My fuel gauge in my 1998 BMW 318is coupe stopped working the other day.
My first thoughts were to check the sender which I believed was on the left side of the car, underneath the rear seat. I pulled out the seat base, removed the cover and used a multimeter to check the resistance of the sender. It showed a value which varied when I shook the car which indicated that it was working.
Time to do some research. The Bentley manual showed that the resistance I measured was correct but also showed a second sender on the other side of the tank.
I measured the one on the right side of the car and it was zero, and no amount of shaking the car would produce any resistance value on my multimeter.
After a little online research I found that the common cause was a faulty sender or a broken wire to the sender. By my logic and experience, senders usually donâ€™t fail completely but wear out in certain parts of their range, but as my fuel gauge hadnâ€™t worked for the last week at all, I assumed that the problem was most likely the common broken wire issue.
I took the fuel pump unit out which involves disconnecting the fuel pipe to it. I depressurised the system first by running the engine then disconnecting the fuel pump. Sure enough there was one broken sender wire.
I stripped back the wire and soldered it back to where it had broken - probably not the best long term repair but hopefully good enough for a few more years. The best repair would be making a â€œmechanicalâ€ connection such as crimping or twisting the wires together as well as soldering.
Ignition on and my fuel gauge is working again.