fuel delivery question on 29-27

[jps]

My car runs fine when the outside temperature is warm (75 F and higher).  When colder, I have some trouble.  My car has an electric fuel pump that someone added before I bought the car, and they also disconnected the mechanical pump.  There are two "new" fuel filters - one back by the pump/tank and another just before the carburetor at the engine.  

 

On cold days (this AM it was about 44 F) the car starts, idles, and runs initially OK, but in less than 1 mile it starts to miss, cough, almost backfire, &/or make popping noises when I try to accelerate.  Associated with this is a sudden loss of power.  From that point on things get worse, and even at idling it runs rough.  I tried adjusting the carburetor air screw (turned it in to get more pressure / run richer) and opened the low speed jet valve on the bottom of the carb a little more than normal but neither one helped.  Adjusting the choke didn't help.  Adjusting the timing (on the steering wheel) didn't help.  Finally it quit at a stop sign and I had to let it sit a few minutes.  I turned on the ignition so that the electric pump could run for awhile before starting, and then it started and ran OK for me to get home.

 

It seems like maybe the engine runs fine until the first bowl of fuel at the carb runs out, and the fuel isn't replenished so that the engine is starved for fuel.  As I mentioned, this does not happen when the temperature/engine is warm.  Does a colder temp cause the electric pump to have a harder load?  Do I need to adjust something other than the choke to compensate for cooler weather - it doesn't seem like the choke is the problem anyway because it initially runs fine and then later acts up.  Plus the choke doesn't make more fuel flow, it just restricts the air.

 

Thanks.

[Mark Shaw]

First check to see if the gas cap vent is plugged.....