My 2005 Chevy Colorado has the I4 2.8L engine and is difficult to start when the engine is cold. It runs perfect once started. What components on this vehicle ensure extra fuel for cold starting? I am not aware of an extra (cold temp) injector or an intake manifold temp sensor to provide the ECM with temp information, so assume the coolant sensor must provide this information in order to extend the fuel injection duration interval? The temp gauge works as expected, so I assume the coolant sensor is working properly. There are no trouble codes stored. Note that I have verified cranking voltage, proper fuel pressure, and that no leak down occurs while sitting. The truck has 85k miles and replacing the plugs and throttle body did not help with cold starting, though it does run perfectly once started, and also starts easily when warm. What am I overlooking?
Thanks,
John
You may be losing fuel and fuel pressure back into the gas tank while it sits. Try this: turn the key to Run (not all the way to Start.) The fuel pump should run for a few seconds. You may hear it. Turn back to Off, then Run. Do this “key dance” a few times and then turn the key all the way to Start.
How does it start now? Can you hear the fuel pump before you start it?
Thank you for your response. The fuel pressure does not bleed down while sitting. It’s at 55 lbs prior to turning the key and instantly jumps to 58 when the key is turned to the on position, so the “dance” does not help. I even added a relay to switch power to the fuel pump while cranking to eliminate any fuel pressure concerns. The fuel pressure is 58 while running and will drop to 48 when full vacuum is applied to the fuel regulator.
Might there be more than one temperature sensor? Maybe the one for the engine control is not OK. There is enough coolant in there - right?
On a fuel injected engine, there has to be four primary inputs during a cold start.
Crankshaft sensor, coolant temp sensor, throttle position sensor, and MAP/MAF sensor.
That’s where I’d look.
Tester
I am only aware of one coolant sensor, and only has two wires. Because the
temp gauge is working properly, I assume the sensor is good.
The crankshaft sensor and throttle position sensor are both new, so that
leave the MAP and MAF sensors.
The MAP sensor is also an intake air temp sensor, so that may be the next
logical step.