89 560SEL fuel pump problem
 

The car has 129k and have no problem starting up, cold or hot.
doing fine in the city while the rpm always below 3000...
however, the car choked when the rpm reach about 3000
even worse when going uphill.

The car has 2 fuel pumps, i am wondering if one of them went bad will cause such problem? Usually i heard a loud noise b4 starting the car and someone from the forum said that the fuel pump is going south. Now my car doesn't make that loud noise but i can still hear the fuel pump is working, i can still hear the noise, it is just quieter.maybe one of the fuel pump is dead?

Thanks for your time!!

There has been debate here as to whether noisy pumps mean trouble or not. I'd suggest replacing the fuel filter if it hasn't been reasonably recently as a first try. It's easier and cheaper than the pumps and may be part of you problem.

jlc

Usually if one of the pumps is dead you can do a flow test by taking the feed line off and either jumpin the relay or having someone crank ( be careful for spilled gas) use a container to catch it. You will see a real good flow if good or just a medium flow if bad. Such problems like yours can be caused by stopped up fuel filter or even bad air filter as well as alot of other things. In order to really rule out fuel system a pressure gauge would be handy here. We have also seen bad ignition components breaking down upon load do this also. A scope would be handy for this also to look at secondary to see if there is any breakdown.

Thanks for the quick reply! So the car will start even one of the fuel pump is dead too?

Yes the car will start but will not accelerate well.