fuel pump noise
I have had a whine noise from the rear of my G-wagen at slight throttle openings. Initially I thought it was from my rear diff but whilst sat in the yard yesterday whilst sat in neutral I opened the throttle slightly & could hear the noise.
I'm now pretty sure this noise is under the boot floor area so I'm assuming this could be the fuel pump?
At tick over there is no noise, slight throttle opening the whine / buzz noise, heavy throttle / engine load and the noise goes away?
Any suggestions?
Fuel pump for the 463 is under the n/s wheel arch.
There is a vent valve positioned on the inside of the o/s inner panel, this can make a buzzing noise on light throttle.
Ah finally someone with the same symptoms! I have had this noise for a year, on and off, and been trying to diagnose it (the clumsy trial-and-error way, not the proper technical-rep way), without much success.
It is not all bad news, 1 thing that did affect it I can share:
under your farside rear fender is an activated charcoal filter (part number A 129 470 0059) that is part of what MB call the "closed fuel evaporation control system", my interpretation is it allows the fuel vapour from the tank to vent out to the atmosphere, once this filter separates the fuel (returns to tank) from the air (goes out through rear side vents outside vehicle). After changing this filter on mine (a pain of a job because it seemed never to have been changed before, and they will not want to budge easily), the noise ceased for 2-3 months.
Interestingly, the old filter, was quite heavy when it came out, and after leaving it in a room for a couple of days (level), I tilted it and out came a good quantity of petrol. It appears to work on the basis of adsorption, and lets the fuel out when the car is not in use, but it obviously has a limited lifetime.
I am on to another clue, underneath the fuel tank, if you look through one of the holes in the protection, there appears to be a cylindrical metal thing, does anyone know what that is? The EPC appears to show two fuel pumps, one with the filter and accumulator package and one on its own with a valve (A0030915301), might this be the thing under the tank.
I'm reluctant to remove the tank protection to find out, as I believe it holds the tank in place, but I know things are not right because...as the fuel level is so low that the engine cuts out on roundabouts and turns, I KNOW there are at least 20 litres in the tank (just drained it today), so something must be stopping it making use of that last quarter.
I wouldn't bother changing the fuel vent itself, as it is a cheap part, but accessibility makes it a royal pain to get to, and it did nothing at all to my problem (I still have the old one, and it cost me a new seat belt..but that's another story).
Anybody with ideas....lemme know!
Btw. the fuel tank operation today was to dismount the charcoal filter and fit it more loosely so it doesn't press against the hoses at the end. I suspect this might have blocked the exhaust route of the vent valve, will see how it goes in the next couple of week.
There are two fuel pumps, one is a limp home mode one, on my mates 300 463 both were located on the off side wheel arch behind the arch liner.
Thanks for the info PP, I guess that is next in line for a change then! Will see how things go afterwards. Out of curiosity, if your mate's 300 an SWB or LWB?
Finally got round to removing the fuel tank protector (which comes out without having to remove the tank), and found the primary fuel pump, before the fuel supply goes to the pump/filter/accumulator group under the wheelarch.
The 2 pumps according to the EPC are the same, so I suppose a change is in order every 2 years or so. The first pump seems to suck from the bottom front of the tank, and I suspect this might be contributing to my problem of not being able to use the last 20litres or so of fuel in the tank.
Hope to change the pump soon and will see if I can put more than 60litres into the tank!
my mates is a swb
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