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tim steadman
New member
Username: steadmat
Post Number: 1
Registered: 04-2009
| | Posted on Saturday, April 25, 2009 - 11:03 pm: | 
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The engine starts fine and after warmup performs well. After about 1 and 1/2 hours of running at 2500 RPM, with a few slowdowns for no wake zones, the engine will start to loose power. The tach will momentarily drop to 2300 RPM, pickup to 2500 and then start dropping again. The power losses keep on fluctuating with the RPM dropping lower every time. Moving the throttle does not help. The engine will then stop.
Attempts to start the engine right after it stops did not work.
The first time this happened we changed the two engine fuel filters. Primed the system using the hand pump and got the engine started. Took about 15 minutes. Engine worked well for about 15 minutes and then started RPM loss again.
The next day changed Racor filter. Experienced power loss and engine failure again after 1 and 1/2 hours running. Engine temperature was normal. Bled fuel filters with no result. After 45 minutes of trying to start the engine with the engine cover off, I thought it might be an overheating problem, I disconnected the fuel return line to check for fuel flow. The engine then started and ran well for another 20 minutes and then had the same problem.
I had the primary fuel pump rebuilt and still have the same problem.
Any help you can give me wold be great!
Thanks,
Tim |
Joe Cazana
Member
Username: sail4evr
Post Number: 38
Registered: 10-2008
| | Posted on Sunday, April 26, 2009 - 01:33 am: |
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What was the condition of the fuel filter that you first removed. Very dirty...not so dirty. Look at the new fuel filter. make sure it is still clean.
I just had to have my tank cleaned and the fuel "polished". I'm not such a believer in polishing but the stalling I had before cleared up. I think there was a layer of crap in the bottom of the tank that would break loose upon occaision and clog the fuel intake. |
tim steadman
New member
Username: steadmat
Post Number: 2
Registered: 04-2009
| | Posted on Sunday, April 26, 2009 - 06:01 pm: |
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The old filters looked clean. Checked the new filters and they look great. The tank we are running from was removed 4 months ago to repair a fuel leak and was cleaned on on the inside.
We took the boat out again and experienced the same problem. opened the bleed valve on engine filters and used handpump to verify fuel flow. Then loosened fluid bolt on overflow valve on injector pump and used handpump and got fuel flow. Disconnected return line downstream of overflow valve, used handpump and had fuel flow. Then turned over the engine several times and had no flow out of the return line. Disconnected feed line at one of the injectors and turned over the engine and had no fuel flow. After the engine was stopped for about an hour was able to start it by pumping the handpump until I felt pressure and having someone else engage the starter while I kept pumping. Put engine cover back on and was able to run for about 15 minutes and then the engine lost RPM and quit again. Was able to start the engine after about 20 minutes using the same procedure and left the engine cover off for the 30 minute run back to dock with no further problems. |
Keith Wetmore
Member
Username: keith_wetmore
Post Number: 4
Registered: 04-2009
| | Posted on Wednesday, April 29, 2009 - 05:24 am: |
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This must be a fuel related problem. If the engine is mechanically sound as it seems to be, then all that remains is fuel starvation, most likely due to the ingress of air into the supply, somewhere.
Put a clear plastic hose into the fuel supply line just before the engine mechanical pump, and hold a torch behind the line to see if any fine bubbles are in the fuel. If the system is self bleeding, these will mostly be returned to the tank on the return line, but can accumulate over time in filters or any high spots. When the engine is slowed, the whole pressure regime in the system changes, and an accumulation of air is released. Depending now on temperature, fuel tank levels, atmospheric pressure etc the engine will slow, recover, or generally hunt. If you stop and restart, it generally improves, until hte whole cycle repeats itself. Irregular firing is the clue to this condition.
I have had the same thing on my Volvo 2003, and what makes it exciting is the engine will cut as one throttles back at, for instance, the entrance to a harbour. Frantic cranking and revving usually gets it going again in minutes, once the blob of air is cleared.
Fuel tanks will accumulate an amzing amount of crud, and filters are notorious for admitting air. Clean out the tank, and double check for air leaks.
Good luck |
Morten Ringvold
Senior Member
Username: haffiman37
Post Number: 3538
Registered: 04-2006
| | Posted on Wednesday, April 29, 2009 - 06:18 am: |
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Or a blocking of the return line, as the engine started after the return had been disconnected. |
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