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Grand Rapids efis

dan carley

Well Known Member
on the efis,where you can read how much fuel you have in both tanks. the readings change when not using the plane? they seem unreliable? any one having problems with this unit?

thanks
dan carley
 
Are you referring to the fuel remaining based on a flow meter or based upon fuel level gauges?

The fuel totaliser based on flowmeter should not change between flights as it is just counting pulses from the flow meter and converting it to fuel used.

However the fuel level is based on a variable resistor on the float or capacitance between the gauge plates if you have capacitance senders.
That reading will depend on aircraft attitude and should normally be read only in the level flight attitude. Also the fact that the senders are located on the inboard end of the tank, they cannot measure the first few gallons of fuel use from full.

Otherwise have a good check for blue stains on the underside of the wings!
 
I have trouble with my fuel level readings also. About every other time I fly the levels will read about a third of what they should. This happens after the engine is running. Sometimes on taxi other times while I am flying. If I cycle the power to the 4000 it will read correctly until the next couple of flights.
 
The resistive fuel sensors increase in resistance as the fuel level drops. This means that a lower reading on the EFIS or EIS is due to a lower voltage recieved at the EFIS/EIS (the supply voltage going through a higher resistance to get to the EFIS).

If it is intermittant, then the likely problem is wiring (bad or broken connection). It does not rule out the level sensor or the EIS/EFIS but look for the most likely cause first.
 
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Both tank indicators are affected the same way. Cycling power fixes them. I believe that points to the instrument.
 
Both tank indicators are affected the same way. Cycling power fixes them. I believe that points to the instrument.

Yes, it points to items common to both sensors.
That likely includes the power supplied to the sensors (wiring) along with the instrument. Look at the point where the 12v supply is split to feed the sensors.
 
One other thing - make sure you're using the regulated power from the EIS and not just bus voltage for the senders.

Bob
 
I am using the power from the instrument. Pretty sure if I cycle power to it and it reads correctly its not the wiring. That was the first thing I checked.
 
I have trouble with my fuel level readings also. About every other time I fly the levels will read about a third of what they should. This happens after the engine is running. Sometimes on taxi other times while I am flying. If I cycle the power to the 4000 it will read correctly until the next couple of flights.

Are you using resistive senders (float on an arm?).
 
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