Diagnose my diesel. - Page 3 - SailNet Community
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post #21 of 38 Old 09-06-2007
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I've been dealing with the same issue on my perkins, it would surge then drop off, then finally die all together, all within about 10-20 mins, and as usual on our way in to the slip.

Checking all the line, replacing all the filters made no difference, it turns out we have a weak fuel pump which will be replaced tomorrow, if that's the end of the problem, I'll let you know
Did you notice a vacuum in the lines and/or racor filter???
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post #22 of 38 Old 09-06-2007
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On my friends diesel the eventual diagnosis was a rusted/clogged exhaust elbow, but in his case the engine did not run above a certain rpm at all. In your case, it would not make sense that it would run ok for 3 hours and then start to exhibit problems if it was the exhaust elbow; I would expect symptoms to be apparent much sooner than that.
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post #23 of 38 Old 09-06-2007
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Originally Posted by avazquez View Post
Did you notice a vacuum in the lines and/or racor filter???

No, everything looks good from the tank up to and threw the filter, although I did replace the bowl cause it looked like it had some hairline cracks.

I have a mechanic working on it now, cause I had to go back to work ( damnit ) but he's pretty sure it a pump problem

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post #24 of 38 Old 09-07-2007 Thread Starter
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Quote:
Originally Posted by poopdeckpappy View Post
I've been dealing with the same issue on my perkins, it would surge then drop off, then finally die all together, all within about 10-20 mins, and as usual on our way in to the slip.

Checking all the line, replacing all the filters made no difference, it turns out we have a weak fuel pump which will be replaced tomorrow, if that's the end of the problem, I'll let you know
HI Poop. Did your mechanic get your engine problem fixed? Your symptoms do sound very similar to mine, only on a smaller time-scale. Someone suggested adding an auxilliary fuel pump to put positive pressure on the fuel supply lines. Let me know.
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post #25 of 38 Old 09-08-2007
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JR, the pump didn't come in today, so I won't know until Monday, but I'll definitely let you know how it turns out

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post #26 of 38 Old 09-08-2007
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My experience with a Westerbeke (Perkins) 4-107 is that these symptoms can be caused by an air leak, in my case at a fuel filter. I have an electric pump ahead of the filters to use to refill them after changing the filter. I could keep the engine running by turning on the pump and pressurizing the line through the filter. It also showed me where the leak was because it began to drip - but very slowly. A small air leak will cause the surging, I know this from experience, but I still don't understand it. Probably an air bubble interferes with the way the governor works.
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post #27 of 38 Old 09-08-2007 Thread Starter
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I'm leaning towards it having something to do with either the mechanical lift pump exhibiting a problem after getting fully heated up, or an air leak which only manifests itself after the fuel lines get fully heated up. I think it has something to do with heat because:

A.) It happens only after several hours which is time enough for the engine compartment to reach it's eventual maximum heat.

B.) The amount of time the engine will run normally after shutting it down, allowing it to cool, and restarting it is directly proportional to the amount of time it was shut down. (I.E. Shut it down for 2 minutes, get 15 minutes of run time. Shut it down for 30 minutes, get an hour of run time, etc, etc)

I think I'll invest in a Mr. Gasket Micro Electric Fuel Pump to put positive pressure on the lines at all times. Maybe this will either fix the problem or show me a leak.

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post #28 of 38 Old 09-08-2007
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although this is quite a bit smaller diesel than i used to work on (v12s-v16) you have check and cleaned the filters and lines/tank. but to no avail. surging problems are either fuel related or control issue. I am assuming this is mechanical governed. I would suspect a broken spring on the governor flyweights / or weak one possibly. But think about this? As the engine warms up and oil thins out, piston rings (badly worn) allow more passage of engine gasses, therefore less efficiency. Do a compression check on all cylinders ( they should be within a few psi of each other). One final point of contention to look at is a sticking valve. This would cause it to stick after it heats up, (stick open) and cause bad running. (remove valve cover and run after heated up) (make a shield out of cardboard to shield against splashed oil). Finally, it could be possible you are still getting air in the fuel injection system somewhere? Use a can of soapy water to spray on injection lines to check for air leaks while running(cautiously to keep from cracking something hot!). and of course, check exhaust system as last fellow replied. You are already doing the things a professional mechanic does, but you will be learning and remembering (as frustrating as it seems) and will gain information about your engine.
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post #29 of 38 Old 09-08-2007
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Johnr,
The electric fuel pump is a good idea. It will help you find out what the current problem is and is a big help in changing filters. A word born of experience. If you remove the filter bleed screw entirely ( to refill the filter with the electric pump after changing it), be VERY careful not to drop the *&^%$ screw. I did and it caused me lots of grief!!!.
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post #30 of 38 Old 09-08-2007
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JR....

If you want to go for the electrical lift pump idea, I can give you the supplier address. I think I can find the invoice somewhere. It was some outfit, and very helpful, in Chicago.

I still suspect your governor, but that will not be a cheap one to fix, methinks.
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