Hey guys I'm new to working on these classic trucks. Always loved their look and style - character. Finally got to buy one this year. It is a '79 F150 4x4 with a 400m, auto transmission, dual tanks, 2 barrel carb. All stock as far as I can tell. 160,000 on the odometer and truck is from Oregon. Problem - it died on me while driving, fired up once, then would crank but not fire ever since. I've changed the fuel filter coming out of the main tank, fuel pump, and another in line filter near carb. I don't think I'm getting fuel to the carb. Filter is clear. If I drop some gas down carb it will fire up briefly then die. Any help is greatly appreciated.

Thanks,
Shawnyboy

 

Well, if you pour fuel in the carb and it fires up it tells me you have spark. You said you did the fuel pump and both filters. The inline filter near your carb.....is it see through, this way you can watch to see if you have fuel flow at the carb? If not, you should pull your coil wire to keep the truck from starting and then disconnect the fuel line and do what you have to do to keep fuel from shooting all over the place and crank the truck and see if you have fuel making it to the carb. If you do then you probably have a carb issue. If you don't have fuel, you may have a clogged fuel line or something in the tank restricting the fuel flow. In that case you are gonna have to backtrack. You can take the output line off the pump and crank the truck to see if you have fuel coming outta the fuel pump, again....do what you have to do to keep fuel from spraying everywhere. If you do have fuel outta the pump then you may have a clogged line between the pump and the carb. You can use compressed air to blow through the line being careful because there may be fuel in the line that will spray out when you shoot air through it. If you don't have fuel outta the pump then you have to disconnect the line coming from the tank and see if fuel pours out of it, gravity should make the fuel pour out. Anyway, try that stuff and post your findings. You should also check to se that none of your lines are leaking fuel, sometimes the leak can suck air into it and instead of the pump, pumping fuel it just pumps air.

 

Yes, filter at carb is see through. Today I have replaced the rubber gas lines between the tank and tank transfer valve mounted on the frame, drivers side behind front door. Also replaced all rubber hoses coming to and leaving the valve. Blew air back from valve to tank - clear, through valve - clear, from valve to fuel pump - clear, from fuel pump to carb - clear. Fuel will free flow from hose when disconnected at tank transfer valve. Filter at pump is bone dry, a few drops at fuel pump. Any other suggestions? Vapor lock?

 

maybe you got a bad fuel pump or you did not get the arm on the fuel pump put in the block right

 

Does fuel flow through the transfer valve from the tank? Fuel should free flow all the way up to the inlet on the fuel pump Unless there is some funky fuel line routing going on, usually the inlet fuel line will be lower than the outlet on the tank so fuel will be at the pump, unless you have a cab mounted tank like I do. The pump is used to pump it up to the engine and into the bowl of the carb, did you try pulling the line off the carb and cranking it? If you have a restriction in the carb, you might not get fuel to the see through filter at the carb, it could be airbound. Vapor lock is not an issue in your case because that is heat related. A bad pump is a posibility, getting the rod into the block is pretty easy on a ford, if you screw that up you will know it. Let me know what you find

 

As was mentioned above, did you make sure the fuel pump arm was UNDER the cam eccentric?

 

I ran into this issue today, I started my truck, backed it out of the garage and it ran fine, it sat for a few minutes idling and then it stalled and would not start again. The truck turned over with no issues but would not start, I poured some fuel down the carb and it started for a few seconds and stalled. I pulled the inlet line from the carb, removed the fuel filter that attaches to the carb and turned the truck over, very little fuel came out?? What I don't understand is the truck ran perfect up to this point, what would cause this to happen all of a sudden?? Does this sound like a fuel pump problem?

 

The fuel pump can go bad without warning and they often do.

 

Since you have dual tanks:

Disconnect the rubber hose from the fuel steel line going to the fuel pump. Get a long 3/8 fuel hose and a gas can. Run the hose from the fuel pump to the gas can and make sure the hose is in deep.

Attempt to start the truck and prime gas into the carb. If it starts and run, you have issues with the selected tank or both or the selector valve.

 

Thanks for the replies folks, I am going to give the gas can trick a try today, I think you may be right on the money, when I poured gas into the carb it ran. I have brand new gas tanks and sending units, I have not been able to draw gas from the main tank only the aux, the gas gauge for the aux says it is full, when I switch to the main tank it will not read the fuel in the tank.


BigRed

 

Well guys this is what I did; I disconnected the hose that attaches to the metal lines running from the gas tanks, I put a longer hose on and ran that into a gas can, I took the other end of the long hose and attached that to the fuel pump where it draws gas into the pump. I tried to start it, it turned over, no fuel, no start, I had to stop and charge up the battery. I have new tanks, new sending units, new selector valve, I am waiting for the part to change the selector switch and I ordered a new fuel pump and fuel filter, any thoughts from you guys would be appreciated.

BigRed

 

If it ran when you pour gas down the throat, you've got fuel delivery issues.

Make sure the fuel hose is on tight; any air and it won't pump worth damn. You don't have to hook up the gas tanks to the gas can. Just hook up the hose from the fuel pump to the gas can. If it still doesn't pump gas in the float, you need either a new fuel pump or adjust the float.

 

Update. Today I removed fuel pump and put it back in just to be sure it was in correctly. Feels like it went in right. Had to apply a little pressure to move pump arm so it would mount flush ( bottom nut). Visually looking in through the block where fuel pump mounts, I can see only what looks to be the bottom of a chain and sprocket. Turned engine over, can't see anything else. Should I see part of cam lobes? I disconnected gas line leaving fuel pump and cranked her over several times. Not a drop coming out. Will try gas can tomorrow. Gas line do turn up, down, sideways, between pump and selector valve so it won't free flow when dc'd from pump. Try again tomorrow.