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Old 16-05-2016, 16:26   #16
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Re: Yanmar 2gm20f air in fuel problems

dont forget to check your tank taps - i had a small airleak in tank taps that cut my engine a few times before i replaced them - think the new ones cost about $15 for a pair from a plumbing supplier. The other airleak i had was in the upside down placement (by me) of the rubber seal on the fuel filter.
Someone else pointed this out a while ago -if you're going to start replacing things on the basis of guessing what might be the problem, start with the cheap stuff - hoses, filters, copper washers, etc. i dont even stop to think about replacing all the rubber hoses in my system if i find even the slightest suspicion of wear in any part of it. In checking the fuel supply lines everything should be absolutely bone dry - any tiny evidence of dampness is probably an airleak in the making if not already happening.
in specific regard to the fuel lift pump - well, i have a spare old one since i replaced it with an expensive new one at the time of the tank tap problem - i didnt mind because it was probably 35 years old but in my experience those lift pumps very rarely need replacing.
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Old 18-05-2016, 14:09   #17
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Re: Yanmar 2gm20f air in fuel problems

I seem to recall there was a problem with 1 and 2gms a few years back caused by undersized 'o'ring seals for the engine fuel filter. If you changed that recently, it might be that. I had a similar problem and found it was because I had not tightened the engine fuel filter bowl seal tight enough. tapping it round another quarter turn with a screw driver and small hammer solved the problem.
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Old 18-05-2016, 14:17   #18
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Re: Yanmar 2gm20f air in fuel problems

Do you mean the on-engine (secondary) filter or the primary filter (typically a racor)?
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Old 20-05-2016, 09:28   #19
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Re: Yanmar 2gm20f air in fuel problems

Make sure those bleeders on the RAC are totally right and right, if you jumped a thread on that plastic screw it's toasted, you didn't say if you checked your elbow, those are notorious
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Old 20-05-2016, 09:28   #20
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Re: Yanmar 2gm20f air in fuel problems

You use pipe sealant on your new RAC?
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Old 20-05-2016, 09:40   #21
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Re: Yanmar 2gm20f air in fuel problems

UPDATE: I pulled the pickup tube from the tank and there is some kind of restriction near the top. Seems like that is probably causing the problem. I couldn't clear out whatever it is so I've got a new one arriving today.
For good measure, I have also purchased a new racor filter head and hose barbs for it. I had already replaced all of the rubber hoses between tank and engine (and the return), so the racor is the next possible place for issues. I am using pipe sealant on all hose barbs.

fwiw - the engine got a new exhaust elbow last year (came up during the survey so was replaced before sale was final). I haven't checked inside the elbow for restriction.
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Old 20-05-2016, 09:44   #22
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Re: Yanmar 2gm20f air in fuel problems

Get a small air compressor, disconnect the vent tube at the filler cap. Insert an air fitting to the vent tube, and pressurize the entire fuel system to 2-3 psi. You will very likely find the leak immediately. Do not put any more air pressure than this or you could blow up your fuel tank. Big mess then.
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Old 20-05-2016, 10:13   #23
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Re: Yanmar 2gm20f air in fuel problems

So when bleeding no air was coming out? And why can you not get the restriction out??
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Old 20-05-2016, 11:07   #24
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Re: Yanmar 2gm20f air in fuel problems

Quote:
Originally Posted by Coconutmunky View Post
So when bleeding no air was coming out? And why can you not get the restriction out??
The blockage in the pickup tube is partial. There was some liquid/junk/dirt stuck around the restriction, but not enough to cutoff flow. Tried blowing air through - which was hard at first and easier after some cleaning. But still something jammed in there. Seems safest to just move on to a new one.

The problem I have had is that the engine has cut out after running for an hour or more. The problem goes away after bleeding the engine - the symptoms seem consistent with a restriction, but not blockage in system. I realize that to get the air into the system it also had to be drawn in through a fitting somewhere - almost certainly in the vacuum side of the lift pump. Since I've already replaced all the fuel lines between tank and lift pump, the only thing left is the racor. So that's going to be new as well.
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Old 20-05-2016, 11:26   #25
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Re: Yanmar 2gm20f air in fuel problems

If it's just gunky I would blast it with a can of carb cleaner and recheck, but you have a new one otw, good practices to replace all the consumables, like those banjo washers you're not supposed to reuse but people do, keep everything clean clean, you might want to have everything pressure tested, things have to be really tight, but within spec
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Old 20-05-2016, 19:50   #26
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Re: Yanmar 2gm20f air in fuel problems

Curious, if you do a post mortum on your old pick up tube after installing new
...if tube had a screen in it , possibly causing restriction/part of restriction.
(as I understand the older gm's had screens in pick up tubes and then on later one's it was removed. Possible because of problem you are facing)
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Old 20-05-2016, 21:06   #27
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Re: Yanmar 2gm20f air in fuel problems

Things get loose over time from all that vibration, retighten frequently
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