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OK, to make a long story short, I have a 1976 Ford F100 short bed that I having a problem with. At first, it seemed simple, but is now becoming aggravating. Just wondering if anyone has an idea. The truck was my dads, and he warned me of the situation...he just never really looked at it much, as he basically used it just for "jobs" around the yard. It has not really been driven for 4 years, and had a 2000 sticker on the plates.
The engine is a 1967 390 out of a Fairlane GT. It has been converted from pointed ignition to electronic ignition. It is also carbureted with a Holley 750. Although only having about 10k miles on the rebuilt engine, it sat for several years under a blanket on an engine stand.
Problem...
Truck will run approximately 6 miles at highway speeds before engine dies. Idling, it would run 17-17.5 minutes before stalling- you could almost set your watch by it.
Upon looking at it, I am thinking either a fuel issue, or possibly a problem with the ignition module (common). Tried another ignition module, to no avail.
I then replaced the inline fuel filter with a new transparent one so I could monitor fuel level, and replaced the rubber fuel lines from the fuel pump to the carburetor. After about 17 minutes, it without warning stalled.
I noticed the accelerator pump under the front float bowl was leaking raw fuel onto the intake. I removed the carburetor, and while taking the accelerator pump off to try and fix the gasket, old sweet smelling fuel ran out of the vent. I then pulled all spark plugs just to see how they looked. Dad says they are not very old at all, but they were all fouled; really wet and dark sandy looking texture. Looks pig rich. The plugs are Bosch platinums with a taperd type center electrode. The electrodes were fouled with deposits enough to where the tapered electrodes were almost rounded off. A brass brush cleaned them up nicely.
I then removed the sight window on the side of the carb, and the float level was low. I adjusted the float until fuel just started to trickle out of the hole. After about 17.5 minutes, it stalled.
I then found two more filters...there is a thimble shaped screen type filter in the banjo bolt on the carb, right at the fuel fitting. Filter was not clogged. I also found out that the mechanical fuel pump has a fuel filter as well. It is a paper filter, and looks like the filter media in an oil filter. There was rusty looking sediment in the bottom of the canister, so I replaced the whole fuel pump rather than just the filter to alleviate any possibility of a bad fuel pump.
I then removed the fuel line going to the fuel tank at the fuel pump. I blew compressed air, about 30 PSI, into the line. I could hear air entering the fuel tank, and when I removed the air nozzle, about 4 oz. of gas shot back out all over the ground before I could hook it back up. Just air I would think could indicate a clogged fuel pick-up in the tank.
It was Miller time when I surpassed the 18 minute range, but just before I was going to shut it off after about 24 minutes, it stalled. It did however start right back up momentarily before stalling again.
The only thing I can think of that I have not tried is maybe the carburetor is loading up after awhile under load (i.e., needle and seat, leaking power valve?). We have a new Holley 600 still in the box that I can try, but I hate to introduce the carb to fuel if I do not really need to. I mean it obviously has air, has spark, timing is right, so the only thing left is fuel...or so it seems.
What at first seemed as a simple fix, is now haunting me. I drive it to work at times (1.1 miles each way) just to move the damn thing. It has never left me walking, but I just gotta get there quick.
Any ideas?
Greg
The engine is a 1967 390 out of a Fairlane GT. It has been converted from pointed ignition to electronic ignition. It is also carbureted with a Holley 750. Although only having about 10k miles on the rebuilt engine, it sat for several years under a blanket on an engine stand.
Problem...
Truck will run approximately 6 miles at highway speeds before engine dies. Idling, it would run 17-17.5 minutes before stalling- you could almost set your watch by it.
Upon looking at it, I am thinking either a fuel issue, or possibly a problem with the ignition module (common). Tried another ignition module, to no avail.
I then replaced the inline fuel filter with a new transparent one so I could monitor fuel level, and replaced the rubber fuel lines from the fuel pump to the carburetor. After about 17 minutes, it without warning stalled.
I noticed the accelerator pump under the front float bowl was leaking raw fuel onto the intake. I removed the carburetor, and while taking the accelerator pump off to try and fix the gasket, old sweet smelling fuel ran out of the vent. I then pulled all spark plugs just to see how they looked. Dad says they are not very old at all, but they were all fouled; really wet and dark sandy looking texture. Looks pig rich. The plugs are Bosch platinums with a taperd type center electrode. The electrodes were fouled with deposits enough to where the tapered electrodes were almost rounded off. A brass brush cleaned them up nicely.
I then removed the sight window on the side of the carb, and the float level was low. I adjusted the float until fuel just started to trickle out of the hole. After about 17.5 minutes, it stalled.
I then found two more filters...there is a thimble shaped screen type filter in the banjo bolt on the carb, right at the fuel fitting. Filter was not clogged. I also found out that the mechanical fuel pump has a fuel filter as well. It is a paper filter, and looks like the filter media in an oil filter. There was rusty looking sediment in the bottom of the canister, so I replaced the whole fuel pump rather than just the filter to alleviate any possibility of a bad fuel pump.
I then removed the fuel line going to the fuel tank at the fuel pump. I blew compressed air, about 30 PSI, into the line. I could hear air entering the fuel tank, and when I removed the air nozzle, about 4 oz. of gas shot back out all over the ground before I could hook it back up. Just air I would think could indicate a clogged fuel pick-up in the tank.
It was Miller time when I surpassed the 18 minute range, but just before I was going to shut it off after about 24 minutes, it stalled. It did however start right back up momentarily before stalling again.
The only thing I can think of that I have not tried is maybe the carburetor is loading up after awhile under load (i.e., needle and seat, leaking power valve?). We have a new Holley 600 still in the box that I can try, but I hate to introduce the carb to fuel if I do not really need to. I mean it obviously has air, has spark, timing is right, so the only thing left is fuel...or so it seems.
What at first seemed as a simple fix, is now haunting me. I drive it to work at times (1.1 miles each way) just to move the damn thing. It has never left me walking, but I just gotta get there quick.
Any ideas?
Greg