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trackdom

Well Known Member
Hi,
I am trying since a long time to get good informations from my fuel float senders
All I get is number 170 for the left tank and 27 for the right one. No change when tank quantity varies.
I disconnected today The wire from The left tank and got 55 .
It seems that all parts are grounded. There is just one wire to connect to The senders, it shouldn't be too complicated, but that doesn't work...? little bit frustrating indeed...
Thanks
 
You will need to follow the EIS instructions to set the offset and scale factors for each sender (0 and 100, I believe). Then, in the Sport you will set the fuel display to either 0-100 (for % fuel) or 0-max fuel. Then, you need to follow the fuel level calibration procedure from here: http://www.grtavionics.com/documents/EIS/Resistive Float Fuel Senders Horizon.pdf

The instructions say Horizon but apply to Sport as well. Skip to section 3.2

It's a bit of a process but should get you sorted out.

Chris
 
Have you measured the resistance of the senders to confirm they are changing as the level changes, and that they are within the expected range? I wouldn't expect both to be bad, however. We can assume they are connected to the EIS as disconnecting them changes the reading.

Did you wire them up with the resistor and 4.8v input as shown on the instructions? If so, and the senders are reading the correct resistances, then there are not many other issues besides a setting issue in the EIS or sport that I can think of.

Chris
 
What I am sure is current comes to eis , but value never changes, 170 for left tank and 55 for right .
When checking ground I can observe that tank skin, sender frame and screw in The Middle are all grounded....
 
The center screw should not be grounded, there should be a resistance between it and ground that represents the sender level. If it is really grounded (0 ohms between it and ground), there is something wrong. There should also be a voltage at the sender wire from the 4.8V that should be connected to it through the resistor as shown in the instructions.

If all of that checks out, and the EIS settings are all confirmed, you may have to talk with GRT. At the very least, I would go back and make sure every EIS and EFIS setting is correct and check all the wiring back to the EIS. The fact that both sides are not reading properly would suggest that either they are not wired correctly, or there is a setting or internal problem with the EIS. Are you reading the fuel level off of the EIS4000 or the GRT Sport display? If the Sport, can you check it on the EIS4000 and see what it reads? Good luck,

Chris
 
Be sure to use a 470 ohm "pull-up" resistor as shown on page 46 of the following document.

http://www.grtavionics.com/User Manual Rev M. with figures.pdf

Did you test the resistance values of the senders prior to installing in the tank to confirm they range from approx 30 to 250 ohms as the arm is moved through its full range of motion? One of mine became damaged after I installed it on the tank and had to be replaced cause the screw wouldn't tighten up. It just turned until the wire broke off on the inside.

Let us know what the problem was when you solve it.

Bevan
 
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No, I didn't mesure resistance before mounting the senders, and of course I don't want to dissasemble The tanks :(
Today I mesured left tank sender resistance , and I found 210 ohms, but eis and Efis indicate 170. So something is wrong in The connexions. I suppose The tank is 30 liters full.I Will empty ? little The tank to see if resistance changes.
Of course when The problem is solved I ?ll let you know .
 
Reverse Sensing

trackdom said:
No, I didn't mesure resistance before mounting the senders, and of course I don't want to dissasemble The tanks :(
Today I mesured left tank sender resistance , and I found 210 ohms, but eis and Efis indicate 170. So something is wrong in The connexions. I suppose The tank is 30 liters full.I Will empty ? little The tank to see if resistance changes.
Of course when The problem is solved I ?ll let you know .
Click to expand...

Also note that the EIS manual example step 1 on page 46 has you setting the Aux Forward/Reverse setting to "Forward", but I'm pretty sure (it was 6 years ago) that when I set up my RV-8, I had to set this to "Reverse".

Skylor
RV-8
 
trackdom said:
No, I didn't mesure resistance before mounting the senders, and of course I don't want to dissasemble The tanks :(
Today I mesured left tank sender resistance , and I found 210 ohms, but eis and Efis indicate 170. So something is wrong in The connexions. I suppose The tank is 30 liters full.I Will empty ? little The tank to see if resistance changes.
Of course when The problem is solved I ?ll let you know .
Click to expand...

