Two things. One, you must make sure that the little rubber plug at the bottom of the fuel pump comes to rest in the correct recess in the tank. This will be impossible if the plug from the old one remained in. It will be difficult no matter what, and if you're doing it with tank in, and more so if with fuel in the tank, it may require some contortion, many tries, and a new vocabulary of expletives. Just keep trying. Before locking it in, the flange of the pump must sit flat on top of the o-ring. You may need to try various angles of approach to get the plug to seat. Your own perspective might be off when approaching it from below, too, so don't be afraid to probe around with the sender to try to find that sweet spot. When it is in right, you'll know it.
The other thing is that the new O-ring will probably be too fat for comfort, and the tabs on the lock ring too blunt. If you do get the flange of the pump seated flat, it will still be difficult to get all three tabs to line up. I suggest that if possible you take a file and sharpen them a little. You may also notice that they are just uneven enough that one will begin to engage before the other two do, and this will help you to get them all in. Again, this is a job that requires a LOT of patience, and a good bit of agility if you're under the thing. It's much much easier to do with the tank out and on the ground.
Finally, if at all possible lubricate both the o-ring and the flange and lock ring with grease. It will go together more easily.
Good luck. Doing this job with the tank in is a pain in the butt. But it can be done.
'er came over and got it out for me. Problem is, he did it so fast I didn't really see how everything came out. Thats where I'm having problems putting it back in.
