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 Post subject: Engine RPM surging - Fuel pickup problem.
PostPosted: 30 Aug 2009 10:13 
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Grinder

Joined: 22 Jun 2008 10:54
Posts: 85
Any diesel diagnosticians out there? On our way down the Jersey coast, motoring in light northerly wind, the Westerbeke 40 began to surge. That is the RPMs increase by about 500 then returned to the original cruising RPMs (2200) and kept cycling like this. This started after about 7-8 hours of running. I shut down and sailed for about an hour, then started the engine again and finished the last 10 miles into Cape May with no problems.
The next day we had the same problem in the C&D canal after about 4 hours running. No sail option here so we brought back the RPMs to 2000 and the surging stopped. I did take it out of gear to see if it surged when there was no load, but this was not a fair test since I observed that if you crank back the throttle to idle then bring it back to speed the surging stops and doesn?t reappear for a few minutes.
The following day was another windless day we motored for 7 hours, but this time at only 2000 RPM. The surging did not happen again.

Now those are the symptoms, can anyone venture a guess as to the cause. Things I have thought of: 1. Hurth clutch slipping after it gets hot, 2. injector pump malfunctioning after same.
Bow

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 Post subject: Re: westerbeke 40 problems
PostPosted: 31 Aug 2009 06:21 
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Skipper

Joined: 27 Oct 2006 10:32
Posts: 827
I would venture that it is a fuel problem in one form or another. It could be the pick-up tube in the fuel tank has a slight blockage at the intake, where it allows X amount of fuel to get sucked up and at higher rpm's, it could cause a surging effect. Another issue could be your injectors, I am not sure the amount of engine hours before you need to re-build these, but I know they do need a rebuild occasionally. You could have some water in the fuel getting by your fuel separator at the higher rpm's and causing an erratic opperation.
I just though of another scenario, your air intake screen couls be getting gunked up too...


 
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 Post subject: Re: westerbeke 40 problems
PostPosted: 13 Nov 2009 15:43 
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Grinder

Joined: 22 Jun 2008 10:54
Posts: 85
The answer to this problem came about when the engine just stopped. The clue was that there was 10 inches of mercury vacuum on the Racor gage which persisted AFTER the engine stopped. Switching filters (dual filter system) did not collapse the vacuum. Problem: a beebee size particle of who knows what had lodged in the opening of the fitting on the fuel petcock. The solution was to blow out the fuel line from the Racor back to the tank attachment point. When done a bunch of solid crap came out.
In talking to a diesel mechanic he said that the 1/4 inch copper tubing that runs from the tank to the engine compartment is to small IHHO because the opening of this tubing is only 1/8 inch and many times the fitting used are slightly smaller so they can clog easily causing as in my case a fuel restriction. A bigger tubing he proposed would have less of a chance to clog and allow the Racor to do its intended job. The present tubing he added is big enough do pass the require amount of fuel when not clog, but is easier to clog. YMMV Rolling Eyes

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 Post subject: Re: westerbeke 40 problems
PostPosted: 14 Nov 2009 15:18 
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Skipper

Joined: 29 Dec 2006 09:38
Posts: 656
Another similar issue that I once had was when the screen on the pick up tube (this was a common way of doing things back in the late 70's and early 80's) became blocked. If you have a screen, I would suggest that you remove it before that causes a similar problem. I lost power in a moderate storm off the California coast (lee shore) and spent the next couple days trying to figure out why I kept getting air in the system and stopping the engine. If the line is blocked the engine will suck air through the weakest seal in your fittings.


 
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 Post subject: Re: westerbeke 40 problems
PostPosted: 11 Dec 2009 10:49 
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Skipper

Joined: 20 Oct 2006 16:10
Posts: 687
Location: Out of Waukegan, IL
Good lesson. I'm changing the subject heading so folks with the issue in the future can find your solution.

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