One More question - Fuel flow meter oscillates on 225 Honda

I fitted a Lowrance LMF 400 Gauge and as my 2002 year engine did not have the NMEA interface that the post 2006 engines have I fitted one of the Lowrance EP60 fuel flow meters.

I noticed when running the Honda on our first trip out that the "current fuel flow" reading oscillated loads.... At idle it would go from 0 to 3 litres per hour and then back down to 0 again over the course of 5-6 seconds. Then as we accelerated upto 20 mph the fuel flow would increase as you would expect but so does the range over which it oscillates....between 30 and 45 litres per hour. Over a 100 mile trip the overall fuel data is good and the trip fuel accurate, however this constant oscillating was odd. Whenever i have used these meters before the fuel flow stays very constant, however this was on other brands on motor.

Is this peraps due to the way that the fuel flow works on a Honda?

I intially checked the sensor to make sure it was not blocked or had a failure. I have followed the instructions to the letter and fitted it vertically just after the filter. I have also checked it is functioning correctly when I syphoned out some fuel from the tank to test it and the reading stayed steady.

I am wondering if this could be an indication of a fuel leak however I can't see anything having check all the hoses.

Chris

I have a flo-scan on the same engine as yours and mine does the same thing. It is my understanding that the needle fluctuations are typical and the higher fuel flow occurs when the elec. fuel pump is filling the VST. Maybe someone else can explain it further?

I have the LMF-200 and EP-10 fuel flow meter on my 2002 BF225 and see the same thing.

Okay - that seems like a majority vote - it is fluctuating. So why is that?

From the Flo-scan installation instructions: "There are four common causes of fluctuating readings: Air bubbles passing through the flow sensor. Temporarily inserting a piece of clear tubing after the flow sensor is an easy way to test for leaks.
Sticky or misadjusted carburetor float valve,or a 4 sided square float valve.
Fuel pump pulsation, Do not mount flow sensor closer than 12" to the fuel pump.
Some anti-siphon valves, again this condition will not affect totalizer accuracy."

On the Honda I suspect it's a combination of the operation of the electric fuel pump, VST and anti-siphon valve. JMO.