Hi all and thank you for your time. I just purchased a 1981 f-150 with the inline 6 and manual trans. It is not running and I was told it needed a new carb. I bought a new carb but then quickly noticed there is no fuel getting to the fuel pump (checked only by disconnecting fuel line at pump and did not turn key). I began inspecting the fuel line under the truck for a filter but I only found this odd looking part that looked like a roll of quarters on end with one line on one side and two lines on the other. It also has an electrical connection. Guessing this is a junction for a second fuel tank I looked but found no other tank. I guess what I'm asking is could this part be causing the no fuel flow problem and is there another component within the tank i need to be aware of that could also be responsible for no fuel flow. Thanks for your time.

 

Welcome to FTE

Where to start?
Has the truck been setting and if so how long?
This could lead to bad gas making it hard to start and run or worst gum up valves making them stick and a rusty tank sending all that to a new carb, not good!

Lets see if the pump pumps shell we?
This fuel pump should be bolted to the motor.
Get a few feet of 5/16 fuel hose as you will need some of it later, and hose clamps to fit the hose.
A small gas can with gas or a can that will sit up on the inner fender.

Remove the fuel line from the tank at the pump and plug it, a bolt works pretty good.
Put the new hose on the pump and maybe a clamp.
Put the other end in the can of gas. Put a little gas down the carb and see if the motor will start and run.
It may start and stall till it can pump gas from the can to carb, if the pump works.
May need a little more gas down carb for it to pull gas from can.

It will either pull gas from can and run or it will not pull and not run.
Pull gas and run is good, no gas, not run not good and the pump needs to be replaced.
Now if the pump dose pump and truck been sitting we need to keep an eye on the oil level.
The pump can be bad and put gas in the oil and the level will go up so watch it.

Once you can get the gas from the can to carb and motor runs we can look at the tank(s)
Do you have a switch on the dash to the right of the HVAC controls for fuel tanks?
Dose the bed have 2 gas filler doors or 1? Someone could have swapped beds and only have 1 filler door.
Where is the tank you have now at, side or rear and do you have a short or long bed truck?

If the truck has been sitting for a bit, say over a year, you may want to replace it.
The old gas can gum up the inside and it can also rust. You can never get the tanks clean enough of the gum or rust and being the tanks are cheap it is best to get anew one and sender.
If you feel brave you can drain any gas in the tank(s) and put fresh gas in just make sure you have a fuel filter between the pump and carb but it will not stop fine rust getting to the carb, ask how I know

If you keep the old tanks replace the old rubber hose from the tanks to the metal lines. It may look good but it can have small cracks that pull in air, not gas, and not leak. Yep had that happen once too.
The new gas blends can also break down the inside of the old hose and block flow, so just replace any old fuel hose.

That thing you said is on the frame rail sounded like a dual tank valve that the switch on the dash works.
If you are sure you have only 1 tank you can take some of that new fuel hose and bypass the valve, Just go from the metal line around the valve to the metal line, If you do have dual tanks and only have funds for 1 tank replace the rear as it may be the larger of the 2 depending on bed size.
You can then bypass the valve and run only the new tank. Replace the other when you can and pipe in the valve after you check it it works.

So with a good tank, fresh gas in it and rubber hoses replaced and fuel pump now ready to pull from the tank see if it will start and run.
You may need to pour a little gas down the carb till it pulls fuel from the tank.
You should be good at this point for fuel to carb if not let us know.
Dave ----

 

I'm not really sure this is necessary. Besides, does he have the money for a new truck?

 

I see we are starting early to day
Thanks it is nice to start the day with a laugh
Dave ----

 

Welcome to the forum. I'm not sure what you mean about turning the key. Were you thinking there's an electric pump somewhere in the system? On a carbureted 6 cylinder engine, the only pump is mechanically driven and is mounted on the side of the engine. Newer vehicles have an electric pump in the tank that pushes fuel under pressure to the engine. Unless an aftermarket electric pump has been added, your truck has only the mechanical pump up front that sucks fuel under vacuum all the way from the tank.


