Fuel level Calibration

After reading the D180 installaton manual I am still confused about how the actual amount of fuel (in gallons) is set...I see the low warning settings but nothing cams to mind about how to 'tell' the D180 how much fuel I have added. I would appreciate some comments to set me straight.

Hey John

There is a section on how to initially calibrate the sensor. ( add 2 gals, then press display button etc. ) After that, when you add gas, the display ask you if you added gas. Just tell it how much you put in.

John Bender

The Dynon knows when you add fuel. It will propt you to tell it how much you added, or you can press "FUEL" and add an amount there, or just hit "FULL" and the preset value of the tank is added. In the -12 I use 20 gallons.

It's all in the installation manual...sender calibration. How to use it after calibration is in the user/operation manual.. The fuel computer is separate from the level indicators. You can add and subtract fuel from the computer at will.

Page 6-5 install manual.

Page 10-2 user manual.

Fuel Sensor Calibration Problem

I did the add 2 gallons thing a couple of weeks ago and got the Dynon message that the fuel sensor value was not changing and to push "yes" if I really did put 2 gallons of gas in the tank. When I got to the end of adding fuel the Dynon displayed a message that the calibration was unsuccessful. I had previously painted the tank and assumed the problem was a poor ground. I reworked the ground but my ohm meter measurements did not show any significant difference in the ohm meter readings from the wiper to ground, (1,063 to 1,106 ohms), as I added gas. So, I got the same failed result today when I tried the add 2 gallons calibration again.

When I painted the tank it was empty of fuel. I placed the tank on one side for a while as I painted. This could have displaced the wiper from the ceramic winding but if this happened I would expect to read an open circuit.

Any ideas or suggestions would be appreciated. I have rocked the wings agressively on the ground in an attempt to un-stick the float if that was the problem without any success.

Thanks,
Bob Kibby "N712BK is a-flying"

Hey Bob

Disconnect the sender wire, and do a continuity check between a known good ground on the frame, and the sender connection. If you have no circuit, you do not have a good ground.

I had a grounding problem when I did my tank. When I "goooo'd" the large plate in front, I did so good, it was not grounded to the tank. This test will prove if you have a complete circuit.

John Bender

Bob Kibby said:

I did the add 2 gallons thing a couple of weeks ago and got the Dynon message that the fuel sensor value was not changing and to push "yes" if I really did put 2 gallons of gas in the tank. When I got to the end of adding fuel the Dynon displayed a message that the calibration was unsuccessful. I had previously painted the tank and assumed the problem was a poor ground. I reworked the ground but my ohm meter measurements did not show any significant difference in the ohm meter readings from the wiper to ground, (1,063 to 1,106 ohms), as I added gas. So, I got the same failed result today when I tried the add 2 gallons calibration again.

When I painted the tank it was empty of fuel. I placed the tank on one side for a while as I painted. This could have displaced the wiper from the ceramic winding but if this happened I would expect to read an open circuit.

Any ideas or suggestions would be appreciated. I have rocked the wings agressively on the ground in an attempt to un-stick the float if that was the problem without any success.

Thanks,
Bob Kibby "N712BK is a-flying"

Click to expand...

Generally the resistance range of the fuel level sender is 30 - 240 ohms (between full and empty).

First check the resistance between the screw and the flange of the sender.
If it is not between 30 and 240, you probably have a sender problem.

If that is ok, check the resistance between the sender flange and airframe ground. It should be very close to zero ohms. If not, you have a sender grounding problem. If it is, then you likely have a problem with the conductor path between the sender and the D180.

Add a grounding jumper

The resistance of my sending unit varies between 200 ohms empty to 30 ohms full. 1000 ohms is way too high. If you do not have close to zero ohms between the flange of the sending unit and the airframe, then try connecting a jumper wire between one of the 5 sending unit mounting holes and airframe ground. If necessary, an internal tooth lock washer between a ring terminal and fuel sender flange can help bite through proseal to make a good electrical connection.
Joe

No fuel sender reading

Took all your good suggestions and measured an open circuit on the wiper. Ordered a replacement sender from Van's and had them throw in a wheel pants kit while they were at it. Also found out that they have received some of the large diameter "O-rings" used to seal the strobe to the mounting plate so they are including one of those also.

