Mercedes Benz repair: Mercedes 300TE 24v, 1990, fuel pressure gauge, spark plug gap

Question
Engine idles really rough. Rotor arm and distributor arm both appear in good condition - with no hairline cracks etc, though lightly cleaned contacts. Checked and adjusted spark plug gap on all plugs to correct 0.8mm which produced a noticeable change to smoother running when idle, but engine still struggles when trying to accelerate (also struggles to deliver power when going up hill).  Original engine roughness returns when down to a 1/4 tank (or below) of petrol, which I noticed immediatley after re-fuelling up to 1/2 to 3/4 of a tank of fuel. (Added fuel injector cleaner to 1/4 tank of fuel before last refuel, as mentioned).

IN addition to the engine roughness, fuel consumption has been going through the roof. Likely to be fuel metering unit?

Any help, guidance would be very much appreciated. Thank you

Answer
You have a station wagon correct? If the answer is yes. Check this out. This vehicle has 2 fuel pumps. If one is not working it will do that. Repl Fuel pump and fuel filter

Ralph
Miami Auto Help Inc

This can be confirmed by a roadtest with a fuel pressure gauge attached to the car and taped to the windshield . Pressure should be 3.3 to 3.8 bars