Does it look like this, although the electrical connection may be different?:



If so, that is the tank selector valve. Even if your truck only has one tank now, it would have originally been equipped with two. Look at the right side of the heater control panel in the cab. Do you see a switch labeled Front and Rear? That's the switch to control which tank is feeding the engine. If you only have one tank now, you can bypass this valve with a short length of hose.


Possibly. Go to page 58 here to see how the switch and control valve is wired:

https://www.garysgaragemahal.com/1981-evtm.html

The valve is spring-loaded. When the valve is powered, the rear tank is connected. When power is removed from the valve, the front tank is connected. On early models like yours, the front tank is the default position in case the fuse were to blow, etc. (On later models, the rear is default.) So if the valve is trying to draw fuel from a non-existant tank, that could 'splain a lot. The quickest thing for now would be to bypass the valve with a piece of hose. Then see if the pump is able to draw fuel.

 

Your other tank is gone, just bypass the valve above and hook the line from the tank you have to the line going up front, going around the valve. That will eliminate one possible problem for now, you can get back to the valve later if you ever get another tank.

You do have to crank on the engine for the fuel pump to work.

 

Thanks all for your input. I understand much more now. Yes KR98664 the part does resemble that fuel tank selector. It's a side tank that I have. I'll first bypass the valve just to rule that out then test the pump per FuzzFace2's instructions. The truck has been sitting for a while so who knows how gummed up or worn out things are so Ill probably end up getting a new tank, hose, sender and pump. Is there any parts i"m missing there? I really don't like being broken down and stranded. Thanks again everyone. Great forum.

 

Should I consider installing an electric fuel pump or stick with the OEM unit?

 

One more question: when I got the truck the carb was unmounted and just laying on the engine. I've figured how to hook up the new carb for the most part but there seems to be a few vacuum lines disconnected and I can't find any info. on what goes where. Do I need to get a chilton's for that or is there another way. Thanks.

 

Keep the fuel pump stock and stay happy.

There should be a vacuum label on the radiator support. Or you can find it on the site Karl linked above.

 

In really hot weather I like a retro fit low pressure electric pump mounted on the frame back near the tank. But you might as well try the mechanical pump you have and see if it works.

 

I found the tank switch and switched it to the forward tank. For giggles i put some air pressure on the fuel line to the tank to verify if the switch was working correctly and it is. I could hear the air in the tank This was also an attempt to possibly dislodge anything that might be blocking the line. So again for giggles i hooked up a tranns fluid pump , it plugged right to the hose and has powerful suction but still I could get no fuel out of the line. Tried more air, more suction, repeat no luck. I put 5 gallons of fuel in there and the gauge reads 1/8 of a tank so it's got gas.Now i can only imagine some sort of blockage floating around the intake tube in the tank. . Seems like I'm having a problem either at the tank or in the line somehow. I assume the tank has a vent so pressurizing the tank wouldn't work to push the gas through. Any and all thoughts are greatly appreciated.

 

I'm wondering if the pick up tube broke off in the tank ?

When you blow air into the tank from the line, can you hear bubbles in the fuel filler tube with the gas cap removed ?

Found this for your vacuum lines, https://www.google.com/search?q=1981...t=gws-wiz-serp

 

Well, I was stuck standing at the front of the truck but I could definitely hear air coming out of the filler tube. Whether it was bubbles or not i couldn't say. Thanks for the link. One thing I did notice though when I was using the hand pump was the smell from inside the tank and it smelled like old bad turpentine or something not like gas. I'll bet it's all in pretty bad shape. It might be smartest to just replace everything and be done with it. This truck probably has other issues I need to find and get fixin. I gotta say though I didn't realize how super cool these trucks really are until now. I glad I got it. Thanks again.

 

Yes, replacing the tank and making sure all the fuel lines are clean will be a big plus. Sounds like you'll be dropping the tank anyways ?

The guy's here will have thoughts on that soon. Yes, these trucks are still pretty common around where I live. On the way to my son's house, I drive past a house that has one that's getting a frame off done currently.