Citroen SM injector points

Hi fellas,

I use the term "full load switch" - as this is how it is referred in Citroen documentation. It is the same switch you refer to as absolute pressure sensor (APS). The throttle switch does indeed have only four terminals.

The APS switch is normally closed but opens on 3-4 hg vacuum (tested and ok).

My current mission is to trace the earths......I find one listed in the documentation that I cannot identify on the injection harness anywhere. I'll persevere with the Bosch pin outs and discover what I can.

Regards,

Rhys

rhysaccess wrote: ...
The APS switch is normally closed but opens on 3-4 hg vacuum (tested and ok).
...

Hi Rhys,
following Bosch and Volker it just works vice versa.
And: The highest vacuum is when the throttle is closed, at idle!

If defectice or maybe incorrect connected the switch would enrich the mixture in all conditions, but not as much at idle because then the idle switch in the TPS has more influence.

Could be a possible reason for the engine running too rich ... would have some influence at idle, too - like you reported

Just disconnect the switch and look what happens. Maybe the engine now runs normal - lean only at full load.

Regards
Norbert

Sorry to interfere again:

Rhys is correct. When we are in full-load, there is no vacuum applied. That's exactly what he alsp measures on a stalling engine as there is then no vacuum. If vacuum fals bwlow a certain level (indicating part-load pr idle-run), then ot opens. So it should show 0 resistance on a stalling engine, but not on an engine in idle-run.

Hi Volker,
I didn't ever check an absolute pressure sensor:

Is this correct: The sensor shows endless resistance when doing the measurements at the ECU -plug
- because there is no vacuum when the engine doesn't run.

But Rhys measured zero resistance in this situation, I remember???

Regards
Norbert.

Hi Norbert,

with stalling engine, there is no vacuum. That is why Rhys has to measure 0 resistance. With a stalling engine we so to say have full-load conditions. Only when the engine runs in idle, we have maximum vacuum and then Rhys should measure infinite resistance.

A bit tricky as you do have to think around the corner. Engine not running has suddenly full-load vacuum = none.

Ok,
I was just confused about the type of switch. It is switching 0 resistance (1) to endless resistance (0), not vice versa.

Regards Norbert