Mechanical Fuel Pump near Injection Pump

[RCW]

Recently, someone posted a diagram of a mechanical engine-mounted fuel pump just before the injection pump (IP).

Tried to find the diagram, but couldn't...

Diagram showed a cam-driven lever-operated fuel pump. Reminded me of many I replaced as a young driver 40 years ago.

Are the Kubota mechanical fuel pumps similar to the fuel pumps of cars/trucks from the '60's and '70's? I understand they serve a different purpose....

I used to diagnose the failure of those car/truck fuel pumps by a drip, and/or bottom of the pump was clean....does that apply to these Kubota pumps as well?

Not related to my tractor....just trying to understand better....

Thanks!

 

[North Idaho Wolfman]

They are similar but a little different, they are low volume low pressure pumps, that also serve as a one way check valve (this is why you never use air on the system as you will blow / crack / warp the plastic reed valve).

There purpose is to help lift fuel back up to the injection pump, they normally go into real use on a very low tank and usually a hill or steep grade where the level in the tank goes below the injection pump level.

They don't drip like an automotive fuel pump because they do not have a weep hole behind the diaphragm, they will seep fuel into the oil if they are really bad.

You can test a lift pump by removing the fuel line from the injection pump inlet, and on cranking, the fuel will pulse out of the line.

I have run into a ton of bad mechanical lift pumps and 99% of the time you never know it.

 

[RCW]

Wolfman - -

Appreciate the detailed response.

I understood some of the differences, but the one about their failure is much different than my early cars and trucks, and good to know!

Since I was of very modest means, I used to do some my car repairs in the back yard of a local garage.

Owner would come out and coach me some, and I'd go at it with my tools.

I try to understand how stuff works....

We were in a very rural place, and he'd sometimes order parts with his discount, even though I was out back working in the rain or snow.....(uphill, both ways!!)

Great guy, while separated by distance for 30 years, I'm friends with him still, but he'd like to retire. His wife gave me a big hug and kiss last year at an auction I saw them at!