Fuel Pump noise in stereo

[bobbysky]

Okay this is on my new to me 09 23lsv with jbl black box stereo.

I got noise in my system. After as much diagnosis as I can figure out, I think it's coming from my fuel pump. It's a pretty low hum that doesn't change with rpm's. I can hear it as the fuel pump primes up, then stops, then when you start the engine it starts again.

Things I've checked and done.

1. Rewired blue seas switch so that + for amps and ignition wire for stereo are on the switch going to second battery. All other house loads and starter are on the first battery. Noise was present before and after rewire. Originally I had the blue seas set up with house and stereo on second battery and just the starter on the first battery there was noise with this setup as well.

2. Stereo positive, ground, mem are wired directly to one amplifier + and -

3. Checked all power and ground cables at battery, starter, alternator, ground bank under helm. All tight.

4. Gains on amps are set a bit above half way, but before you scold me, I installed a 7v line driver eq. With that line driver I was able to turn my gains, all the way down. But the noise was much more amplified than it currently is without the eq. Other accessories actually presented noise with the eq as well, Interior LED's, blower, and bilge. So I removed the eq, this stopped the accessory noise, but not the fuel pump.

5. When I had the eq installed, I completely bypassed the jbl black box and wired directly into the amps and noise was still present. And yes I wired + and - and switched directly to the amps for the eq's power source.

6. Tried new RCA cables to the amps verifying they are no where near power and ground cables, noise still present.

7. Ground loop isolator. This stopped the accessory noise when I had the eq hooked up, but not the fuel pump noise either with the eq or without.

I feel I have tried everything I can to rid the system of the noise. The only other thing I can think of is taking out the jumper ground between the two batteries and running a separate ground for the house and starter, so that the stereo is on it's own completely separate ground circuit. The other thing I was thinking is that I haven't found how the fuel pump is grounded, and maybe there is a lose connection on that causing a noise issue, but that doesn't explain the accessory noise I heard when the eq was present. Is there just this much noise with all the electronics in these new boats?

I'm stumped any advice???

[Deephaven]

No one should scold you for setting your gains anywhere as long as your input sensitivity matches where they are set. I've run quite a few amps that have NO noise when the gains are pretty much cranked. In the world of Ipod's as sources and such this is a regular reality and exactly why there is a gain knob. What someone should do is scold you for wasting money on a line driver when it did absolutely nothing for your application. Exactly why I despise the carte blanche recommendation of them. Nice work on tracking down the "need" for it.

It sounds like you've tried a lot of things. Just to clarify. All your stereo grounds are common? ie, none to a different location? Have you tried to ground your RCA's? Is it there with no RCA's attached to the amps? Is it in all your amp channels or just some?

[bobbysky]

All amps are common grounds, one big wire to a distro block then to amps. Funny you mention the rca's, so I have an amp hooked up for tower speakers but I haven't got my rev 10's yet so I can't confirm if there is any noise on that amp or not. But I did try rca's from the front and rear outputs of the jbl box to my in cabin speakers with no solution. And for my sub amp I'm not sure if it's causing noise or not, never put my ear up to the sub with the engine running.

If I unplug the rca from the amps then I believe it gets rid of it. Could the JBL black box be the cause of it? I tried unplugging the mux controller that runs to the jbl to isolate the the mux switches from the black box, but that didn't help either.

Edited May 1, 2012 by bobbysky

[shawndoggy]

when you had the EQ installed, did you get the noise on the aux input too? Did you try the eq without the black box plugged in, but say running an ipod through the aux input?

Do I read #2 above to state that you moved the black box power and ground right to the stereo battery?

[TallRedRider]

This might sound mighty foolish, but I was tracking down this same exact scenario in my Mastercraft. After double checking everything, I realized the noise was not even coming from the stereo, the freaking fuel pump just made a high pitched noise that sounded like it was coming from the stereo. Not too long later, the fuel pump failed and the problem was fixed with the new fuel pump.

Just figured if I was dumb enough to not realize where the sound was coming from, that maybe it could happen to someone else. That high pitched noise just filled the room, and I could only assume it was coming from the speakers.

[Bobby Light]

I'm with Tall on this one, I have the same boat and same noise but its not in the stereo its the fuel pump making a high pitch whine. I too thought it was the stereo for a minute but eliminated that possibility. The sound is very decieving.

BTW when you get that noise squared away throw that eq/line driver back in and see what you think. It's a good addition to the black box systems.

Edited May 2, 2012 by Bobby Light

[bobbysky]

Yes I tried bypassing the blackbox all together and running the iPod directly of the aux. Also yes I'm running the stereo positive and ground directly to the amp and the keyed power to the blue seas on off switch therefore bypassing having to turn on the malivue to run the stereo.

No the noise is definitely coming from the speakers not the fuel pump itself.

Oh and when I had the eq in it was awesome. But couldn't handle the amplified noise.

Edited May 2, 2012 by bobbysky

[shawndoggy]

I'm pretty sure you just need to work methodically back up the signal path component by component. Start at the amps and run a known good source (ipod?). Then work back up to the black box. Something in the chain is causing the noise if it's not there with the RCAs unplugged.

