The fuel guage on my 2017 Grand Cherokee is malfuncting.   My guage indicated 1/4 tank full.   I went to fill it up and it only took about 6 gallons before the gas started to back out of the filler tube.   The guage reading only showed it was 1/2 full.  I see a measuring stick into the filler tube to confirm it was full.    I drove about 10 miles and the guage reading changed from 1/2 full to just above 1/4 full.   I am assuming the floats on the main or transfer fuel pumps.  I plan to test them to see which one or both may be giving bad readings.  Can the pumps be replaced without dropping the tank on my vehicle?   

Thanks in advance for any advice.