Problem after rain fall.

Dear Dr. D-jetro

My car (Isuzu 117 coupe, year 1972 by Bosch D-jetro control) has strange problem.

Condition :
My car was placing at my car parking without body cover cloth (Usually body is covered by cloth). And the heavy rain was fall during the night. After the rainfall was stopped in the morning, car body was wet (of course bonnet was closed). There was no rain leakage into car room (ECU was not wet). And each all sensor of D-jetro was not wet.

Only the time my car body was wet after rain, the Air-fuel mixture level become thick and it was hard to get engine started.　(First explosion only and could not keep idling) . And I found out the spark plug become black (as attached photo). 

In sunny or cloudy day, this problem never happen.  Do you have any idea Why this problem occurs?

Thanks and regards

Shimizu 

 

Hi Shimizu,

first of all welcome to Jetronic.org. I have never seen any Isuzu with D-Jetronic. Is there any documentaton available? I know that Bosch licensed D-Jetronic to Isuzu but I do not know whether they did further development on it. Also I have no component list. All that would be very interesting. Of course in English as I do not know Japanese. Do you also have the Bosch type ECU and MAP sensor in your car and trigger contacts? Oh you made me curious.

Now regarding wet and rich mixture. I see 2 possibilities. Either it happens in ignition and spark wanders somewhere else. Or you have a shortcut in wiring that is enhanced by wetness. Especially engine temp sensor or line to cold start valve are suspicious.

Hallo Volker,
so steht es bei Wiki.
Da die Nachfrage nach dem 117 Coupé stieg, entschloss sich Isuzu, nachdem sich General Motors an der Firma beteiligt hatte, 1971 zur Aufnahme der Großserienproduktion. Der 1,8-Liter war nun serienmäßig und in verschiedenen Varianten erhältlich, mit oder ohne Einspritzung und mit einer oder zwei oben liegenden Nockenwellen.
Möglw. ist ein seltenes Mod. mit GM Einfluss ?
Gruß Hans-Jürgen

Hi Shimizu,
this is really a big surprise to me you meeted the forum with your ISUZU car.

Any information about the car and the injection system would be very interesting and helpful for us - even in Japanese because we could see the graphics and read the numbers noticed there....

I think the problem will be related to the ignition as Volker stated before. Is this a Bosch ignition system with Bosch components?
Distributor caps tend to get wet inside, and old, dirty cables and rotors get wet too and mislead the spark.

It's never a good idea to cover a car with a carpet against the rain, because the humidity can't get out and stays under the carpet.

Regards
Norbert

Dear Volker,
Dear Norbert,

Thank you very much for your information to solve the problem.

(1) Let me introduce my Isuzu 117 using Bosch sensors. It seems the basic component is Cioroen DS (1969～1072).

・Injector : 0280150004・MPS:B280000120・ECU : B280600409 （original:0280000022)・Throttle valve switch : 0280120010
・Fuel pressure regulator : 0280160001・Auxiliary Air Valve : 0280140013・Distributor assy : B231040436・Temperature sensor (coolant) : 0280130014 ・Temperature sensor (air) : 0280130006

(2) Now it is getting warm in Japan, the cold start valve is not attached with the manifold. And ignition coil system is strengthen with using new resistor and coil (Isuzu genuine parts). To solve the problem (as Volker mentioned), the cold start valve is not the source of problem because it is not attached now. Is the problem come from short circuit of wire harness of temperature sensor (coolant), right? I like to know how to find out short circuit of wire harness. Please instruct me.

(3) I would know it is not good for car to cover carpet because of keeping humidity inside. But I do not have built garage. So it is forced to place flat open area with covering carpet. 

Thanks and regards 

Shimizu

Hi Shimizu,

What I meant is a disconnect of water temperature sensor would make ECU beleve that you are in Sibiria and enrich mixture accordingly. It is roughly 3-fold fuel then. When humidity creeps into ignition distributor you will have spark going wrong ways and bypass spark plugs.

Now thanks for your kind reply regarding components. May I ask back for clarification?

