so i finally got around to taking my truck to a local shop... unfortunately because of restrictions where i live i cannot do any more than extremely minor repairs at my own place... and i also currently lack the tools and know-how to properly tune a carb or check/change the timing (eventually i'm sure i will, but now... not so much) i was dreading a big repair bill, but when the shop looked my truck over, all they did was clean out a bunch of sandy crap out of my carb (apparent leftovers from my engine fire a while back) and change my fuel filter...they also told me that my fuel pump is supposed to generate 5-6 psi, and it was making less than 5. they only charged me 40 bucks for that.. yay. but they told me i should consider having one (or both) tank(s) dropped and cleaned out, because it's extremely likely that at the very least my auxiliary tank is full of rusty crap and that's what's causing my issues... and quoted me several hundred to do it (apparently that involved them removing the tank(s), taking them to a nearby radiator place and having them do the flushing, and then reinstalling). several hundred that i do not have at the moment.

my husband was planning on swapping the pump (we already have a spare, just never installed it), but i was wondering about the tanks. i can get a brand new rear tank off rockauto for around 70 bucks, and in about a week and a half i'm headed back to another location where i have a little more flexibility in what i can repair/replace. i should be able to do something like remove a tank as long as i'm not obnoxious about it. is it worth it to just replace with new instead of spending hundreds to have someone else clean it? or is there a way i can clean it myself?

 

Most definitely replace it.
There is no inherent value to the original parts, and no benefit to keeping them.
To make it easier, you should also consider buying a replacement fuel sending unit, as it will also be coated with rust.

The rear tank comes out from the bottom, I'm not sure how it will be with the box on, but it was easy with it off

Sorry, I have no personal input on the front tank, I hope one day to have one...

Those fuel tanks are also available aftermarket and if the price is comparable to what you've been quoted for cleaning... I'd buy new/aftermarket.

 

Just change out the tank. If you start with the rear, it comes out from the bottom. Also, make sure that the sending unit tubing is the same size as the rest of the line going to the carb. If not, you may end up with gas flow/supply issues. Total time for the job was about 3 hours. Some thing to consider: If you have an FTE local group, make friends with them. Usually one out of the bunch will be able to lend a valuable hand to get the job done. One last item......drive that tank as close to empty before doing the work.

 

Keep spare fuel filters on hand if it clogs again...Get a new steel rear tank and sending unit since you are replacing the tank anyway. Look into a poly tank as a never rust again option. Then get a new one for the front (2wd is steel?) I do believe.

78/79 duel fuel tanks frame switch-Duralast/Universal 3 port fuel selector valve used with SW48 toggle switch Part Number: FSV4

There are two differences between the tanks. Tanks with EEC have a hole in the top center of the tank. A rubber grommet and check valve are pressed into the hole. A line goes from the check valve along the inside of the passenger side frame rail to the engine compartment where it hooks up to a charcoal canister. Non-EEC tanks don't have this hole. The other difference is the nipple for the breather line that is located right next to the nipple for the filler hose is located 180 degrees opposite.
If you are going from an EEC tank to a non-EEC tank you must also change the fuel cap to a vented style. The EEC tanks are vented through the EEC system and use a sealed fuel cap. Non-EEC tanks vent through the fuel filler cap.
If you run a non-EEC tank and a sealed cap the minimum is you'll have fuel starvation problems, at worst a collapsed fuel tank.
- Is your truck a long bed 4WD? Does it have evaporative emission system?
There are two possibilities with the plastic tank.
79 F150-350 regular cab, 133" WB 4WD, w/ evap. emissions system, 24.8 gallon mid-ship plastic tank
D7TZ-9002-C
Same w/o evaporative emissions system 26.3 gallon plastic tank
D7TZ-9002-D
Fuel sender
76-up F100-350 >s/n C00,000
Use with aft axle steel tank, includes gasket
D7TZ-9275-D
Bob Hoover Ford-Mercury, Vienna, IL (618) 658-9218
Brighton Ford, Brighton, MI (800) 336-3305
Beau Townsend Ford, Vandalia, OH (937) 898-5841
Own Ford, Jarratt, VA (434) 535-8515
Vintage Fords, Beaver Dam, WI (877) 846-8243

 

Disconnect the wire that goes to the fuel sending unit at the tank. Ground that wire to the frame, making sure the frame is clean. Turn the ignition to the "run" position and watch the fuel gauge. If the gauge swings all the way to full, either the sending unit itself is bad or it has a bad ground. If the gauge stays on empty then either the gauge is bad or there is a wiring problem.

