From ex Auto sparks now retired at 76, completely up ON"Bosch K & KE system, The Injection loom does not "plug in" as you say to the main wiring harness, its incorporated with the main harness, which also goes to the 2 ECUs [ Silver & Black ]...with the exception of the Fuel Pump / cold start thermo Timer / 5th Injector / Fast idle control... this loom is totally hard wired and completely separate from the main harness and both ECUs, the "Black" plug you have goes to the Idle control Valve under the manifold......yellow will be "coolent sensor"....brown will be Thermo timer....Blue 5th injector....Green [ if later engine only] will be knock sensor. Fuel Test to start with [ as I feel you may well have "gummed" up metering unit and or all 4 injectors]...so....all 4 injector must be lifted out with there pipes connected...then bridge out 30 & 87 on relay plug...pump now runs, check at all injector Tips there is no Fuel seeping / not even any dampness of fuel as with this Test 35psi will or should be present at the injectors....pushing down the metering Flap slightly will cause the pressure to rise to 42psi approx. and fuel will spray. note these cars if the metering unit "Duff" due to bad old Fuel now gummed up, they will with good ignition system "Fire up" as the 5th injector will spray fuel directly into the manifold...hence it will burst into life on the Fuel in the manifold only....hence stop after a few seconds. so something to go on.....theres loads more. Peter