Fuel tank sensors don't work

[zeehag]

i have an analog system... stick with markings i need to recalibrate for new tank. is always accurate and backed up by a nice translucent inspection plate thru which i am able to check levels accurately.
as i tend to cut it close, this is a tried and true method
i have known the fuel tank gauge fail blues in past and refuse to spend good dough on that (useless) feature. have fun kids. i will continue to arrive with 1 ounce of fuel in my return lines without engine cutting out from fuel starvation.
get a dowel and mark it with known quantities of fuel in tank. black magic marker works nicely for at least 3 yrs.

[CaptTom]

I envy anyone who can "stick" their tanks with a straight rod. Mine have two 90-degree turns in each fill hose. The best solution I've come up with is a flexible electrician's fish tape reel:


This one is under $15 at Home Depot, but I imagine there are lots of different styles sold at any place that has basic tools for electrical work.

I had to pull the plastic tip off the end, and I marked it at regular intervals (inches) so I could use it on my two different size tanks. I made the marks using a file.

[Cavalier]

Originally Posted by gilligansail

I have US sensors with Blue Sea Systems and they are inaccurate despite multiple attempts to calibrate

Any advice on the best sensors? Or how to solve this problem?

Thanks

I have two VSM422s and i'm using all 3 US tranducer slots on each.. so 6 total. 3 fresh water tanks, 2 black water and 1 diesel.

Apart from 1 (forward) of the water tanks and the diesel tanks, all of the other tanks are rectangular and the level gauge works fine. However, I had issues with the calibration of the diesel and the forward water tank. I decided to 'play' with the forward water tank (FG built into stringers) calibration as it was easier to drain and refill (water), and found that the biggest single issue was that the tank volume stated in the manufacturer's manual was incorrect.

On to the diesel tank.. i'd always had an issue, that whenever I ran it "dry" (i.e. to the bottom of the pick-up tube), I would then fill it to the top using the auto-calibrate scheme and a constant fill rate. At the top, it would read 100%, and when it returned to the bottom it would always state 8% left - quite a big offset!

I then decided to physically measure and recalculate the volume of the diesel tank which the placard on it, and the manufacturer's manual stated as being 50USgal - the measured internal volume turned out to be 46USgal (maximum), the form of the tank is basically a horizontally apportioned rectangle with the aft section chamfered dramatically, such that the first 25% of the tank volume (from full) is a rectangle, followed by a sloping section (of reducing area) down to a square at the forward end and bottom of the tank.

Once i'd reset the tank volume in the VSM422's configuration for the actual tank volume (not assumed), and recalibrated i.e. started from 10-30% full (was closer to 10%), ran the fill timer and then inputted exactly how much diesel had been added (from the pump), then the issue of the inaccurate "gals left" reading has disappeared.

As a general rule, it's worth double checking the volume of your tanks anyway, as most placards simply state "gal".. leaving you wondering whether it was an Imperial gallon or a US gallon.. the imperial gallon being 20% bigger than a US one.. I can only assume the VSM422 (made in WA) uses the US gallon!

[zeehag]

capt tom--i can because i donot stuff the stick down the fill which has convolutions the gods had fun imagining. the top inspection port opens with threads and i measure there. much less aggravation than bend this here, and stick can be shorter.

[Pete7]

Originally Posted by belizesailor

The Stick is a good option if workable on your boat, but unfortunately for many sailing vessels its not feasible.

Absolutely a 4 foot garden cane has lived on board our yacht for nearly 30 years to dip the tank.

[gilligansail]

I just bought the boat so I have not recorded my fuel consumption yet. I want gauges for water, fuel and black water.

[gilligansail]

Thanks, I have the VSM system too. I went through the calibration with the tech support at Blue Sea and the recommended switching to Wema sensors. I just spoke with the tech who installed this system for the previous owner and learned that they have been struggling with it for years.

My problem is that the sensors tell me that i have and empty tank when in fact its half full or completely full. So huge errrors. I'd be happy know 1/4, 1/2, 3/4 full

[Cavalier]

Originally Posted by gilligansail

Thanks, I have the VSM system too. I went through the calibration with the tech support at Blue Sea and the recommended switching to Wema sensors. I just spoke with the tech who installed this system for the previous owner and learned that they have been struggling with it for years.



My problem is that the sensors tell me that i have and empty tank when in fact its half full or completely full. So huge errrors. I'd be happy know 1/4, 1/2, 3/4 full

Out of interest, how close is the transducer.to the edge of the tank walls? How deep is the tank?

Sent from mTalk

[ranger58sb]

Originally Posted by gilligansail

Thanks, I have the VSM system too. I went through the calibration with the tech support at Blue Sea and the recommended switching to Wema sensors. I just spoke with the tech who installed this system for the previous owner and learned that they have been struggling with it for years.

My problem is that the sensors tell me that i have and empty tank when in fact its half full or completely full. So huge errrors. I'd be happy know 1/4, 1/2, 3/4 full

Can't tell if you mean you already have WEMA (KUS) sensors or not...

But generally if a float-type sensor always or usually shows empty or very low on the gauge when the tank is filling, it's because the float can stick at or near the bottom of its range. We'll call it "sludge"...

In those cases, it can sometimes be an easy fix to remove the sensor, clean it all with something like muriatic acid so the float will travel freely on the shaft, and then stick it all back in and reconnect the wiring to the gauge.

Even the new (stainless) WEMA sensors can get stuck, usually after some years and probably depending on whether you use a tank treatment (and maybe depending on tank treatment product effectiveness). Easy to pull, clean, replace.

You'll want to pump out and rinse a few times before doing the work, but it usually isn't all that gross if you've prepped for it.

-Chris