L4240 Stalls when the ambient temp is hot.

[rScotty]

????
A diaphragm pump creates a small vacuum on the intake stroke to suck fuel in, then a check valve on the inlet closes as the diaphragm moves in the other direction to create a positive pressure (~4.0 to 4.5 psi) and the outlet check valve opens to port fuel to the IP.
The "vacuum pumps" I'm familiar with are used to pull air out of a tank, etc.

The difference is just terminology. All pumps are pressure pumps on the output side, so it is common in industry to differentiate pumps by the way that the intake is filled. A vacuum or suction pump like the diaphram pump you describe has an intake situated above the level of the fluid. On the intake stroke it has to create an partial vacuum so that air and gravity pressure on the fluid can push the fluid up into the pump intake.

The other style pump has an intake is below the level of the fluid being pumped so that the intake is always uder positive pressure by the fluid.

Technically, I'd agree with you - the diaphram pump you are describing works as a vacuum or suction pump on the intake stroke and like all pumps it is a pressure pump on the push stroke.

Just to be confusing, there is also a "vacuum actuated" pump where the diaphram itself is worked by varying pressure instead of by a mechanical plunger or cam.

rScotty

 

[jonsstihl]

Well, I will have to check mine out and see if it has a lift pump. I assumed if there was one it would have been before the filter so I was looking upstream. That looks like it is installed on the high pressure pump.

 

[Bob_Young]

What happened to the OP? Did he get his tractor back? Does it still stall under high ambient temps? Has he found a solution to his problem? If so, what was it?

My 2007 MX5000 ran hot. Would work its way up into the red on the gauge just running at PTO RPM with no load if ambient was 80 or higher. Solution was to take the hood off so heat couldn't build up in the engine compartment. There wasn't any way for heat to escape. Now it never gets beyond half-way on the gauge...even if it does look terrible with the hood off. It never stalled though.

Interesting to hear that Kubota was experimenting with changes to meet Tier 4 in that time frame.
Bob