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Post by MickeyB on Jan 16, 2020 15:09:28 GMT
I had a problem a few years back where I kept having engine cut outs for no known reason. After 3-4 different technicians and years or searching, it was solved. The suspected air was not to blame but rather a fuel return 'bit' not working, and causing a problem somehow. So my questions are thus 1) HOW did this cause the stoppage after 20-40 minutes running (no warning, all good up until it just dies) 2) By removing it how did it fix it? 3) Is it needed? 4) Is it worth replacing? www.yanmarshop.com/catalogue/servicebom/yanmar-marine-805147/marine-main-engine-small-gm-series-3gm30f-yeu-fig-45-fuel-pipe-jointI suspect I do need to replace it, just don't understand why it now works... So in the picture, the broken bit is item 17 (or something upstream from this), a small square JOINT as it is named. The fix (please don't laugh) was to disconnect the pipe going from 17 to the tee piece - item 31. Item 31 was replaced with straight pipe just joining the fuel tank and return pipe directly. The pipe from 17 then had a suitable size bolt put in with plumbers tape and sealed with jubilee clips. This has worked for the summer holiday and no problems what so ever. Can someone please explain how blanking this 'fixed' the problem - what this bit does that doesn't mind being blanked off and how this very simple joint can fail? Many thanks for advice. (Aside - the engine website is a fantastic resource and find!!! We should have a page of USEFUL external links) Mike |
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Post by zaphod on Jan 17, 2020 2:36:30 GMT
It looks to me like that part 17 is simply a machined block. The returning fuel enters the block, and then exits the block via the check valve (part #18) to continue it's way back to the tank. I would assume the check valve is there to prevent backflow of fuel and air. The check valve may also serve to maintain back pressure on the fuel return system.
My guess is that check valve is faulty and is not opening when it should.
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Post by MickeyB on Jan 17, 2020 6:42:47 GMT
Zaphod you are a hero! By you mentioning part 18 - I did a google search and found this GEM of information...
'E' series only GM engine fuel return line non-return valve
“... If the engine starts then dies and bleeding the fuel solves the problem, this check valve may be faulty. It could be corroded or worn. Part Number 128296-59940 and 22190-120002 Seal Washer Qty -2-“
That is EXACTLY my problem, off to buy a new valve assembly.
These forums are simply brilliant!
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Post by MickeyB on Jan 20, 2020 9:04:43 GMT
Just putting this here so others can find more information in the future.
The value '18' in the diagram goes the other way, rather than to the tank it sucks from the return pipe and redirects fuel going back to the tank into the system again. When too much air is in the return pipe, it MAY get sucked back into the system and hence the air in the fuel pipe syndrome.
I cannot find any great reason for plumbing this failure point back in (even though it is obviously there for a reason) and so I am going to leave it off. Everything runs fine with it....
An experienced mechanic here in Malta told me that the return pipe just sends all the fuel back into the tank for it to begin its lifecycle again, the '18' part is just a shortcut and takes the fuel before it goes back to the tank. Seems rather overkill to me if this is true and an example of over engineering for not much good purpose.
But of course, I could be wrong. Please let me know if I am wrong...going to leave it plumbed OUT of my system until told otherwise.
Mike
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Post by zaphod on Jan 20, 2020 16:23:51 GMT
Just putting this here so others can find more information in the future. The value '18' in the diagram goes the other way, rather than to the tank it sucks from the return pipe and redirects fuel going back to the tank into the system again. When too much air is in the return pipe, it MAY get sucked back into the system and hence the air in the fuel pipe syndrome. I cannot find any great reason for plumbing this failure point back in (even though it is obviously there for a reason) and so I am going to leave it off. Everything runs fine with it.... An experienced mechanic here in Malta told me that the return pipe just sends all the fuel back into the tank for it to begin its lifecycle again, the '18' part is just a shortcut and takes the fuel before it goes back to the tank. Seems rather overkill to me if this is true and an example of over engineering for not much good purpose. But of course, I could be wrong. Please let me know if I am wrong...going to leave it plumbed OUT of my system until told otherwise. Mike I am curious if that experienced mechanic is one of the many that were unable to figure your problem out? I don't profess to be an expert on that particular engine, but in my experience they don't put components in for no reason. You should be very wary of just deleting components from your system without fully understanding what their function is. If I am understanding your temporary solution you have simply bypassed that check valve and piped that line back to the fuel return line. The purpose of a check valve is to allow flow in one direction while preventing flow in the other direction. One has to assume that there is good reason for only wanting fuel to flow in one direction on that part of the system. You may find out that reason the hard way... |
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Post by johannes on Jan 20, 2020 17:32:42 GMT
This information is from another forum:
” On the GM series there is already a check valve in the return line. It isn't used as a check valve. The excess fuel doesn't go through the injector pump. There is a tee banjo fitting at a high point where the fuel enters the injector pump. I believe this design is to help keep air out of the pump. To keep the fuel under pressure at the entrance point to the injector pump and to keep the fuel from just draining down the return line away from the tee point there is a check valve downstream of the tee. ”
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Post by darryl on Mar 23, 2020 7:30:11 GMT
The Japanese-built GM series engines (vs. Euro-built -YEU engines) did not have this check valve plumbing at all that I know of. Not sure if the 2GM20F –YEU engine has this. My guess is that the check valve was designed to flow towards the return line Tee though perhaps with some spring back pressure to maintain fuel pressure (which is quite low ). By chance I came across a Tech Note from the Yanmar dealer Toad Marine : shop.toadmarinesupply.com/ships_store/?p=details&mfc=Yanmar&sku=129301-52020They describe a fix; removal of the check valve function by replacing with other Yanmar plumbing parts. Not sure if this is sanctioned by Yanmar whom I have a query placed with. According to Toad, the symptom is mainly in poor starting for the 3GM30F-YEU engines and occurs when that valve doesn’t properly seal; apparently air might enter from the return line such as when the temperature of fuel cycles after shutdown. On the other hand if it is constantly leaking there would be reduced pressure or no pressure to the fuel injection pump. This could explain the problem described by MickeyB. |
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Post by MickeyB on Mar 23, 2020 10:28:37 GMT
Many thanks to all who responded.
I am getting even more confused by all this engine jargon. Strange how they have different version of the same engine for different markets, assume it could be safety or pollution differences.
It does indeed appear that my engine has at least two distinct flavours. One with the offending piece, and one without.
Since mine started with it, and broke with it, and appears to be running with it 'removed' I am still going to leave it off and investigate more.
Thanks for everyones input.
Mike
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Post by Charlie-Bravo on Mar 23, 2020 18:21:43 GMT
Just a thought, and not claiming any expertise, but, a fuel return line in the tank is sometimes a lot higher up in the tank than the main fuel line, whilst you have plenty of fuel in the tank, and the return line is full of fuel , and its end submerged in fuel all will be well without a return valve as both lines are full of fuel. Once the tank level goes below the return line height in the tank, it may be able to suck air without the one way valve ....... just thinking that the one way valve was popped in for a reason, perhaps that's why, and food for thought.
CB
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