Beneteau fuel gage wildly wrong

[davefromoregon]

My fuel gage shows full until there is perhaps 10-20% left in the tank. Then it goes to empty really fast. Is this normal Beneteau behavior? This has been the case for a while. I had a guy try to service it and he found nothing.

Thoughts?

[snokid]

pretty easy fix...

take the sender unit out measure the tank, when the tank is empty it would be 0" to the bottom of the tank, then when it's full say it's 12" now take the sender and move the float...when the float is at the top what does the gauge show? when at the bottom?

if it's wrong either you need a new sender or there's a bad connection, check the connection first most likely the problem...

Bob

[LongRange]

Many or most of those senders rely on electrolytic capacitors in their circuit boards, which provides a kind of built-in obsolescence.

The cap, which probably cost around a cent when purchased in bulk, will inevitably leak or dry out after a few years, due to a combination of heat and corrosion. Deprived of design capacitance, the electronic circuit will then cease to work or produce increasingly odd and non-linear readings.

To make it less likely that the offending cap will be located and replaced through judicious application of a small soldering iron, the entire circuit board is sealed in epoxy, thus forcing the purchase of a replacement $250 sender

[svHyLyte]

Our fuel gauge only roughly approximates what's in the tank. As a result, we largely ignore it and instead keep track of hours of run-time. In our case, our engine--a 4-108, has an average fuel consumption rate of .9 gal per hour, so 9 gallons per 10 hours of run-time. We record the hours run after every use and when we've hit the 80% mark, head for the nearest fuel dock. Of course, in addition to the 20% of capacity left in the tank at that point, we also carry a spare 5 gallons in a fuel jug, "just in case". When we refuel, the jug goes in the tank first--through a filter funnel--and we then finish refilling the tank, and the jug, again through a filter funnel, at the fuel dock. I prefer going to fuel docks that have a fair amount of traffic from larger power boats as I suspect the fuel is "fresher" than it might be at other, less trafficed locations. In any case, it is wise to maintain a fuel log as a matter of course, IMHO.

FWIW...

[Blue Stocking]

Originally Posted by svHyLyte

Our fuel gauge only roughly approximates what's in the tank. As a result, we largely ignore it and instead keep track of hours of run-time. In our case, our engine--a 4-108, has an average fuel consumption rate of .9 gal per hour, so 9 gallons per 10 hours of run-time. We record the hours run after every use and when we've hit the 80% mark, head for the nearest fuel dock. Of course, in addition to the 20% of capacity left in the tank at that point, we also carry a spare 5 gallons in a fuel jug, "just in case". When we refuel, the jug goes in the tank first--through a filter funnel--and we then finish refilling the tank, and the jug, again through a filter funnel, at the fuel dock. I prefer going to fuel docks that have a fair amount of traffic from larger power boats as I suspect the fuel is "fresher" than it might be at other, less trafficed locations. In any case, it is wise to maintain a fuel log as a matter of course, IMHO.

FWIW...

X2 Best way ever.

[davefromoregon]

Originally Posted by svHyLyte

Our fuel gauge only roughly approximates what's in the tank. As a result, we largely ignore it and instead keep track of hours of run-time. In our case, our engine--a 4-108, has an average fuel consumption rate of .9 gal per hour, so 9 gallons per 10 hours of run-time. We record the hours run after every use and when we've hit the 80% mark, head for the nearest fuel dock. Of course, in addition to the 20% of capacity left in the tank at that point, we also carry a spare 5 gallons in a fuel jug, "just in case". When we refuel, the jug goes in the tank first--through a filter funnel--and we then finish refilling the tank, and the jug, again through a filter funnel, at the fuel dock. I prefer going to fuel docks that have a fair amount of traffic from larger power boats as I suspect the fuel is "fresher" than it might be at other, less trafficed locations. In any case, it is wise to maintain a fuel log as a matter of course, IMHO.

FWIW...

I have found that my usage per hour can be quite variable. .5 to 1.1 gal per hour so I'd really like a working gage.

[Pete7]

Ours can vary too so we use a very accurate fuel gauge, it's a garden cane with permanent pen marks on it.

Dave, when you say the last 20% empties really quickly presumably the bottom of the fuel tank is some sort of taper or curved base so it drop more quickly.

Pete

[davefromoregon]

When I say the last 20% empties quickly, it means the gage goes from showing 20% to out really quickly. Presumably, it is actually much more depleted.

I believe the fuel tank has more or less a flat bottom. It is located under the aft berth. That said, I'll investigate that.

[BrianGJS]

Our fuel gauges were considered only a suggestion and that was being kind. When I took them out to replace them they were the arm and float variety and surprisingly the culprit was rust. This in diesel tanks! I replace them with SSL25 senders that are accurate and and a much better design.

