hummm... My Q is fine today.

[BobE]

OK I'm worried. I remember reading that hum is a big warning flag.

Yesterday about 2 blks from my house w/ air conditioner & radio I heard an odd sound. Parked & turned off air & radio, hear hum from the rear of car. Turned off engine, then turned key to 'run', heard the pump for a second or two like normal. Started eng again, hum returned. A couple of hrs later it was back to normal as it was this morning.

[jamesmost]

a new fuel pump is in ur immediate future

[superuber]

Could be fuel pump. How many miles? Ever replaced it?Did you just fill the tank? I have heard pumps make noise then be fine. sometimes a full tank will put a load on the pump.

http://community.webshots.com/user/neheadsuperuber

[DrewQ45]

sometimes a full tank will put a load on the pump

Actually, it's the near empty tank that puts more load on the pump. A full tank is easier to pump from based on higher pressure at the bottom of the tank. Constantly running on an empty/low tank is the fastest way to kill a fuel pump.

[BobE]

It's about time for fuel, tank is near 1/4.

105K on my 95Q, I don't think the pump has been changed. I had never heard the pump, other than a second or two at turn on.

DIY?

[superuber]

funny, almost all the pumps I do the tank is full. I think the weight of the fuel puts pressure on the pump. Yes, running a tank low puts stress on it. if it sucks air and garbage from the tank.I can see both issues.

http://community.webshots.com/user/neheadsuperuber

[Rex]

The "advantage" of a fuller tank is gas acts as a coolant. The pump immersed in fuel helps keep it cooler. The humming is actaully from the FPCM (Fuel Pump Control Module), which is a result of the increased resistance of the failing pump motor. Delaying replacement will only double your costs (or more) as when done early the FPCM does not have to be replaced.

Don't forget to get the replacement O-ring, but if you call Joe/Infiniti of Scottsdale, they'll remind you.

It's and easy job and there's a great post by tangalora to walk you through the process.

[superuber]

As long as the pump is surrounded by fuel it can cool. It does not have to be full. With a full tank the pump impeller has to work harder to turn because of the extra pressure. The fuel is not just running through a holewhere pressure causes it to run through faster. I have seen many pumps stick because of a full tank, whack the tank with a hammer, bingo! You are right about getting it done asap!

[DrewQ45]

As long as the pump is surrounded by fuel it can cool. It does not have to be full. With a full tank the pump impeller has to work harder to turn because of the extra pressure. The fuel is not just running through a holewhere pressure causes it to run through faster. I have seen many pumps stick because of a full tank, whack the tank with a hammer, bingo! You are right about getting it done asap!

Be care about the advice you give online. "Whack" and fuel tank are not really words I would use in the same sentence. Tap maybe? Not saying you don't know what you're doing but there are others that might take you very literally and puncture the tank.

A full fuel tank gives a positive pressure which actually aids the pump in it's job of fuel delivery... Reason why your car will always feel faster and smoother on a full tank versus empty. Going from full to empty, the pressure decreases and so does that "full tank" feeling.

[BobE]

Thx Rex, I found the 5 pg article. I've not ordered from Joe, I save the 800 # somewhere. My plan is to get the new pump ordered today or tomorrow. What I've read sounds like a few day (& not a lot of driving) should be pretty safe. BobE

added:Just found this site: "Congratulations! You've found the Online Savings Center for Infiniti"

Or Call 866-374-3419 For Instant Internet Savings (Pinnacle Infiniti)

[superuber]

Yea, after reading some posts you may be right! anyway, its usually the dodge products we hit. no loss, right? Of course I don't know what i'm talking about, I'm really an actor!

http://community.webshots.com/user/neheadsuperuber

[maxnix]

What I've read sounds like a few day (& not a lot of driving) should be pretty safe. BobE

Right, until your FPCU is fried.

Need to read more.

[Q451990]

I don't think the initial hum is a cause to park the car, just to make sure your replace the pump within a week or two! Mine hummed for about 20K before I got around to replacing it (after the FPCU forced the issue). I knew about the issue and advised everyone to replace thiers immediately, but procrastinated too long. Luckily mine died in the driveway at start-up, and I have a couple of spare cars.

I think the average life of a fuel pump appears to be about 80K, but I'm sure that varies greatly with fuel quality and fill-up habits.

Not to be confrontational, but Rex mentioned that the hum comes from the FPCU. That's the first time I've heard of that... In my experience, the hum is definately from the pump, not the FPCU.

Heath

[BobE]

Thx Heath, yesterday was the 1st time it hummed. I'll get one ordered tomorrow. Everything Infiniti web price was $230 but said to call to confirm. BobE

[redmanfx]

Just keep fuel in the tank, say 1/2 or more and you should make it until your new fuel pump and O-ring arrive. Many of us have driven with that "hum" for months before changing it, but ran the risk of frying our FPCM like idiots>> Changing the fuel pump is almost like a right of passage!

[BlackBirdVQ]

A full fuel tank gives a positive pressure which actually aids the pump in it's job of fuel delivery... Reason why your car will always feel faster and smoother on a full tank versus empty. Going from full to empty, the pressure decreases and so does that "full tank" feeling.