[Bobby Light]

Worth a shot, I know the noise you're speaking of. Keep us posted on what you find causing it. I would work my way backwards in the ayatem until it goes away and you'll find the culprit.

[bobbysky]

Just went and plugged iPod directly into cabin speaker amp, noise still present. Unplugged rca cables completely, noise still present. Turned off amp noise went away, obviously. So I'm thinking ground but I'm pretty sure I checked all the culprits. When I put my ear up to the speakers I could still here accessory(leds, blower, bilge) noise as well, although faint, when the eq was hooked up it amplified that and fuel pump noise to unbearable levels.

Could I have a bad amp?

[Bobby Light]

If you removed the signal input (RCA's) to the amp and it still makes the sound than you have a ground issue or bad amp.

[Deephaven]

And if it's the amp, it's probably a ground issue in the amp. If they are out of warranty it's worth pulling the cover and checking the ground path.

[Earmark Marine]

Bobby,

You are not quite done yet.

You cannot have meaningfull diagnosis until you have confirmed you have good voltage. So make sure you are well above 12 volts.

You cannot have good voltage without good grounds. Measuring with low current draw with a meter can be deceiving as a bad connection may not be exposed until you are passing some decent current. So double check all grounds and in particular the helm buss ground, amplifier ground and the battery to engine block ground. Give a good pull on the terminations. Bad connections can appear fine.

Disconnect all in-boat speakers and the connecting in-boat wiring. Use a test speaker and a short jumper lead on one channel only. All it takes is the tiniest, single strand of wire to be touching something it shouldn't. And if it was related to a tweeter you would be unable to measure a short downstream from a filter capacitor. Once you circumvent the amplifier's internal isolation with an external short you will invite every form of noise possible into the audio path. Keep in mind that RCA grounds and speaker grounds are well above true ground.

If you still have noise with no amplifier input and a test speaker/jumper wire then it is either a bad amplifier or a boat-specific problem.

All boats are going to have some noise and ripple carried on the supply/ground. It is just a matter of how much is normal. However, with amplifiers DC/AC/DC power supplies, the audio section is normally totally isolated from any noise that travels down a primary supply cable.

Any amplifier manufacturer can give you the factory specs on the intended resistance value between the RCA ground and speaker output ground and the primary ground. If you measure a discrepancy from the factory specs then you have a pretty good idea how the noise is getting into the audio path. You normally wouldn't have to send the amplifier in to determine a noise-related problem. But if you find the problem it is usually a very simple repair.

If this doesn't reveal the cause of noise then we can go onto diagnosing the boat.

David

[bobbysky]

Thanks David I'm going to give that a shot and see what I come up with.

[sledandski]

Bobby,

I know that this post is a year old but I was wondering if you every found the issue or if anyone else has solved this?

I have a new to me 2002 21 lsv and have the same issue. Only difference is that I basically have a head unit and 4 speakers (stock system). When the dealer took the boat in on trade they put in some cheap head unit as the old stock one did not work. They also replaced 2 of the speakers. The noise is only present in the rear speakers and it sounds like the fuel pump. You hear the fuel pump when the key is turned on and then when the boat is running. Weird thing is that you hear the noise even with the stero turned completely off and the music switch on the dash off. At some point the boat is going to get a new head unit but not sure if that is going to change this.

Thanks

[sledandski]

Alright ignore this last post. It's not the speakers. Even when they are totally disconnected I still get the noise. It's coming from a fuel tank fitting. I'll make a new post with more details after I do some more digging.

[Earmark Marine]

In your case, I'm not convinced the noise is coming from the speaker....just the proximity of the speaker. Why? Typically any entry path of induced noise in a simple non-amplified system would affect all sepakers.

Remove the rear speakers entirely and listen again.

Some speakers feature a small inductor/coil capable of picking up noise. For the speaker's voice coil to pick up noise the magnetic field would have to be crazy. In that case I would focus the fuel pump and wiring.

David

[grandude]

Are you sure it's not the alternator noise coming thru. I chased a problem like this for several hours one time and finally found the alternator to be the cause. I found it by powering the amps with a battery that was not hooked to the charging system of the boat, The noise would come back every time I introduced the charging system into the equation. I called an alternator mfg. and they said that this could happen if the @#$%^& was bad or going bad. I forget what part of the alt. that he said. Replaced the alternator and problem solved. At least in this situation.

[sledandski]

I did some more digging and even when I have the stero off and the rear speakers completely disconnected the noise is still there. It seems like it is coming from the fitting in the middle of the rear of the gas tank (I can feel the vibrations when I put my hand there). I think there might be a check valve in this that is rattling something aweful.

Here is a link of the video I took of the fitting while turning the key on. At like 2 seconds you hear what sounds like really bad interference. It shuts off at the end of the video because the fuel pump is primed and fuel stops moving. It will come back once the engine is started and the whole time it is running

[sledandski]

So after looking online a bit there is a chek valve on this joint. I'm going I pull it apart this weekend and see id the spring is broken or something. Dealer said that the check valve is there in case the boat flips over so that all the gas does not run out (uscg regulation). He said I can just pull it out. I think that I will pull it out to verify that is the problem by then a new one is going in if that does fix it. Bakes has them for $30