Runs for 20 minutes, gets hot and shuts down. Still has spark

You will find the filter under the car in front of rear wheels.
It will have a cover on it so remove the screws to get to the filter.If you need to change it read the manual or you can get fuel all over the floor. As well as the filter you will need the copper washers that go in to seal the banjo joints.

You mave have a leak if it blows cold and then hot if that's so there's low of freon

Make shure the RPM meter is working. If this signal from the ignition control unit is missing the fuel pump will turn off the fuel pump after some seconds.

You have a weak fuel pump or clogged fuel filter

Fuel filter is by the fuel pumps under rear passenger side of car. There is a plastic cover there. Also Look into your coil being bad, also wires, plugs cap and rotor. Ignition issues also can be caused by the OVP relay, the box with a fuse in it by the battery.

engine wiring harness upper and lower could be degraded, coil could be bad, throttle positioner, fuel distributor could be bad and depending if its a half year car and you have an OVP that could be bad. Also after a full tune up have someone adjust the duty cycle.

It sounds like a fuel delivery issue. Mercedes recommends replacing the fuel filter every 60k. If it has been longer than thast since the filter change start there. Fuel pump relays are another common problem on this era. They are located behind the battery. Remove the plastic cover and you will se 2 black relays( yours may have a mass relay if it is a 90 model year, it will have a plastic knob on top that you turn to the left to unsecure it) IT will say kickdown on it the climate control is the other relay and it will say klima. Look for signs of corrosion on the solder pins. If your fuel pump(located at the right rear) is very noisy when it operates I wouild recommend replacing it. During this era of Benz about the only way to diagnose this would be to run a bunch of fuel pressure tests and to drive vehicle with a meter on the relay and on the pump to see if the relay cuts out or the pump cuts out. I always recommend to do both pump and relay because they can cause one another to fail. good luck.

The fuel pump relay needs to be replaced. it is behind the battery and the fire wall.

maybe the coils or sparks need to be changed

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