You can measure the resistance to ground with an ohmmeter - as you did - but the EIS does not measure resistance, so it should not read 210 ohms. The EIS measures the voltage present at that point, due to the current flowing from the EIS 4.8 volt source, thru a bias resistor, then thru the sender resistance. It then scales the data to get gallons.

You can do these tests, with the EIS power ON:
1. measure the voltage at the sender. It should be more than zero but less than 4.8 volts.
2. Disconnect the wire at the sender and measure the voltage (power on) on the wire. It should be 4.8 volts.
I believe you do need to set the EIS to 'reverse sensing'.
 
Today I made some mesurments on left tank .
At About 30 liters I mesure 210 ohms
Tank empty I mesure 240 ohms , that seems normal.
I mesure 4.75 v at The wire when Power is on.
But eis and Efis always indicate 170 for left tank and 29 for right one.
So problem is at 470 ohm resistor, that I.ll Check tomorrow.
 
trackdom said:
Today I checked The connexions and all is normal...I don't see any solution ...
Click to expand...

Interested to hear ideas as it appears I am having the same issue. Good voltage and resistances, EIS configured as instructed, but values remain unchanged no matter the fuel level.

Chris
 
Get a voltage reading at the fuel sender with power on. What is it?
Are you sure the resistors are 470 ohms?
 
concerning 470 ohm I think they are, but to be sure I'll mesure.
I didn't mesure voltage at The sender , just de connected wire at 4,75 v .
 
Drawing is not readable...
With words....
Coming from Eis 4.5 v wire is connected to Both 470 ohms resistors, then each resistor is connected to aux and sender corresponding to each tank.
What else?
 
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There is no way to wire resistors I suppose ....
 
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I mesured resistors and found 470 ohms
I mesured voltage at sender, tank empty, and found 1.60 v .
But eis always shows 170 ....
 
Now repeat with tank full. If the voltage is still 1.6 volts, the sender has an issue. If the voltage changes but the EIS does not, then the EIS has a problem.
 
Both Eis indications don't vary so I suppose senders are ok .
Did I miss something in The Eis programmation?
Eis sends informations to The EFIS, but always The same one...
I am waiting for a response from Grt ...
That's The very last thing that doesn't work in my RV8 !! I fly anyway, but for long trips I.d like to see accurate fuel gauges.
 
I am seeing a constant 1.6V at the sender and a constant 175 ohms, no matter the fuel level. This leads me to believe it is a sender problem in my case. I am wondering if the float is somehow stuck - the wings had been stored upright in a cradle for over a year. I think my only option may be to open the tank.

Chris
 
My tank float stuck after I installed it after Weep No More sealed the tanks. I removed the fuel line and finger filter and was able to insert my inspection camera from HF and slid it under the float to pop it free. I reattached the finger filter and fuel line and verified the resistance changed (and voltage) as I put fuel in 5 gallons at a time.

Try that before taking the tank apart.

TJ
 
I find it strange that The two floats could be stuck ... To day I fill with 30 liters and mesure voltage, hoping that voltage changes....
 
To day I mesured voltage at sender ...I found
Empty. 1,6 v
16 l. 1,19v
23 l 1,08 v
32 l 0,82 v
So sender works but Eis doesnt vary ....
 
trackdom said:
To day I mesured voltage at sender ...I found
Empty. 1,6 v
16 l. 1,19v
23 l 1,08 v
32 l 0,82 v
So sender works but Eis doesnt vary ....
Click to expand...

Did you verify that the scale factor (SF) is set to 100 for both tanks and the offset (Off) is set to 0?

GRT has an online calculator to determine the SF and OFF based on the readings with the tank empty and full. It is here:
http://www.grtavionics.com/floatfuel.php

TJ
 
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Good news

I decided to resolder all The connexions between senders, aux2 and 3 , +4.5v , and resistors. Now Eis Numbers change as tank is emptying....I have just to reverse aux2 , and change aux attributes , and then calibrate...That should work! :)
 
That doesn't work...Numbers don't vary when tank empties...So I give up , and I.ll fly without fuel gauges.
At The next inspection I ll remove wing root fairings to Check again...
 
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