Mystery problem?

[Tim64]

My truck has a mystery problem. You can drive it all day at 40mph or less, but when you get up to 45-50 mph it’s like it runs out of gas and quits. It starts right back up with no problem, so that leads me to believe it’s not an ignition problem. I have put two different fuel pumps on it, and it does the same thing. What do you guys think?
Thanks, Tim

[psychorodder]

Had the same problem on my 65 drove me nuts, it was a piece of plastic partially blocked in fuel line. I cleaned out it was ok just my thought.

[53lowdown]

Fuel filter. Try replacing the fuel filter. This is exactly how they act when the fuel filter gets plugged up because only a small amount of fuel can get through. When idling or driving slow it's getting plenty of fuel, but when you go faster it runs out of gas.

[rickf]

As pointed out, some kind of corrosion or blockage in teh fueld line is likely.

You've put in two fuel filters already, not likely two in a row were bad, so that is probably okay. I presume you are talking about in-line filters here.

Some carbs also have built in fuel filters, like my Holley. I had sort of an equal-but-opposite problem Sometimes my carbs would leak gas, it came running out on a throttle shaft mostly, just poured if engine (fuel pump) was running. Sometimes it was fine. It turned out there was a spring that holds the element in place in the built-in filter. This spring had borken, and sometimes the end would poke through and prevent the float needle from seating. Found and fixed during a carb rebuild.

Anyway, for your problem, if you have asuch a filter it might be clogged. It is easy to overlook since it is "hidden" in the carb body.

[kris's66lwb]

had the same prob re place all the hoses filters and pump but there was a little pump on my holly that craped out

[19GMC63]

yeah, more than likely a blocked/clooged line or filter.

Also check the metal lines, especially around the fuel pump because sometimes they will get bent and crimp at the bends, restricting flow.

[Tim64]

The gas tank was cleaned out and sealed. It has all new fuel lines, and new filters. The carb was rebuilt, but it is a crappy carb to begin with. The line going to the carb does have a little too much crimp in it, I'll try that and let you know what happens.
Thanks, Tim

[ChiefRocka]

I would check the float operation and the adjustment of the needle.

[Tim64]

Hey get this a buddy of mine said why not try driving that truck once without a gas cap. I said hell it's the same cap its had on it since I got it and I didn't have this problem before, but guess what it worked. I know the tank has to be vented. I guess I need a new vented cap. Crazy!

[Stepside65]