So I finally got my 1976 f250 on the road after buying it, it ran great about a month ago when I drove it home from where I bought it, and it always fired up and ran awesome when I was moving it around the yard or letting it idle. Today I went to get it registered so I drove it 5 minutes to a gas station and it ran great, I filled it up then left the gas station once I hit the highway and got up to speed it started sputtering and eventually died. I pulled over and started it up again, it was ok for a couple seconds but once I got up to highway speed it started sputtering and died again and didn’t start again. I looked at the carb and when I hit the throttle there is no gas coming out. I pulled the fuel line and a little gas dribbled out but that was it. I want to flush the whole system but don’t know where to start, any ideas? While this started the horn started honking but I’m just thinking that’s bad timing.

 

Always look at the fuel filter first. if it has the original style filter on the carb, you can almost expect that to be the problem.

 

Ok will check that after the weekend, thank you

 

It could also be a clog or sediment in the line from the tank. Disconnect the line from the fuel pump and the sending unit. Use compressed air and blow it out good. The PO could have also installed a filter between the tank and pump also and it could be clogged. Original style filters, next to the card, are relatively cheap.

 

Or bad gas,,,,

 

I have a very similar issue if not the same as you just as described. Still trying to work it out. 1973 F250 4x4. Pretty sure I do not have the original tank behind the seat so I am not sure it is the correct one but that is not related to the issue of fuel

-Side Note: Looking to replace that tank but cannot locate one for a 1973 F250. Up to 1972 sure. I was looking at this dated thread and got a PM out to that OP regarding the tank he used to replace in his 74. Blue Oval has reproduced is D0TZ-9002-A = Original applications: 1961/66 F100/800; 1963/69 N500/750; 1967/69 F800; 1967/72 F100/750. Thread: https://www.ford-trucks.com/forums/1...-gas-tank.html

Back to the Fuel Issues. I am having the same kind of intermittent fuel issues with the sputtering out. Truck runs fine but this same crap comes back to haunt me. I have a glass in line fuel filter between the tank and my pump that I know has clogged up with tank sediment before (filter not the pump). I cleaned it, put it back in and it drives fine even when I have seen crap in there. Still this problem would pop up but very, very rarely. I think I narrowed down how it may be happening.

This may not have the same cause, but when you mentioned the tank fill up and then immediate pull over issues, I literally just had that happen to me three days ago. I have two pumps (carter and Mightymite) that I can switch over so it is not a pump issue. Carb is clean as is the filter between the pump and carb. I have had the tank out for new carpet and did a weak gas rinse out of the tank before but I know there was/is sediment still in the tank. Carb is clean, pumps both work and can swap, everything else seems good. Everything is fine from a sitting resting tank (any sediments are theoretically settled at the bottom of my tank). Truck runs great. No issues, starting, driving for months. As long as the fuel in the tank does not get all the way down or down to less than 1/4, everything remains fine. It could go a year, as it has, without this BS happening. Then, when I run the gas down to the bottom of the tank OR I drive a very bumpy road OR let the tank get so low that the new gas completely stirs up the sediments in the tank, it is stop and go, stop and go, stop and go...almost like dealing with vapor lock.

I think it is fuel starvation from periodic sediment obstruction somewhere from the bottom of the cab tank to my first glass inline fuel filter. Somewhere, before getting to the fuel pump, it is getting blocked is my thinking. If I stir up the fuel in the tank in any substantial way I mentioned above and this crap seems to happen. I seriously feel the tank is my issue and I would consider it as a possibility in your case as well.

On that note: Let me know if any of you know about the tank I mentioned above for a 67/72 being used in my 1973. I may even have a 67/72 in there now (it was orangish in color from another truck).

 

I TOO had this problem both times i used my truck for sustained highway speeds farther than ten minute drives for beer/groceries but it never quit on short drives all hot summer long.
- i suspected dirty rusty gas tank and since sender was bad too i replaced both
- -also replaced the carb for idle/choke/driveability issues
BUT i have yet to need to drive on highway since then, so i will see this weekend if the issue is gone.

 

Ok so I no longer think that something is clogged. I looked at it today and I took the connections apart where the valve to chose between the gas tanks is and I was getting gas to there so then I took the line off the carb and turned it over and I was getting gas (it actually started because the gas from the disconnected line was shooting gas into the carb 😂 so for future reference, point the line the other way when you disconnect it) so once I figured that I was getting gas too the carb I decided to just try starting it and sure enough it fired right up.

So I was hoping that it just fixed it’s self so I took it for another drive and sure enough when I hit 50 mph it started bogging and sputtering I slowed down and was able to get it running again until I hit 50 and it did the same thing. so after an hour of driving back roads and testing stuff I have it figured out.

it idles great, and you can pin it and it has power and runs great until I hit 50-60 mph after that it bogs down and starts sputtering until I slow down below 40 mph then it will pick back up and run nice till I hit 50-60 then it does the same thing. It doesn’t matter if I slowly speed up to 50-60 or if I pin it to 50-60 it will bog and sputter and the more throttle I add once it starts sputtering the worse it gets.

Any ideas?

