Bleeding, bleeding engines !?

[STATUE]

I have a Vetus M2 engine.
Launched last Friday and engine started as normal.
Went onboard today Tuesday and had to bleed air out.
QUESTION: How is it air can get in ?

 

[srm]

QUESTION: How is it air can get in ?

If you have a gravity feed with the tank above the engine pump its not very likely, more likely that fuel will leak out of any potential leak. On the other hand, if you have a suction feed with tank below the engine pump every joint and connection in the system is a potential source of air getting in. All will need checking.

 

[Boater Sam]

Mechanical fuel lift pump with a leaking diaphragm? Is there fuel in the lube oil?

 

[Daverw]

Just had something very similar, always stared 3 sec for past 5 years then two weeks ago at least 5 cranks with rough running fir 15 seconds. Found looseish banJo tail, no diesel leak but enough to allow drain back to tank

 

[Billjratt]

Any rust spots on the fuel filter cans? Or are they recently changed and maybe not quite sealed. Otherwise check the pipes and if all else fails -paint them...!

 

[LittleSister]

If you have a gravity feed with the tank above the engine pump its not very likely, more likely that fuel will leak out of any potential leak. On the other hand, if you have a suction feed with tank below the engine pump every joint and connection in the system is a potential source of air getting in. All will need checking.

And just to make life more interesting there are commonly fuel tanks about the height of the engine, so when full the lines can leak fuel out, while when nearing empty they’ll leak air in!

 

[Birdseye]

Absolute classic on launch. Often it is sim-ply the waving about on the hoist that dislodges air bubbles so bleed and leave it a day or so to see if the air returns.