Citroen SM injector points

BTW,

a differential pressure switch would have been the solution, but it is a much more expensive technology. With a dp switch one could have set a condition like "If manifold pressure is 60 hPa below environmental pressure of this car, then activate switch." That would have accomodated for other altitudes than sea level. It is too expensive to do. I just spent more than 200€ on a dp sensor for adjusting and testing MAP sensors. I first set enviromental pressure to a fixed value and then I set differential pressure between this set enironmental pressure and inside pressure.

If I got you confused now, here is a Wikipedia article on pressure sensors .

Hi Rhys,
I now corrected the English version of the checklist following your annotations..
Would you please 'check the checklist'?
jetronic.org/de/forum2/jetronic/19-messp...nts-by-car-model#170

This is very worthy for us - now I can correct some car-specific checklists, that must contain the same error concerning the full-load-sensor.
We had the same error conncerning the ground lead of the TPS once before. Maybe some more checklists are faultily.

Concerning your car: You told us new injectors were installed. Are these the correct genuine Bosch types or Compare types?

Regards
Norbert

Hi Norbert,

The updated SM pin-out list seems fine - with the exception of pin 9 (still shows 12, rather than 11).

It is always frustrating to find faults in factory technical documentation. The SM wiring diagram omits to illustrate a critical earth - this same error is contained in the "Kundendienst-Anleitung" D-jet manual on the DS & SM I sourced from Partsbob at Bosch.

My mind turned to the injectors yesterday too. They are genuine Bosch 0 280 150 043 (photo attached). Should be ok.

If the pain in my back from yesterdays SM work subsides, I'll get the readings that Volker recommends later today.

Cheers,
Rhys

Hi Rhys,
thank you for your correction. I will correct my error.

One more question: Is the colour-coding of the wires correct? We found out before the wires aren't coloured at DS21/23 as being noticed in the Bosch instruction.

Regards
Norbert

Hi fellas,

Norbert: The wires at the back of the ECU block are all black. Each wire has a tiny white adhesive tag with its corresponding ID number.

Volker: The spread sheet with resistance values you requested are attached, If I have misinterpreted requirements, identify the deficiency and I'll get the required information.

The injectors location on the Maserati engine are buried beneath the plenum castings, so fitting the connectors requires ones hand to be mutated somewhere between an octopus tentacle - and a monkeys claw. Some of the connectors seemed to only just be engaged so I measured the pin-outs 3 -6 again.

Regards,
Rhys

Hi Rhys,

that looks better then before. All injectors have correct resistance, cables to ground and from ECU are okay. We have a bit variance like 0.5 Ohm, but the rest fits and I contribute it to measuring tolerances.

Hi Volker,

So....am I left with what is likely a faulty ECU?

Cheers,
Rhys

Hi Rhys,

after you have measured all sensors at ECU connector and those values were correct, then there is only two more things to check:

1. Close the fuel hose to the cold start valve.
2. There is a second throttle switch on Citroen SM.That had nothing to do with D-Jetronic but it somehow involved. I will have to read that function again.

If both are correct, ignition is verified, then indeed we are down to MAP sensor and ECU. As your MAP sensor is of type 1, with rivets and still originally potted, it can hardly be mistuned. What was repaired on your ECU and how was it tested afterwards?

Hi Rhys,

I've checked the secondary throttle switch, it is only for the additional throttle switches and idle-speed control.

So we are left with

1. Cold start valve
2. False air leakage -> Use brake cleaner to check if engine speed would change
3. Leaking injectors -> Make spray test and replace rubber sealings
4. Completely misadjusted ignition timing
5. Finally ECU

Hi Volker,

Yes, secondary switch only operates electro valve to operate vacuum actuator - to close secondary throttle butterflies at idle. All adjusted and working ok (unusual for I.E. SM).

I have disconnected cold start injector lead to isolate the cold start injector as being a possible cause while testing this mixture issue.

Even though type 1 MAP sensor seems OK - idle still runs rich (with adjusted idle switch) - so I rule out MAP sensor for now.

So -

1. Re-test all connections with brake cleaner and look for change in engine speed.
2. Re-adjust ignition timing (not touched for a while)
3, Suspect ECU
I will contact local company that repaired/tested ECU previously. What questions must I ask to understand that they know what they are talking about, or that their testing is adequate?

Thanks again,

Rhys

Hi Rhys,

it is not enough to electrically disconnect cold start valve. You should disconnect it from fuel as it could be leaking even that is is electrically diconnected.

Regarding your ECU: Ask them how they verified proper function after repair. Did they check all function block's operation against references? Maybe you can find someone with the same type of ECU down under. That is easier than sending it to Europe for verification.

Regarding ignition timing:

It is not enough to just adjust it at one point. You must also verify that ignition timing speed and vacuum adjustment works properly. Therefore normally workshop manuals normally contain a value for adjustment plus 2 for speed reference and vacuum advance.

What about air leakage and injector spray test?

Hi Rhys,
one more idea: What about the vacuum tube towards the full-load-switch?
Some models have a calíbrated, very close borehole in the intake manifold that could be blocked.
The full-load switch would then constantly send 'full load'.

Regards
Norbert

Hi Norbert,

The full-load switch has no restriction in the hose. It draws from one of three tubes on the LH plenum (Decel, full-load , MAP sensor). Tubes are ok, but the switch being isolated removes the possibility of earthing pin 14 and the ECU fully dosing.

Hi Volker: I will undertake all that you recommend.

Is this a foolish idea? Remembering that even at idle - my mixture is too rich. Would assessing the running vehicle on a Volvo 164 ECU (which I can access) - on idle circuit only, be a way to isolate a ECU dosing problem? I can work out differences in the injector pin-outs......and the mother boards seem similar?

Cheers,
Rhys

Hi Rhys,

that is too difficult to answer right away. I will have a look at it tomorrow. Is there no SM club in AUS where you would get another ECU for testing?

However I would also need the Volvo ECU no, as there are several.

Moin,

citroensmaustralia.com/

seems, that they are only daily availiable ...

Mit sonnigen Grüßen
Hans