What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Fuel quantity floats upside down?

Gregmarlow

Well Known Member
All signs point to me installing the float in the right wing upside down. Is anyone in a position to see if that's possible due to the hole pattern? Just want to know before I dive in to fix it. Hate to unseal a tank for nothing. Going to try and get a boroscope in there but knowing first would be a huge help.

Thanks.
 
Last edited:
Do I understand that the wing is still off the plane? If so, easy: wing right side up, measure float resistance, it should be around 30 ohms. Flip wing upside down, float should measure around 200 ohms.
Edit. Backwards, see Scott’s correction, below.
 
Last edited:
If you install the proper sender in the proper tank (left in left, etc.) I don't think it is possible to install one upside down.

When installed properly, the steel arm that points towards the inside of the tank should be angling towards the bottom.
 
Do I understand that the wing is still off the plane? If so, easy: wing right side up, measure float resistance, it should be around 30 ohms. Flip wing upside down, float should measure around 200 ohms.

I think it is the other way around

When the tank is empty the resistance is highest (240 ohms), and when it is full the resistance is lowest (30 ohms)
 
Greg- I’m getting ready to install the end ribs on both wings, so it was an easy check. Best I can tell the Vans supplied fuel sender plate can only be installed with one hole pattern on the end rib, assuming all the nutplates have been installed properly.
Just for grins, I rotated the plate 360deg trying to align the holes in some other fashion.....no joy. I’m pretty confident that there’s only one viable hole pattern.
I also put the right wing sender plate on the left wing end rib, and it was the same story....it worked but only with one hole pattern....
Not sure of the nature of your issue, but I believe I read a few days ago that both wires should look identical isometrically. The only difference is the way you insert the float in the swing arm ( per the plans).
Knowing the pain you have just endured, hopefully there will be a simple fix out there.
 
Perfect, thank you

Well that's good, about the hole pattern. They were qb wings so I'm assuming everything was correct. Now I just have to figure out why my ohms are messed up. I'll check tomorrow what it is reading with 15 gallons in there.
 
Well that's good, about the hole pattern. They were qb wings so I'm assuming everything was correct. Now I just have to figure out why my ohms are messed up. I'll check tomorrow what it is reading with 15 gallons in there.

Perhaps a bad ground?
 
I don't think a horoscope will be much use to you unless you want to predict the winning lottery numbers! :D
 
Slightly off topic note

When reading about floats I always remember an experience circa 2001.

I partnered with a friend of mine on a 1970 V35B Bonanza previously owned by his father-in-law. "The fuel gauges have never worked right." he said.

Each bladder in a Bonanza has two fuel floats (upper and lower) with different resistance ranges connected in series. The hole patterns prevent you from installing them incorrectly.

But, never underestimate creativity. Flip them around and put them in the wrong wing and they will definitely go in and never work correctly.

Worked perfectly after that was sorted out.

Don
 
40 ohms at the sender, but...

Checked the ohms at the sender, with 15 gallons it was 40 ohms. Looks right.

However, going into the fuel tank calibration, (dynon hdx) it shows .82 volts.

Ideas? Thanks.

Greg
 
I?m not familiar with the HDX, but your readings may be okay. Typically the efis will supply some voltage (10 volts? With GRT?s EIS it?s 5 volts) thru a bias resistor, often 470 ohms. So 40/510 is 0.08, times 10 volts would be 0.8 volts. So it may be correct, you need to look at the circuit.
 
5v

Its 5v supplied but the .8 volts on the EFIS doesn't match up with the 40 ohms its reading at the sender.
 
Head scratcher.

Okay, here's where I'm at. Right tank 40 ohms measured at the sender, and at the EMS connector. I have 15 gallons in there, so that's about right. The left tank measures 130 ohms (1.9v in the calibration screen) with 10 gallons, and that tank calibrated semi-successfully, at least up to 12 gallons or so then it stopped changing with additional fuel. Not ideal, but I can live with that.

But the right tank when calibrating showed .8 volts empty and did not change with fuel quantity additions.

Using pin 20 for the left and 21 for the right. Pins on the EMS look fine. Checked ohms at that connector and the left shows 130 ohms and the right 40 ohms.

So maybe the float is stuck?
 
Agree, maybe the float is stuck (let?s see if I get it right this time - stuck high?). Some have fixed this by hitting the top or bottom of the tank, or maybe the sender/rib, with an open hand.
The float can?t ?see? the top few gallons due to the wing dihedral, this is normal.
 
Some senders have more friction than others Particularly when they are new. When the engine is running it induces vibration that makes the float friction not matter, but when stopped the floats often don’t move the arms to the proper position. When I do calibrations, I hit the top of the inboard part of the tank with an open hand after doing an add of fuel, until the voltage stops changing. This usually produces a very accurate calibration.
 
Speaking from experience, I can confirm it is possible to install the plate with the fuel sender upside down in an RV7. It happened after removing the plate to fix a small leak in the tank.
 
Speaking from experience, I can confirm it is possible to install the plate with the fuel sender upside down in an RV7. It happened after removing the plate to fix a small leak in the tank.

The screw pattern in the sender flange is indexed, so it can?t be installed in a different position.
The large cover plate is not indexed so it requires being installed in a specific orientation. That is part of the reason it has a flat on one edge..... to match the proper orientation depicted in the plans.
 
That did it! A few hard slaps to the inboard part of the tank, both top and bottom, and then up and down on the wingtip and now its reading correct. Thanks Scott and everyone for the tips. Now my plane is done! Just waiting on the DAR.
 
That did it! A few hard slaps to the inboard part of the tank, both top and bottom, and then up and down on the wingtip and now its reading correct. Thanks Scott and everyone for the tips. Now my plane is done! Just waiting on the DAR.

Looking forward to the first flight video!
 
Back
Top