Polo Strange Noise Near Fuel Tank

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matthew.bicknell
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Polo Strange Noise Near Fuel Tank

Post by matthew.bicknell » Wed Jun 13, 2018 11:40 pm

Hi all,

Wondering if anyone could shed some light on what the strange ticking/vibrating noise is that is coming from near the fuel tank under my car. The noise started about 3 weeks ago from memory.

The noise can be heard inside the back end of the car especially around the rear footwells/tunnel.

I have attached a link to my onedrive folder containing 2 videos: 1 of the underside of the car and another of the inside of the car demonstrating the sound. There is also a photo of the idling RPM too.

https://1drv.ms/f/s!AkMrqw9ifexFnDNgHv7snELkfvlJ

The noise seems to be coming from the cylindrical silver thing under the car that is shown in the video but I am not 100% sure what this is.

The car is just out of warranty by 2 months so hoping someone could give me some suggestions.

Thanks,

Matt

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Re: Polo Strange Noise Near Fuel Tank

Post by RUM4MO » Thu Jun 14, 2018 6:29 pm

That silver cylinder is the fuel filter/pressure regulator assembly. I’d expect any noises to come from either that or the low pressure fuel pump which should be down there - thoughI’ve never actually spotted it.

I’ve never been aware of any noises from that area on my wife’s August 2015 one that is same as your model.

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Re: Polo Strange Noise Near Fuel Tank

Post by matthew.bicknell » Thu Jun 14, 2018 11:37 pm

Thanks for the info RUM4MO

Going to contact the dealer and see how I get on. Shame the car is just out of warranty though.

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Re: Polo Strange Noise Near Fuel Tank

Post by veteran » Fri Jun 15, 2018 12:17 am

On my Polo 1.2, under the rear seats, there's a large access cover and electrical connectors for what I understand to be one of two fuel pumps. Its position corresponds to the top of the fuel tank. It's noise coming from that that you can probably hear. Just lift you rear seats, pull aside the bit of carpeting there, and you'll see what I mean. It's no surprise therefore that you can hear it "inside the back end of the car, especially around the rear footwells/tunnel".

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Re: Polo Strange Noise Near Fuel Tank

Post by alexperkins » Fri Jun 15, 2018 1:02 pm

The TSI has a high pressure fuel system so its quite possible its the fuel pipes vibrating against the plastic housing underneath and should be fixable by adjusting their position slightly.

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Re: Polo Strange Noise Near Fuel Tank

Post by wolfie » Fri Jun 15, 2018 3:45 pm

alexperkins wrote:
Fri Jun 15, 2018 1:02 pm
The TSI has a high pressure fuel system so its quite possible its the fuel pipes vibrating against the plastic housing underneath and should be fixable by adjusting their position slightly.
I've also posted on about this subject in another thread. Now this is all based on thinking about it, as opposed to having any real proof, but here goes. I'm of the same mind as yourself, I suspect the "tick" is simply caused by pressure pulses coming back down the fuel lines from the high pressure pump. I suspect the fuel filter has a none return valve and that the pulses may be causing it to close under certain cercumstances, thus you hear the "Tick"

The TSi fuel system is quite complex, the lift pump in the tank is controlled by a little PWM gizmo so the fuel delivered to the high pressure pump can actually vary in pressure even before the high-pressure pump does it's stuff.

If I'm 100% honest I bought my little Polo 1.2Tsi as a keeper, though I'm not sure it was best decision I've ever made as they look as if they have the potential to have quite complex problems as they age. That's not counting the known issues like cam chains. (I'd want mine done if I kept the car much longer) I actually caught myself looking at a CityGo the other weekend so I must be getting that itch to swap.

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Re: Polo Strange Noise Near Fuel Tank

Post by RUM4MO » Sat Jun 16, 2018 4:55 pm

alexperkins wrote:
Fri Jun 15, 2018 1:02 pm
The TSI has a high pressure fuel system so its quite possible its the fuel pipes vibrating against the plastic housing underneath and should be fixable by adjusting their position slightly.
Alex, remember that while the TSI engines have a high pressure fuel system, the electric pump near the tank is only a normal pressure one, ie known as low pressure and it lifts the fuel up to the mechanical high pressure pump which is mounted above the cam shafts. Your points about fuel pipes moving and so maybe causing noises is spot on though. The only trouble I've had with a 2015 1.2 16V TSI 110PS is the low pressure fuel line was banging off or just touching and so chaffing the rubber and polishing the A/C discharge pipe, I sorted that with a bridging clip so that it gets held away from the A/C discharge pipe - ie like it should have been for that age of car going through the factory!

