Engine Performance problem
2002 Cadillac Escalade Ext V8 All Wheel Drive Automatic 80'000 miles
I have a 2002 ext that cranks longer than normal when warm after sitting, seems to start fine when cold, it has been doing it for months, always start, just takes longer than normal, also runs a little rough for a couple seconds after the hard start.
I would check the fuel pressure during the hard start. It could be bleeding off back through the pump, and/or slow to build causing an extended crank. The rough run could be due to low initial pressure. It should run in the neighborhood of 45 psi, and should build at key on for 2 seconds. The fuel filter should also be checked and replaced if it has been in service for some time.
October, 20, 2010 AT 12:56 AM
The fuel pressure does bleed down over time but not fast, it always comes right up to 50 psi on the 2 second prime.
October, 20, 2010 AT 11:47 PM
It would help to have the pressure tester installed when the vehicle is exhibiting the long crank, see if it has to reach a certain pressure before it lights off. There are not too many causes for an extended crank, and often times it is fuel related. If it was a cold concern, I would also consider fuel quality, but that does not seem to be the case. I would not confidently suspect a crank sensor that has hot soak issues, or increases resistance as it soaks, it is possible. You can check spark and injector signal, and if those are all present during the start of the long crank, I doubt it has a problem. This being an 02, it does have a fuel pressure regulator, and a return line. You could possibly crimp a flexible part of the return line and see if the extended crank is still present. If there is a vacuum line off of the regulator, check for liquid fuel in it. I have provided you a diagnostic chart for hard start, it is a general listing of possibilities, some of which I highlighted already.
DEFINITION: Engine cranks OK, but does not start for a long time. Does eventually run, or may start but immediately dies.
" Refer to Important Preliminary Checks Before Starting in Symptoms - Engine Controls.
" Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Engine Controls Schematics.
" Search for bulletins.
" Test the engine coolant temperature (ECT) sensor for being shifted in value. Connect a scan tool. Compare the engine coolant temperature against the intake air temperature (IAT) on a cold engine. The ECT and IAT sensor values should be within 3 C (5 F) of each other. If the ECT sensor is out of range with the IAT sensor, check the resistance of the ECT sensor. Refer to Temperature Versus Resistance for resistance specifications. Replace the ECT sensor if the resistance is not within the specification. If the sensor is within the specification, repair the ECT signal circuit for high resistance.
" Inspect the mass air flow (MAF) sensor installation. A MAF sensor that is incorrectly installed may cause a hard start. Important: The embossed arrows on the MAF sensor indicate the direction of the intake air flow. The arrows must point toward the engine. Install the MAF in the proper direction. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement.
" Inspect the camshaft position (CMP) sensor for proper mounting and/or a bad connection. A long crank time occurs if the PCM does not receive a CMP signal.
" Inspect the fuel pump relay operation. The fuel pump should turn ON for 2 seconds when you turn ON the ignition. Refer to Fuel Pump Electrical Circuit Diagnosis.
" A faulty in-tank fuel pump check valve allows the fuel in the lines to drain back to the tank after the engine stops. Refer to Fuel System Diagnosis.
" Inspect both injector fuses for being open. An open injector fuse causes four injectors and four ignition coils not to operate. Replace the fuse. Inspect the injector circuits and the ignition coil circuits for an intermittent short to ground.
" Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis.
" Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis.
" Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis.
" Test both injector fuses for being open. An open injector fuse causes four ignition coils and four injectors not to operate. Replace the fuse. Inspect the ignition coil circuits and the injector circuits for an intermittent short to ground.
" Inspect for proper ignition voltage output with J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis.
" Remove the spark plugs and check for the following: - Correct heat range
- Wet plugs
- Improper gap
- Burned electrodes
- Heavy deposits
Refer to Spark Plug Inspection in Engine Electrical.
" Determine the cause of the fouling before replacing the spark plugs if the spark plugs are gas, coolant, or oil fouled. Refer to DTC P0172 or P0175 for diagnosis of the rich condition. Refer to Spark Plug Inspection in Engine Electrical for diagnosis of coolant or oil fouled spark plugs.
" Inspect for bare or shorted ignition wires.
" Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis.
" Excessive oil in combustion chamber--Leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical.
" Low cylinder compression--Refer to Engine Compression Test in Engine Mechanical.
" Combustion chambers for excessive carbon buildup. Clean the chambers using top engine cleaner. Follow the instructions on the can.
" For incorrect basic engine parts. Inspect the following: - Cylinder heads