To pop the plug off for the test, you can barely get up in there with your head and see the plug. While looking at it, VERY CAREFULLY use a screwdriver to pry it off. AND I MEAN VERY CAREFULLY. It is only pushed on like a 1/8". This is only if you can’t get it with your hands.
Once you have done the test (above) and decide it’s the sending unit. And you have cleaned the ground and that did not work. Then disconnect the ground again and fuel line and read on….

If you can't get either one disconnected, no worries you will have a little more room once the tank is dropped down a little. But make sure you have some wire slack in the plug connector.
Run the tank dry or almost or siphon it empty, I would not do it with ½ a tank of fuel, but if you just have to, just use a big floor jack and a piece of 2x2 plywood. It’s not heavy at all, unless you have it full or 1/2 full of gas. JUST DRAIN THE TANK!
Loosen the filler and vent hose clamps at the tank end and maybe you can pop the lines off? But most of the time you have to just loosen the clamps and wait till the tank is about out.
With the jack in place, or not, just loosen the hdwr (2 bolts) on the front straps, and remove the tank straps aft hdwr all together, then swing the straps out of your way.
Slide the tank to the dvrs side about 1/2" and then pull out or let the passenger side come out of the frame. Then disconnect the elec connector and eng feed fuel line if you could not get to them earlier.
Then slide it as far as you can to the right and pop off the filler/vent lines. Sometime you need to carefully put a flat tip screwdriver in between the rubber hose and the tank to break it loose. The filler neck and vent lines get stuck to the metal pretty good sometimes. Get to rough and you will tear them.
Once the tank is removed there is a lock ring that comes off with a screwdriver or punch, look for a small tab that has been bent over to lock it. Un-bend it, tap off the lock ring, remove the sending unit.
Insp the underside of the tank where the support straps rest, lots of dirt and moisture build up there, and that causes the bottom side corners to rust out. You can also come reinstall time replace the anti-chaff material. Old 2" ratchet strap work great, glued to the support straps.
Insp the inside of the tank, might be a great time to replace it all together? Before you reinstall anything connect the electric connection and ground to the sending unit. Wire it up under the truck so it is not hanging by the connection. And with the key in the 1st (on position) you should be able to move the float arm and see a difference in your gauge?? It is always easier to do this with a helper.....
Also before install, paint the complete tank with some good paint. Even spray on bed liner or undercoating??

 

That is a copy of paste of what worked for me a while back. I just put it all in there so adjust accordingly. Front tank is not that bad since it is a 2wd you have straps and not a skid plate cradle. I think you can get a poly front also?

Plastic Gas Tanks for Chevy, GMC, Ford, Jeep, Toyota and IH Scout Vehicles

MTS COMPANY, L.C. - Plastic fuel tanks for Jeep, Ford, Chevy, Scout, ******, and Toyota

Fire up Google and see if you can locate a local "You do it garage" they rent the space and tools to do the work yourself.

 

It looks like they have a SC and mid ship tanks are not available, anywhere, I guess. Just realize that you will also have to remove your hitch. My plan on my SC is to replace the aft tank and clean the mid-ship tank. Also replace filler hoses on both. I am not worried about my senders cause they both work fine. Por-15 makes a kit for cleaning and sealing fuel tanks. They have video on how it works. If you go through the trouble of cleaning it, seal it also. Do not use nuts and bolts to clean it, they are a pain to get back out. I would use a chunk of chain.

POR-15® Fuel Tank Repair Kit

 

the rear tank was driven dry 7 months ago and not used since, so it should be pretty darn dry by now.. and the fuel gauge to that one tank doesn't currently work. it *does* work for the front tank.

i didn't even know that a "do it yourself" garage was a thing! i'll have to check into it! thank you for that bit of info!!!

 

Here's something that I saw someone else do. It's not a real solution but more of a low cost workaround until the piggy bank is full enough to fund a real solution. Install a fuel filter with a spin on element like this one.
It has a much greater capacity for crud than the typical inline filters do. I'd also suggest a see-through filter between this spin on filter and the carb. When you see a lot of junk in the one closest to the carb, replace it and get a new cartridge for the big one.
It worked well in the case that I observed and it might well work for you long enough to implement a real solution.

 

our current plan was to put a standard metal fuel filter in an accessible location before the pump, replace the pump (because we already had the replacement anyway), and just not use the rear tank till we can replace it...


but i like the idea of that larger capacity filter.

we already have a see-thru filter with replaceable cartridges just before the carb...

 

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