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Re: Polo Strange Noise Near Fuel Tank

Post by matthew.bicknell » Wed Jun 20, 2018 10:00 pm

Took it into the dealers and spent some time with the master tech going through this (luckily for free mind you)

He disconnected the fuel pump briefly and the noise stopped, reckons it might be a noisy pump...going to put in a claim of gesture of good will to VW uk, hopefully I will be lucky.

Do fuel filters have a tendency to make a noise at all or are they a silent part do any of you know?

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Re: Polo Strange Noise Near Fuel Tank

Post by alexperkins » Wed Jun 20, 2018 11:55 pm

Fuel filters don’t tend to make noise. It’s just a static filter. No moving parts

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Re: Polo Strange Noise Near Fuel Tank

Post by wolfie » Thu Jun 21, 2018 9:41 am

alexperkins wrote:
Wed Jun 20, 2018 11:55 pm
Fuel filters don’t tend to make noise. It’s just a static filter. No moving parts
Ah right, cheers for that. I sort of rationalised that the "tick" may simply be originating from a non-return valve within the filter under certain conditions. More trying to convince myself it would be a cheap-fix as anything, though it never is, is it!

I really don't know what's going on with Vdub build & quality, it appears to have gone down the pan. They're probably cutting corners in order to save enough pennies to pay all their fines.. :lol: :lol: :lol:

What's more scary is the price of a new feed pump. A quick 30 second 'Goolge' has them ranging from £210 ish, to over £300. I can't find any high-pressure pumps listed, but I dread to think how much one might be.

Thanks

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Re: Polo Strange Noise Near Fuel Tank

Post by RUM4MO » Thu Jun 21, 2018 6:37 pm

Don't some of these cars have a pressure regulator built into the filter housing, originally it was located in series with the filters but eventually it was moved inside the filter? I can't say if that makes any difference, I'm just raising the point.

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Re: Polo Strange Noise Near Fuel Tank

Post by wolfie » Thu Jun 21, 2018 7:38 pm

RUM4MO wrote:
Thu Jun 21, 2018 6:37 pm
Don't some of these cars have a pressure regulator built into the filter housing, originally it was located in series with the filters but eventually it was moved inside the filter? I can't say if that makes any difference, I'm just raising the point.

This appears to be the same type of filter fitted to the Polo Tsi. Bit of a ropey video, but it does look as though it may possibly contain a non-return valve of some sort. (I wouldn't be 100% though just from that)

https://www.youtube.com/watch?time_cont ... ZNyKB5rjik

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Re: Polo Strange Noise Near Fuel Tank

Post by RUM4MO » Thu Jun 21, 2018 11:08 pm

Sorry, I should have said, if the filter only has 2 pipes it will not have a pressure regulator incorporated into it, but if it has 3 pipes it like the one in that video it will have a pressure regulator in it.

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Re: Polo Strange Noise Near Fuel Tank

Post by matthew.bicknell » Thu Jun 21, 2018 11:34 pm

Image

From this photo (under my car) you can see the fuel filter has 3 pipes (2 on one side and 1 on the other) Would that be correct to assume it is pressure regulated? If so can these make a noise when they need replacing?

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Re: Polo Strange Noise Near Fuel Tank

Post by RUM4MO » Fri Jun 22, 2018 12:23 pm

I can't see the picture, but if there are 3 pipes associated with that filter, then it will have a built in fuel pressure regulator.

Your next question I can't answer, ie "can it make this noise etc", sorry, someone else might improve on that.

Edit:- on the "when they need replaced" front, my wife's old 2002 Polo 1.4 16V 75PS had a separate filter and regulator although the regulator was mounted onto the end of the filter, a silly idea really as after many years the regulator casing was probably fit for replacing along with the filter - VW Group do not it seems give that filter a service life. Now that Polo was sold at 13 years old and 105K miles with its original filter and regulator still on it.

So, if your problem is the regulator, then it has failed or being forced to make that noise for some other reason - or the source/root cause of that noise is elsewhere.
Last edited by RUM4MO on Fri Jun 22, 2018 12:30 pm, edited 1 time in total.

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