flush old fuel out of system 1985 240

Howdy Volvorados,
I want to either treat or flush my fuel system. The 85 240 wagon I
just bought had about 1/2 tank of fuel, but the car sat for a long
time - only being started occasionally. I don't know how old the fuel
is, I usually give it 6 months life and it could be that old. I am
wondering if I should drain it, or just add something like SeaFoam or
some other fuel additive.

I want to change the fuel filter (external) as well, but not sure what
to do about the fuel.

Also, symptom dujour is when I start the car it fires right up, the
engine hums a bit until warm (like belts rubbing or maybe vacuum).
Then, when I start working the accelerator it starts choking out. I
can pump the gas pedal, get it idling strong- then when I accelerate
the pedal it starts dying.

I am thinking fuel first, then maybe plugs and wires for spark, and
lastly air intake.

Thoughts?

Jamie

 

Update: found out gas is from last August. I may just SeaFoam it and
change fuel filter.

 

Problem solved!

Vacuum leak. On top of throttle body are 2 vacuum hoses - 1 small and
1 large. The large went to an elbow T-connection and one tube was
split. I repaired the tube and the engine runs STRONG!

Tomorrow we degrease. AYYYYEEE!!!!