1971 Body/Chassis FSM

1971-74 F Engine FSM

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Fuel System

Gas Tank Repair

I knew that the fuel tank was leaking from a stupid attempt two years ago to put fuel in it. Also the tank had no cap on it just this:

Gas Door Filler

Fig. 1

So we all know what fun this was going to be.. After checking the inside of the truck for any kin of the 20W-50 enhanced spider, I removed the tank.  Fig. 2 shows what I found on the bottom front..


More Holes

Fig. 2

Who shot my tank?!

Sending Unit

Fig. 3

Sending unit

Drying Tank

Fig. 4



No wonder it leaked!  My next step was to take the sending unit out (Fig. 3) and get all the other junk out of the tank.

Cleaning the Tank

I dropped a large handful of old lug nuts into the tank and spent about 20 minutes with earplugs on shaking the daylights out of the tank! The amount of rust that came out was impressive!  I then used a magnet to get the nuts out and then attached my shop vac to the inlet to blow/vacuum  the remaining stuff out.  Next I put the drain plug in, masked off the sending unit hole with duct tape and poured muratic acid in the tank.  After sloshing this around for a bit I drained it back into a container then flushed the tank with water.  Next I hooked the vac back up and dried the tank thoroughly by pulling air through it for 30 minutes. When that was over there was no noticeable gas smell! At this point I was wondering how to seal the tank without spending a fortune on a tank sealing kit that would not last any way.  I considered welding it but I'm still learning how to weld and the thought of blowing myself up was not that appealing! Since the tank was probably going to leak again I decided to do the cheap and dirty fix.  I know it will rust and leak again so let it, I can repair it properly later when I learn to weld.

To fix the leaky tank I cleaned the bottom of paint, acid washed to bare metal, enlarged the holes with a punch then fiber glassed the whole front bottom! (Fig. 5)

Fiber Glass Mesh

Fig. 5

Very ugly fix but cheaper then a used metal or new poly! It has held three years now.  I know it will eventually fail but for now it'll do..I reinstalled the tank in the truck after cleaning out the area where the tank sat.  Like my riveted on, galvanized, stove pipe repair panels ,courtesy of the PO? :-) See Fig. 6.

Under Tank

Fig. 6

I now wanted to check the lines from the tank to the fuel pump.  I disconnected the line on the fuel pump side and hooked an air hose to it... nothing came out but a lot of air was going in.. Ok now what? The rubber line from the fuel filter to the frame hard line looked more like a sieve than a hose.  Another trip to the auto parts store for fuel line, hose clamps and a new fuel filter.  After replacing the line and filter I now had air all the way to the pump.  I reconnected the tank line and used my Mity Vac to pull gas from the tank, through the line, and out the filter.  After connecting the fuel pump inlet line back up I took the outlet line loose and cranked the truck.  Fuel spurted out strongly! So... disconnect the line from the carb to the fuel pump and blow it out then reconnect both lines. I then removed the fuel bowl bolt and filled the fuel bowl with fresh fuel.  I now had a clean, primed fuel system! I tried to pull the choke out, ut ooh choke not moving now, grrrrrrr.... Clean and lube choke cable and throttle assembly linkage until they both operated smoothly. 

Now I was ready to start the truck! Choke out, pump the throttle six times, turn the key and..

SHE STARTED!!! I could not believe it! After sitting for 5 years! I had good oil pressure, no fuel leaks and after she warmed up a bit she even idled sort of smoothly :-) Feeling brave I pushed the clutch in and tried the transmission.  Hmmm clutch feels funny and trans grinds like the clutch is not pressed ...

Next Up: Clutch Section ...:-(

Related Links

Making New Fuel Lines




1971 Body/Chassis FSM

1971-74 F Engine FSM

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