Update:

After much reading and research, I found a MB article which states that EHA voltages and current can remain for up to 15 minutes after switch off. I’ve carefully examined the wiring diagrams and pin 30a OVP relay, is connected to pin 1 CIS-E and is live/hot at all times but is fused via th10A fuse on top (OVP). So that now makes sense.

I removed the CIS-E unit cover and soldered a wire directly on pin 13 (02 sensor signal). When all powered up it measured 0.45V. Don’t know where the signal is generated. (Neither does local MB dealer) There is definitely no Lambda sensor fitted as I fitted complete exhaust including front pipes and just performed head overall and cylinder head gasket change)

MAS pins 12, 17, 18, 8, 11 are connected to CIS-E pins 11, 42, 3, 27 respectively. Pin 9 MAS to pin 45 CIS open circuit which is what I expected.

Connected meter to X11 pins 2, 3 KOEO read 28.9 % (engine cold) turned key and sat at 49.6% up to operating temp and beyond. I then cleared fault code 9 on CIS memory and took it for a drive.

With meter in car, only on deceleration from high speed did the % change and it rose consistently to 88.9 -89.6% every time. When I got home and checked memory fault code 9 also reappeared.

I also asked my local MB dealer if they could tell me the EHA currents measurements for my vehicle but the said the car was too old and did not have that information. – Great.

Does the fault seem to be a fuel pressure related fault?

I was going to swap the EHA with the one off the 103 engine. When I unscrewed that one there was no fuel pressure but as I tried to remove mine, fuel squirted out at high pressure until the pressure had gone (Both had ignition off!) I swapped them over and the EHA current was still around 11mA.

Is it normal to still have fuel pressure at this point after switch off?

Could the fuel pressure regulator be at fault?

Does the MAS unit only pulse the fuel pumps or are the on all the time during the engine running.

(The 103 300e has now gone so I can’t swap the FPR.)

Once again

Thanks Tony.