Mercedes Benz repair: how test fuel pump, air control valve, fuel pump relay

Question
Shane, on my 1990 420SEL have to pump accelerator several times before engine turns over, more so when whether warms up. The Economy meter is way over to non-efficient reading. Changed spark plug wires, rotor and idle air control valve but still same problem. Car idles when stopped okay sometimes (early am) but stalls out as day wears on. Wondering if fuel pump but how to test if that is case or is there other culprit.

Thanks

David


Answer
you need to jump the fuel pump relay  with a short wire jump 87 pin and 30 pin. should sound like it kicks on but that will not tell you if you are getting enough fuel in the rail I would start there though, then check your spark plug cylinders for gas overload, could be a bad injectors but Im thinking more on the line of fuel pump