I have heard of a trick where someone took the back seat out and cut an access hole in the floor board. But I have not tried that myself, as the idea of cutting metal and creating sparks right next to the tank just was not very appealing to me.
I have done a couple on Blazers in my driveway. It is really not hard to drop the tank and change it. If the pump still runs at all, you can take the fuel line off at the filter and point the hose into a bucket or catch-pan and turn the key on and off for a while to pump the gas out of the tank. Then you will need to jack up the truck and put a jack stand or something under the frame rail. Then slide under there and disconnect the filler neck hose, the return line hose, and any other hoses that you see. Then just loosen the bolts on the bands holding the tank in place and it will come down. Be ready to hold it so you can get out from under it and go around to the back of the truck and unhook the lines and electrical connector from the pump. Then slide the tank out from under the truck, turn the metal retaining ring to release the pump, and replace it.
Installation is the reverse of removal.
When you get everything back together, make sure to put a few gallons (four gallons was enough for me) in the tank. Turn the key on for three seconds, then off. Repeat this twenty five times. This will prime the fuel system and get air bubbles out. The truck should start right up after that.
I probably missed a step somewhere. There are some good guides on YouTube, as this is a common problem.
The first time I did one it took me about four to five hours from start to finish. The second one took me two and half. Mainly it took this long because I had a near full tank of gas to pump out each time.
While you have the tank down, it is not a bad idea to clean it out while it is down.
Saturday, July 1st, 2017 AT 12:54 PM