I have a ca18det in my datsun 1200 and wanted to know how to wire the ecu etc? I mean what colour wires from the harness goes to the ignition switch via a relay

See Tommo's wiring Thread

http://datsun1200.com/modules/newbb/v ... at&topic_id=41988&forum=1

the engine starting but it is running really rich either that or the spark is weak. how to resolve this issue?

Did you fiddle with black box thing on throttle body? This can do that.

the throttle position sensor? no I didn't move it

Most people straighten it up, and the results in the ECU thinking it's off idle and add more fuel like a accellerator pump jet.. Also, chipped ECUs will run like crap too. There are too many floating around these days. Unlikely to be weak spark with 4 coils, unless all 4 are cooked. Check your earths and measure the 12V at the coils while engine is running. Could also be old and leaky injectors.

I checked the coil pack for battery voltage.. good
I checked for continuity on ground circuit .... good
I removed all injectors and cleaned them .... doubt all 4 are leaking

changed the plugs again last night and the car ran like a beast for about half an hour and then started to run on 3 cylinders.. pulled all the plugs and all were black and fowled... any other advice? also someone was telling me that it could be the air flow sensor... I checked it against the factory service manual and it's within specifications ... running out of ideas here guys

perhaps the ecu still thinks the engine is cool and continues to dump extra fuel? problem with temp sensor?

Maybe check the ecu for fault codes.

Check the temp sender for the ecu. It should be 70-90ohms at 60deg and 21-24ohms at 100deg. or code 13 should show in the ecu if it is faulty.