12v Yanmar Lift Pump

[Mookie B]

I rebuilt my YSM-8 a few years ago and bypassed the mechanical lift pump in the process when I found the pump's membrane was ripped. I installed a 4psi 12v pump that runs when the key is on and makes bleeding is a snap! The pump lasted for a few years and finally bit the dust this winter, so I replaced it with the same model. The engine ran at the dock yesterday (predominantly at idle) for about a half hour to top-off my batteries. When I secured the engine, I checked the pump on a whim--it was quite hot to the touch! I'm ashamed to admit that I never checked the temperature of the previous pump during operation, but it is likely that it got as hot. Should I be concerned? The pump (both times off eBay and from two separate vendors) was supposedly diesel-capable, but is it working too hard to push what little fuel I use? Finally, would it be in my best interest to find a lower PSI pump (pass-through capable) installed on a switch for bleeding and get a replacement mechanical pump to put back in the fuel system for normal operation? Thanks for any help!

 

[sailaway78]

My first thought

My first thought was that maybe the fuel filter was getting dirty, causing the pump to have to work harder. Don't think that is the case though, as it will only pump so much pressure, regardless of resistance. I have a 12v pump on my Yanmar, but it doesn't run constantly, just when needed for bleeding, etc. However I don't think mine ever gets more than luke warm at any time. I don't think it should get hot though.

 

[Stephen K]

Re: My first thought

Here's another thought...some fuel pumps have their own internal filter (or screen) that may be getting clogged, thus causing it to work harder and overheat. I must say that I have never touched mine while running to see if it gets hot...although I don't think it should.

 

[Roger Long]

makes bleeding is a snap

What makes it even easier is to run a wire from a 12 V source to a doorbell or other push button switch in a handy location and then to the pump. When bleeding, you can just push the button and get brief spurts when you want them. The alarms will go off a well if it's wired like my engine but this is a minor annoyance and will alert you if the switch should short out.

It also can help starting to push the button just before engine start until the pump stalls out.

I don't know why your pump is getting hot but it doesn't sound right.