Starts but won't run!

[gogo34]

It ran fine yesterday but today it's acting up and I've done nothing to it. It starts fine every time. I pull out the choke and hit the button and it starts right up but, after about 5 seconds it starts to sputter and stalls out. Every once in a while it will just about cut out then catch itself and keep sputtering for 5 more seconds then die. It seems as if it's starving for fuel after the initial 5 seconds but, after it dies, I can start it right back up again. It's a 66 IIa with a Rochester carb. I tried cleaning out the sediment bowl on the fuel pump but that didn't seam to make it any better.

Any ideas?

[SafeAirOne]

I wonder if the fuel in the bowl on the carb isn't being replenished. Once it runs dry, the engine stops.

[TeriAnn]

Has the carb been on the engine and running OK previously or is this a new conversion?

Before the engine dies do you do anything to increase the load on the engine like try to move it?

Assuming it starts, then dies at idle and out of gear and that this has previously been a function system I suggest a fuel starvation problem.

Disconnect the fuel line going to the carb, point it at a container and give the priming leaver a half dozen or so pumps while you watch the stream of fuel coming out. There should be a strong fuel flow with each pump. If you have a fuel pressure gauge you should be seeing around 3 or 4 lbs pressure.

If you do not have a lot of fuel coming through you either have a blockage or the pump isn't pumping. If you have an inline fuel filter, replace it and try again. Look at the fuel sediment bowl. It should be full of fuel without water or a large sediment buildup.

NEVER remove the sediment bowl unless you have a new rubber gasket in hand. The fuel hardens the gasket and once hardened it is next to impossible to reseal it after removal. You should always have a spare sediment bowl gasket in your truck.

If the sediment bowl has particles, remove the bowl and check the screen. Clean if needed. If there is air in the bowl you have a clog or air leak towards downstream.

If the bowl is clean, there is a new or no fuel filter and the pump does not pump chances are good that there is a hole in the diaphragm. Pull the pump and install a rebuild kit.

If you have plenty of fuel coming out the fuel line when hand pumped there is a good chance that there is a problem with the float valve in the carb. Pull the top of the carb and look at the float valve. The floats should move freely and the needle should also move freely. There should be no sediment build up in the float chamber.

Note: Most fuel and ignition systems problems have the same symptoms. When you have a fuel related problem it never hurts to check the point gap and inspect the rotor and cap. You might also have a dieing coil. Never focus completely on one system and ignore the other.