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