car is running ruff when cold hesitates,pops in plenum when engine cold,need to allow warm up for 5 mins,mechanic told me both fuel pumps putting out low pressure,i replaced them with high flow pumps,also told me to replace the overload relay behind battery it was putting out fluctuating voltage 12-14 volts,replaced,then told me it needs an oxegan sensor,the engine still hesitates when cold loss of power,i still need to replace the o2 sensor and the fuel filter,does this sound like it could be the cause of the issues?when cold and not allowed to warm up,car barely moves with full throttle then bucks,then kicks in then loss of power,till i let up on the throttle and it warms up

Have you checked the fuel pressure? Throwing parts to cure an issue is not the right approach. You must diagnose the problems you are experiencing logically. Have you checked to see that your O2 sensor is within specs and functioning correctly before you replace it? You may want to do a search to find out how you can check for stored codes.

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1989 300CE

mlozzi, do all of the symptoms you've described go away and stay away when the motor comes up to operating temp? No bucking, no loss of power, nothing rough-running?

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

hi cal, yes when the engine warms up she purs like a kitten,strong runs very good,im changing these parts due to the mechanics diagnose,and the fact that everything on this car is original parts,21 yrs old,i can only imagine what the filter looks like inside,the fuel pumps were leaking gross particles and gunk.

Good plan. Performing normal maintenance is always a good place to start. Then, when all filters, plugs, plug wires, distributor cap and rotor, voltage regulator brushes, OVP and fuel pump relay have been replaced, and maybe a couple of bottles of Redline injector cleaner run through the motor, then diagnosing the other mechanical/electrical systems on the car will be much more fruitful.

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

Make sure you dont have a check valve between the fuel inlet and the return line. If the check valve is there and its bad it WILL cause very low psi of the fuel feed line.

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1985 300D 198K sold
1982 300D 202K
1989 300E 125K
1992 940T

"If you dont have time to do it safely, you dont have time to do it"

"The democracy will cease to exist when you take away from those who are willing to work and give to those who would not."

its funny you say that, there is a metal valve located in line next to the fuel filter,it looks like a fuel pressure regulator,i thought maybe it was the fuel accumulator,i wonder if the technician checked the fuel pressure coming off the pumps directly or from a port under the hood.i will look into the check valve,if its still bogging down after i replace the fuel filter,also,does anyone know where the fuel pump relay is located?thanks guys for all your input.and they say to many chefs ruin the stew,lol!!