I'm looking to do an m-unit blue installation, referencing this diagram - https://drive.google.com/open?id=1OsEEKz-IGU5K4YCM8C0w0rMpGC3xcnVf



I've got an '85 K100

I've read the below:

The starter relay and Fuel Injection relay close, Hall sensors get power.
The FI relay energizes (+) the fuel pump, the idle switch, the injectors and the air flow meter.
The Jetronic receives (pin #4) the signal that the engine is starting and it sets itself on starting mode (enriching the air/fuel mixture)
Electronic ignition module pin # 9-10-14 send power to the ignition coil
Electronic ignition module pin #8 send engine rpm info to pin #1 of FI computer
Electronic ignition module pin #7 send ground to the coil of the FI relay as soon as the starter switch is depressed. The ground will stay on after the starter switch is released as long as the Electronic ignition module receives a signal from the Hall sensors.

I'd like to know if there's any problem with having the fuel pump energised as soon as the ignition is turned on, as opposed to when the starter button is pushed.  Would the fuel pressure regulator just circulate the fuel around to the tank until it was needed when the starter is pressed?
Also if there's any problem with pin 9 on the Temperature Sensing Switch Unit being energised with the ignition, rather than the starter switch (receiving power from the Fuel Injection relay).

Reason I'm asking, I'd like to remove the 10-15 Amp fuse in the diagram, and use the m-unit blue to provide power from one of the Aux outputs.

https://drive.google.com/open?id=1mIf424Kflcrttxx1V6iHm0PonYbjRELR

Thanks for any help

Hi,

You mentioned you are trying to troubleshoot the electrical system on your K100, but are you aware that the schematic you are using is a K75 schematic?

Bob.

PS: By the way, if it is helpful, I have the entire Haynes K75/K100 repair manual in PDF format.....all 236 pages of it

nods wrote:

I'd like to know if there's any problem with having the fuel pump energised as soon as the ignition is turned on, as opposed to when the starter button is pushed.

Would the fuel pressure regulator just circulate the fuel around to the tank until it was needed when the starter is pressed?

The reason why the pump won't start until you hit the starter ....AND... will automatically stop within a couple of seconds if you stall, is for safety. It is a German regulation that applies to any motor vehicle.

If, for any reason,the motor stops (a crash, or even  just a stall) a timer cuts off the pump within a couple of seconds. This timer is "resettable, and basically, and is reset by the motor every revolution, so the safety system continually resets the timer before the timer has a chance to cut off the pump....UNLESS the motor is stalled.

Bob.

Thanks Bob.  Yeah upon reflection, I didn't like the idea of the pump running with the engine off.  I'll keep it the way it is.

And yep the K75 schematic is just the best one I've seen with the m-unit integrated into the diagram.  I don't think there's any major differences between the K75 and K100 diagrams?