May sound like a dumb and obvious question, but I want to be certain. I've been having issues with my '79 F150 351M running one minute and the next, dieing repeatedly. I installed a clear inline fuel filter so I could watch the fuel delivery to the carb.
Just today, I cranked it up with no problem and watched the filter immediately fill up with fuel. Drove it til I reached normal op temp and parked it. I popped the hood immediately upon killing it only to see that there was hardly a drop in the filter. I cranked it back up and watched the filter for about 45 seconds until it died for lack of fuel in the carb bowl. The filter never filled back up!! You could tell that the pump was making an attempt, because occasionally, it would spit a little gas into the filter....Now the dumb and what seems to be, obvious question. It's got to be a bad fuel pump, doesn't it? Need affirmation before I jump in and replace it. Thanks all!!!

 

autozone sells a small one you put in the fuel line.....$12.00 should run 5psi to 9psi. it is near the high performance section.

 

What are you referring to, onetontruck? I bought the manual fuel pump that mounts onto the block of the engine and runs off of the cam. I have not installed it yet because I want to know if this is most likely my problem before I go to the trouble. Please clarify what you are meaning.

 

with the gage in line just like the fuel filter you can watch the pressure to see what your pump is doing. you could still have something in the tank or whatever, or a carb problem but the gage would help. i took the gage back off after i got it all running right.

 

I can see that I'm not getting any fuel to the carb by looking at the clear fuel filter. My question was is this most likely the fuel pump or should I look somewhere else as a possibility?

 

my filter has half air sometimes i have a large clear one also, and does not look to be getting fuel but i put the gage on it and i know it has fuel pressure to the carb, you could have something blocking the tank or lines but not very likely

 

could still be you carb not feeding, that why i said to get the fuel gage, should read 5 to 9 psi.......if it does then it is not your pump or tank or whatever, that will tell you that you are getting fuel to your carb or not, also your pressure will drop at higher rpm's but should not drop below about 4psi if it does then your pump is weak....check at 3000 to 4000rpm's and idle

 

Once again, the filter was completely empty just after shutting the engine off. It must have drained very fast, in the time it took me to get from the drivers seat to the hood and open it. When I started it up, it started very quickly and ran on the gas that was in the carb bowl. It ran about 30-45 seconds before starving for fuel. In the time that it was running, the filter never filled up. Not even half full. It remained virtually empty. I know the pump was not getting fuel up to the carb, I just want to know if there could be anything other than pump that I should be looking at.

 

blocked fuel line? or pick up in tank.......sounds like the pump, but what if your float is not letting fuel in, no flow,
also pressure should hold in fuel line for awhile but you can't tell without a gage on it. you can not tell what the fuel is doing by looking at the filter, mine doen't look like it's doing anything. with my old carb the fuel drained down, with the new carb it don't.

 

Thanks! I'll dive in to it tomorrow and see what I can find. I appreciate your insight.

 

how much was the pump? could just put it on see if that's it or not, hope you get it fixed.......see ya, going to bed.

 

let us know what you find out.

 

I have a '79 F150 w/ a 351M that runs fine in the morning, then I park it. If I try to run it about 30 minutes later, it starts and then dies about 35-45 seconds later. I thought I was having an ignition problem, so changed the ign. module. This didn't cure the problem. Next, I installed a clear inline fuel filter just before the carb and witnessed something very strange. After the engine had been running for awhile to norm op. temp, I would kill it and pop the hood. In the time it took me to leave the drivers seat and pop the hood, the fuel had drained completely out of the filter. Naturally, I figured I would just start it up and watch the filter fill up with fuel. WRONG! I cranked it and it never filled up. It died after idleing about 45 seconds...about the time it would take to consume the fuel in the carb bowl. I assumed I had a bad fuel pump, so I changed it today. Same thing happened again!!! I'm not sure what could be causing this. It was suggested that possibly something is in the tank that is blocking the fuel suction line. I have to give this a try as I have no where else to turn.

 

Check for cracks admitting air into the fuel lines on the suction side of the pump.

 

Hi Farmnaggie,

Just a thought, but check that annoying little 6" piece of rubber fuel line that is located under the bed, drivers side...see if another inline filter was installed there by a previous owner. Just a thought. I found 3 filters on mine.... one there, next to the distributor cap (clear like yours), and another threaded into the 2150 Carb.

Just my 2 cents.
Steven.