Cold Natured
#2
11-07-2007, 03:56 PM
RE: Cold Natured
Hi CB, it could be a cold start injector, or temp sensor problem. Does it run alright after it warms up? Here's some info I found on another board on the issue.
Since cold starting requires considerably more fuel than a warm engine, it must have some means of enriching the fuel to air ratio until the temperature of the engine rises to where the fuel will vaporize more readily.
The cold start injector (or valve) is mounted in the intake manifold at a centrally located area where it can open and allow extra fuel to enter the engine. This is in addition to the normal fuel injection system. The extra cold start injector is electronically controlled by the computer (ECM) and when the temperature sending units signal the computer that the engine is cold, the computer will send a signal to the cold start injector to inject fuel at the same time as the normal injection system. This makes the air fuel mixture richer to compensate for the cold engine requirements.
The cold start injector delivers fuel to all the cylinders and is controlled by a thermo switch and time control. Thermo switches are located in an area in the engine where engine temperatures can be sensed such as the coolant or head temperature. The temperature sensor has the ability to open the switch when the engine is warm enough to run on the regular injection system or close when the engine is cold and needs more fuel. It activates the cold start injector until the temperature deactivates the thermo switch. (The temperature rating on the switches can be checked in shop manuals).
Whether the sensor is controlling the cold start injector long enough can be felt by cold engine hesitations after the vehicle has run for a few minutes and prior to normal engine temperature. If the temperature sensor rating is too high or staying on too long, there can be some flooding or black tailpipe smoke generated for awhile at about normal engine temperature and also lower gas mileage. It is critical that the correct temperature sensors are used so as not to overload the catalytic converters and foul the oxygen sensors or cause the cold start injectors to work improperly.
HOW TO TEST A COLD START INJECTOR -- when the cold start injector is in a hard to reach area, a pressure drop test with the injector in place can be made. A pressure gauge can be installed at the fuel filter location (as illustrated in the fuel injection cleaning system by Airtex) or at the fuel rail connector. The fuel system can be pressurized by momentarily by-passing the fuel pump relay and then connecting an injector activator to the cold start injector to energize it. This will cause a pressure drop on the gauge if the injector is working. It can also be tested to see if up and then activating the cold start injector. The engine should falter or miss when this is done and possibly black smoke appear from the tailpipe due to the excessively rich mixture.
When the cold start injector is easy to get to and can be removed easily, it may be removed and activated in a container to check the fuel spray pattern. This will enable the injector to be cleaned with a commercial spray cleaner if desired when the spray pattern is not conical or when the injector drips while pressurized.
Loss of electrical power could also be a reason for the cold start injector not working. This can be checked by disabling the engine so it won't start and then connect a test light into the cold start injector connector. The test light should stay on for a short duration when the ignition is turned on. A stop watch can be used to measure the duration of the light staying on. Shop manuals will tell how long each duration of activated injector time is required. The above test should be performed on an engine that is cooled off and prior to start up in order for the injector to work in the time established for proper performance.
Winterizing your vehicle is still a wise precaution, but it now requires a different technique due to fuel injection. The cold start injector has replaced the old choke problems and will make for a better performing engine if certain precautions are taken to assure that it is working properly.
The cold start injector (or valve) is mounted in the intake manifold at a centrally located area where it can open and allow extra fuel to enter the engine. This is in addition to the normal fuel injection system. The extra cold start injector is electronically controlled by the computer (ECM) and when the temperature sending units signal the computer that the engine is cold, the computer will send a signal to the cold start injector to inject fuel at the same time as the normal injection system. This makes the air fuel mixture richer to compensate for the cold engine requirements.
The cold start injector delivers fuel to all the cylinders and is controlled by a thermo switch and time control. Thermo switches are located in an area in the engine where engine temperatures can be sensed such as the coolant or head temperature. The temperature sensor has the ability to open the switch when the engine is warm enough to run on the regular injection system or close when the engine is cold and needs more fuel. It activates the cold start injector until the temperature deactivates the thermo switch. (The temperature rating on the switches can be checked in shop manuals).
Whether the sensor is controlling the cold start injector long enough can be felt by cold engine hesitations after the vehicle has run for a few minutes and prior to normal engine temperature. If the temperature sensor rating is too high or staying on too long, there can be some flooding or black tailpipe smoke generated for awhile at about normal engine temperature and also lower gas mileage. It is critical that the correct temperature sensors are used so as not to overload the catalytic converters and foul the oxygen sensors or cause the cold start injectors to work improperly.
HOW TO TEST A COLD START INJECTOR -- when the cold start injector is in a hard to reach area, a pressure drop test with the injector in place can be made. A pressure gauge can be installed at the fuel filter location (as illustrated in the fuel injection cleaning system by Airtex) or at the fuel rail connector. The fuel system can be pressurized by momentarily by-passing the fuel pump relay and then connecting an injector activator to the cold start injector to energize it. This will cause a pressure drop on the gauge if the injector is working. It can also be tested to see if up and then activating the cold start injector. The engine should falter or miss when this is done and possibly black smoke appear from the tailpipe due to the excessively rich mixture.
When the cold start injector is easy to get to and can be removed easily, it may be removed and activated in a container to check the fuel spray pattern. This will enable the injector to be cleaned with a commercial spray cleaner if desired when the spray pattern is not conical or when the injector drips while pressurized.
Loss of electrical power could also be a reason for the cold start injector not working. This can be checked by disabling the engine so it won't start and then connect a test light into the cold start injector connector. The test light should stay on for a short duration when the ignition is turned on. A stop watch can be used to measure the duration of the light staying on. Shop manuals will tell how long each duration of activated injector time is required. The above test should be performed on an engine that is cooled off and prior to start up in order for the injector to work in the time established for proper performance.
Winterizing your vehicle is still a wise precaution, but it now requires a different technique due to fuel injection. The cold start injector has replaced the old choke problems and will make for a better performing engine if certain precautions are taken to assure that it is working properly.
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