86 420sel hard to start
 

but when it starts
the ideal is high and put it in gear it runs for a few minutes
before the ideal drops and kills the motor

if i have my foot on the brake and foot on gas
it will run , but its scarry comming up to the light not knowing if your going to get stuck
on the freeway it fub like a champ

OK, thats idle which in your case is not ideal.

Check the two rear fuel pumps, they are in series, and make sure the connectors on them are clean and the wires are not broken. There should be four rubber boots on the connectors as well.

Make sure the fuel filter is new. You will need to clamp the hose connection from the gas tank, which comes out of the middle of the floor and goes to the lower pump. There are also check valves at the output end of each fuel pump.

There is a test for the proper amount of gas delivered in a minute. It currently escapes me.

The fuel pump relay controls the cold start injector so use a test light to check for power to the cold start injector during starting. In MB parlance, brown is ground.