Fuel issues
 

Hi all, I have a 1955 F-350, I use it a lot to get work done around the neighborhood. Unfortunately whenever I drive it for more than 30 minutes or so it begins to sputter and chug like it's running out of fuel, it's strange because I made sure all the lines are clean and the gas tank is brand new. Replaced my fuel filter twice just to be sure, I've also pretty much rebuilt my ignition system though the plug wires are still very old and need to be replaced. It's got a 6v positive ground system, mechanical fuel pump, 239CI Y block V8. The pump isn't the issue as I've watched it fill an empty filter in less than 3 seconds. I suspect maybe the float is the issue because it didn't do this when I first bought the truck. Another modification I made was adding a 190 degree thermostat, after this change is when I noticed this issue, vapor lock possibly? Once the engine cools down it will run good again for awhile. Thanks for your time and knowledge, hope someone knows what it could be.

Re: Fuel issues
 

That would be my first thought as the THERMO is too hot for the engine. It is meant for a late model emissions engine.

Vapor lock, gasoline phase separation and boil-off.

What engine does it have? Mechanical choke?

Re: Fuel issues
 

Vented fuel cap? Just another cheap guess to try before throwing $$ at the problem.

Re: Fuel issues
 

... and/or defective condenser ...

Re: Fuel issues
 

condenser, or coil, would be my first guess.

Re: Fuel issues
 

If your gas line runs close to the exhaust anywhere, a bit of aluminum foil wraped loosely around the line will reflect the heat. Maybe even under the hood, Temporarily for trouble shooting.

Re: Fuel issues
 

Even though the tank etc. is new, how old is the fuel? I’ve got cars that don’t go a lot of miles, and I’m seeing clean, good looking fuel become a problem is as little as 4 months. Especially filled in the fall and started in the spring. Much more vapor lock problems than the old days. I don’t know how they blend winter/summer now, but it seems to me the Reid vapor pressure wasn’t as big a difference in the past. I blame it on the ethanol, but I’ve got no evidence. Drain it, fresh fuel, problem goes away. Both the cars and small engines, I just went thru this on my back up generator after a winter with no long power outage.

Re: Fuel issues
 

mechanical choke yes, vented cap yes, ignition system is completely new and done to factory original specs. I went ahead and got a 170 degree thermo and we will see if that fixes it.

Re: Fuel issues
 

Thank you all for the pointers, I drive this truck daily at least 10 miles a day, I have a nice brand new factory spec fuel cap on my brand new tank, since its driven so often the fuel never goes bad, the ignition is brand new and to factory specs, 6v positive ground system. My suspicion is that the fuel lines are becoming hot from the engine and its causing the fuel in the lines to prematurely vaporize (vapor lock). Originally it still had the 50's thermostat in it that was stuck open which was causing overcooling and condensation buildup in the engine. This winter was very cold so I put in the 190 thermostat to give it an edge in the cold but I think this is too hot and is causing excessive fuel line temps. Let me know if this sounds too far fetched. Haven't changed anything but the fuel filter yet and it seems to be doing a little better but still struggles after a long drive of over 20 miles at highway speeds (55-60mph). This truck serves an important role on my ranch so its crucial that it runs to its full potential as I cannot afford anything newer.

Re: Fuel issues
 

The ignition system is brand new but I tested it since making this post, thank you for the insight. All is well with the ignition system.

Re: Fuel issues
 

Two Pages Must Read -

https://www.thecarburetorshop.com/Ethanoluse.htm

https://www.bellperformance.com/blog...s-of-stale-gas

You might want to consider a fuel stabilizer if gas sits in that tank for extended periods.

You are out in farm country. Is E0 (no ethanol gas) available for farm equipment?

Re: Fuel issues
 

Collapsing fuel line or vent plugged up. I know you said you had a new cap but it could have a restriction inside it. Had that happen on a new Ram Charger.

Re: Fuel issues
 

1955FordF350, if you get air whooshing in or out of the tank when you loosen or remove the gas cap, the vent or vented cap isn't working.

Re: Fuel issues
 

What kind of fuel are you using? Unleaded and has alcohol in fuel? Here in MI we can ge "rec fuel" with no alcohol mixed in. My 1934 and 1957 run much better on that fuel. Just a thought.