Bleeding Air

[thaeni]

I have a Yanmar 3gm30F. I was wondering if it was necessary to bleed
the system when just changing the primary filter. Filter is located about
4' behind the engine.

 

[Don S/V ILLusion]

Generally not but I don't like surprises so I do it and then run the engine for 15 minutes or so just to make sure.

 

[Warren Milberg]

I agree with Don. I generally do not need to bleed the engine (2GM20F) when I change the primary and secondary fuel filters. I fill up the filter housings with new diesel, screw them back in place, and then start and run the engine for 15 min. If no huffing, puffing or stalling occurs, I'm good to go. I've only had to bleed the engine once in 8 years when I did the annual filter changes -- and it was my error. I did not ensure the "O" ring on my Fram filter housing was properly seated after changing the filter and screwing the housing back into place. This allowed some air into the system and the engine quit running after a few minutes. On my boat I now use an articulated mirror and flashlight to inspect the underside of the top of the cartridge holder (where the "O" ring fits).

 

[Ken13559]

if air finds its way into the high pressure pump, can it be bleed?
will it create air lock in the hp pump?

 

[Dan Hill]

Air in the injector pump won't lock itself in, but is a pain to clear out. Injector pumps are made to pump liquids and don't do well with air. Best procedure is to loosen the high pressure injector lines @ the injectors and crank the motor til only clean fuel and no air comes out, messy and time consuming. The best practice is to not introduce air during the filter change, fill the housings before assembly as Warren stated. Only risk is a possible small fuel spill, bleeding air from the injector pump will make a much bigger mess. I've serviced hundreds of diesel motors and have had to bleed only a few.

 

[alexco38]

There is usually a bleeder screw on the filter housing to bleed off the air after filter change. Check Racore web site. The only problem is that they don't tell to install some kind of pump to squeeze fuel into the filter housing.

The easiest way is to install a squeeze bulb in line of the fuel pickup. Squeeze bulb is the one used for outboards. Yes it is compatible for gas and diesel.

 

[Don12364]

My Self Bleeding Test

My understanding from the manual is that modern? Yanmar fuel systems are self bleeding. By that I believe they will handle moderate amounts of air.

As a test I changed the large Racor filter and did not fill it with fuel; i.e. I left it empty. Then I cranked the engine on the starter and initially it fired up right away then stopped as the fuel in the lines was used up.
Next I turned the key again and it took quite a few seconds but sure enough it started right up again and ran perfectly for 15 nminutes.

BTW I was mindful of the problem of filling the exhaust with water but this did not occur.
NOT TO BE RECOMMENDED but just to prove a point.
My engine is a 3JH2E.

 

[Steve Dion]

Donalex:

I think that the JH series of engines are self bleeding, the GM's were NOT. That does not mean that they cannot handle a little air in the system.

When I replaced my Racor 110 filter with the dual 120's we just let the system bleed itself. I was amazed after having a GM in my H31 for 20 years.

 

[Ken13559]

I've checked my friend's 1GM10 and bleed air bubbles from inlet to high pressure injector. Still engine won't start as we crank till battery when flat. We noted, no fuel coming from high pressure pump outlet. Engine was running fine prior to him running the engine with tank valve shutted.

 

[John T1594]

Bleeding

To my way of thinking, having to bleed the air out of the fuel system by cracking each injector line, cranking the engine, etc, etc. would be such a pain in the ass that I never want to go there if I can avoid it. On my boat (H340), with an 3GM30F engine, the tank is above the primary filter so I purge the filter using gravity and the bleed screw on top when I change the filter as alexco38 suggests. I always change my secondary filter at the same time and then make sure I bleed the air from both the filter and the line going to the injector pump. Plenty of pumping to make sure I have no air in the system. What do they say about an ounce of prevention...?

 

[Dan Johnson]

Ken...

as everyone has pointed out, bleeding takes patience. You need to bleed at the injectors to get any air bubble out of the high pressure pump. On the 3GM there is a bleed screw hidden by the water hoses that will bleed air out at the pump itself. If no fuel is coming out of an injector feed, there's still air in the pump.

Second thought: running with the fuel tank cut-off valve closed will create a vacuum. Once a bleeder is opened, a lot more air than you think may have been drawn in.