I have dual tanks. On a recent trip the truck ran out of gas in the primary so I switched over the aux. When I went to fill it, it only took 12 gallons to fill the primary. Believe this is an 18-20 gallon tank, and I've put close to 18 in it before.


Any ideas what the issue might be? I have a stock fuel pump that obviously is working fine because it works when the tank is full, and it pulls from the aux tank just fine. I've tested it at between 7-8PSI.

 

The dip tube on the pickup may be cracked or broken part way up so it sucked air before it sucked all the gas out of the tank or you could have had a bunch of crap come loose from the inside of the tank that plugged the pickup screen.........

 

hm...ok. How do I pull that out to check it? Being that it's in cab I would have figured the tank was gravity fed and just had something like a radiator petcock to control fuel into the lines. Hoping the tank doesn't have to come out, or that I have to drain it to see what's going on.

 

Where ever the sending unit is SHOULD have the connection to the pick up tube? I believe that are on the top edge of the tank?

 

Ok, that doesn't look bad....not home right now to go check for myself. Unbolt and lift out.....


I'll take a look at it in the next couple evenings.

 

Is that pickup a part you can still buy? Assuming it does have a hole in it (which could well be the case after 40 years), hoping it's something that's still available.

 

Safety 1st..Good ventilation, like truck outside, both doors open and a fan pushing air thru if the tank is full. Do not be smoking your favorite stoggy.

I personally have not pulled a in cab tank sending unit, but I can't see it being that hard.

I am pretty sure that sending unit is available, the price might be WOW. Pick up tube can be repaired modded, copper float itself should be locate-able also.

 

BAM 1948-1979 V8 Ford Truck Gas Tank Sending Units And Related Gas Tank Sending Units And Related - Macs Auto Parts

Gas Tanks and Sending Units | 1957-72 F100 - F250 | LMC Truck

Ford F100 Fuel Tank Sending Unit - Best Fuel Tank Sending Unit Parts for Ford F100

 

Gonna run it down until it sputters out again...that should leave about 7-8 gallons in the tank. Truck sits outside and I'll probably do the work through the back window to avoid taking the seat out.

 

Excellent!

 

D-Rat, I just removed my in cab tank in my 75 F250 4x4. The sending unit is just that, a sending unit. It does not pick up fuel.. There is a separate connection to the drivers side of the sending unit that is the fuel pickup (it is on top of the tank). It appears to be permanently affixed to the tank, as I could not figure out how to get the pickup tube out of the tank. It has a flare connection to the fuel line going under the cab to the manual fuel switch.

 

43-4016 SENDING UNIT 1 $49.95 In Stock $49.95

This is the part number from LMC that I ordered. It is just like the sending unit I pulled from my tank.

 

hmm. If its a permanent part of the tank thats not good. Cant think of any other reason it would act like its out of gas when it has 7-8 gallons left. Sending unit is just for the gas guage, right?

 

Correct. I had the same problem with my 64's in cab tank. Half a tank, maybe even a bit more - bam! It would shut down just like it was out of fuel.

It COULD be one of the rubber hose connections, there is a short hank connecting from the in-cab tank fuel pickup tube (next to the frame, underneath the drivers side.) Commonly overlooked. It might be leaking a bit of air. I never was sure what fixed it in my truck. Replaced the tank, fuel hose, fuel pump etc. I was sure the pickup tube had a hole in it. The old tank looked amazingly clean inside though, and was never able to see anything wrong with the pickup tube. It would only take a pinhole though. They aren't removable as such.

 

8 bolts pull the seat..you never know what you might find, maybe a build sheet?