Intermittent Engine Fault - Yanmar 2GMF

Blue Drifter

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9 Jan 2012
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Glasgow (boat at Troon)
:confused::confused::confused::confused:

Appreciate some advice. Currently in Howth on my way back to the Clyde. Engine has been fine all trip but last couple of days has developed an apparent fault. Engine starts and generally runs well but occasionally the revs reduce to tick over for about 20 secs or so and then recover. Happens randomly but could be once an hour or maybe slightly more often. Engine has not stalled and otherwise appears Ok. I did change both fuel filters (Cav and Yanmar fine engine filter) about 20 engine hours ago. It is the intermittent nature of the problem that has me perplexed. Grateful for checklist to work through.
 

pcatterall

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2 Aug 2004
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Home East Lancashire boat Spain
Doesn’t sound exactly like fuel but if you link it time wise to your change of filters then it seems the most likely place to start.
Possibly something blocking the flow then being released while on tick over?


I had some problems after changing filters recently and asked on the forum advice on the sort of torque which can be put on the filter bowl when tightening up ( bearing in mind the glass bowl !) the advice was more or less as much load as I could using a normal length spanner by hand. I had been over cautious and using that advice solved the problem.
 
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This happened to my engine this week, but not for 20 seconds...more like 2 or 3 seconds, I changed the filters which were clean, it was then that I noticed the rubber fuel pipe was damp at the connection to the primary filter, so I cut about an inch off the pipe and put it all back together, it seems OK now ...so air getting in somewhere?
 

Blue Drifter

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9 Jan 2012
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Glasgow (boat at Troon)
Thanks for the responses, took the Cav fuel filter/water separator apart and very careful put back together again replacing the numerous o rings. Cured the problem, I had thought that if air was getting into the system it would have stopped the engine but it appears the Yanmar can cope with small amounts.
 

Topcat47

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2 Jun 2005
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If you're running constantly for more than 30 mins at a time, I'd also suspect a blockage of the tank breather. I've had that problem myself. Poking a bit of stiff wire down mine did the trick for the season. When I removed the tank for cleaning (don't ask) there was a lot of CR4P in the breather pipe. Not enough to stop air flowing in, but certainly enough to mean the tank couldn't quite keep up with the fuel being used at cruising revs.
 
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