NAA Fuel starvation

[mstanfield]

I hope you guys can help me...

NAA under load mowing runs fine for 1 hour or more, then acts like it is starved for fuel. I have: 1) sloshed out tank, replaced coil, boiled and cheaned carb, new fuel line, new vent cap, cleaned radiator/new antifreeze, new valve/sediment bowl. Keep in mind I have ran this tractor hundreds of hours....and something just "happened" to cause this. I did notice, before making the above repairs, that the fuel was boiling, and thought I have vapor lock. All of the above stopped the boiling; actually tractor ran better than ever. Now the starvation issues is back.

A friend mentioned I might have a lean condition causing overheating, but the tractor does not act hot; guage shows ok.

I don't know what to try next?

I'd appreciate any help

Thanks!

 

[Geo-TH,In]

I had a similar problem. The coating inside my tank was flaking off. It looked like gray primier. I cleaned the tank and make a big mistake by adding an in line fuel filter. On hot days, the heat would cause a vapor lock starting at the filter.

You have three screens in your fuel system, one inside the tank, one at the bowl and one at the brass fitting going to the carb. There is a bolt/plug on the botton of the carb bowl where you can drain the carb. When it stops, open the plug and see if you're carb is out of gas. Mine would have to cool off for about 10 minutes before the fuel would begin to flow.

I replaced the gas tank and made a larger heat shiel out of aluminum so no heat from the radiator or muffler could get to the tank. Also made a heat deflector to keep the heat from the muffler getting to the carb. If the fuel in your tank is boiling, I would make some heat deflectors.

Hope this helps,
George

 

[mstanfield]

George: thanks for the input. I had some minor debris in the tank, did a quick cleanout. I checked all of the screens you mentioned, with no debris seen. I am going to try and pull the carb plug the next time it happens to check for fuel. Also, all heat shields in place with no holes.

On another note, the tractor does not "die"...just acts like somebody is pinching-off the fuel; would stop if I didn't clutch...

Any other thoughts??

 

[Charles Krammin]

I had a similiar problem on my Ford 600. When it happened, I took of the gas cap off and could see the bubbles coming up thru the outlet. Engine, and all other components, had been cleaned and checked at recent overhaul. All shields were in place.
Attributed it to alchol in gas, which I buy fresh at gas station.
I did however experiense octane pinging, under very heavy load. Distributor was new. I didn't put the timing light on to see what it was set at, but retarded the spark manually, and haven't had the problem lately of gas bubbling. I use 87 octane gas.
Charles Krammin SW MI

 

[ericlb]

did you find anything in the screen in the elbow on the inlet to the carb? there has to be a blockage somewhere, if there is debris present you may have to do the "drill" several times to get it all cleaned out, what kind of fuel flow do you get now, when you remove the plug on the bottom of the carb?

 

[Geo-TH,In]

The factory heat shields don't prevent the heat from the radiator from hitting the gas tank. I extended my shields to go all the way forward to the fan shroud.

I'm no expert, however I think the boiling point for gas is much lower than the boiling point for water. Therefore, the heat from the radiator on a hot day, could be enough to cause the gas in the tank to boil. I've heard of there people saying they had gas boiling in their ford tanks because ford hides the tank under a hood.

 

[Geo-TH,In]

I just paid $300 to have new wires and plugs put in my 2007 GMC truck which has less than 50,000 miles. The plug would only act up at 55-65 mph. Never thought it was a bad plug. I thought it may have been starving for fuel. If all else fails, try plugs, they are cheap.

 

[awhtx]

Condensor in distributor is bad.

 

[36 Coupe]

A problem with a bad condenser will show up in a few minutes.It will mimic a gas problem.If the engine is left to cool a bit it will restart but act up again.Had it happen with a Model A Ford.Only had it happen once in 50 years.Father in law said put a new condenser in it .He was right.The Ford had the distributor on top of the cylinder head close to the exhaust manifold.

 

[36 Coupe]

You may not see any gas when you remove the plug in the carberator.Theres a passage between the bowl and the plug that plugs with rust.