Hi, I have a problem with my 2004 TJ SE (2.4L) intermittently not starting. I have had this problem in some respect for nearly six months. I live close enough to work/school that I can walk to work which allows me to investigate problems on my own and not always hand it to a mechanic.
First my Fuel Gauge stopped working properly(Sometimes it would be accurate and sometimes it would say empty). Then one day I drove a few miles and parked, when I came back to the TJ after a few hours it wouldn't start. I was very conservative with the quantity of gas that I had in the tank so I knew it wasn't empty. The battery was fine, but I didn't want to have it towed so I push started it and the engine caught. I was able to start it a few more times before it went out on me again.
This time after reading almost every post I could find and being unable diagnose it anymore or get it to start, I had it towed to a mechanic. To my amazement they said that it was starting fine and that the fuel gauge probably didn't work because the sending unit was bad. They did suggest that the bad gauge implied an aging fuel pump and quoted me ~$900 to fix it. Because I don't have that kind of money to put into a solution that might fix the problem I just paid them for the diagnostics(which they weren't going to roll into fixing the problem anyway).
Of course it died again and I reread all of the forums I could find and looked through the FSM and did all the diagnostics that I have the tools for. But I also had some info from the mechanic so I was pretty confident in the fuel pump module as the problem. So I bought a Mopar fuel pump module and installed it myself. At this point the TJ starts but the fuel gauge just sits a empty.
I have run a few tanks of gas through it now, but a few days ago it decided not to start in the morning when it was ~30F outside. the engine was turning over but not starting. A few days later and a little warmer, it decided to start.
Does anyone have any suggestions as to what I might test to narrow down the problem? I have tested the cluster so I know that works fine. I have also attempted to mimic the resistance that the ECU expects from the FSU as described in other posts, but with no effect on the gauge.
Any help would be greatly appreciated! Thank you!