Fuel pump humm?

[911hillclimber]

987.2 2.9 with 92k on the clock.
Runs very well and smoothly.
Anyone had a pump humm when car running, esp the high pressure pump on the engine?

 

[malarcy]

Don't think the 2.9 has a high pressure fuel pump - that is on DFI engines only isn't it?

 

[911hillclimber]

Hope and think you are correct. No such pump on the humble 2.9 engine.
The rear humm I’m trying to identify on the car sounds just like a fuel pump, hence my suspicions of the pump on the engine, if it has one.
Thank you for the reply, it all helps me.

 

[malarcy]

Have you considered anything on the serpentine belt - a/c, power steering, alternator, waterpump - or the pulleys themselves - you can remove the belt and run the engine briefly to see if the noise goes away ( only if you can reproduce stationary of course) - or manually spin the various bits to see if you can feel any roughness in the bearings ?

 

[911hillclimber]

The humming chimes in at 40 mph no matter the gear/ revs, does not change with road speed until 60 and then drowned out by tyre and engine general noise.
Belt changed last service.
Many think it is tyre noise, can’t get to the bottom of it.
Ruins a good car.

 

[Motorhead]

As Paul has indicated, only the 3.4L engine in the 987.2 series had the DFI engine with a high pressure fuel pump Graham, so you can discount that as being a source of your problem, although a pump of some kind could be a source since it seems as though it’s a constant frequency, which would rule out anything engine-related like ancillaries.

Definitely I reckon that it would be worth trying a nitrogen fill for the tyres, the rears at least. It shouldn’t be too expensive and I’m sure that you can find a tyre shop in your area which offers the service if you look online. For context I think that Lexus was the first manufacturer to use it for their first car, the LS 400 which was noted for its refinement, and maybe in part to overcome an NVH issue. If it doesn’t work then I guess that a tyre-related source would drop down the list of possible sources even if it couldn’t be ruled out completely, and a nitrogen fill has other benefits including a more consistent tyre pressure with temperature and better pressure retention.

Jeff

 

[911hillclimber]

Thanks Jeff and Paul too.
Im a bit of a dog with a bone on these things, got to find a solution but the simplest way.
Nitrogen fill is easy I think, lots of industry round here and big tyre fitters.
Will try it when back off holiday.
I think my long long suffering wife is ready to give a permission for 2 new rear tyres just to shut me up…

 

[Motorhead]

Have a look at this Graham. As a 987.2 Boxster owner you’re eligible to sign-up, and you can get free nitrogen refills at a Porsche dealership … although most likely you’ll have to wait months to get an appointment!

Custodians

Join the Custodians membership programme for access to Classic Genuine Parts, exclusive membership packs and the ORIGINALE magazine. Sign up now.

www.porsche.com

Jeff

 

[911hillclimber]

Thank you Jeff, but a local fitter can do this for me just down the road, prob on the day.
Finding time is the awkward bit, every day seems free on the wall chart, but something suddenly arrives!

Drove the car at 34 psi all round on Sunday last and the drone seemed less pronounced, but that might be just a bit of jet lag as we got home a few days before...

Have more than a few details to sort on my '73T 911 as we are hillclimbing it at Shelsley Walsh for a bit of a 'lark' at their Classic Nostalgia weekend.

 

[Motorhead]

Driving in this extremely hot spell, tyre pressures and tread temperatures are all over the place Graham, and which could affect the drone. A nitrogen fill’s probably the last throw of the dice for something relatively cheap and easy to try before you’re into a possible tyre change.

Hope the hillclimbing goes well this weekend … and that the old girl behaves herself!

Jeff

 

[911hillclimber]

Thanks Jeff. The hill event is weekend after this coming, hope the temps will have dropped (a lot) by then.

The 911 is cosseted as much as the Boxster, but is a very simple car owned for 38 years now, it has only broken once in that time when a new clutch friction plate failed. Hill climb starts are usually very hard...
And the 911 is harder to drive to compared to the Boxster!

Great fun though.
Am I allowed to bring an old 911 into all this modern water cooled stuff? lol

 

[Motorhead]

Absolutely Graham! Much as I admire the later 9XX cars, you really can’t beat a genuine 911.

Some great pics there.

Jeff

 

[911hillclimber]

None mine, but by Stuart Wing a real pro at catching cars 'just so'.

We are allowed open pipes for the meeting, so lots of evocative soundtracks...
Oddly, the open 911 engine meets the correct noise levels with all 3 pipes open.