Chrysler Repair: The 93 concorde again.....

Question
Just changed the fuel pump in my car and the gas needle is all over the place now. Sometimes it will display what should be the correct amount of fuel based on my last fill up and how far I've driven but most of the time it's where it wants to be. I'm not confident that the problem is with the actual sender unit though because of other little electronic bugs I've noticed (door chime doesn't always work, dash lights getting bright when I turn the dimmer down) I have a multimeter that I use to check my battery from time to time but I have no idea how to use it to check this issue or what to do if, heaven forbid, it's NOT the fuel pump.


Oh and I've notice the electrical problems become more obvious in the rain or after I drive through a car wash.....

Also thanks with the previous help with the shift solenoid, Ordered one from ebay, had a local transmission shop put it in and it's been driving fine. Except for when it rains. I usually have to turn the car off and try it again.

Answer
Hi Steven,
Did you also replace the level sensor or did a new one come with the pump unit? There are some details about changing out the level sensor if you had to do that which might not have been observed. The level works by changing the resistance to ground on a dark blue wire that runs from the fuel tank module to pin 23 of the gray plug at the body computer. It would be a bit tricky to observe the variable resistance (or the variable current flow) through that wire unless you cut it and put a milliamp meter in series between the float unit and the pin 23.
Did you have the manual pages that describe the change out of the pump module? It may be that it is mechanically bound-up which is producing the variable readings. I could copy a couple of pages from the '94 manual I have that describe changing out the float level unit and postal mail those to you.  
The electrical variability associated with rain/wash water may be due to a wet/dirty multi-wire plug at the bcm. There are three plugs on the top side of the bcm unit and a possibility is that water is leaking down from a leak at the lower edge of the windshield and falling on the plugs of the bcm directly below. If so, that could also cause the variation in the fuel gauge reading. So check for that and if present either fix the leak or cover the top of the bcm with plastic to shield the plugs.
Please read the PS (below) and respond to it.
Thanks,
Roland