1991 300CE, 180m. I have owned the car since 112m and have only spotty service records back to 87m.

What is typical service life for fuel pumps? I am getting a funny noise from right rear after a warm startup. So far it has happened only about three times. Sounds like a dry pumping noise. The noise is brief and then goes away. Car drives pretty normal but I am having a more difficult warm start then usual. Car sometimes lugs a bit but then smoothes out.

Also is it essential to clean out the gas tank before putting in new fuel pumps? How is this done or is it a job best left to a shop?

Thanks,

glenmore
1991 300CE
1999, 2000 C280
2000 C230K

When was the fuel filter last changed?

If long ago, I would start there.

RayH

Fuel filter and accumulator changed 4/07 at 143m.

I'm assuming fuel filter is good because car idles fine and no problems at highway speeds.

This is the easiest fuel pump and fuel filter to change out if you have to. You can also check it out and tap on it while someone turns the key to check intermittent operation. Mine had two pumps (something they did to minimize vapor bubbles forming or something). I replaced both trying to resolve a start issue and it was not the problem but I don't need to worry for a while now. Start by jacking up the car (passenger side) and removing the plastic cover over the fuel pump assembly (it's like 4 small philips head screws). You can see everything and go from there. Good luck!

Start saving up for a couple of new pumps.
When they start getting noisy - normally higher pitched whine - then they are on the way out.
They might just stop working while you are out driving in the middle of nowhere.

Mine made that noise for about a year before they had to be replaced. Of course it took a few months to get to the point were we replaced them (mine had 2 pumps). When we tested the pumps...one only activated 20% of the time when a current was sent to it. My car only had 97k on it at the time (95 e320). Replacing the fuel filter again may not be a bad idea. I installed oem 2 bosch pumps and cost $$$.

Yep...definitely not the least expensive parts on the car...actually, cost way too much!