Recently purchased an 02 Grand Cherokee, 4.0L, and a high pitched whining noise has developed from the back of the vehicle, almost like a harmonics noise. I have determined that it is coming from the fuel tank. I am assuming it is a noisy fuel pump. If you turn the key to on position, but not starting the engine, the noise will appear briefly until the fuel system pressurizes and then stops but while running, the noise is there all the time. If you remove the fuel cap, noise becomes more pronounced slightly louder. There are no other issues at this time, vehicle runs well, no hesitating, starts right up. I have not checked the fuel pressure. When vehicle was purchased, it had a trouble code P0442 indicating a small leak in the evap system. After speaking with my jeep parts guy he recommended I replace the fuel cap. I replace the cap (with a Mopar cap) and cleared the code. Code did not come back and currently there are no pending codes. I am wondering if anyone had this experience before and is this just simply a noisy fuel pump or is it an indication of impending pump failure? Should I be considering replacing the pump? Possible other problems causing the noise such as recirc evap lines? Any help would be appreciated.

 

I have this problem now, after changing the fuel filter. I checked the new noise coming with the agency workshop, and demanded changing the new filter again, but they tried a new filter and that noise remained. They tell me it should be the fuel pump noise which was damped by the dirty filter earlier. I decided to change the pump, but after I experience fuel supply problems from that pump!! Because I am not sure...

 

I've been told that some of NAPA's pumps make a little more noise that an OEM pump does, but yes, I would suspect a pump that all-of-a-sudden starts to make noise. If you can afford it, change it now before you are left stranded. JMHO.

 

I wonder why we are not getting a fuel filter with a MOPAR sign now and what we get is a china made one without that mark !!
The MOPAR part # is given on a sticker on the nylon cover sachet only, which made me think that noise is from the filter. Changed it on the warranty in the agency but the same noise stayed. That's why they told me it shd be the fuel pump in the petrol tank. I wonder why they did not think of an access below the spare wheel housing for maintenance ....!!!!

 

An access cover would be too easy! I've seen cars where the owner has cut his own, however.

I once asked my dad why it's so difficult to work on cars. He said "They don't want you working on your own car, that's why!"

 

Your Dad Dave is Right !! They do not want U to do it Yourself, or check the actual problem. Trying the fuel filter first, then the pump, and of course, change spark plugs, and also the coil...etc... is much better!! Many parts are sold and lots of costly work hours.