• Injector is 0 280 150 004 are green type
• ECU has a strange no B280600409, I will have to investigate. Can you share a photo?
• MAP sensor B280000120. No. surprises me. Would expect 0 280 100 120 . That would be the one also used in Vega. Can you share a photo?
• Fuel pressure regulator and damper are standard
• Auxiliary air valve should have the small filter screwed in
• Throttle switch is from Saab 99
• Distributor assy no is unknown to me. Does it have trigger points? Can you share a photo?
• Temperature sensors are standard

Hi Shimizu,
I have some adds to what Volker posted before.
As he does, I'm awaiting your answers with great interest.

- It is essential to know which ECU ('main unit') is used because they often differ not only in the internal design but in the outer BUS layout.
Some of the connections are all the same, but some differ - and this is essential.

- If you can tell us the number  of the ECU we can tell you about the readings you can do / have to expect at the  25-poled BUS.

It's not helpful to read values  directly at the components, because faults in the wiring harness are not detected this way.
Therefore we do all the readings at the plug towards the ECU, mostly with the ECU unconnected.

You find a list of all ECUs known to us and their external connections here:  jetronic.org/index.php/en/cars/d-jetronic/56-connector
 
Regards
Norbert
 

Dear All,

Thank you for sending messages.

Attached are the photos of ECU and MPS sensor and trigger point contact and distributor. 
In the past I heard from Bosch guy that initial "B" of ECU AND MPS sensor parts number means to made specific purpose such as test, Rally, or something like that. ECU has 25 poles.

Yes, distributor has trigger contact point as attached photo. 

Regards

Shimizu

ECU AND MPS sensor photo are attached.

Hi Shimizu,

thanks for the pictures. Indeed ECU and MAP sensor as well as trigger contacts look like original Bosch D-Jetronic. B means special application. Could be that Bosch did not consider Isuzu as big enough to justify a fully qualified product. Only guessing.

Should I once have the chance to read out ECU and MAP sensor, I would do so. Do you know whether your MAP sensor has a diaphragm and is of type 2. I believe so. From pictures it could also be a type 1. But my guess is no. And it is not anywhere close to Citroen. It is a mixture of everything. It would be goof to have the chance to read your MAP sensor before diahragm tears one day. If only you would live inside EU. Transport to and from Japan is so expensive and takes so long.

Hi Shimizu,
unfortunately we don't know much about the system - but it's a genuine Bosch D-Jetronic as you told us,

You want to do some readings - and this will be possible.

You can take the harness-connector out of the ECU (Take off the plastic cap, remove two screws <maybe a part like a frame made of plastic> and pull the plug...)

The connector is 25-poled, but not all of them are used - some are NC. <It could be helpful to know which are NC>
The pins should be numbered from '25' (harness-side) down to '1'.
Maybe the leads themselves are numbered, too - or coded by colours.

You can't damage anything if you take care not to connect other lines towards '16' and '24' that are positive (+).
All others are ground, signal or output lines, can cause no harm when the plug is not connected to the ECU.

For some of the readings like the one you intend to do you can disconnect the accumulator.

For reading out the engine temp sensor you have to read the resistance between pin 23 (all the same at all ECUs) and pin 11 (ground).
Values should be (tolerance within 15%)
                       
0° C        32° F         5,9 kOhm
  20° C     68° F        2,5 kOhm
  40° C    104° F        1,2 kOhm
  60° C    140° F       600 Ohm
  80° C    176° F       325 Ohm
100° C    212° F       190 Ohm

Regards
Norbert


 

Dear Norbert,

Thank you very much for your detailed suggestion.
This Sunday, I checked the value of engine temp sensor between pin 23 and pin11. It was as below.

13.5° C   3,5 kOhm

It seems it is no problem, right?

Regards

Shimizu

Yes, Shimizu,
this value should be within the tolerance.

Does the problem still exist ?

Are you interested in doing a full check?
You would have to find out some parts of the pinout by yourself.
But if you can operate a multimeter you could do the job.

At first, look at the troubleshoooting-section: jetronic.org/en/d-jetronic/troubleshooting - most of the tests are the same for your car, too.

If you have questions: We are here!

Best Regards
Norbert

Hi SHimizu,

according to Chapter Troubelshooting that value seems to be okay.