First, great forum! I just registered and this is my first post, but I have searched many threads in the past and there is a lot of good info.
Here's the problem: Gas gauge was not reading properly on '99 GTP (purchased approx 6 months ago). Fluctuating from full to empty. Removed fuel pump assembly and checked sending unit. Confirmed sending unit resistance was bad...dead spots, etc. Purchased new Bosch assembly (unit taken out was original unit and extremely difficult to re-install (see below), so replaced pump and sending unit to avoid having to repeat in future). Installed new unit and gauge appeared to work properly from full tank down to about 1/4 tank. Now it is stuck at 1/4 tank, even with tank empty or fuel.
I have jumpered 50/100/150/200/250 ohm resistors across the connector to the level sending unit, and I get what appear to be proper gauge readings varying from empty (50 ohms) to full (250 ohms), so I believe wiring/PCM/gauge is ok. I have seen some postings on internet that state this is a 45-90 ohms unit, but I think it is 50-250 ohms.
When installing fuel pump assembly via trunk access hatch, it was very difificult due to the need to compress the springs almost completely to get the lock ring in place. Now, inspecting tank from below, it seems the bottom of the tank is 'sucked in' or collapsed upward. So I'm thinking that's the reason for the difficulty in installing the pump assembly, and I'm wondering if the tank deformation has caused the float arm to get caught and stick at roughly 1/4 tank. I added gas, roughly 1 gallon at a time, such that there were about 2 gallons (starting) to around 9 gallons when stopped, and the sending unit resistance stayed steady right around 70 ohms, and the sending unit voltage remained steady around 1.1 Volts. Per my checking with resistors, this voltage seemed to be right for 70 ohms resistance.
So, any thoughts on the 1/4 tank reading? Could the float arm be stuck? What would cause the fuel tank to 'collapse' to begin with? Any advice appreciated.
Thanks
