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Old 27-01-2008, 23:34   #1
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Yanmar 2GM Air in Fuel

All I did was change my darn Racor filter!!! I put it all back together and started bleeding the lines with the hand crank of the lift pump. I've bled'em over and over and over again. It'll look fine... I'll start the engine... it'll run for about ten minutes... and then, kaput! After that, I'll open up the bleeder on top of the engine mounted filter and find it full of air.
Obviously, I'm sucking in air. But where???!!! OK, I could be pulling the air in anywhere from the lift pump back to the diesel tank, right? But the most likely places where the problem would be are where I messed with stuff.
So, I pulled it apart again. I chopped off the old ends of the hoses that attach to the housing and reclamped them. I took the filter apart and tightened everything back up.
But I'm still ending up with a bunch of air! I feel like I'm on crazy pills!!!
Now, I'm thinking that something is not seating right on the racor, but How could I make sure? I don't want to just go and buy a new one. The whole thing is like a hundred bucks, and if its fine, I'll be stuck back at square one. After all, what if my darn lift pump itself is letting the air in?
I was thinking about TEMPORARILY applying something to the outside of the racor, around the bolt head and around the filter (maybe a putty or adhesive) for troubleshooting purposes. I was thinking that maybe I messed up the threading on the filter housing, thus causing the leak.
Any suggestions, ideas, words of encouragement???

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Old 28-01-2008, 00:55   #2
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Hang in there ,re do what you already did and when you get the engine started loosen off the bolt on the injector about half a turn or so do one at a time you will see a slight mist bubbly air fuel mix coming out from below bolt head this will let the air out retighten then do the next run motor at1000 rpms approx takes about 30 secs for each injector to bleed out the air.Good luck Geoff.

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Old 28-01-2008, 03:00   #3
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The o-ring on the engine fuel filter is a common source of leaks if not fitted properly, and the bleed screws can easily be stripped if over-tightened.

* Use a folded paper towel or toilet paper to check around joints & screws for leaks.

Bleeding GM series engines:
Open the small BLEED SCREW on top of the engine mounted fuel filter and operate the fuel lift pump by hand*.
After the fuel filter has been purged of air, close the bleed screw (don't do it too tight, it's only little) and open the one on the fuel injection pump.
Again, after the air has been purged, close the bleed screw.
The engine should now start, if not you will have to bleed the high pressure side as follows:
Crack the pipe nut at each injector, open the decompression levers and rotate the engine with the starter motor.
When the air appears to have been purged (the fuel looks clear, not whitish), tighten the nuts firmly, close the decompression levers and start the engine.
Check for leaks and clean up any spilled fuel.

* If the hand priming lever doesn't have any resistance through any of its travel, rotate the engine crankshaft through 360degrees, using the starter motor or crank handle (decompression lever "Open")
There is no resistance to the hand priming lever because the internal actuating arm is on the top of the cam that drives it. Rotating the engine crankshaft 360deg will turn the camshaft 180deg, the arm will now be on the back of it's cam and you should feel resistance when operating the hand priming lever.
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Old 28-01-2008, 03:28   #4
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The usual culprit

Leme see.

Runs for 10min. That would be at idle so I'm guessing 100-300cc of diesel (4-12oz) or about the capacity of the secondary filter.

I'm guessing faulty lift pump. Works fine by hand but the pump is possibly worn or the diaphragm might be split. Particularly if you are lifting the fuel more than 450mm (18").

I have watched a mechanic blow into a fuel line to make sure it is clear but I cannot possibly recommend this.

In my case I jury rigged a temporary tank above the engine to check it out but this didn't work. In the end I installed an electric fuel pump after the filter but below the tank. Ended up replacing the engine but thats another story.

The tank is full, right?
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Old 28-01-2008, 03:58   #5
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what model Racor are you working with?
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Old 28-01-2008, 09:48   #6
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I pulled off the engine fuel filter and pumped the lifter pump lever a bunch in an attempt to ensure that the air was entering the system prior to the engine filter housing. I watched at the point in which the fuel enters the engine mounted housing and saw that the fuel did enter with air. As I pumped, it went "squirt, squirt, squirt .. bubble, bubble, bubble... squirt" if that makes any sense. Then I put the housing back together and had to go to work. So, It does look like the problem is before the filter... Im gonna keep at it.
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Old 28-01-2008, 10:20   #7
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If everything was OK before you started, it's just about got to be something that you did the first time, i.e. at or near the Racor filter. Make sure the o rings are absolutely in place.

Depending on how your fuel lines lie, you may just not have a leak, but just a bubble in the line which doesn't pump through. It might reach the engine after the rpm reaches a certain point. The resultant fuel flow at high rpm would push the air to the engine where simply pumping the lift lever didn't.

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Old 28-01-2008, 10:36   #8
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Originally Posted by never monday View Post
what model Racor are you working with?
again, what model Racor do you have?
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Old 28-01-2008, 20:56   #9
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My Racor filter element is the R12S guess that means I've got a 120 series Racor... and guess what... I found an air leak.

I dismantled the Racor again and left just a little bit of fuel in the bottom of the bowl. My idea was that I could then pump the lever on the lift pump and (if my Racor was all sealed up) watch the clear plastic bowl fill will fuel. Instead, I saw the fuel in the bottom of the filter start bubbling with air!!! I could not see that with it full!!! Turns out it was coming from one of the drains in the bottom of the bowl. But not the one I loosened and tightened to drain the fuel. Nope. It was the other one. I don't even know how that drain got messed up. All I can imagine is that I some how hit it or something.

Now, I need a new bowl. Time to start ordering...
Thanks for the support.

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2gm, fuel, yanmar

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