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is this norm - maybe (long) (archive)

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Posted by milton on September 09, 1999 at 11:15:10:

In Reply to: Noisy Bosch fuel pump on my tii - is this normal?? posted by Oliver Holm on September 09, 1999 at 00:47:43:

Oliver

Yes, they make noise. However, the sound shouldn't be competing with the radio. On my tii, I have to turn off the car to hear the pump (sometimes, I even have to go around to the back to listen for it).

Two things come to mind. There is a canister of about 4-5" in diameter which should be installed in the mount directly after the fuel pump. This is an expansion tank which serves two functions. First it smooths out fuel flow, but it also dampens the fuel pump noise. Make sure that this was not eliminated when the pump was replaced - I don't know if it will lead to failure of the pump, but why chance it? Secondarily, you need to check the operation of your fuel system. Since you report that the noise increases as the car has been run for awhile, I imagine that you may be overburdening the pump somehow. I would check to see that the fuel pressure regulator is functioning properly. You do this by measuring the fuel pressure, and you want about 28psi in the fuel lines preceding the pressure regulator. You will find the regulator in the fitting on the back of the kugelfischer pump where the fuel return line exits. Unscrew that fitting (14mm) to inspect the regulator - you can blow it out with carb cleaner, or dissasemble it for a soak. Beware of two things when working with the regulator. The clip that holds the spring in the pump is easy to loose and hard to replace (outside of Germany at least), and the O-ring sealing the fitting to the pump is of an odd metric size and can be difficult to replace without a good set of metric O-rings. Bob Murphy of the tii register can provide more information and details about servicing the regulator, and there is an article devoted to this part in one of the old register articles.

The other test you should do with the pump is a flow test to figure out how many liters per minute the pump will flow. I would suggest you do this both cold (before startup) and hot (after the noise has increased) to compare flow results.

I imagine that if there is not enough pressure, you can tax the pump over time leading to high sound levels, or that if you are running too much pressure it could have a similar result. Note that if you don't have enough pressure in this system, you motor will be running lean which can be dangerous to your motor.

All this said, I can share a couple of my experiences with tii fuel pumps.

1) if you run out of fuel and the pump runs dry, you will quickly damage the fuel pump - it is cooled by gasoline.
2) Bosch is not infallible - particularly with these old parts that have been sitting on shelves forever. I have purchased a brand new fuel pump that did not flow at all.
3) Check your fuel filters and screens before suspecting the pump. Unfortunately, few of us actually check these on a regular schedule and if flow turns out to be your problem, look here first.
4) If you aren't confident with the operation of your pump, take the time now to locate an inexpensive replacement (bought my last one for $70 from an Import Parts shop that had two on their shelves for years) and put it in the trunk. It is shamefully easy to replace if it fails and when it fails, it can do so dramatically (here today, gone tomorrow).

But remember, you may not have a problem. It does make noise (first think I listen for when I turn the key every morning). And, my assessment of loud can be very different from yours (my favorite seat at a concert or nightclub is right next to the speakers). Besides, my car is much louder than a stock tii (aftermarket exhaust) and my stereo level usually reflects my taste in concert seating. Plus, you describe the sound as whirring - which is exactly how I'd describe it.

Milton

: As far as I can remember, because its a tii, the pump is electronic, as opposed to mechanical pump on standard 2002. We had the 'original' pump replaced last year, and ever since installation the newie has been quite noisy, the volume (noise, that is) varies a bit, mostly it seems to be depending on whether the engine has been running for a while, say, when I've been for a bit of a spin its really noisy, like when I'm iddling at the lights I can hear it whirring from the cabin very easily-it competes with the radio. My understanding is that it should only be working hard enough to maintain fuel levels getting to the engine,and then just circulating excess fuel, but it seems to be sending fuel around at a much faster rate than necessary (I'm guessing). I'm afraid its going to wear itself out or something! Is this normal? - when the local Bosch dealer listened to it he just said: "so??" really helpful! Does anyone have any advice??

: Thanks in advance
: Oliver




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