First off I bought this 93 Jeep Cherokee Sport w/ a 4.0 Liter for $400 so I am not looking to dump a bunch of money into it. The jeep was sitting with the fuel tank out (because of a bad fuel pump) for about a year before I bought it. When I got it home I installed a new Airtek (yes cheap AutoZone junk) Fuel Pump in the tank after I did a thorough cleaning. I replaced all of the hoses going from the tank to the metal fuel lines and installed a new fuel filter.
The Problem:
When you start the Jeep it runs perfectly. It has no lack of power, no hesitation, no smoking, no ticks, knocks, or any other noises. After 5 minutes the fuel pump starts "humming". The humming is the normal fuel pump noise only 100x louder.
After 5 mins of the humming the Jeep will start bogging down and missing under heavy acceleration.
After 10 mins of humming the Jeep will start bogging down under even normal acceleration. You can get it up to 55mph at this point but only if you barely push on the gas pedal and very gradually accelerate.
After 15 mins of humming the truck will barely run and eventually shut off completely; however it will start back up, but shuts off after a couple seconds.
If I turn off the ignition for 1-2 minutes, I can start the Jeep back up w/out humming and the 5 min before humming / dying cycle will start all over again.
The times listed above are under normal acceleration. Under heavy acceleration, the truck will start humming and shut off completely within 5 minutes.
When the pump starts humming, if you put your hand on the hoses by the tank the biggest hose only feels like its vibrating really bad.
Also it does not matter if the gas tank is full or empty, the problem never changes.
The things I have tried:
I am not a mechanic but as soon as I heard the humming I immediately thought it was a bad fuel pump. I took the pump out and exchanged it for a brand new one. I also bought another new fuel filter and reinstalled the new pump and filter. The problem is still the same. No changes at all, the times didn't even change.
*When I pulled the first new fuel pump out, the rubber spacers on the top and bottom of the cylinder pump were slid into the middle of the pump. I will post the picture of the pump after I took it out of the tank when I find it.
At this point I took it to a mechanic and paid him to track down the problem. A day later he tells me that he has no idea what is wrong with it. He put a fuel pressure guage and let it idle for over an hour. The fuel pressure was a steady 31psi (exactly where it should be). The voltage was also exactly where it should be and never swaggered. However he only tested both at idle and never under a load.
When the mechanic couldn't figure it out I called Airtek tech support and they said it's either a bad fuel pump or another problem, but they were not mechanics so they could not help me. The only advice they gave me was to exchange the pump yet again.
Hesitant to pull the pump again since both fuel pumps had identical problems and the origional went out for a reason, I decided to talk to a Chrysler mechanic. The mechanic told me it sounds like my catalatic converter is bad. I replaced my whole exhaust system and the problem didn't change.
I then turned to Yahoo! Answers and the only good response I got was to replace the Ballast on the drivers fender under my hood. I replaced it and still no change in the problem.
At this point I started trial and error. I have replaced all rubber hoses under my hood to make sure there were no vacuum leaks. I have also took off my gas cap to see if it is a ventilation problem. The problem still exists and has not changed at all!
Other ideas I have that haven't been tried yet:
- Check the Fuel Pressure Regulator (doing this tomarrow, I will post results)
- Check the voltage under a load (if its high or low, what would cause this? possibly the computer? any info on this would be great)
- Replace the fuel pump relay in the fuse box under the hood (just thought of this while writing this, will do it tomarrow)
- Exchange my fuel pump yet again, maybe it really is another bad pump?
If anyone has any suggestions, ideas, or simliar problems that they have solved please let me know! I am quickly running out of ideas and I would love to get this Jeep running correctly.
Help Please!!! :rof:
The Problem:
When you start the Jeep it runs perfectly. It has no lack of power, no hesitation, no smoking, no ticks, knocks, or any other noises. After 5 minutes the fuel pump starts "humming". The humming is the normal fuel pump noise only 100x louder.
After 5 mins of the humming the Jeep will start bogging down and missing under heavy acceleration.
After 10 mins of humming the Jeep will start bogging down under even normal acceleration. You can get it up to 55mph at this point but only if you barely push on the gas pedal and very gradually accelerate.
After 15 mins of humming the truck will barely run and eventually shut off completely; however it will start back up, but shuts off after a couple seconds.
If I turn off the ignition for 1-2 minutes, I can start the Jeep back up w/out humming and the 5 min before humming / dying cycle will start all over again.
The times listed above are under normal acceleration. Under heavy acceleration, the truck will start humming and shut off completely within 5 minutes.
When the pump starts humming, if you put your hand on the hoses by the tank the biggest hose only feels like its vibrating really bad.
Also it does not matter if the gas tank is full or empty, the problem never changes.
The things I have tried:
I am not a mechanic but as soon as I heard the humming I immediately thought it was a bad fuel pump. I took the pump out and exchanged it for a brand new one. I also bought another new fuel filter and reinstalled the new pump and filter. The problem is still the same. No changes at all, the times didn't even change.
*When I pulled the first new fuel pump out, the rubber spacers on the top and bottom of the cylinder pump were slid into the middle of the pump. I will post the picture of the pump after I took it out of the tank when I find it.
At this point I took it to a mechanic and paid him to track down the problem. A day later he tells me that he has no idea what is wrong with it. He put a fuel pressure guage and let it idle for over an hour. The fuel pressure was a steady 31psi (exactly where it should be). The voltage was also exactly where it should be and never swaggered. However he only tested both at idle and never under a load.
When the mechanic couldn't figure it out I called Airtek tech support and they said it's either a bad fuel pump or another problem, but they were not mechanics so they could not help me. The only advice they gave me was to exchange the pump yet again.
Hesitant to pull the pump again since both fuel pumps had identical problems and the origional went out for a reason, I decided to talk to a Chrysler mechanic. The mechanic told me it sounds like my catalatic converter is bad. I replaced my whole exhaust system and the problem didn't change.
I then turned to Yahoo! Answers and the only good response I got was to replace the Ballast on the drivers fender under my hood. I replaced it and still no change in the problem.
At this point I started trial and error. I have replaced all rubber hoses under my hood to make sure there were no vacuum leaks. I have also took off my gas cap to see if it is a ventilation problem. The problem still exists and has not changed at all!
Other ideas I have that haven't been tried yet:
- Check the Fuel Pressure Regulator (doing this tomarrow, I will post results)
- Check the voltage under a load (if its high or low, what would cause this? possibly the computer? any info on this would be great)
- Replace the fuel pump relay in the fuse box under the hood (just thought of this while writing this, will do it tomarrow)
- Exchange my fuel pump yet again, maybe it really is another bad pump?
If anyone has any suggestions, ideas, or simliar problems that they have solved please let me know! I am quickly running out of ideas and I would love to get this Jeep running correctly.
Help Please!!! :rof:
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