Fuel pump humming.

Discussion in 'Engine' started by John Jones Jr, Apr 14, 2014.

  1. John Jones Jr

    John Jones Jr Hardcore MB Enthusiast

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    I noticed yesterday after coming back from a 60 mile trip the fuel pump was humming and I mean really humming, not the light sort of humming one normally associates with an externally mounted fuel pump. And it was the same today.

    Now, I replaced the pump with a quality Walbro only 3000 miles ago along with the fuel filter, the only other difference is that I have in the last week filled the tank to the brim twice and let it run on both occasions to either a 1/4 or nearly empty.
    One other point that came to my attention is that the humming is barely noticeable from a cold start, it seems the humming is induced when the pump has run for a couple of hours.

    Normally, I would reckon the pump is on it's way out in the above situation, if it was an old pump but since it's not I'm at a slight loss. Anybody got any ideas other than a fault with the new pump?

    What has crossed my mind is that I've recently ran a lot of fuel through the system including two full to the brim tanks, is it possible that the fault is due to fuel filter becoming partially blocked, after using all that fuel suddenly it cleaned out the tank thus the pump is under pressure, gets hot and excessively hums?
     
  2. AndyPCD

    AndyPCD Registered User

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    What car is it on. Is it the 202.

    If it is i would be looking at the fuel filter first. Have seen this once before on a 203. It would only start to buzz when the car had been driven for a while.

    Replaced it with a genuine filter and the noise disappeared. It had been fitted with a aftermarket one.
     
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  3. OP
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    John Jones Jr

    John Jones Jr Hardcore MB Enthusiast

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    Just what I was hoping to hear Andy, thanks.
     
  4. Touche

    Touche Active Member

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    Could be fuel filter. Could be the something touching the fuel pump. Could be the fuel pump.

    Easiest thing to do is change the fuel filter and check there is nothing is touching. A genuine one only costs a few quid. See what happens, hopefully it'll do the trick.

    Else you can get a cheapo pattern pump from Eastern Europe on ebay such as this for just over £40 delivered (I think they're about £250 from a stealer):
    MERCEDES C Class A208 S202 W202 C208 CLK 1993-2002 Electric Fuel Pump 1.8L-3.6L | eBay
     
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  5. OP
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    John Jones Jr

    John Jones Jr Hardcore MB Enthusiast

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    No, there's nothing touching the pump, so I'll go with a new filter first and see what's what after that.

    If it's the pump that became faulty of it's own accord which I'd be a bit surprised at (rather than a clogged fuel filter causing the problem and possibly damaging the pump) I'll opt for a Bosch pump as I reckon they are a better investment that the real cheapo's. If the filter is clogged and the pump is doubtful and I'll get another Walbro.

    Fingers crossed the car makes it to the south coast tomorrow early a.m., hopefully it does and then I'll get the filter changed down there.
     
  6. OP
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    John Jones Jr

    John Jones Jr Hardcore MB Enthusiast

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    A little update: inspected the new'ish fuel filter today and it was for of crap, the petrol that came out of it looked like muck! The pump is still humming, not as much as it was but humming 'I'm kaput, replace me!' So, dirty tank = new pump required, life...
     
  7. E270 Owner

    E270 Owner Hardcore MB Enthusiast

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    I would flush the tank and lines before fitting the new pump.
     
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  8. OP
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    John Jones Jr

    John Jones Jr Hardcore MB Enthusiast

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    Any idea what's the best way to flush the tank on a W202 (saddle type tank) without removing it?
     
  9. horatio

    horatio Hardcore MB Enthusiast

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    I fitted a Sytec (rebranded Walbro) and it whined - sent it back and they said it wasn't faulty. It was fitted with a new Hengst filter.

    Replaced it with a Bosch one and its totally silent.

    * BTW I bought the Bosch from the green spark plug co. and they were great.
     
    Last edited: Apr 15, 2014
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  10. OP
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    John Jones Jr

    John Jones Jr Hardcore MB Enthusiast

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    I can't blame the Walbro even if I reckon the Bosch is the better pump (well, you pay for what you get at the end of day, no doubt). This pump simply failed or is failing due to loads of dirt in the tank. In fairness to it, when I originally fitted it was less noisy that the Bosch I took off.

    I'm still in two minds which pump to get this time, might go for a cheap & cheerful one initially (like Touche posted) just in case I don't manage to clean the tank out fully, or if I've any doubts about it's cleanliness. I'll check out the above company you mentioned anyway, cheers.
     
    Last edited: Apr 15, 2014
  11. OP
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    John Jones Jr

    John Jones Jr Hardcore MB Enthusiast

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    No humming now, just a mild buzz! :D, due to a replacement fuel pump & filter. .

    I had fitted a new filter just prior to having the car on the rolling road last week, and as I mentioned in this thread the filter that came off was full of dirt and it was a lot of dirt considering that filter had only done 3000 or 4000 miles. While fitting the pump this morning where I used the facilities of Pit Start - About Us run by Kushan, I also changed the oil & filter while I was there. I inspected the one week old filter (blew it out) and fuel coming out was as clean as whistle - mind, there still could be dirt trapped in that filter too but seems unlikely. So, on that basis I didn't clean out the fuel lines even if good practice would dictate otherwise. But, I suspect the original filter I fitted last year did its job even if the pump got wrecked.

    Anyway, two fuel pumps & three filters later...:wallbash: :D
     
    Last edited: Apr 22, 2014
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