All-in-all, it was a great shopping day at Van's!

Bob Kibby "N712BK"

Does the Dynon display complete range?

My Dynon is set to display in litres. When I fill the tank (75-80 litres), the Dynon displays 62+ litres. This stays constant until the tank contains less than 62 litres at which point the display starts to count down.

Is this correct?

Cheers...Keith

Hey Keith

On this side of the world, ours reads 16 gals until it gets below 16 gals. Just the way it is set up. Sounds like yours if fine.

John Bender

Keith,

That's the way mine works. Full tank measures 16 gallons, stays at a reading of 16 until the level falls below that. Not sure of the logic behind that design, but that seems to be the way it works.

John

Thanks

OK, good. One less thing to do ;-)

Old thread, but I just did the tank level calibration (twice) as per the Vans PAP procedure. On our side of the world, the Skyview calibration menu has you add 10 litres at a time until you get to 60 litres (15.8 gal). However, each time the highest reading I got on the Skyview fuel level widget was 56.6+ litres (15 gallons). I assume that was because the sender float couldn't go any higher. However, I was expecting to hit closer to 16 gallons (61 litres) before that happened. Just wondering if others are seeing less than 16 gallons as the maximum screen value.

The highest fuel level displayed depends on how the float arm is bent. It could be as high as 18 or 19 gallons. The main concern is accuracy at low level.

If I remember correctly, the instructions for calibrating have you elevate the main gear, easy to overlook. That would make a difference.

Thanks Joe. You're right of course, the low end is more important, but I was just curious to see if I was the odd man out. I'd thought I'd adjusted the float arm as per the book, so was a bit surprised to get a lower than expected reading.

Did that Bill. The main gear was on blocks and the cockpit rail was level.

Mine goes to 14.8 Gal and stops. No biggie. It's pretty accurate at the lower range.

Thanks Randy. Sounds like we built the same tank.

FWIW, this is my ultimate gauge for those who still use (and have) the windows. Never fails or needs calibration.

Window Gallons
4 --------5.5
8 --------7.5
12--------9.5
16--------11.5
20--------13.5
24--------15.5
28--------17.5
32--------19.5

Initial calibration was made using fuel containers. Roughly 0.5 Gal. / window.
Very convenient to prevent overfilling if you use cans to fill your tank.
The initial calibration was made after emptying the fuel tank and fuel lines, you may find some difference from your experience due to the capacity of the fuel lines.

Here's a shot of the graphic I made for the side of my tank. Just FYI for us old "sight glass" tank owners.

f1rocket said:

Here's a shot of the graphic I made for the side of my tank. Just FYI for us old "sight glass" tank owners.

Click to expand...

Nice sticker Randy, but I am concerned if you are actually referencing it for minimum fuel for take-off.

It looks like when you installed it you positioned it too low. The four gallon indication is when fuel is mostly covering the third window segment from the bottom. It looks like your label indicates lower than that.

rvbuilder2002 said:

Nice sticker Randy, but I am concerned if you are actually referencing it for minimum fuel for take-off.

It looks like when you installed it you positioned it too low. The four gallon indication is when fuel is mostly covering the third window segment from the bottom. It looks like your label indicates lower than that.

Click to expand...

Geez, I'm surprised my wings haven't fallen off (countersunk wing rivets under the wink walk) by the time I've run out of gas!!

I was pretty anal about measuring the fuel. On my tank with the airplane level, the right most sight glass circles equal even gallons. So my sticker is placed correctly.

However, I will double check it the next time I get the fuel down that low. I may have made a mistake. I would never take off with the fuel that low in any event but it needs to accurately reflect the proper fuel level in the tank so thanks for pointing this out. I had two of them made at the vinyl shop so it's an easy thing to peel this one off and install the other one.

f1rocket said:

Geez, I'm surprised my wings haven't fallen off (countersunk wing rivets under the wink walk) by the time I've run out of gas!!

I was pretty anal about measuring the fuel. On my tank with the airplane level, the right most sight glass circles equal even gallons. So my sticker is placed correctly.

However, I will double check it the next time I get the fuel down that low. I may have made a mistake. I would never take off with the fuel that low in any event but it needs to accurately reflect the proper fuel level in the tank so thanks for pointing this out. I had two of them made at the vinyl shop so it's an easy thing to peel this one off and install the other one.