I disagree, based on dyno results I've compared- my engine does not care if the tank is full or on fumes, it has the same AFR and timing, same EGT and same power. Its faster with a empty tank as it has to haul around less weight, full tank of gasoline is going to be around 100lbs as each gallon of gasoline is approx 6lbs- its heavier when the gasoline is cooler and more dense. How can you not feel 100lbs worth of weight vs 20lbs ? I guess it doesn't make a big diff on a car the size of a Q due to its porky weight, but when you have a car thats light, every gallon of gasoline counts as dead weight. Hence why drag racers tend to run their cars with close to empty tanks.

[DrewQ45]

I disagree, based on dyno results I've compared- my engine does not care if the tank is full or on fumes, it has the same AFR and timing, same EGT and same power. Its faster with a empty tank as it has to haul around less weight, full tank of gasoline is going to be around 100lbs as each gallon of gasoline is approx 6lbs- its heavier when the gasoline is cooler and more dense. How can you not feel 100lbs worth of weight vs 20lbs ? I guess it doesn't make a big diff on a car the size of a Q due to its porky weight, but when you have a car thats light, every gallon of gasoline counts as dead weight. Hence why drag racers tend to run their cars with close to empty tanks.

So am I the only one that feels like the engine is more responsive when a car (any car) has a full tank of gas versus bordering empty? No I haven't dynoed my car with various gas levels but this has been my life long observation using the good old butt-o-meter. Pulling out of a station with a full tank, the car feels noticeably different than it did when I pulled in. I understand what you're saying about drag racers but they are usually running racing fuel, specialized fuel pumps and don't have 20 gal fuel tanks...(the serious ones) so it's a bit like apples to oranges.

Anyone else care to chime in?
Modified by DrewQ45 at 7:32 AM 6/1/2006

[maxnix]

BBVQ is correct, you are also in that the fresh tank of gas is colder and more dense, so a little more energy per unit volume than after it is heated.

All supposing there is no condensation or other contamination from bad UST.

Now we have to add ethanol to the list of dilutants. Q45tech has some good posts on this topic, among many others.

[ceningolmo]

Just keep fuel in the tank, say 1/2 or more and you should make it until your new fuel pump and O-ring arrive. Many of us have driven with that "hum" for months before changing it, but ran the risk of frying our FPCM like idiots>> Changing the fuel pump is almost like a right of passage!

Agreed! It was the first job I ever did on my Q, and it gave me the confidence to work on some other things. In fact, I just did my second fuel pump last night by changing out the one on the Silver Q.

My Silver one has been humming since I bought it in March. Since I wasn't driving it much during that time I wasn't too worried about the risk. But, still, there was always the chance of frying the FPCU...and that = bad.

BTW... both times I have changed out my fuel pumps I have noticed a significant difference in performance afterward. The car definately has more pep in its step.

[DrewQ45]

My Silver one has been humming since I bought it in March. Since I wasn't driving it much during that time I wasn't too worried about the risk. But, still, there was always the chance of frying the FPCU...and that = bad.

Aww phoeey... go ahead and fry that baby. This guy named DrewQ45 has a few to sell anyway!

[BobE]

Thx guys, I put the new pump in today. I'd printed out the great post by tangalora which I referred to many times.

[BobE]

Shoot - last week I couldn't even pronounce Meck-A-Nick now I are one!

My Q now runs like it did when I bought it 2 yrs ago.

So if my fuel pump was having to hummm at max speed just to idle & drive gently around town maybe at WOT it could not feed enough fuel. Anyway WOT starts strong like always but now as the tach climbs it compresses me back in the seat like I remembered. Yep, I'm smiling.

[Q45tech]

You hear the hum because the worn fuel pump slows down [rpms] and thus the emitted sound frequency drops...............the sound deadening is tuned for a higher frequency with a new pump............not to mention the frequency response [sensitivity] of human ear increases as the frequency get down to 500-2,000 Hz.

Easy to look with an oscilloscope and measure the pumps rpm...... new vs used vs failing.

http://www.reliance.com/prodserv/motgen/c7090/

[Bayarea Q]

I replaced my humming fuel pump. Exactly 13 months ago at Marin Infiniti. Bought the pump from Joe, 95Q with about 130K (Original pump)

To my surprise my car died on the way home last week. Took to shop & it's the FPCU....looks as though the dealer was right these should both be replaced at the same time. Master tech says the FPCU was at 10.5 ohms, and needs to be about 2.5.

They gave me the old FPCU and I took apart. The bottom right prong was toast...and on the inside the wire turned into a little puddle. My point being my preventative maintance didn't work out this time. This $1K job hurt a little because I just put a new set of 245/45/17 W rated tires on. (Drives great by the way) and a new radiator.This morning I was greeted by the TCS & slip buttons lighting up my dashboard. I guess I new it was only a matter of time before Q45 Tech's warning of the 120K - 150K expense came true.

[BobE]

"not to mention the frequency response [sensitivity] of human ear increases as the frequency get down to 500-2,000 Hz."

Actually the human ear is most sensitive around 3.5 KHz.