Hello it is a pre-HE motor. I wonder what the function is of wire 12, goiing to the ECU and to the trigger board. (the one with the Hall in my case)
Can someone explain that? What is eg "direction" doiing in the TPS . Whats the normal voltage level of pins 14/16/12/20/9 . To what is the other side of switch D connected. Diagram (http://www.jagweb.com/aj6eng/djetronic.php) is not so clear. Thanks

 

That YB wires is I think the signal wire for the ECU to indicate trigger board activity, and thus trigger the injectors. It travels via the throttle switch pin #12, and to the ECU pin #12.

My understanding of direction would mean the rotational direction of that switch. Looking at the top as installed on the capstan, "anti-clockwise".

Voltage?? no idea, never probed any of mine.

D I reckon is the vac operated fuel enrichment switch, and one wire is from the ECU, the other side is earth, and that richens fuel by about 10-15%.

 

Thanks for info Grant.
What is the direction of that switch meaning to the ECU? It signifies one time more throttle and another time less throttle as one pushes or releases the trottle?
and another question: Do you know how the overrun cut off functions and how the ECU knows when to apply?

 

I guess lower vacuum will provoke that enrichment?
Apparently 3 wires?
That ground connection is not indicated in the diagram? Strange...

 

That throttle switch is a stepped arrangement, and as the throttle is opened, that switch moves over the segments, and each segment "triggers" an injector pulse. Thats why with a PreHE as you open the throttle with Ign ON, engine OFF, you will hear the injectors "click" at each segment.

The MAP sensor, on the radiator support panel, converts the vac signal to a recognised signal for the ECU related to load etc.

Never noticed the wiring diagrams that specifically way back then, I just knew how it worked and made sure the connections were in place. The OLD enrichment switch on Sir Arthur had the earth wire as a very short pigtail that soldered to the switch metal mounting plate, giving the earth as an "internal" path. The HE switch has 2 seperate wires.

I never over analysed teh D Jetronic, I just made sure the wires were all in good shape, and went to where they were meant to, and the throttle switch was set correctly at idle, and that is a PITA to get correct, and thats basically it.

I dont think the 3CU has a fuel shut off at idle over run, never thought about it really. If it does, then the idle setting of the throttle switch would be the critical trigger point.

My 6CU should have had one, but I doubt it worked, and I only noted that when I fitted the 16CU, and that fuel shut off was very noticeable indeed.