You have an in tank electric pump and your truck has a carburetor. You might be able to use the 86 FI sending unit, then plug the return line. The only question would be the fuel pump compatibility for a carburetor. Also you could keep your existing sending unit and rebuild it by changing out the float and sending unit and install a new pump. You will have to determine if a compatible pump only is available.

 

I pretty sure (but i haven't checked ...) that i've a return line, even if the 460 has a carb.
According to the service manual :

 

OK,makes sense then. Low pressure pump and a return line. Now take a peek up over your axle and what do you have in there? If a replacement for your pump can't be found replace the fuel sending unit and float and keep the pump going. The sending unit/fuel pickup is only a round plate with tubes and wires going through it...and the plug in. Very easy to clean up and repaint and replace needed elements. Don't paint the tank side. You will also need a new metal retainer ring and gasket.

 

Even if you find replacement pumps, you might consider putting them on the shelf until a pump stops working. Sometimes original parts are better. It's one of those cases of "if it works don't fix it." Yes the tank is difficult to remove but if a fuel pump goes you will have to do it. Fuel gauge issue only? It's optional so do yourself a favor and drive it on the front tank and switch to the rear as a reserve and note the mileage.

 

Yes i think i'll wait before replacing the rear unit. As you said i'll drive with the front tank. But i must also drive sometimes with the rear itsn't a good thing to have too old fuel in tank.

 

My 86 f350 has the rear plastic tank. The pump you need is Airtex E2091S. This is the stock replacement . The tank has a small hole compared to the side tank. The rear tank only uses two wires.It takes me about 1.5 hrs to change it. You can get the airtex at Napa or on line.
good luck Rodger

 

You bet. Drive the front tank for 200 miles, then switch to the rear for 200 miles. While you're driving around on the rear fill the front and visa versa. I am assuming that you get better mileage than 11 mpg and you have 19 gallons in each tank. Adjust your expectations accordingly.

 

Just some news about fuel gauges indicator: yesterday i drove the car with a friend and tell him that these truck has two tanks with a switch to choose the tank. I drove with the rear tank (as usually) and i switched to the front tank. The gauge indicated 3/4 full (as usual ...) but after 200-300 meters the truck slow down and engine stalled. I switch immediatly to rear tank and as the car continued to roll the engine re-started. I was a little surprised ! I didn't use the front tank, only on some occasions some months ago and only 1 or 2 miles.
I left my friend and tried other tests. At iddle in P no proble with front tank so i drove again the truck. After 300 meters the engine died and the car stopped (speed was very low). I switched to rear tank and the engine re-started. So ther's a problem with the front ! I opened the cap and could listen to the (electric ) pump but but the noise resonated a lot in the tank. As i was in a hurry i didn't make other tests but i suspected that the tanks was empty and the pump was defused during the acceleration.
Today i decided to put some gallons in the front tank, even if the gauge says 3/4 full... After refilling 4 gallons i switched to front tank, no problem !!!! So my gauge reading is false ! With the supplementary 4 gallons the pointer is exactly at the same place: 3/4 ...
Remember that i've also a false reading about the rear tank, the gauge says 0 (or below 0) since 15 miles and i've only drove the truck 30 miles since full tank refilling ...

I think about inverted connections on the tank selector valve but even with 4 gallons the rear tank gauge says always 0 .... I suspect that the two tank senders are shot

 

It's quite likely the sending units are bad. Very common in our older trucks. I would fill up both tanks and then record the mileage and use the front tank only till it runs out. Determine the number of miles either by calculation or use the trip meter if you have one. Then switch to the other tank and go fill up the front and see how many gallons (liters in your case) it takes and calculate your mileage per gallon or liter as the case may be. Repeat for the rear tank. Then you will know your use-able capacity in each tank. If you don't have a trip meter pick a round number to refill at and use the odometer.

Use 100 miles or 200 miles which ever makes the most sense and switch tanks on that number of miles. Just remember to refill the previously used tank in the next mileage interval. If you pick 100 miles then you will likely have gas left over when you switch, which can be used as a reserve if you forget to switch and buy more gas.

With a trip meter it's much easier to keep track of where you are on fuel use. Hopefully you have that option...but many trucks do not...good luck!

BB2

 

Why the guessing on MPG?
You need more testing. On the tank reading 0 pull the wires off sender, check to see what ones are for the pump & gauge. Pump will have 12 volt power all the time the fuel gauge will have about 5 to 7 volts if using a test light will blink.
The blinking one put to a good ground and with the key on the gauge should move to F. If not you have an issue from tank to gauge.
An do the same for the other, when the plug is pulled the gauge should go to E. Do the same test as above and if the check out replace the senders.
Dave - - - -

 

I'll test the senders next week. I remember that when the rear tank is full the gauge indicates between 1/2 and 3/4 but after some miles (10 to 15) it decreases to 1/4 then (after 40 miles) to 0.
The front tank is always at 3/4.