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BF 225 Knocking noise from low preasure fuel pump

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Fishingpcola

New member
I was flushing the motor by running it and I had the cowling off. I could hear a knocking noise that I thought was under flywheel cover. A buddy of mine came over to help diagnosis the problem. We discovered by placing a thumb on the value cover and moving down that it seems to be the low preasure fuel pump making the knock. It had the hardest vibration. Could this be a caused by using ethanol gas 5% a few years. Last year I switched to straight gas. Does anyone have experience with their low preassure fuel pump knocking? Thanks, this is my first post.
 
Never heard of one knocking before. Guess it is possible. When they fail, they normally fail completely. Remove the pump and inspect and bench test it with a 12 volt source. How old is the engine, how many hours? Does the knocking change with the engine RPM's? If so, take a close listen to the area above the cavitation plate. It's possible that the intermediate shaft bushing is failing. If so, you want to fix it ASAP.
 
The motor is an 02 with 790 hours on it. I have only changed oil and plugs on a regular basis. I was told the other day about the shaft bushing and plan on inspecting this week. The knocking does change with rpms. This pump is driven by the cam shaft not electronic so don't think I can bench test.
 
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I learn something new every day on this site. Didn't know that the old fuel pumps were mechanical beasts. So, it would not be unusual for it to be knocking if cam arm was worn, or some other issue with the diaphram lever.
 
20130408_20384111.jpgIf Im not mistaken, the low pressure pump is mechanical...it has a shaft that contacts a plate on the rocker arm assembly in order to pump the diaphragm. Maybe Rocker arm needs adjustment
 
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You are absolutely correct - don't know where my head was on that one - old age Brain F__T. Obviously, there could be several parts that could cause a "knock." Pull the pump and pull the valve cover to check if anything has come loose or worn out.
 
OK. I am going to pull off the fuel pump and inspect. Since I have the throttle body and air intake off, I will pull the value covers off and inspect and adjust values. I also will pull the foot off inspect and replace bushing. Since I have 790 hours on the motor the timing belt probably needs to be adjusted as well.
 
you should probably replace the timing belt pulleys, i had 762 hrs when my timing belt pully seized and threw my timing belt off at 5200 RPM..I had to replace all 24 bent valves..FYI I think the book says to replace every 500 hrs on the pulleys
 
I do not see anyting in the maintenance schedule on timeing belt pulleys, but you are not the first person that suggested that to me. The griend who is helping me threw his belt with less than 300 hours. On the maintenance schedule I am looking in the Owners Manual. The shop book may have something different, I will look tonight.
Thanks for the input.
 
On page 3-1 it says to check/adjust every 200 hours. Pages 3-22 & 3-23 in the shop manual discusses the procedure. I don't ever recall seeing a schedule for replacement. However, on Honda automovive engines, the replacement interval is typically at 100,000 miles. I would suggest that translates to roughly 1000 - 1200 hours on a 225 outboard.
 
We checked the pulleys and they were in great shape. The only valve that needed adjusting was the value that operates the fuel pump. I hope this corrects the knock.
 
I had a problem with my low pressure pump, it turned out that the springs inside had broken up. I don't recall hearing any knocking sounds, but the symptoms were very much like there wasn't any fuel getting to the spark.
 
What I had discribed as a knock is actually a ticking noise. The ticking noise is the plunger on the low pressure fuel pump. I believe everything to be fine.
 
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