Fuel Tank / Sending Unit Replacement

[RedKing7]

It's been awhile since I've been on this site. I hope that someone can help me or point me in the right direction.

I have a '72 Challenger Rallye; I'm the original owner.

I'm having trouble getting gas out of the tank / sender unit.

Can anyone weigh in on experiences in replacing the tank / sender unit?  Can I replace the sender unit without removing the fuel tank?  With this being the original tank, should I replace it with a new one because of potential sludge issues?

I've looked at some so-called new fuel tanks out there on the web, but none seem to be an exact duplicate of what I have.

Thanks.

[70chall440]

If you think there is "sludge" in the tank, then it needs to come out. It isn't that hard, remove the rear valance, disconnect the fuel line and fuel gauge wire, support the tank and remove the 2 9/16 strap nuts.

To your question, you should be able to remove the sending unit without dropping the tank. You might want to put an electric pump on the fuel outlet and see if it pulls fuel before removing the sending unit, it might be something else like a blocked line, bad pump, plugged filter, etc.

[JayBee]

Can I replace the sender unit without removing the fuel tank? 

If that's all you're interested in doing then absolutely. I've done it numerous times. Just make sure you're well below 1/2 tank of gas. Some have removed the left tire also.

[RedKing7]

Thanks 70chall440 and JayBee.

I did connect an electric fuel pump to the line coming out of the fuel sender unit (very near the tank) and could only get a few drops out.

Will try to remove the sender unit after I remove the left-side muffler to get a little room to work. Will see where that goes.

[70chall440]

Its not all that hard but you need to use a brass or piece of wood to rotate the locking ring so that you don't create any sparks seeing that you are right there at the tank. The ring rotates counterclockwise (as I recall) about a quarter turn and then should be free. Once you have that loose, then you can pop the sending unit out. It will have to be twisted a bit to get out because the pickup tube is bent at an angle (so that it is parallel to the bottom of the tank when seated).

[RedKing7]

Okay guys I need some follow up help.

I finally got the new sender unit by mail and here is what I've run into.

If I hook up my electric fuel pump to a hose and put it through the tank hole where the sender unit goes, I can pump gas out.

Before I put the sender unit in, I can blow air through the unit with my mouth and hear it come out the other end where the filter is.

However, when I install the unit and hook up the electric fuel pump directly to the sender unit with a short piece of fuel hose I can't get anything out of the sender unit.  So, the questions are:

1) How much gas needs to be in the tank? (I probably have a couple of gallons because the depth appears to be about and inch or so.)

2) How long should it take to saturate the filter on the end of the sender unit so that it can pull gas through the filter and the sender tube?

3) Any other thing that I'm overlooking or should check?

Thanks

[70chall440]

If you are not pulling any fuel then there isn't enough in the tank. If you are concerned, pull the sending unit back out, put it into a bucket (even with water) and use the electric pump to try it out and make sure it works. Make sure to dry it out and then put it back together (assuming it works), add some fuel to the tank and pump some into a bucket (to clear out the pump) before connecting up the whole system.

[RedKing7]

Added a few gallons.  Solved the problem.

[70chall440]

Excellent