[Indybrad]

I have a 78' Dodge B300 Maxi with a 400, 2 barrel. It had sat quite a while when I had bought it, we replaced wires, plugs, dist cap, fuel filter, drained gas out of tank. Would run and drive would get up to 40 or so and then backfire and die. So bought a remanufactured carb and installed a new manual choke thermostat, it has been timed, now what it does is it will start and run maybe 10 to 15 seconds and then die, you can give it gas and it will stay running but when it idles down it dies. So I don't know what to look at, I was told the intake manifold had a lot of carbon built up? We have seafoamed the engine and run some through the gas tank with the old carb, it looks as if it gets gas when you open up the choke and press the accelerator down, it shoots gas. Don't know what it could be, fuel pump, coil, egr, ballast resistor. Any help or ideas would be greatly appreciated.

 

[ImperialCrown]

Welcome to Allpar. It's possibly a fuel supply problem. Fuel doesn't do well if the vehicle sits for a spell. I have seen fuel pump diaphragms fail when they are allowed to dry out. The neoprene cracks and the fuel pump can leak fuel into the crankcase or out the vent tube when resuming pump duty.
The fuel strainer sock inside the tank can also varnish up with old fuel and restrict fuel passage. Fresh fuel won't immediately dissolve the varnish.
If you supply fuel to the carbuetor directly and it keeps running, check the fuel pressure from the pump-to-carb and fuel line vacuum from the tank-to-pump.

 

[TWX]

Did the big blocks ever get those nylon timing gears?