Yanmar diesel troubleshooting

[tom@dullstreefa]

My Yanmar diesel engine on my LT35 has begun to intermittently lose power in the middle of a cut. I can restore power by squeezing the fuel bulb 2-3 times. I notice the sediment bowl is filling up with air, so where could air be leaking into the fuel system? Could the fuel pump be bad and not able to keep up? I tried to look for some discussion threads about this but didn't find any (or don't know the site well enough yet to find it). Has anyone had this issue who can give me some advice? Thanks!

I am brand new to this forum and am looking forward to the discussions on several topics!

[ladylake]

 I'd start by checking the fuel line between the tank and fuel pump, maybe a filter in the tank, quick connect o ring bad,  cracked line, even a loose clamp.  Fuel pumps do go bad also.   Steve

[mike_belben]

All hoses fittings strainers o rings etc etc etc on the suction side are sources for air leak.  If you install a clear test hose youll be able to see them. 


Hoses will let air in under vacuum ut not leak.  They also delaminate and flap shut internally with no evidence.  

I have always used goodyear wingfoot air hose (because i have tons of it.)  Any trouble i just replace.  It is much much cheaper than fuel rated hose and msds reveals the exact same composition in the goodyear offerings.  

 All compressors spit out hydrocarbon oils and fumes so theyre made for it.  Diesel is fine in them.

[tom@dullstreefa]

Thanks for the help, folks! I will be following up on your suggestions to see if I can solve this issue as it is very annoying and detrimental to my efficiency.

[Southside]

Not familiar with your Yanmar but on mine it has both an IP and a 12V lift pump.  Is yours the same?  IF so is the lift pump before or after the sediment bowl?  Does this happen regardless of how much fuel is in the tank or only at lower levels?  How is the condition of the primer bulb?  They do go bad, de-laminate, crack, etc and will cause issues.  I replaced one on my Lull that was OLD. The new one lasted maybe 6 months and was causing me issues so it went away and I put on a lift pump instead.  

[mike_belben]

You MAY have rock catcher screens inside your banjobolts too.   My komatsu and kubota both do.   Theyll plug up when you get the tank low and the floaties get sucked in. 

[tacks Y]

I would add a 12v lift pump at the tank. On my Baker they did after having trouble, a lot easier on the injection pump. I put one on my Duramax for this reason.