Can I get the fuel pump wiring diagram?

LIETUVIS

MEMBER
1990 MERCEDES BENZ 190E
1.8L
4 CYL
2WD
MANUAL
180,000 MILES

Hello, looking for your help, I think there is a problem with the fuel pump wiring regarding fuel pump activation and working conditions, maybe a wire somewhere split but I'm not sure what color wire is.
I changed the fuel pump, fuel pump relay, but still no fuel pumping out.
Once the ignition is on there is only 1 second fuel pump is working and then cuts out.
I tried to disconnect the fuel pump relay and bridge pin 30 and 87 and its initiating fuel pump to activate as long as there are these pins bridged- fuel flowing and pump is working.

I assume I'm having issues in wiring between ECU, or others relays and fuel pump, maybe you could share wiring diagrams for fuel system, as much as you can obtain, I will investigate where my problem is.
For a reference engine code m102 if it helps (1.8engine) 1990 years, model 190e.

Thanks

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

First, I attached the wiring schematic for the powertrain control systems. I highlighted the fuel pumps so you can find them more easily. Also, the schematics were two pages. I had to cut each one in half to make them readable for you.

Next, are you aware there are two pumps on this vehicle? Also, it is normal for them to prime for approximately 1.5 seconds when the key is first turned on.

From that point, they will shut down until there is an ignition reference provided to the ECM indicating the engine is running. If there is no ignition reference, the pumps will not actuate.

With that in mind, check to see if there is spark to the plugs to make sure they are getting spark.

Let me know what you find.

Take care,

joe

See pics below.

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