[tbetts007]

My Jeanneau does the same. I pulled the sending unit and manually moved the float and the gauge worked great. I pulled the unit again after running the engine for 30 hours or so. The gauge still read full because the fuel was still to the top in that part of the tank. I can only guess to the tank design. Is there a reservoir separate from the main tank? I can only see a little if the tank through the opening but it looks like just one tank.

[FabioC]

I have the same issue on a new Jeanneau (very similar tank configuration as the Beneteau), and it is driving my nuts...
The method of counting the hours is not very reliable, since the fuel consumption chart from Yanmar seems to be ultra conservative. The result is that every time we fuel we basically have no idea how much fuel we need and we have to closely listen for the tank getting filled so as not to overfill. Carrying an extra 5-gallon jug of fuel "just in case" also makes me uncomfortable...

A technician came to service the gauge, and found out that the top and bottom level are working, but could not really do much to calibrate for anything in between. Right now, it "always" shows full (I typically chicken out when I think we have consumed 60% of the fuel and refuel then, so I assume that it eventually drops, but have not seen it yet).

Are there types of fuel gauge that are more accurate than the basic kind that comes with the boat? I think what we are seeing in the Jeanneau's and Beneteau's fuel gauges is an intrinsic accuracy limitation of this type of gauges, so the only solution is probably find a different type of gauge.

[Jd1]

Some of the manufacturers trouble shooting procedures are not accurate. I had the issue with the fuel reading being wildly inaccurate. I went through the manufacturer recommended procedure but it told me everything was fine. The gauge was accurate when the tank was empty and when it was full. I pulled the sender only to find it was fine (it was a BIG pita!). Turns out there are two coils in the gauge and one had decided to die .... so it kinda worked. A new gauge was installed and all is well.
Depending on the shape of the tank and measuring method, precision can be all over the place but a functioning old style float sensor is just fine for the vast majority of uses. You will quickly get used to the non-linearity due to the tank shape.
There are only two systems more accurate - a flow counter and a certain digital sensor that can be calibrated precisely to the tank (you start with an empty tank and take a reading, add a bit of fuel and take a reading etc etc. Once calibrated the display is as accurate as the calibration.)

[paulie4203]

I recently had the same issue, but on our boat. I went to utube and there are a plethora of videos. I took their advice and pulled the sender. It is the type which has a float on the end of an arm. It wasn't working! I put my ohm meter on it and confirmed that it didn't work. Important to note: there are different senders, some ranging 33-330 ohms, 10-220 ohms(mine), etc. and vice versa (330-33, etc.). The sender has to be matched to your gauge. Got the new sender online for $38 and it's perfect! but go to utube first because it might only be a bad connection. Good luck!

[sailah]

Originally Posted by paulie4203

I recently had the same issue, but on our boat. I went to utube and there are a plethora of videos. I took their advice and pulled the sender. It is the type which has a float on the end of an arm. It wasn't working! I put my ohm meter on it and confirmed that it didn't work. Important to note: there are different senders, some ranging 33-330 ohms, 10-220 ohms(mine), etc. and vice versa (330-33, etc.). The sender has to be matched to your gauge. Got the new sender online for $38 and it's perfect! but go to utube first because it might only be a bad connection. Good luck!

This is 100% right. Gauges are calibrated for various ohm ranges. Best bet is to check your sender and see what resistance it puts out at empty vs full. I suspect the sender works perfectly fine because you are getting readings and the gauge also works.

Once you determine the ohm range of the sender, buy the right gauge and hook it up. I just had to do this exercise on my old jeep because it had a fuel injected tank installed and the sender wasn't compatible with my gauge.

Here's a selection of gauges, note the ohm range varies.

https://www.amazon.com/s/ref=dp_bc_6...&node=15729721

To check the ohm range you'd either need to pull the sender or check the resistance on both a known full and known empty tank or extrapolate. You just need a basic multimeter to do it, let me know if you need better instructions.

[nigel1]

Originally Posted by davefromoregon

When I say the last 20% empties quickly, it means the gage goes from showing 20% to out really quickly. Presumably, it is actually much more depleted.

I believe the fuel tank has more or less a flat bottom. It is located under the aft berth. That said, I'll investigate that.

On my Bene 473, the fuel tank is deeper at the forward end as compared to the aft end.
The original gauge fitted by Beneteau was a float type, I pulled that and replaced with a Wema S3 sender and Wema FL-2 flange adapter.

https://wema.co.uk/collections/carav...nt=29703058119

https://wema.co.uk/collections/flang...ts/fl-2-flange

Much more reliable than the original.