single tank truck from '77 or later around? They should be able to tell us if the single tank is the rear, or the side tank I would think.
Is yours an early '77 with the in-cab tank? Or a later one with all the '78 changes?

In the interest of full disclosure, my '79 originally came with one tank, but the owner before me installed an aux tank with all OE stuff, so it's not easy for me to remember with 100% accuracy which one he told me it was. And I don't have a dash switch with indicators, but that would not be accurate either, depending on how the lines were connected. I do seem to remember he said he added the rear though.
So I'll go out on a limb and say it was the rear tank that was added later. One current reason I think this is the case is because the front tank had it's full complement of filler neck and molded plastic filler neck shroud (whatever that thing is called) while the rear tank only had a filler neck floating in air behind the door, and no plastic bits or rubber seals.
I put them in later after getting them out of a junkyard. I can remember this, but the proof to me is that the shroud/cup/dust shield thingy still has the pink marker mark on it from the Pick-n-Pull where I got it.
Pretty sure the old owner told me he could not find one and the dealer was out, so he left it off.

Puts me sitting squarely on the side-tank-as-main column side of the fence, at least for '77.5 and later trucks.

Paul

 

It looks like people have contradictory ideas in this thread so I'll add my own observations.

My 1978 F-250 and my 1979 F-350 4x4 both have aft-axle tanks and side tanks. The 78's side tank sprung a leak in the line so I disconnected the line and stopped putting gas in the side tank. I ran off the rear tank and had the selector switch to "main" to use it.

The 79 leaks fuel if I fill it all the way so I usually kept a small amount of fuel in it and mainly used the rear tank. The selector switch is set to "main" on that vehicle also.

The rear (aft-axle) tank is the main tank in these two vehicles. I do not know about trucks that had in-cab tanks and also an auxiliary tank.

Dennis

 

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

 

Hey Vinford, sorry I totally ignored that part of your question. But it seems that even in '77 that would have been some aftermarket switch. Can you post a picture of yours?
I've never seen a factory switch that was not in the A/C controls like Number Dummy was saying. At least not the later years like ours.

Does yours have two gas doors?
If not gas doors, then two surface mount fuel caps? If so, are they both slightly recessed, or body colored matching slight indents?
Or is one of your tank filler necks in the cab?
I guess I should just ask what month your '77 was built. If it's a later one (considered a "77 1/2") then it would have gas doors.

Thanks for any info. But a pic of your under-dash switch would be great. Especially if it looks professionally done, like a factory piece.

Paul

 

Factory installed mid-ship & aft axle fuel tanks: 1973/76 Stylesides have exposed fuel caps, 1977/79's have fuel doors.

All 1977.5 or 1975 1/2 or whatever you want to call it...applies to, is the last High Boy was assembled before serial number Y20,001 which occurred in February (mid-model year) 1977.

 

I do not have my truck at this home right now so I cannot go out and look at it but here's what the "1979 Ford Truck F-100 Thru F-350 Series Owners Guide" says about the instruments and controls for the dual fuel tank trucks.

If your vehicle is equipped with dual fuel tanks, the level in either tank may be checked by reading the fuel gauge with the fuel selector switch in the desired position. This switch also controls the fuel flow from either tank to the engine. The fuel valve is energized when the fuel selector switch is moved from FRONT to REAR position, allowing fuel flow from the rear tank. On vehicles equipped with dual fuel tanks, the FRONT position supplies fuel to the engine from the midship fuel tank. The fuel valve is protected by the fuse labeled "AUX TANK SOLENOID" on the fuse panel.

Actually I thought the switch read "AUX" and "MAIN" but this manual calls them "FRONT" and "REAR".

Dennis

 

My 78 F150 Ranger Lariat - main is front, aux rear. Yes, for sure, for sure. Also... owners manual says so.