need help on reading

[1iwilly]

hello to all
need help how to interpret this all the sudden i've seem to run out of gas when gauge read 1/4 left i took out the assembly on the dr side syphon pump seems to look ok i disassemble it put in new oring but it seems to be hit and miss have a old faithfull 5 gal jug for back up here is the info when doing option 6 on cluster=TNK=28.3/2.7/31.1L
which is right side and left side and what should i look for when i get close to 1/4 tank. also is there a way to test the syphon pump.thanks