Citroen SM injector points

rhysaccess wrote: Hi Volker,

On a separate issue.....

I understand that the idle switch activates the ECU to run on lean idle mode independently of the MAP sensor. When I remove the MAP sensor of an idling Volvo P18000ES at the workshop (both vacuum or electrical connector) it dies. What is the relationship of the MAP sensor to the idle circuit?

Cheers,
Rhys

Hi Rhys,

I oversaw that question. When you remove the MAP sensor, the ECU cannot provide the basic injection pulse any more. However, when idle-run contact is closed, it supersedes the MAP sensor pulse forming.

Hi fellas,

The APS switch is indeed counter-intuitive. Normally closed while the engine is off, open at idle (high vacuum) closed again at speed (low vacuum). Either way, mine works fine.....and been electrically disconnected while I try and source the running rich issue.

I completed construction of my break-out box today (attached) and repeated testing of the ECU connector. It is clear that the pin out instructions have some errors.

Idle switch should be 17 and 11 (not 12), throttle switch should be 9 & 20 and 11 (not 12), APS should be 14 and 11 - but 0 ohm (not infinity). I wish the Bosch details were correct....because there would be my problem....but I fear it is not the case.

I'll check my readings one more time, and post the results within the next day for some further scrutiny.

[quoteI oversaw that question. When you remove the MAP sensor, the ECU cannot provide the basic injection pulse any more. However, when idle-run contact is closed, it supersedes the MAP sensor pulse forming. ][/quote]

As the car dies with just the vacuum line removed from the MAP sensor (while idle switch is closed), the sensor cuts all injector pulses?

Thanks for the continued interest in my D-jet issues.

Regards,
Rhys

Hi Volker, Hi Rhys
I now found the following information in a Bosch / Citroen document:

"The pressure switch <...> (full-load switch) gives the
control unit the information “full-load enrichment”. The
pressure switch is connected to the common inlet duct by a
hose and reacts to the pressure difference between inlet
manifold pressure and atmospheric pressure (switch closes
when pressure difference lies between 1-3/16” and 2”
mercury column and opens again when pressure difference
lies between 2” and 3-3/16”mercury column)."

Maybe you both didn't notice the switch's 0-1-0 function at rising pressure difference.

In the case the switch is defective, it could therefore be the reason for the engine's running rich as I suggested before.

Regards
Norbert

Edit: Rhys, I now noticed your new posting.
Following the Bosch document the APS must read infinite resistance when the engine is off.
My document is for DS21, but the APS will be the same type???

rhysaccess wrote: ...
Thanks for the continued interest in my D-jet issues.
...

This image is hidden for guests.
Please log in or register to see it.

Sorry, Rhys.
You do a great job. A lot of work you already did...

But I must go to bed now. It's 1:50 PM in Germany now and I have to get up in the morning...

Regards
Norbert

Hi Norbert,

I would think the switches are similar in function, but they have different part numbers. DS is 0 280 100 011 & 0 280 100 023, while SM is 0 280 110 003. I would imagine the Maserati V6 cam arrangement would produce different vacuum readings from the 2.1 & 2.3 litre Citroen 4 cylinder
With the switch just providing an earth to the ECU at speed for a full mixture dose - would not removing the switch isolate this issue?

Cheers,
Rhys

Hi Norbert,

sorry, what you find only describes the hysteresis of the switch. In idle we are at low pressure. Then we approach full-load and at 1-3/16 to 2" below atmospheric pressure it closes. When throttle is then closed again, pressure falls and switch will close at a similiar but not the exact same pressure. That is then a bit lower at 2” and 3-3/16” below atmospheric pressure.

There is no 0-1-0 action. it is simply signalling full-load at certain absolute pressures. Only in your document that was translated into differential pressure. What Rhys has measured was correct. But Rhys if you want, just pull of the electrical connector and you will see that it does not affect idle-run and part-load.