Had a nice diy job today. My E 320 has an ice cube for a fuel pump because OEM MAS relay type is not available. w/ help of an electrician, we pried open the wirings of my daily driver 87 230 e so that we could copy how it is wired and apply it to E 320 and found out the following information.

31: ground (brown)
15: +12v ignition on (Fuel pump cuts off after 1.5 sec)
50: +12v from starter/crank input
30: + 12 volts from battery (red wire)
87: power to fuel pump
87k: transmission kickdown
87v: power to cold start valve
TF: connects to pin 9 of a 25 pin ECU (no current: will run PFR even when not connected
TD: very important signal current but not 12v
(green with yellow stripe)
from airflow sensor (got the idea from a BMW diagram)
:acts as a fire safety device in case of accidents:
cuts off signal when air flow is in 0 position
when engine dies. if we pull out this wire, PFR cuts out.

Since an MB can be run temporarily from ice cube, we found out that 87k and possible 87v and TF are not necessary for normal operation. But TD should be connected otherwise engine stalls.


My E 320 uses a MAS relay with 18 pins and our plan is to try to much first the color coded wirings and if we fail, the next step is to trace the TD up to its source so that we can have an idea where its signal is coming from. ( ALSO the ECU of E320) is very much different and hope that the signal is not coming from the ECU because we are afraid that we might burn it)

We also found out that both MB although of different model
follow the same wire coding.


To make it look original MB, we pried out an extra socket from the 230e and use my spare, a repaired/soldered PFR for 4 zyl.
thus it will be easier to buy a PFR because a 4zyl PFR is more available and cheaper.

we did not removed my original socket in case i want to revert back to its specs.