Citroen SM MAP sensor 0280100036 not working

Howdy all,

I'm currently assessing the remaining few tasks. One of these is engaging with the company that rebuilt the ECU (for around $1400) 14 months ago.

While it is claimed that around 80 Citroen SM's have been imported to Australia & New Zealand - few are D-Jetronic. SM Australia imported many of these, just about all from the USA - where D-jet SM's were never sold. They, therefore, have limited expertise in this area and no I.E.parts to speak of (based on my conversation with them a month or two ago).

I know of a couple of D-jet SM's 1000's of Kms away. These strangers would be as reluctant to lend me a ECU, as I would be ....in their place. An unknown performing ECU (if I could find one), is no big step forward. But I'll still try and source one.

Still some checks to be made in the mean time.

Regards,
Rhys

Hi Rhys,

now I understand why you find no SM ECUs in down under. When I read the repair prices for ECU repair 1400 AUD or 950 €, I am shocked. Maybe I should emmigrate to Australia What I can offer as help: I'll try to find an ECU for you here in Europe, verify it and then send it to you.

Hi Volker,

Yes - you immigrating to Australia.....would work for me. But you would make a better living teaching Latin - than selling d-jet services in this part of the world.

I checked the operation of the cold-start valve tonight, and re-check fuel pressure. All ok.

A colleague (experienced Volvo mechanic) encouraged me to try a used Volvo P1800 MAP sensor we had lying around and demonstrated that adjusting the rear screw of the MAP sensor - at idle- affected the running.

Out of interest we hooked up the gas analyser while the car was idling, and found that via the MAP sensor, we could adjust the CO from 7-8%, down to around 2%. While still at idle, we could Adjust the potentiometer on the ECU down to almost 0. This event is consistent with my colleagues extensive experience with Volvo D-jets.

This is the first time I've had the car running within these lean parameters.

This experience seems at odds with D-jet theory. What are your thoughts?

Regards,
Rhys

Hi Rhys,

first of all: Latin was my performance course in highschool, I even learned ancient Greek as well: Australia insula est. Ceterum censeo D-Jetronicum conservandum esse ! So where can I sign to become a rich man in Australia ?

With your Volvo MAP sensor now you are raping your D-Jetronic. You abuse that wrong MAP sensor like a potentiometer. Why? Potentiometer is only active when idle-run contact is closed. Then it overlays the effect of MAP sensor transformation with a steady voltage level. What you and your firend are doing is a bit strange. You are abusing a totally different type 3 MAP sensor to replace your type 1 MAP sensor. I am not sure about your specific MAP sensor, but if I compare other type 3 sensors to other Citroen type 1 MAP sensors, type 1s have a much shorter tuning range (max vacuum 0,5 Bar) and they have a lower transormation level. Now you come with a type 3 sensor and on top you change its adjustment dramatically. A few degrees of screw turn shift the armature drastically. That is why you use the poor type3 sensor like a potentiometer now. It's a bit like raping the system.

Your friend can forget his Volvo sensor. It lef unusable now.

Hi Volker,

Rape? - I say the D-jet system asked for it.

The Volvo MAP sensor (type 2 not 3) was to just try something different......no-one is getting married. As offensive as the brief mating might be, it caused flexibility in mixture adjustments not experienced to date. Actually a refreshing change.

With the idle circuit enacted on the ECU and tangible adjustment achievable via the potentiometer......why was the MAP sensor having an effect ....as well? The adjustment from the MAP sensor should have no effect at idle?

Would not adjusting the original SM type 1 sensor achieve a similar result as the loan type 2? (or send it to Bosch for rebuild) Is this any demonstration that my existing MAP sensor may be the cause of the rich mixture?

Cheers,
Rhys

Hii Rhys,

no your D-Jetronic system did not ask for rape

I assumed you had a type 3 as you can only adjust a type 2 after you remove the potting. Type 2 and type 3 MAP sensors have a higher transformation level. I alwasy use the word supersede when I talk of the idle-run potentiometer overlaying the effect of the MAP sensor transformation. A type 2 and type 3 MAP sensor has a higher level of transformation than a type 1. Additionally you change ist setting heavily by changing the zero position of the armature. That has the effect that you now create a different level.

There is a 5% chance that your MAP sensor has a broken aneroid cell or spring inside so that it heavily deviates. But generally type1s are very robust. And as yours is with rivets and still originally potted, I have always stated that it should be 95% okay.

Having said that one can never be 100% sure if it is not verified.