Yanmar diesel - fuel line problem, lesson learned

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Apr 20, 2010
119
Hunter 34 San Mateo
Loose banjo fitting sucking in air. After spending numerous hours on my fuel system and consulting many people to solve the problem, my mechanic advised me the cause was a loose banjo fitting letting in air which starved my engine of fuel causing it to not start.

Apparently, idling at minimum RPM causes the engine to vibrate too much and the banjo fitting can become loose. My mechanic recommends not idling at minimum RPMs, but getting the engine spinning to a point where it is not vibrating too much. Also, my mechanic recommends inspecting and tightening the banjo fitting at every oil change.

--Dan
 

Benny

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Sep 27, 2008
1,149
Hunter 320 Tampa, FL
I agree, good recommendations. Don't forget the cooling hose clamps as they may also be affected by vibration. Yanmar engines do not take kindly to idling at low speeds. Let it idle around 1000 RPM.
 

Alan

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Jun 2, 2004
4,174
Hunter 35.5 LI, NY
Just be aware that banjo bolts are hollow and are not capable of carrying the same torque as a solid bolt. It is much easier to sheer the banjo bolt head off.
 
Oct 14, 2005
2,191
1983 Hunter H34 North East, MD
Benny has a good point...

at my last insurance survey, my surveyer found the hose into the raw water pump starting to split at the clamp. He said the probable cause was idle vibration as it wasn't supported near this connection. He did recommend idling the engine at a smooth RPM below 1,000.
 
Oct 9, 2008
121
Marine Trader Sedan Mystic, CT
Is there a way to know how tight it tight enough for those banjo washers. I have one that I have tightened but still has a small drip. Is there a correct torque measurment?
 

Vinny

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Apr 6, 2006
343
Boat Less New Bern NC
Is there a way to know how tight it tight enough for those banjo washers. I have one that I have tightened but still has a small drip. Is there a correct torque measurment?
Check the bolt for cracks around the hole and distortion if they have been over torqued in the past.

The new washers have a rubber finish that will seal better than the old crush ones did. They are available in all the different sizes for all of the fuel line fittings. I think there are three or four different sizes and some are used in pairs.
 

Alan

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Jun 2, 2004
4,174
Hunter 35.5 LI, NY
Torque them to 300 in/lbs and you'll be safe. Don't forget to replace the sealing/crush washers every time you open the line.
 
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