Ok, so I just bought a 2000 Jeep Grand Cherokee Laredo 4.7L for $1500 with a few minor issues. Once I got it home I realized the issues were worse than advertised. I won't complain much for $1500. Upon inspection, I started it multiple times and drove it and it all seemed fine. Once I got it home and let it sit for a while I went to start it again and it wouldn't. After about 30-45 seconds of holding the key and pumping the gas pedal it would finally start. My initial thought was that it had something to do with sitting on an incline. All the times I started it before bringing it home it was on flat ground and started fine. Now, when it comes to troubleshooting vehicles I don't know much but I know how to turn a wrench and with a little instruction could fix almost anything on my own. I was thinking that it was the fuel pump causing this issue but after talking to some more knowledgeable people I was told that if the fuel pump wasn't working properly, it wouldn't start at all. I was then advised to check to see if there was pressure at the fuel rail and if there wasn't then it was a bad injector(s). So I took a screw driver and depressed the shrader valve on the fuel rail and not a drop of fuel came out-- no pressure. I then got it started and used this neat little trick of putting a screw driver at the base of each injector and putting your ear to it to listen for the clicking of the injectors. I couldn't tell if any of them were not clicking but this could be due to the fact that the engine has an audible tick in the first place; bad lifter rod I'm assuming, but that's another problem for another time. I also turned the key on 3 time in rapid succession and the code P0463 (Fuel Level Sending Unit Volts Too High -- Fuel level sensor input above acceptable voltage) came up on the dash. As a last effort, I had someone turn the key on while I listened in the back and I was able to hear the fuel pump "turn on". So ultimately I am at a loss and am still unsure of whether the issue is with the fuel pump or the injectors or something else entirely. If someone could shed some light on this matter for me, it would be greatly appreciated. Thank you!

 

go to autozone (or some other auto parts store) and check out their fuel pressure test kit. its free. connect to the rail and report back your pressure. also note the time it takes (if any) for the pressure to drop and by how much. that's where I would start.

 

It could also be a leaking check valve at the fuel pump. If you want to go to the trouble, you can pull the fuel rail and injectors off the engine, wire-tie the injectors to the rail, and pressurize them. You should be able to see one dripping or spraying if it's leaking. Oh....right! you have 2 rails. Same thing.

 

"P0463 (Fuel Level Sending Unit Volts Too High.." means open circuit, its not seeing any resistance from the fuel sender, so that could indicate time for a fuel pump assembly, but...before I shelled out for that, I would recommend what is said above, go get a fuel pressure gauge at harbor freight and check it running and the bleed down tests.

 

I appreciate all the reply's. I intend to start cracking into it tomorrow and will reply with what I find. Thank you!