Carb problem

A

ABento

Senior Member
Working on a 59AB its in a 34 1 1/2 truck, gas tank is under the seat.
If it sits for a few days it won't start,its not getting gas, the carb is empty, I have the fuel line looped above the fuel pimp but that didn't help, if I pour a little gas in the carb it fires up and runs and will start and run great if it runs every day, can the fuel pump be weak to where it doesn't pull the gas up from the tank after it has dryed up but will work once it runs.
 
If you are running a 94 type carb, it is most likely a leaking power valve. Holley power valves for the 94 work exactly like a PV out of a 4 BBL and look the same. However, there is a difference in the mounting surfaces and the improper type will invariably leak down overnight. Since most Holley PV's available these days are for the later model carburetors, this is a common problem with old Ford's. In the alternative, the power valve itself may have a leak. Either way, the solution is to replace the it with a good properly fitted power valve. A good source would be Daytona Parts or Charlie Scwhendler in New York. I personally would avoid Vintage Speed.

In an earlier thread, I think we came to the conclusion that the proper PV for a stock or near stock engine is a "6.5". (This the vacuum reading under which the power valve opens. They come in a variety of values, depending on application.)
 
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I will add another possibility. It's possible that what you are experiencing is normal. Depends on what you mean by "a few days".

The carb bowl will evaporate dry within days. How many days depends on how dry it is in your garage, how much ethanol they put in the gas where you live, etc. In my conditions two or three days is no problem. Seven days or more, I expect to have to crank a while. And the Ford fuel pump was made "just good enough", so it takes some time cranking to fill the bowl.
 
It gives fits at about 5 days, I can crank it and it won't pickup fuel, battery is good, 6 volt, big cables spins like its 12 volt just won't pick up fuel, another truck a 40 cabover it looses fuel but cranking it over it will pick up, its just this one won't.
Will the power valve cause it to not pickup fuel, yes its the 94 I went thru it about 3 or 4 years ago.


Thank you
 
No the problem of getting fuel to the carburetor is either the fuel pump, the lines to the pump, or the tank vent. Are you still using the hydrostatic pick up in the tank? If so it should be carefully inspected for cracks in the solder joints even where the lines enter the sending unit.
 
Not using the hydrostatic set up it had rotted and fell apart I have a short nipple sticking up from the old plate to draw fuel, I have a vented gas cap but I'll check it again, the lines are good and the fuel filter is clean, what has always made me wonder is the line from the tank to the pump is 1/4 in and I've left it plumbed that way, BUT the truck starts very good every day or couple days, I'll check the above items and it looks like I'll dig into the fuel pump and power valve.
 
You can add a electric fuel pump near the tank and put a switch on it to prime it for you when it sets awhile. keep in mind the old cars tend to run less fuel pressure then the later ones, but you can buy low pressure pumps if you want to run it all the time or add a fuel pressure regulator. I just kick mine on till it shuts off and then let the mechanical take over. just something to consider if it bothers you that much. Ron
 
Slightest air leak anywhere on the suction side is a problem. Pump will suck air easier than gasoline. Common problem is air leak at the sediment bowl's gasket.
 
I had thought of the electric pump but was gonna hook it to the stomp starter so that it only ran when starting, but I'm just a little on the hard headed side, it worked fine till a few months ago, but I'll recheck the lines and glass bowl along with the other things that have been pointed out.
 
JayChicago said:
Slightest air leak anywhere on the suction side is a problem. Pump will suck air easier than gasoline. Common problem is air leak at the sediment bowl's gasket.
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Wouldn’t the leak in the sediment bowl gasket be obvious as a fuel leak?
 
I had this problem with my ‘50 when I first got it. I’d take the air filter and hold my hand over the carbnwhile I jumped the solenoid, you could see the filter fill up right away then the car would start right up. About a weeks worth of sitting and it wouldn’t pump fuel. I replaced the fuel pump to solve the problem.....Mark
 
JohnI said:
Wouldn’t the leak in the sediment bowl gasket be obvious as a fuel leak?
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No, a leak anywhere on the supply side of the pump will only allow air to be sucked in, as this is under negative pressure, not positive pressure. The leak can be anywhere from the gas tank all the way to the gasket on top of the fuel pump itself. If once you do get it running, if it runs without hesitation under load, then I’m stumped, but an air leak will cause a stumble when calling for more fuel than can be delivered.
 
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