Re: [Amel Yacht Owners] Bleeding off air in Yanmar 75 hp

Bill & Judy Rouse <yahoogroups@...>


I am glad you got this far.

On a Yanmar with a water sensor inside the fuel filter housing, it is always best to remove the two bolts securing the filter housing to the motor, then unscrew the housing from the plastic nut without turning the nut and twisting the wires. As soon as you begin to loosen the housing from the nut fuel will begin to run out through the plastic prepared.

My guess is that you did not place the O Ring at the bottom of the fuel filter. Possibly you did and it is not seated properly,  or maybe you forgot to properly lubricate the O ring. It is also possible that one of the wires are in the nut threads.

There should be zero diesel leaking from any point on your engine.

I hope this helps you. Let me know if it does.

Bill BeBe 387
Currently Martinique

On Mar 18, 2016 15:34, "Ben Driver/YAHOO joedoakes66@... [amelyachtowners]" <amelyachtowners@...> wrote:


Thanks for the good advice.  It turned out to be an air leak in the bottom of the primary filter.  I removed,  cleaned, and carefully threaded bottom water sensor on (being careful not to damage wires) then opened bleed screw and to remove air and motor now runs well.  

When Bill said it was near impossible to pump primer when bleed screw is tight, I realized the problem.  I could pump and fuel was escaping through threads in water sensor cap.

Thanks again.  

Ben Driver
La Bella Vita
SM #347

On Mar 18, 2016, at 8:48 AM, 'Bill & Judy Rouse' yahoogroups@... [amelyachtowners] <amelyachtowners@...> wrote:



If you can pump the manual pump on top of the fuel filter housing on the Yanmar, you probably have not sealed the filter and you are sucking air which is causing your problem. When the filter is installed correctly, it is near impossible to pump that manual pump unless you open the screw that Mark describes.

It is a little tricky to replace that fuel filter because of the wires that go to the sensor at the plastic nut at the bottom of the of the filter assembly. If you try to unscrew and screw that nylon nut, you may damage the wires, twist the wires, and/or get them into the treads. Loosen the entire assembly from the motor mount, then turn the assembly holding the nut stationary. As soon as you complete about 1 turn, fuel will begin to drain from the drain hose which is about 1 foot long and attached to a fitting on the nut. The drain hose gets brittle and may have fallen off...if so, replace it. To remove the filter from the assembly continue to turn until the plastic nut is loose from the bottom of the filter...reverse the process when placing a new filter. Use the drain hose to capture most of the fuel. Protect the 175amp alternator from fuel spills. When everything is back together, open the vent screw (purple or blue) and pump until no air is coming out. Remember, if you have a dual Racor, the point on the short tip of the valve handle points to the active filter...NOT the long handle.

It is possible that after you do the above correctly that you will need to bleed each of the injectors as Mark described. Be sure that you do not fill up the muffler with salt water. It is best that you have some experience with you when you do this the first time.

I bet that there is a youtube video of this out there. I did a search on "Yanmar fuel filter replacement" and saw several that may help you. The real issue for you is probably the wires on the nut at the bottom of the filter assembly.

I hope this helps.

BeBe 387
Pitons, St. Lucia

On Fri, Mar 18, 2016 at 3:03 AM, 'Mark Erdos' mcerdos@... [amelyachtowners] <amelyachtowners@...> wrote:



There are a couple of different processes. On the 4JH4 there is an air bleed nut on top of the fuel filter assembly. You will find the nut in-line with the fuel line on the top of the housing for the fuel filter. Loosen this nut 2-3 turns. Feed fuel through the pump by pushing the lever on the side of the pump up and down until no air comes out of the nut and then tighten it. You can also crank the engine with the nut loose rather than pump the fuel with the lever. This is all that needs to be done. The engine may run rough for a little bit until the all the air is purged out. I am not sure if the 4JH3 is set up the same way.


On some other engines, you need to follow each fuel line to the injectors. Loosen each fitting and crank the engine. Crank the engine until no air comes out – usually about 10-20 seconds per injector. I put a paper towel under each connection so I can see the fuel coming out. You really need two people; one to crank and one to watch for the bubbles to disappear.


IMPORTANT - While cranking the engine without it firing, be sure to open the drain on the water-lift muffler. If you crank the engine for more than about one minute without it firing up, you will back water up into the cylinders since the water pumps is running. The exhaust will not be under enough pressure to push the cooling seawater up out of the boat. This is not good.




With best regards,




Super Maramu 2000

Hull #275

Currently cruising:  George Town – Great Exuma Island - Bahamas


From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Thursday, March 17, 2016 9:24 PM
To: amelyachtowners@...
Subject: [Amel Yacht Owners] Bleeding off air in Yanmar 75 hp



I could use some help bleeding air out my Yanmar Deisel.  I changed the primary and secondary fuel filter on Yanmar 4-JH3-TE for the first time - I bought this boat recently.  Not sure why but cannot keep engine running.  I bled-off Racor then primary on engine but engine runs roughly for about 5 minutes and then stalls.  I can keep it running if I pump the primary filter continuously (this is primer on top of the fuel filter).  If I put boat in neutral and advance throttle, it momentarily revs then it shuts down.  clearly not getting fuel.


Up until I changed filters, motor ran flawlessly so clearly my problems are result of my recent maintenance. 


i would appreciate any suggestions.


New SM owner

Ben Driver

La Bella Vita

SM #347

Currently in Puerto Del Rey Marina, PR


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