冷車噴油嘴的問題:Problem with cold start injector

冷車不好發動及油耗過大可能的原因之一，因為引擎溫度訊號不良或是靈車噴油嘴堵塞或內漏。拆開來測試看看，原廠零件不便宜，大部分的保養廠商都會少裝一個零件可能導致漏真空。

 Problem with cold start injector / thermal time switch circuit 

The cold start injector provides a brief blast of fuel only when the starter motor is running (when the key is in position III). It operates based on info from a thermal time switch, which tells the cold start injector when the engine is cold. If the engine is warm, the thermal time switch breaks the circuit and the cold start injector doesn’t fire.

Testing the cold start injector is fairly easy. Just remove it from the intake manifold (and make sure to bolt down the ground wires again). Now have a friend start try to start the car while you hold the cold start injector in a small bottle or napkin or some such. If it sprays out fuel, you’re good to go. If it doesn’t, then you’ve got a problem.

The best way to try and solve this problem of whether it’s the cold start injector or the thermal time switch causing the problem is to get out your voltage meter and hook it up across the two little plugs in the plug that hooks up to the cold start injector. If, when you start the car, you get 12 volts across the cold start injector plug, then the thermal time switch is working and the cold start injector is faulty. If you don’t get 12 volts across the plug, then the thermal time switch needs to be replaced.

Cold-start valve

Parts:
1. Electrical connection
2. Fuel supply with strainer
3. Valve (electromagnet armature)
4. Solenoid winding
5. Swirl nozzle
6. Valve seat

The cold-start valve
The cold-start valve  is a solenoid-operated valve. An electromagnetic winding is fitted inside the valve. When unoperated, the movable electromagnet armature is forced against a seal by means of a spring and thus closes the valve. When the electromagnet is energized, the armature which consequently has lifted from the valve seat opens the passage for the flow of fuel through the valve. From here, the fuel enters a special nozzle at a tangent and is caused to rotate or swirl.The result is that the fuel is atomized very finely and enriches the mixture in the manifold downstream of the throttle valve. The cold-start valve is so positioned in the intake manifold that good distribution of the mixture to all cylinders is ensured.

Thermo-time switch
The thermo-time switch limits the duration of cold-start valve operation, depending upon temperature.The thermo-time switch consists of an electrically heated bimetal strip which, depending upon its temperature opens or closes a contact. It is brought into operation by the ignition/ starter switch, and is mounted at a position which is representative of engine temperature. During a cold start, it limits the “on” period of the cold-start valve. In case of repeated start attempts, or when starting takes too long, the cold-start valve ceases to inject. Its “on” period is determined by the thermo-time switch which is heated by engine heat as well as by its own built-in heater. Both these heating effects are necessary in order to ensure that the“on” period of the cold-start valve is limited under all conditions, and engine flooding prevented. During an actual cold  start, the heat generated by the built-in heater is mainly responsible for the “on” period (switch off, for instance, at –20 °C after 7.5 seconds). With a warm engine, the thermo-time switch has already been heated up so far by engine heat that it remains open and prevents the cold-start valve from going into action.