No vacuum twin commander 674

[Charleytuna]

Back story on John deer. Part of fuel cap disintegreted into tank. Black gunk. Cleaned tank. Replaced fuel filter and line. Cleaned carb twice. No fuel out of pump. Replaced pump. Still weak erratic flow. Will run if l hold choke closed with finger. Vacuum gauge shows alternating positive and negative pressure. Pulled head with breather. Reed valve looked fine. Scratching my head now. Is there another reed valve in other cylinder. Should I check that breather in middle. When choked engine sounds smooth. Thanks

 

[Hammermechanicman]

Did you pull the pickup tube out of the tank and made sure it is clear?

 

[Charleytuna]

Its clear. Will siphon with line down low. ABS clicks also.

 

[Rivets]

Positive and negative pressure is what the pump needs to work properly. Sounds to me like you have a lean running condition, which means time to clean and rebuild the carb.

 

[Charleytuna]

Oh ! So the vacuum is not really a vacuum. I thought the needle should stay on the neg. side. Time to clean carb better then better again. I got same vacuum reading on dipstick, breather and pulse pump hose.

 

[Rivets]

The positive and negative pressure is the pumping action. I suspect the you should look closely at the float level. Post engine numbers and I’ll try to find a manual for your engine.

 

[Charleytuna]

Got a manual. Its time for a closer look at carb. Thanks alto.

 

[Mower King]

Oh ! So the vacuum is not really a vacuum. I thought the needle should stay on the neg. side. Time to clean carb better then better again. I got same vacuum reading on dipstick, breather and pulse pump hose.

Putting a vacuum gauge on a mower engine gives you NADA!
Make sure you have a good full stream of gas to the carb, not just a trickle of gas. Running good / smooth with the choke on, is a carb problem.....as long as you have enough gas in the carb to begin with!