My fuel guage on my blazer sometimes usually whenits cold but sometimes even when its not cold it will say i have a full tank when i really have half a tank why could this be? It does usually go back down when i drive for a bit. and usually only happens right when i start it up.

 

I had the same problem, it ended up being the fuel sending unit in the gas tank

 

how much does a new sending unit cost? ..how do i get to it to remove it and install a new one?

 

A couple hundred bucks and it's only available at a Chevy dealer as far as I know. Might as well replace the pulsator & pump while you're in there as they always seem to go bad.

You have to remove the gas tank. Draining it first helps or you'll also need a floor jack for support.

1. Remove tank shield.
2. Remove screws holding filler neck flange to body behind filler door.
3. Loosen tank strap bolts. Tie off the straps with wires so you can drop & hang the tank about a foot on the right/rear corner.
4. Jam your head up between the right leaf spring & tank. Then try to get one of your arms on top of the tank.
5. Disconnect all hoses & wires from top of tank.
6. Loosen hose clamp and remove filler hose from side of tank.
7. Drop tank to floor.
8. Carefully chip dried old sealant away from sending unit lock ring.
9. Turn locking ring to release sending unit and carefully lift from tank.

I've done this so many times because of this piece of crap pulsator I can do it in my sleep.

Next time, I'm pulling the carpet from the cargo area and cutting a hole in the floor.

 

Actually you can get the whole thing as an assembly from different aftermarket sources. Look at O'Reilly's, Autozone, etc. (whatever your local flavor) adn yes, they are a couple of hundred but you get everything to do the job. Be sure to replace your in-line fuel filter too or most of the time the warrenty won't be any good. Dealer = Stcker Shock

 

That's good news. When I first changed mine a couple years ago, the pump & pulsator were the only things available as after-market.

I just checked Advance Auto Parts... about 100 bucks for sending unit with strainer, 100 bucks for lifetime pump... then you'll need a pulsator (20 bucks?) too.