1990 Mercedes Benz 190e Engine shuts down after starting

DEMAR

MEMBER
1990 MERCEDES BENZ 190E
6 CYL
2WD
AUTOMATIC
160,000 MILES

Hello!
My 1990 190e will start but will not run long. When it actually runs, it cuts off after 5 seconds. It got worse over a 2 month period. It used to run fine after waiting 20 minutes, now it will not stay on at all. It cranks strong, all wires, plugs, rotor and cap are new. I tried to replace the MAS relay(Fuel pump/ac compressor) and that had no effect. I checked the OVP and the other two fuel pump relays and I cannot figure this out. What else could I have overlooked or what's left to test?
Thanks,
Demar

1 Reply

DAVE H

MECHANIC
13,383 POSTS

Hello. Thanks for the donation. Much appreciated

Start by checking for good fuel pressure and test the fuel pump is working by supplying a direct 12v feed to it.

FUEL CONTROL
FUEL DISTRIBUTOR UNIT (U)
Fuel is metered and delivered to individual cylinders in direct relation to air intake volume, which is determined by airflow sensor plate position. U consists of fuel distributor with differential pressure regulator, Electro-Hydraulic Actuator (EHA), and airflow sensor with airflow sensor position indicator.
COLD START
Cold start valve operation depends on coolant temperature and cranking signal. Duration of cold start injection is in direct relation to coolant temperature. Should engine start before cold start valve completes its cycle, cold start injection is canceled. Voltage is supplied by fuel pump relay.
CRANKING ENRICHMENT
Amount of enrichment depends on coolant temperature. During engine cranking cycle, enrichment signal does not fluctuate.
WARM-UP ENRICHMENT
Fuel enrichment depends on coolant temperature. A lower coolant temperature results in higher voltage to Electro-Hydraulic Actuator (EHA). This changes control and system pressure differential to enrich fuel mixture.