I have a 05 trailblazer ext ls 4x4 with 4.2l 6 cyl engine. i am replaceing the fuel pump assy because the guage is reading empty or 1/4 all the time. i figure i would replace the whole unit while i had the tank off. i wanted to see if anyone has directions on how to do this. i have been working on cars all my life, not an expert at all but experienced. have replaced in tank fuel pumps before on different vechicles, but i know info helps to see the hidden connections ect. Thanks to everyone who post here it helps very much.

 

This will cover 85% of the job you have ahead of you:
GMT370 Fuel Tank Removal

 

A couple of things not covered in the above:

First and VERY important: once the tank is out and you're removing the sender/pump assembly, be careful what tool you use to remove said assembly. The factory service manual will list which tool you need, they can usually be found on ebay for cheap. (I got mine for $15.) I highly recommend getting the proper tool first. It is possible to use a punch or drift to remove the retaining ring; if you do make damn sure it's a brass punch. Steel makes sparks and could ruin your whole day. (Sparks, fuel vapors, you get the idea.)

Second: Sometimes GM uses a sticky kind of sealer to cover the whole top of the assembly to seal it. Nasty stuff to clean up. Plan on at least an hour--or more-- to clean the stuff off if it's there.

Third and VERY important: This is almost never mentioned in the manuals but it is critical. When you lower the tank, NEVER rest it directly on the ground. Always use something like a piece of cardboard to protect the metal of the tank. Scratches can ever so slightly reduce the rust protection's effectiveness. Corrosion can weaken the tank over time and potentially cause an explosion in an accident.

Fourth: A floor jack makes it so much easier to raise and lower the tank. Make sure and use a block of wood to spread the load out. Be very careful not to deform the tank. Don't use the jack to force the tank into position. If the tank does not move freely into position, jockey it around by hand to get it where it needs to be. Deforming the tank even a little can screw up the the fuel level readings.