New Fuel pump noise after replacement

[ericthered]

With 149K on my '94 Q45t I decided that my intermittent fuel pump noise was louder than it should be. I've driven over 250K in three different G50's, and had never done this before, but this car is a keeper, and I hate to worry about reliability. When I made the change, the FCPU looked cherry inside.

So the former loud HUMMMM is now replaced by the usual lesser humm (fuel pumps all make some noise, IMO), which is nice - but also a hissing sound, almost reminds me of the sound house plumbing makes while a toilet is running. As if the fuel pump is running at a higher speed, and I hear the flow of fuel. I've driven it over 1500 miles since. This noise is heard all the time, full or empty tank, highway or driveway.

This is my 3rd Q and I have never heard this before. Any ideas on what this is? And how I might make the noise go away?

Eric

[1990QOwner]

Was the replacement pump you put on it new or used?

[ericthered]

New from Scottsdale, as usual.

[maxnix]

And new O ring also?

Does you gas cap have pressure?

Most experienced G50 users never go below quarter tank full.

[ericthered]

You mean the o-ring between the tank and the fuel pump flange - no. Didn't come with the pump :-( It was a pain to get the old one seated correctly, but got it eventually.The tank holds pressure at the cap, so it is OK.

[Jesda]

You -MUST- use a new o-ring.

[maxnix]

You mean the o-ring between the tank and the fuel pump flange - no. Didn't come with the pump :-( It was a pain to get the old one seated correctly, but got it eventually.

One has to order it, but Joe and his crew invariably suggest it as the old may look good, but is not as compliant. Then of course even torquing of the screws in a star sequence is required.

But, it is truly holding pressure long term.....

[Q451990]

I think it might be worth checking your fuel pressure (t in right after filter and tape gauge to windshield) to see if it's running in a higher mode than it should. I guess it's possible to get a pump with a defect??

Heath

[Q45tech]

Did you clean out the fuel tank and replace fuel filter prior to installing new pump?

Ethanol in gasoline reacts badly with fuel pumps and tank insides and rubber hoses and injectors.

Use E10 at your own risk and reserve extra funds to frequently replace fuel system components.

http://www.jwardell.com/mini/2...blems/

http://eied.deh.gov.au/atmosph....html

[StarPD]

Did you clean out the fuel tank and replace fuel filter prior to installing new pump?

Ethanol in gasoline reacts badly with fuel pumps and tank insides and rubber hoses and injectors.

Use E10 at your own risk and reserve extra funds to frequently replace fuel system components.

http://www.jwardell.com/mini/2...blems/

http://eied.deh.gov.au/atmosph....html

Q45tech, I note that many of your posts rag on the so-called "oxygenated" fuels, like the ones that have ethanol or MTBE as additives. I can't agree with you more. Those adulterated fuels suck big time. I can tell the difference in power and fuel mileage when I go somewhere I can get what I call "REAL" gas.

Problem is some of us live where there is NO choice. In Phoenix, where I live, I have to go so far for real gas that I burn it all up returning home. For us, we are just screwed, plain and simple.

I hate to tell you, but you can expect it where you live too if you are anywhere near a large city, or in a place like SoCal. Even rural areas can expect to see the crappy alcohol or ether diluted fuel sooner or later.

I guess there's no real answer. Those of us who live where we have no choice are just stuck. I would however like to see car makers design fuel systems capable of handling the "gasahol", and even provide updated components (like injectors) that will tolerate that crap for older cars.

Sorry for the rant, but having to burn that stuff is bad enough Being reminded of it just gets me going again. Giving up 15% power and fuel economy, not to mention fuel system component life is the pits.

[Q45tech]

Make your own gasoline, or remove the ethanol from gasoline, or move to an area temporarily without ethanols.

The choices are endless...............or accept the minor consequences and change fuel components as they fail.

[ericthered]

Seating the O-ring was the hardest part of the whole job for me.The bugger would slip out one side of the groove when the rest was seated.But I have heard the vacuum when I opened the gas cap after the first time I ran the car.

The tank was visually completely clean when I looked in, the same before versus afterwards. I changed the fuel filter between 5 & 10K miles ago, but they last longer than that.

I can check the fuel pressure, I think I have the gauges to do so buried somewhere, that might give me another diagnostic clue.

This noise occurs with or without the gas cap, too.

But seriously, so far no one has suggested why this hissing noise started the moment I installed the new fuel pump. I guess this hasn't happened to anyone else before?

[maxnix]

Probably not, but we all use new O rings. The one or two that didn't had to redo it with a new O ring.

[ericthered]

Just drove the car for the first time since Friday.

No noise!

Filled it with gas.

Still no noise!?

Didn't do anything to fix it, but noise is gone.

So I am unenlightened but happy, :-) (for now)

My real guess was that the FCPU was telling the fuel pump to pump more than it should, thus the hissing sound from excess back flow. Or maybe is something in the gas return circuit that didn't work right. Maybe purging the gas (using the standard pull-the FP fuse method) left air in it that cuased it to temporarily malfunction.

Theories abound, but maybe, hopefully I will never need to know!

[1990QOwner]

That is very odd. Could it have been the new pump breaking in or something? It also could be something to do with the fuel pump control module. My fuel system went down a while back and the shop told me it was the fuel pump. It ended up being the fuel pump control module, the actual pump outlasted the control module. You may want to check into it so that it you aren't stranded somewhere when the thing finally snaps.

[maxnix]

My fuel system went down a while back and the shop told me it was the fuel pump. It ended up being the fuel pump control module, the actual pump outlasted the control module.

The shop was probably correct. It probably was the fuel pump (or a previous one) drawing too much current in failure mode that did in the FPCU.

[Magnum PI]

how much is a new FPCM and how difficult is it to install? I recently had stalling and sporadic rough running. But added seafoam and it seemed to get better. Also found a tiny vacuum leak in a plenum hose, but doubt that was the problem. Fuel pressure checked out fine and we even ran it for a long time to see if it would drop. Now it runs great, but thinking it might be the control module or the fuel pump.

[1990QOwner]

I got a used one off of eBay for about $50 shipped. Most people on the forums don't like getting anything but new OEM. I'm guessing you can get one from Joe at Scottsdale Infiniti for around $200 to $300 (wild guess). It is quite easy to replace once you get to it. It is located right under the rear sundeck to the right side of your fuel pump, there are 2 modules there and the fuel one is the smaller one. When you get your replacement one than you can just unplug the one and plug the other in, it is quite simple. But you do have to take out the back seat and the rear sundeck to get to the bolts. Use the search feature and you will find detailed threads on every step of replacing it. Let us know how it goes.

[1990QOwner]

The shop was probably correct. It probably was the fuel pump (or a previous one) drawing too much current in failure mode that did in the FPCU.

I still have the old pump, it never even made any noise while in service. I tested it after and it still goes fine...and besides it would work on and off before I replaced it. When I installed the new one than it did the same thing, it worked for a second or 2 than the car would die.

[Magnum PI]

Thanks, I may look into this if the symptoms return. It is frustrating, but for a 14 year old car, it still is an awesome example of excellent engineering.

[maxnix]

I still have the old pump, it never even made any noise while in service. I tested it after and it still goes fine...and besides it would work on and off before I replaced it. When I installed the new one than it did the same thing, it worked for a second or 2 than the car would die.

Without psi data vs. rpm and throttle opening, these observations are inconclusive of anything. Either pump may be fine.

[DrewQ45]

I have two FPCUs on the board if needed...

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