SailNet Community - View Single Post - Yanmar starting question
View Single Post
post #16 of Old 04-19-2009
Senior Member
Join Date: May 2007
Posts: 558
Thanks: 3
Thanked 3 Times in 3 Posts
Rep Power: 10
Originally Posted by nk235 View Post
SteveNMD - Thanks very much for the detailed post on how to bleed the system. How come you don't have to bleed the secondary fuel filter (racor) before going to the primary on the engine? Also why don't you recommend putting fuel back into the filters after changing them?

Barry - Thanks as well - I am hoping it is just a cool air thing because it does start right back up after it has been running.

I guess either way I will find out but thaks again for all the help everyone
Actually the Racor is usually referred to as the primary filter. You don't have to bleed this first because in a "normal" setup you have to suck the fuel through it using the low-pressure pump. Unless the primary filter has a built-in hand pump there is no way to bleed it by itself. The built-in pumps are nice, but not necessary at all.

The reason not to fill the filters first is because it can cause air to be forced into the high-pressure system. I can't tell you how many times I've seen this happen... You change the fuel filters and topping them up with fuel to avoid so much manual pumping. Then you start the bleeding process. However since there is clear fuel in the hose from the Racor thought the lift pump and up to the secondary filter (the one attached to the motor) you get clear fuel spouting from the vent screw very quickly. Happy with your brilliant idea to pre-load the filters you move on to the next bleed point at the high-pressure pump inlet. Again, a few strokes and you think you are done so you button everything up and fire the up the engine. It starts right up and you smile proudly. After about 5 minutes of running the engine sputters and quits. What happened is that there was a big slug of air in the top of the Racor (even though you mostly filled it). This slug of air travels through the system and ends up in the high-pressure side, which is when the engine quits. Now you have to start from square one and bleed the low side and then the high side. I find it easier to just stick to the procedure pump the lever as needed. Yes, you can pre-fill a little fuel, without causing problems, but I don't think it's worth the trouble.

Regardless if you are having problems with air in your fuel system or not at the moment it's good to know how to bleed the system. Practice in your slip so you can do it easily at sea.
SteveInMD is offline  
Quote Share with Facebook
For the best viewing experience please update your browser to Google Chrome