R50 Fuel Problem!

[MCOpath]

For a few years I've had the following the problem;

After driving around either a few minutes or a few hours, once my truck is parked and off, I always hear a loud humming/whining noise coming from the rear end - fuel tank area. The noise normally lasts from five to ten minutes then gradually fades out. If I release the gas cap and tighten back up, the noise goes away immediately!

I've had the "vaccum cut valve" replaced twice at the dealership over the years but the noise keeps coming back.

One other thing, not sure if it's common on Pathfinders, but every time I re-fuel, there's always a strong lingering smell of fuel inside the cabin - which goes away after a few minutes. Any ideas? Is it time for a new fuel pump?

Any help is greatly appreciated!

[Densetsu]

Likely all these problems are related to the EVAP system in one way or another. Is the SES light on? It comes on in most vehicles when anything goes faulty with that system.

The easiest thing to do would be to change the gas cap and see if the noise goes away. Could be something as simple as the pressure relief valve in the cap being stuck shut and causing havok in the rest of the EVAP system.

[MCOpath]

I've tried two new gas caps - same issue. No SES light nor am I getting any service codes - plugged in my code scanner this morning. Weird eh?

[Issac]

There is a recall that was released by Nissan and I don't have it to link to but you had better check it out right away!

It is regarding a rust problem in the fuel fill tube. The tube rust out, leaks fuel. I think they didn''t prime/paint the tube and it is a real problem, because Nissan is taking care of it...It goes up to late 2001 models I believe, but regardless, it looks real similar. I have a 2002, and none of those issues. Mine was just after the recall.

Contract Nissan and you can look online for recalls. I think (not sure) Edmunds.

[WINNIPEGS_MOST_WANTED]

humming/whining sounds from the back usually indicate the fuel pump in my experience...

[edit]Sorry just read the full post. It happens once the vehicle is off...[/edit]

[fueler]

Mine has always made wierd whining/hissing noises after turning it off. If will sometimes stop abruptly and then start doing the noise again.... a few times until its cold I only notice it in a quiet garage

[Issac]

also checking clamps and hoses closely for leaks. It could in the return or any connection possibly.

if it changes with temp this might be a reason. Fuel filter replacement would not hurt either.

I had a high mileage car and it seemed every clamp was loose with age. And I mean every.

[MCOpath]

Yes. I received the recall in the mail a couple of months ago. I thought the same exact thing so I took the Pathy to the dealership to get the fuel filler tube checked out. According to the service advisor, everything checked out ok.

[MCOpath]

Exactly! The noise is most evident in a quiet isolated environment such as a garage. Although lately, it's so loud I can hear it anywhere! Am I going nuts??? My wife sure thinks so...

[Issac]

you are the year in question and also the model production it appears. I wonder about the smell?

I am sure since you are on all the other things so well, you have surely replaced the fuel filter. This getting clogged could be making the pump work overtime, also the inlet line would probably have higher pressure levels (I would guess).

If you are using injection cleaners recently, this might have broke much free.

For example I started using this stuff in excess all hopeful, and got all kinds of gunk moving. Then I changed the filter cause it was bad, the humm went away mostly.

No joke, it happened again in a few weeks. Again a filter, and no more problems.

It was not a pathy, but the humm was related to effort. Tank levels seemed to effect it too. In the infiniti, the fuel pump was not submerged with less than 1/3 or 1/4 tank. It was loud and then at fillup was dunked so to speak. I had heard about keeping the tank above 1/3 or so but never knew why till I pulled the whole thing out. Dry with low tank. Dangerous work too I might add so be real careful of you do something so dangerous. Ground, air, fire ext. , etc. That job made me real uncomfortable.

Thats all I got, but maybe ideas.

Good luck. Sounds like you are on it and I bet you get it!

When it sits overnight, do you turn the key and listen to the humm? It should be getting it up to pressure for a second or two. If it hums a lot, you might have a leak. Add the smell, and it sure is looking that way to me.

Trace the lines Under Pressure. Use key to re prime. I just had a real battle with this on another car because it has to be under full pressure to leak on it. So I had to check, reset key, check, reset key....and sure enough, a leak was found with little bubbles.

[MCOpath]

Thanks for the info Issac. Fuel filter has been replaced twice at every 20k miles. I've got roughly 77,000 miles on it now. Never been a big fan of fuel system cleaners and purifiers - personal reasons.

What you said in your earlier post makes sense. The noise is most evident when there is about 1/3 (or less) of fuel left in the tank. I'll continue my observations to confirm the volume of fuel related to the mystery hum.

As a Pathfinder owner and to others as well, what brand and type of fuel injection cleaner do you personally use on your own? I can't $afford$ to rule anything out at this point! Thanks!

[fueler]

I use seafoam in the gas tank to clean out the injectors I wouldn't worry about the noise. Like I said, my R50 has also always made a weird whining noise after shutting it off, and at 145k miles i still haven't experienced ANY problems.

[Buzzman]

Tank levels seemed to effect it too. In the infiniti, the fuel pump was not submerged with less than 1/3 or 1/4 tank. It was loud and then at fillup was dunked so to speak. I had heard about keeping the tank above 1/3 or so but never knew why till I pulled the whole thing out. Dry with low tank.

That's one good reason to never run your tank to empty. The fuel pump is in the tank, and the gas acts as a lubricant for the pump. If the pump runs when it's dry, it will fail prematurely.Try explaining that to the wife and kids when they run the car/truck until the low fuel light comes on. They don't understand why I get pissed off.It's also not a good idea to run the tank to empty in cold weather. When the tank is low on gas, condensation will form inside the tank, causing more problems.

[fueler]

Try explaining that to the wife and kids when they run the car/truck until the low fuel light comes on.

HAHA what an impossible task. My girlfriend gets angry now when I try to explain this, because she's heard it so much. She starts yelling "YES I KNOW THE FUEL PUMP IS OVERHEATING AND THE CAR IS SUCKING UP ALL THE CRUD FROM THE BOTTOM OF THE TANK - YOUVE TOLD ME A MILLION TIMES AND I DONT CARE" and still stays empty. Her Honda Accord has problems at only 130k miles. But never in my car!!!

[SnowSurfLax]

Haha! I have the opposite problem! Whenver the light comes on my wife freaks out. I have to constantly explain to her "No, you are not about to run out of gas and get stranded. Yes, you need to get gas now."