1987 mercedes 300E wont start. the oil pressure is

Check all the fuses first . Clean up all the earth points on the body ,and grease them .Move all the wire conections under the bonnet make sure they are all on tight. Check the battery voltage .Anything under 12 volts is not fully charged .Sounds like a bad earth ,Hard to find these, if i am not able to look at it . .

Check your ground from battery cable to ground spot,check fusible links from positive battery cable.

You should want to hear it cranking with a fully charged battery. Maybe it will start at normal cranking speed.
Too much friction, resistance in the engine? If oil is too heavy, it might cause that. How does the oil appear? Black and gooey? Any indication of sludge-give it a pass-the owner has not done regular maintenance.

charge battery fully do not jump it turn key on for 30 sec than offf ,car should start

Check cold start valve, and thermal timer switch

Make sure the battery is fully charged. If it starts by jump starting it. Your battery needs to be replaced. If it turns really slow, the starter needs replacement.

Try to reset your security system by inserting your key in the drivers door and rotate on and off-if that doesnt work try all locks that way

sounds like the fuel pump! have to test it and the relay! could be hunderd or a few bucks.

Aee thw fuel system.

hello,hoping your freon is full,check your fuse for air con system,maybe your pressure sensor in your dry tank is defective, check your aircon relay in back of your battery,pull out,check if have burn smell,before you replaces the relay try to check first the resistance of your magnetic clutch,ty