Hey all,
I am working on a 77’ F 150 with a 4.9L. I am confronting several problems on a single front (all at once). The first was an intake manifold leak, which sounded like a train whistle driving down the road. I replaced the gasket and added some #3 Permatex to it, which will hopefully cure the leak.
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The second and most recent problem was a “No start” scenario. I started the truck and pulled it into my garage for storage. Approximately one week later, I attempted to start the truck, but no luck she would not fire.
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I began diagnosing the problem and learned the engine was not receiving fuel. I performed a fuel volume test, which failed, and began to check the fuel lines. I found the rubber lines at the fuel tank selector switch was rotten and had collapsed.
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I replaced all of the rubber fuel lines located at the fuel tank selector switch and again attempted to start the motor with no result. I re-checked the fuel line, running to the engine, and discovered the new line was at a ninety degree angle, causing the line to be partially pinched. I removed the fuel line and replaced it with a longer piece of rubber fuel rated hose.
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After replacing the hose, I discovered the same situation and removed the fuel filter bracket, allowing the hose to hang freely and unobstructed. I again tried to start the motor with no result. I attempted to prime the engine, so I would not deplete the battery, but I quickly learned no fuel was reaching the carburetor. I attempted to run the engine, feeding it fuel to keep it running in hopes the fuel pump to pick up fuel and supply the engine with fuel.
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After several attempts, I was unable to get fuel to the carburetor. My question is this, is it possible to burn up the fuel pump by running it dry, such as a restricted fuel line? Am I overlooking something? Any idea or direction would be appreciated.

 

perhaps a clogged strainer in the fuel tank or a hole in the sending unit pickup... does your oil smell like gas? fuel pump could've gone bad as well

 

A couple notes to make:

First, I am sorry to say this, but you should not have used Permatex, or any kind of sealant, near an intake runner. This is a very high vacuum area, and sealant here will blow out. Sealant changing shape in any seal will lead to a leak, whether its a water pump, oil pan, or in your case an intake manifold. Not only is using it going to give you problems, but you don't need it in the first place. A new gasket and proper torque sequence is all you need to seal the manifold. If it's still leaking after properly torquing it, it's warped.

Second, there are many steps to check why you are not getting fuel:

A. There is a foot-long length of rubber fuel hose that connects the fuel tank to the metal line that runs the length of the frame. This is almost always ignored, and any rupture here will cause your fuel pump to lose suction, and lead to a no-start situation. So check this.

B. Crank the motor over with the distributor cap off and watch the rotor. Make sure it's turning. If it's not turning, then the camshaft or timing gears broke, so the fuel pump won't turn.

C. If all of these check out - your camshaft is turning, your fuel lines are completely rupture-free, and you're still not getting gas, the fuel pump is gone. Fuel pumps only cost $20, so it's not a big deal to replace it.

And to answer your final question - yes, running a fuel pump dry can ruin it, especially an older one. This is one of the most common ways that older fuel pumps go out. Run it out of gas one time, and not long after the fuel pump goes out. Pretty common actually.

Hope that helps.

 

Thank you FMC 400,
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I am always open to criticism and it looks like I will be putting on another intake/exhaust gasket, as soon as I have someone check it at a machine shop. I am using an Offenhauser intake manifold, like so many others, and have had one intake leak after another. This is my third try at fixing the problem, so I figured the worst case, with #3 Permatex, is I would have to replace another gasket and have a whole bunch on cleaning to do.<O</O
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I will check the fuel line from the tank to the metal line as you mentioned. I may just replace it, since it is probably original and rotten anyway. I am certain the camshaft is turning, because the truck will run fine if I am feeding it fuel myself. Any idea how I can retain the factory fuel filter guard and still use rubber line without causing a kink in the hose?<O</O

 

I'm not quite certain what you mean by "factory fuel filter gaurd," could you describe this more? From what you're saying, it sounds like you're having a problem with a rubber fuel hose making too sharp of an angle and pinching off. Try shorter hose if you can, or rearranging the fuel filter. Again I'm not quite sure how to answer the question until I know more about what you're asking. You might also look for a stiffer hose. For example, you should only use hose rated for fuel when working with fuel lines. This is because fuel is very corrosive. Fuel hose has more webbing in between the inner and outer layers, so it will be stiffer. If you're just using vacuum\PCV hose for a fuel line, I can see how it would buckle very easily around a sharp turn.

 

Underneath the cab, on the left side of the truck, near where the cab and the bed meet, there is a fuel filter bracket which appears to act as a mount and gard as well. Between the filter and the metal line running to the engine, is the fuel tank selctor switch. Connecting the three componets together was 3/8 rubber fuel line.

I replaced the rubber fuel line with 3/8 rubber fuel rated hose. The inital problem I had with the replacement fuel line was the sharp ninety degree angle (from the selector switch to the fuel filter). The hose was too short, causing it to bind. I replaced the hose a second time with a longer piece, thus eliminating the kink in the hose and allowing me to further diagnose my no start issue.

The rubber line I removed from the fuel filter appeared to be pre bent, allowing the extreme angle to function properly. However, I was not able to locate a replacement, so I had to use bulk fuel hose.