Would old fuel prevent my truck from starting?

[mrcomedy104]

I have a 1972 c20 that has been sitting for a little over 3 years, I recently swapped the motor. It has a new fuel pump, filter, the fuel that's in the tank is from the time when the original motor blew. Would the fuel in the tank cause the motor not to start? It fires up with starter fluid, but as soon as it's gone or I stop spraying, the truck shuts off
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[mongocanfly]

Yes it can...gas breaks down over time ..I would clean the fuel system really good.. are you getting gas to the carb?..some carbs have a internal filter..don't forget it..replace any rubber hoses in your fuel system..the ethanol in gas nowadays will break down the rubber..

[68gmsee]

Whether it starts or not depends on a lot of things. As mongo mentioned clean all the filters, lines and take the top of the carb off and clean the bowl. Remove the fuel line to the carb and make sure the pump puts out at least a pint of fuel in 30 seconds or less.

I worked on one once that sat for about the same time or maybe longer and it started. Smoked some and idled rough but it ran. We took the carb top off and there was sediment in there so we cleaned it all up and replaced the fuel with new fuel.

[Bigdav160]

Do you have an accelerator pump shot from the carb?

Anecdotal I know; I had 10 year old gasoline in my boat (vented gas cap with no evap equipment) and it started without ether. Just a strong battery. It did run poorly but it ran. I had to dump a bunch of "heat" in the tank afterwards.
My neighbor just gave me a BMW M3. It has been sitting 3 years and with a new battery fired right off and ran pretty well.

I suspect perhaps your fuel pump has died, or the hoses between the frame and pump is sucking air.

[mongocanfly]

He said he has a new pump but that doesn't mean it didn't get crap sucked into it..with all this ethanol gas we have nothing rubber will last for very long if you don't treat it or burn it..

[Wrenchbender Ret]

We started one up with 5 year old gas. It ran good but before long the valves started hanging up. Wound up had to do a complete valve job on it.

[GRX]

Yes, most definitely! Aromatics have evaporated. Flush out the entire system. Diluting with fresh gas will not do.

Have also seen plenty of engines go to crap when the intake valves stuck in the guides then met Mr Piston.

[TJ's Chevy]

Get that gas out fast and flush the entire system.