 

maybe that valve, wether electrical or mechanical/manual isnt opening 100% , which could explain fuel starvation only at high speeds/fuel use.
- i dont use my front tank so i might bypass this switch altogether.
another reason i suspect the switch itself is mine was tampered with either by a previous owner trying to diagnose a fuel problem or a thief cut/disconnected a line to drain fuel.

 

Are you running ethanol blend fuel?

If you're not, the previous owner might have and it has made all the rubber in the fuel system soft. I am wondering if the fuel starvation is more due to RPM/engine load instead of speed specifically. I would check the rubber fuel hoses in every part of the system and see if any feel soft. Perhaps when you hit 50-60 mph at whatever RPM you are at, the fuel pump is pumping faster and the engine is demanding more fuel which may collapse a soft fuel hose and cause restriction. You slow down, the fuel pump is demanding less and the restriction allows enough fuel through that the engine doesn't starve.

The diaphragm in the fuel pump might be getting weak or softened due to ethanol and might be leaking. If it is leaking you might see some fuel leaking out of the weep hole on the fuel pump. You can take a look at that when you're checking the fuel hose connecting the pump to the hard line on the frame rail.

I would check for vacuum leaks as well.

Have you been into the carb or know if the PO was?

Might be float level too low and starving at faster speeds/higher load? Too small of jets and it is leaning out?

I would check all the rubber hoses, fuel pump and filter before tearing into the carb.

A couple other options are it could be vapor lock or ignition timing is out of adjustment.

Hope that gives you some ideas on where to start.

 

So after a while I took a look at it and pulled the fuel filter off of the fuel pump, it was dirty so I took it out and did a test drive with out the filter and it ran just as it should so that was the problem so I will get a replacement filter then it should be good to go, thanks for the help.

 

So I know it’s been a while but the problems have re occurred, it was running great for all of 1 day then it died on me again, so this time I dropped the fuel tank and completely cleaned it out. I blew out all the lines and I put a little connecter in so I can bypass the valve to switch tanks just in case something is wrong with it. Then I took the old fuel pump out and blew air through it to get any clogs out. I put the pump back in and I then tried to start it and I was getting no gas, so I went and bought a new fuel pump, I then went to switch it out but the new one was the wrong size. But when I had the old one out I pumped the lever and put my fingers on the inlet and outlet side and the inlet was sucking and the outlet was blowing so I put it in again and after turning it over for a while it started. I’m thinking I some how I put the pump in wrong the first time. So I let it idle for a good half an hour to 45 minutes and it was idling pretty good it had the odd “ surge” but I wasn’t too worried about it, I then went out to test drive it and it stalled and I went to start it and it spudders but won’t start. I’m thinking about re building the carb, is that a good guess?

 

I suspect you still have a fuel flow problem.

Did you find a lot of sediment and junk in the tank when you cleaned it out?

If there was a lot of junk in there, blowing air through the lines may not have been enough to completely clean them out, especially if the main steel line on the frame rail is badly corroded inside. It may look okay outside, but inside might look like an old cast iron sewer pipe completely filled with corrosion and it just won't flow enough fuel, even though you were able to blow compressed air through it. I am going to guess your air compressor is putting out at least 50 psi if not double that. A carb fuel system runs at pressures much, much lower and may not be able to overcome the restriction like your air compressor can.

I am not sure if it was suggested before, but if not, what you might try is bypass the fuel lines all together, connect a length of rubber fuel hose to the input on the fuel pump, run that rubber hose straight down into gas can, make sure the hose is fully submerged and fire the truck up. If it runs well that way, there is an issue in the lines and/or tank. If you still have the same issue, check the line between the fuel pump and carb. Might need to change any fuel filters you have between pump and carb again as well. They might have been plugged again, especially after you removed the filter from the pump itself and ran the truck that way for awhile. If you happen to have a fuel pressure/vacuum gauge or can locate one, might not be a bad idea to check your fuel pressure too, you can hook one of those up inline between pump and carb using a t-fitting and see what the pressure is. you should be 5-8 give or take half a point, I can look up the exact spec if needed, but if the reading comes back less than say 4.5psi you are not getting enough pressure to the carb.

 

Ok I kind of skimmed over the posts but someone said check? all rubber fuel lines.
Just replace ALL RUBBER FUEL LINES with new as you CAN NOT see what they look like on the inside.

Think about this for a min.
It idles ok but under high load you THINK it is running out of fuel?

So you can not crank the motor over or let it idle for testing other than to know fuel is getting to the carb as it is not under a load.
I would do 2 things at this point to see if it is a fuel issue or not.
1- mount a fuel psi gauge some where on the hood / wind shield with a long hose so you can see it when driving.
This is a sure fire way to know if it is a fuel issue or not.
2- drive it where it is safe to do so and make it happen and keep your boot in it till it shuts down and pull to the side of the road. This works even if no gauge.
Pull the air filter make sure the choke is open all the way, look down the carb move the throttle and see if fuel squirts.
No fuel you go fuel issues it is that easy!

I can also see you hurting the fuel pump when you tried to blow air thru it as you can blow a hole in the rubber diaphragm and if that happens fuel can leak into the crank case thinning the oil.
No more guessing on the fuel issue, test with the PSI gauge and know!
Dave ----

 

Fuel pumps can and get pin holes in the diaphrams....they will start up but when you step on the gas they will starve for fuel... initially it is very slight but then progreses to failure.