Isuzu Repair: 99 Isuzu Rodeo, isuzu rodeo, fuel gauge

Question
I purchased this vehicle from my parents for my son and when we got it the fuel gauge didn't work..i've read others comment about this same problem.  My son knows about how many miles he can go on a tank of gas and has done quite well in not running out of gas (resets milage with every fill up)...well he has had a problem and we don't know where to start...the truck won't start sometimes..we had it towed to a mechanic(who said possibly the fuel pump needed to be replaced) and then decided to look at it at home so towed it back home before the mechanic could look at it and it sat for a day then my son went out and tapped on the gas tank and it started right up...didn't happen again for a couple of months and when it did he tapped(like hard taps with a golf club) on the gas tank again and it started...well this time all the tapping isn't helping and he's stranded...please help

Answer
Well I don't know how many times people have laughed at me for telling them to do this but thanks for being on my side Ursula:) Well the problem lies within the fuel pump solenoid drive. This just gets worn out with time or the fuel pump is installed wrong or air is getting into your system somewhere(not pressurized correctly) I would recommend having a voltage test done on the fuel pump although if you have to hit it with a hard object I would almost guarantee that the fuel pump is your culprit okay? Any other questions dont hesitate to ask.