Click to expand...

Sorry Randy, I didn't mean to induce defensiveness or sarcasm.
It is actually an important detail, which is why it was well documented in earlier plans pages when the sight window was being used. Early Section 51 pages have a detail that shows where the label should be located, and I think the PAP may have also specified to fill the tank with 4 gallons and place the label accordingly.
If you installed it using that technique, then I guess you are fine.... but it looks lower than any I have seen. So, my post was in the interest of the safety of a fellow RV-12 pilot. This is after all just an internet forum.... you can take it or just ignore it.... your choice.

As for the wing walk comment, that is kind of a cheap shot.
I am so tired of people justifying mods that they have done, by saying their airplane hasn't come apart yet so how can it be a problem?
To put it bluntly, that is about the lamest response anyone could ever give.
Lets suppose someone does a mod to their aerobatic RV that does actually reduce the usable wing strength from 6 g's to 3.5, and then they fly for 10 years never exceeding 2.5 G's.
Because of that history, they proclaim to the entire world how great of an idea they invented and that everyone should do it to. But no one (even the designer/innovator) knows the truth. Is that a good situation? Is that person being responsible?

I did not say your wings are going to fall off. It would require some serious analysis and testing to say that.
What I do know, is that what you did went against accepted industry standards for aircraft construction. It is not possible for you to machine counter sink holes in the wing walk area on an RV-12 wing for 1/8" rivets, and not have compromised the strength to some degree, unless you replaced the wing walk doubler with one made from material at least .050 thick. How much it has been compromised is anybody's guess (unless someone chose to do some FEA analysis and static testing, to find out).

If anybody needs to worry about a half inch misplacement of a level placard I conclude they are cutting margins too close. I think the placard looks great!

Fuel tank calibration problem.

Just did the calibration and got a problem.
When the tank was empty the voltage was 2.8 and it stayed at that until 6 gallons were in. The voltage decreased at 8 gals and 10 gals then stuck at 2.16 all the way to 16 gallons.

No ground wire is installed as others have reported.

Any suggestions ?

Make sure the fuel sending unit is grounded. If it is, then the problem might be the way that the sending unit is installed. Or the sending unit could be defective. Pull the sending unit out, ground the steel part with a jumper wire, and move the float up and down while watching the fuel level display.

Shirley,

Your ground is probably OK. Wouldnt work at all if you had a bad ground. Could be the sender arm is just sticking due to friction. Before you pull the tank apart to check it the try calibrating again and introduce some vibration to the tank as you proceed. Just tap on the cover plate with something hard. If this works, I wouldnt worry about it until your test flights. Chances are it will work fine when the airplane is in flight with normal vibrations and sloshing.

John

Thanks guys.

Checked the continuity of the screws, sender plate and wire. All OK as per previous advice on these forums.

With 16 gallons aboard suspect a stuck float arm as the Skyview voltage and the multimeter reading (135) all point to it been stuck at half way.

Rocked the wings and moved the tail up and down at the same time. Bingo.
Skyview volts moved to 0.66. Multimeter to 35. Problem fixed.

Got a very strong smell of fuel in there though. Not had that before even on the engine runs. No sign of leaks anywhere.
Wonder if it is the new vent or the rubber connector on the filler neck letting fumes out ?

When I've filled the tank up into the filler neck in the morning, I've had fuel dripping out of the vent later in the day, probably due to expansion as the temperature warmed up. On a few occasions I've also had a fuel smell in the cockpit on climb or manoeuvring (steep turns) with a very full tank, particularly if turning to the right. No obvious sign of any leaks inside the cockpit, but drops of fuel residue on the underside of the fuselage downstream of the belly vent. The smell disappears shortly after levelling out. Clearly filling above the tank vent inlet level is probably not a good idea. Just wondering if others have had similar experience.

Similar experience

If you have the "new" tank vent installed and are using an unvented cap, then when the temperature goes up on a full tank there is nowhere for the expanding fuel to go except up the 3/8" vent and out onto the ground or hangar floor. There is very little room in the 3/8" tubing so some fuel is lost.
I found this out soon after putting in the vent pipe and changing to an unvented cap.
Now I only fill the tank up to the filler pipe when I will immediately be flying.