Bubbles in fuel?

[Stephen Trapani]

Does it make sense that my Yanmar 2QM15 would get tiny bubbles in the fuel that would prevent me from bleeding it and re-priming it? I ran the motor with the priming pump valve at the top of my racor fuel filter un-screwed down which probably let air into the fuel causing the motor to die. I did this once before and was able to bleed and reprime, but yesterday when I tried to bleed it there were many little bubbles in the fuel, unlike before. Sorry if I'm using the wrong words or not explaining myself well. Do I have to just let it sit and then bleed it again?

 

[Stu Jackson]

It sure sounds like you have an air leak somewhere.

 

[Steve Dion]

Stephen:

Have you tried just using the thumb pump on the fuel pump to slowly get the rest of the air out of the system.

If that does not work, I would think that Stu is correct regarding some sort of a leak (maybe at the filter?).

 

[Stephen Trapani]

That little finger pump on mine doesn't seem to work. I always use the one on the racor. But the racor won't pressurize that part of the system? And yeah, won't the filter leak if you don't screw it down like I did?

 

[Allan12210]

I'm in Stu's camp regarding a possible air leak in the system.

If the filters are getting clogged then the fuel pump will have to pull harder to move the fuel to the engine. That increased suction can pull air in from many sources. Check all your clamps on the hoses. Also make sure there aren't any little cracks in old hoses. Make sure that bleed screw has a good gasket under it and be sure your filters are tightened against their respective seats. Consider a vacuum gauge on the fuel line to help determine if a filter is starting to load up.

 

[Steve Dion]

Stephen:

You need to make sure that the cam lobe is not in the "UP" position. You may want to hit the key "quickly" to rotate the cam and see if there is any movement in the pump.

 

[Stephen Trapani]

Steve, what key? Are you talking about the finger pump? How do I know if its working? Seems you can pump it forever and nothing happens.

 

[Steve Dion]

The ignition key! There is a cam that goes around in the fuel pump. If the cam is at the high spot you will NOT be able to pump it. Once you get it off the top position the thumb pump "should" work!

 

[Benny17441]

I quckly tire from flipping that thumb pump when bleeding air out of the fuel lines. If it does not clear quickly I resort to to the engine starter to do the job. Open the compression release valves and turn the engine with the starter, this will activate the fuel pump and send fuel much faster than you could do it by hand pumping. It is best done with two persons one to operate the starter button and another to open and close the bleed screws. Get the screw at the filter and the other at the injector pump.
Don't know about the 2QM but the 2GM series are quite tricky to bleed.

 

[Steve Dion]

Here is something that is a little off subject, but check out page 7 for remote oil filter adapters that are good for many Yanmars.

http://www.mackboring.com/CMFiles/Docs/3rdMBAccessoriesCatalog.pdf

 

[Charles Erwin]

Stephen

Start at the tank. Inspect fuel hose sections from tank to the motor lift pump. Look for visible cracks in these hose sections. Look for failed/broken hose clamps.

Expect to find air ingestion paths in the hoses/failed clamps in the hose sections as follows: (1) tank to Racor and (2) Racor to motor mounted lift pump. If the Racor is compromised - plugged up - the lift pump will draw air into the tube system on the motor side of the Racor. If the Racor element has not been changed, change it, fill it via the push pump, then close (screw in) the Racor push pump. Check the push pump screw in top has its seal intact so air cannot be drawn in via the push pump.

As to lift pump activation by the thumb lever - the camshaft activates the motor mounted lift pump. If the cam is rotated "up" the thumb lever will have no effect Rotate the motor clockwise 1 revolution so the cam lobe will be "down". Then the thumb lever will activate the pump. Also make sure the thumb lever is pushed fully down as you pump it up and down.

When you use these pumps - both the one on the Racor and the motor mounted lift pump lever - see to it the bleed screw (the one on the top of the motor mounted filter canister) is cracked open. It is at the high point of the fuel tube system - thus air rises to this point and so also escapes at this point.

Proceed in order - from tank to Racor to lift pump to motor mounted filter canister - you will be successful. Get back to us on this.

Charles

PS. I will be up around 10am for consult - if necessary.

 

[Stephen Trapani]

Hey Charlie! Nice meeting you in Oly! I'm going to go through what everyone has advised (the boat is now at West Bay Marina). But no one that I can see has addressed my original question of whether me failing to screw down the pump on the Racor could have caused all this. Sorry if I missed it or it is the wrong question. And I did fail to screw it down.

And oh yeah. You were a huge help. Thanks! Monday was very very crazy splashing the boat. I'll tell you the story.

 

[Charles Erwin]

No matter what you might have done - go through the same detailed fuel bleed regime either way. You know where to find me.

Chas.

 

[Steve Dion]

Stephen:

I just was fishing around on the internet and there is also a recommendation that you change the o-ring on the Yanmar filter every time it is removed too. This could also be a source of air leakage.

Did you loosen any fittings with Banjo (copper) washers? They should be changed if you open any fittings that use them.

So many places to look and so little time!

 

[Bill Roosa]

I'd not recommend bleeding using the starter for the following reason.
When you bleed the fuel lines you should pump to presurize the system, crack the screw/fitting you are working onand release the pressure and air, then tighten the fitting and then take your finger off the pump to start to repressurized the system. If you just maddly pump the pump (ie with the starter) you will get both pressure and vacume as you crack the fitting and can actuall spend all day suckng air and bleeding it back out.

course a man with an experience is never at the mercy of a man with a theory.

 

[Stephen Trapani]

Resolution

So, thanks to Charles Erwin's help and the great detective work of the service tech at H&H Diesel in Tacoma, the milky substance coming out of my injection pump was correctly diagnosed as water! Turns out that while on the hard, so much water got in the fuel that the Racor was entirely filled with water, preventing me from noticing that there was a problem. I think the fuel filler cap must not have been tightened down all the way at some point. Once the water was bled out the motor started and runs great once again.

So if you see latte looking milk coming out of your injection pump, don't open a coffee shop, you've got water in the fuel.