Grand Rapids EIS Inconsistant Fuel Level

The fuel level sensors on one of my GRT EIS systems is giving me fits.

Using resistance type fuel level sensors and have the resistors installed per instructions.

The system has been calibrated and is working normal most of the time.

Occasionally on power up I will notice that the displayed fuel level is less than it was at shut down by 3-7 gal or so each side. By powering down the EIS and restarting, the system will display the correct quantity.

There is no indication that there is a problem other than by me noticing the level is not correct or by manual cross checking the level with the fuel totalizer.

I have been taught in flying to "never trust the fuel gauge" but I still don't like equipment that in not working correctly.

I called GRT and the only advice I could get from them is you must have a loose wire on the fuel gauge. Checked and found nothing. Also unlikely as both tanks do the same thing simultaneously.

Anyone run into this?

Ask GRT how the loose wires (one on each tank) know to tighten themselves up when the EIS is rebooted.

grt fuel level

I am having the exact same problem. See this thread
http://www.vansairforce.com/community/showthread.php?t=119409

After this I sent the instrument back to get it checked and they could not find anything wrong with it. My wiring looks good.

The one thing common to both tanks is the regulated 5 volt line (is that what you?re using?). I?d try to get a voltmeter in there, see if that voltage is varying.

dougmattson said:

I am having the exact same problem. See this thread
http://www.vansairforce.com/community/showthread.php?t=119409

After this I sent the instrument back to get it checked and they could not find anything wrong with it. My wiring looks good.

Click to expand...

Doug, your posts are from quite a while back.....you just learned to "live with it?"

grt fuel level

Pretty much. When mine happens it is usually a few minutes after takeoff. I cycle power and it stays correct after that. I was going to put a meter on the excitation voltage like was suggested but I guess it doesn't bother me enough yet. If the voltage is dropping I don't know what to do about it.

Check the sender ground. The best way is to have a separate ground wire under one of the sender screws.

Carl

grt fuel level

Thanks for the suggestion Carl. I do have the senders grounded. I don't think a ground problem would be likely to affect both tank level readings at the same time and then both be cleared from cycling power. So far it only happens once in awhile and only once a flight then.

Like Bob Turner said, I have had sporadic problems with the 5 volt supply line. In my case it is NOT the GRT unit but rather my harness. In the first case, I found the crimp where I split the line to the two tanks was (to my great surprise) not good in my original manufacture. Replaced. Many flight hrs later with a reapearance of the problem, I found the industrial D-sub female pin that I used had loosened up on the male pin exiting the EIS. A light squeeze fixed it.

Many hrs passed and the issue recently returned so I will either squeeze it again or replace that female with the machined tubular aircraft female type. I bought some a while back, just for this eventuality.

Just happened again today for me. I had just fueled both tanks and on power up was showing less than full.

Per GRT I noted the MAP which is a separate Aux input, then power cycled the EIS. On restart fuel shows correctly and MAP showed the same as prior to restart.