I recently bought an 86 f150 short bed. The previous owner removed the front fuel tank. I've found the correct size fuel tank on Craigslist and would love to get the dual tanks back.
So the question is how should i go about doing this? I'm fairly new to this style truck so I'm not sure how the fuel system operates. Hopefully someone who has done this can give some information for me.

It seems different years and engines have different setups. Mine is a 300 l-6 for the record

 

Welcome to the forum.
It may take a little time for others to help be cause of the holidays but they will come.
Till then look over the link to Gary's site, he is a member on here.
IIRC there is a section on duel tank set ups.
Dave ----

 

I would not do it. People have a lot of problems with these dual setups, they usually fail eventually and they are a pain to get working again. I suggest you get a 38 gallon Bronco tank and put in the rear if you need all that fuel capacity. You do lose the spot for your spare tire though if you go this route.

If you insist on the dual tanks, you will need to modify the bedside, add a switching valve and it's plumbing and wiring, and a switch up front to activate the valve and to switch the sending units for the fuel gauge.

 

Like i said. Previous owner removed the front tank. So the filler and the switch (inside the cab) are still there. Assuming the previous owner wasn't a total animal the wiring should still be there as well.
I knew i would need the selector valve on the frame. I also know I'll need the sending unit for the new tank.
What i don't know is how the fuel system works on these trucks. I looked online for a sending unit (rock auto) but they don't show one. They do show a mechanical fuel pump so should i assume all i need for the new tank is a sending unit? Or are they showing the wrong part. Maybe i need an in tank pump?

 

Welcome to FTE!

You haven't told us enough about your truck for me to know what page on my web site to direct you toward. But, assuming it isn't a pen EFI'd 302 go here: 1985 on F-Series - ???Gary's Garagemahal. And an 85 EFI'd 302 is here: 1985 F-Series 302 w/EFI - ???Gary's Garagemahal.

As for how it works, without knowing what you have go here: 1986 EVTM - ???Gary's Garagemahal. You might need Fuel Tank Selector & Gauges or Electronic Fuel Pump Control.

In future, either put the info about your truck in the first post or, better yet, in your signature.

 

Boss300, I can see you edited your first post.
So it is a 86 F150 short bed with a 300 six and came with factory duel tanks that the PO removed the front tank.


As you saw Gary pointed you to the 302 side of the duel tank setup. I think in that same area he may have the 300 six setup if not knowing Gary he will get it posted if he has it. May take a bit with the holiday and all.


When you get the time maybe get under the truck to see what all you have. The valve may still be there and you might be able to tell if the rear tank has a pump in it. I want to say if the rear tank has a pump it would has 4 wires going to the sender but could be wrong.
Check Gary's site both for the fuel system setup & wiring as it would also show how many wires go to the tank.


Again it may take some time for people to get back here because of the holiday.
Dave ----

 

For an '86 w/a 300 six the wiring is shown on Page 95 here: Fuel Tank Selector & Gauges - ???Gary's Garagemahal. And it implies that even in '86 that engine still had a mechanical fuel pump, meaning no in-tank pump.

 

Then I would think it would make it easier to get it back working..........but I have been wrong before, just ask my wife
Dave ----

 

I think I see a few sending units on ebay, but they are around $200. They have a bunch for the 302 efi, not very many for the 300 six. When you are looking at the pictures, make sure you get one that has only one pipe connection, not two. The 302 efi is the one that has two with a return line.

You didn't say what year tank you found. I believe it was 85 when Ford changed the size of the sending unit hole to a large diameter to accommodate the electric fuel pumps in the tanks. That makes yours even more oddball, you need the non-electric pump sending unit with the larger diameter.

If you happen to have found a earlier tank with the smaller hole, you might be able to plug in a earlier year truck and be able to find a sending unit for it.

 

Dave - I agree that '85 was the first year for the large-mouthed tanks. That's shown here for sending units: Fuel Senders & Pumps - ???Gary's Garagemahal. There are two small-mouth senders, E0TZ 9275-F and -G, for the 16.5 and 19 gallon mid-ship tanks in 80-84.

And for 85/86 there are 2 large-mouth senders, E5TZ 9275-G and -H, for the 19 and 17 gallon mid-ship tanks, respectively. (Note the reversal in order!) These are the 1-tube style sender, meaning for a mechanical pump with no return.

 

Gary, IIRC the 19 gal tank is for a LB truck.
Think the 16 gal is for the SB trucks. I had this same issue when trying to get a sender for my 81 Flair Side truck and think it was you pointed me to A1Auto.com
Dave ----


edit: just went back over it you got it covered but for others they now know what tank to what bed.

 

Thank you for pointing out they switched to large mouth senders in 85. I was assuming they used the small ones for carb applications and used the large ones for efi. I think i may just pick up an entire set up from my local junkyard. They've got plenty of these trucks so I'll be sure to get the right one. And i don't believe the selector valve is on the frame still. But even if it is I'll be replacing it before i put a new tank in.
So for the 300 l6 did the switch in the interior control which fuel pump was pumping?
right now the rear tank pumps regardless of switch position so I'm sure I'll be rewiring part of this system.

 

Your truck has one mech pump on the engine. So you have the very simple 3 port valve, the store may still sell this, I haven't looked. The dash switch had two sides with 6 terminals(dual pole, double throw). One side switched the valve, the other side switched the sending units.

The fuel injection trucks had the more complicated valve. I am a little scetchy on how that worked, I know the later trucks with the single high pressure pump in each tank used a mechanical switcher valve that worked on pump pressure to switch. I thought the earlier trucks with 3 pumps(low pressure in each tank, one high pressure pump on the frame) used the 6 port electric valve like the 460 trucks used to switch the low pressure pumps and the feed the high pressure pump on the frame. But some of the posts and questions lately are pointing to them using a mechanical switcher on some of the early trucks also.

 

I think you missed something - I don't believe you have pumps in the tanks. Instead, I think you have a mechanical pump on the engine. And, you really need to understand that because it makes a big difference. First, the selector valve is quite different. Second, the wiring is different. Etc.

So, if you get an "entire setup" from the salvage you will have to find one from a truck equipped the same way. And, from what I can tell, that would only be with either the 300 six or the 351HO.

 

IF you have a mechanical fuel pump (look on the side of the engine block)
They also offered a mechanical pump with the 460... but the valve is six port like a diesel.
It doesn't really matter which engine or weight class, just that the truck has a mechanical pump and the correct diameter tank bung for the sender.