Hard starting C5

[Randis]

1999 C5 everything stock. 72000 miles. Car starts good when cold. Have problems when warm. If you shut it off and restart right away it starts fine, but if you wait 10-20 minutes it usually fails to start on the first or second try. The motor cranks good but it doesn't start. Always starts by the third try. When it starts You don't see any smoke from the exhaut and it runs fine. I had the fuel filter changed, didn't help. Fuel pressure checked out fine. You can hear the fuel pump running for about 3 seconds when turning on the key. Different garages all suggest putting different parts on and see what happens. I would like to hear from someone who has seen this problem before. Thanks Randis

[Fixvet]

Check for trouble codes on your DIC. There's a thread by a guy having a/c blower issues on this page with instructions if you don't know how to do it. Very simple.

Post your codes for all can to see.

[c4c5specialist]

Hi there,

At first, I would suggest that you check your throttle body and see how dirty it is.

Remember, that the ECM only knows the original idle air rate and it is LEARNED. When it becomes dirty with carbon type substance, it can cause a hard starting condition.

Allthebest, c4c5

[Randis]

I read your reply and reset all the codes. then I ran the car until it was warm, shut it off and tried to restart it. It wouldn't start on the first try(cranked and cranked but no start) second try fired right up. Rechecked codes and got 28-TCS 1255H. Thanks Randis

[ToolGuy]

Originally Posted by Randis

I read your reply and reset all the codes. then I ran the car until it was warm, shut it off and tried to restart it. It wouldn't start on the first try(cranked and cranked but no start) second try fired right up. Rechecked codes and got 28-TCS 1255H. Thanks Randis

Have you ever cleaned, or had the throttle body cleaned as C4C5 is indicating above?

When it does not start after being warm, have you stopped cranking and stepped on the throttle pedal once, let it go and then tried cranking it?

Just wondering it if is indeed sticking from being dirty and stepping on it once will unstick it enough to let it start.

[Randis]

Yes I had the throtle body cleaned and it didn't help. I have tried restarting it like you suggested, didn't make any difference. Have tried every different way to start it that I can think of(key on and off many times before cranking, gas petal pumped before or during cranking, petal held to the floor).
Thanks again Randis

[ToolGuy]

Well I'm out of ideas... Here's what the GM manual states.

Hard Start
Checks
Action

DEFINITION: Engine cranks OK, but does not start for a long time. Does eventually run, or may start but immediately dies.

Preliminary
Refer to Important Preliminary Checks Before Starting in Symptoms .
Inspect the PCM grounds for being clean, tight and in the proper locations. Refer to Engine Controls Schematics .
Search for bulletins.

Sensor/System
Check the operation of the Column Lock System. Refer to Diagnostic System Check - Body Control System in Body Control System.
Inspect 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, test the resistance of the ECT sensor. Refer to Temperature vs Resistance for resistance specifications. Replace the ECT sensor if the resistance is not within the specification. If the sensor is within the specification, repair ECT signal circuit for high resistance.
Inspect the Mass Air Flow 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 Air Flow (MAF) Sensor Replacement .
Test the Camshaft Position Sensor (CMP) performance. A long engine crank time occurs if the PCM does not receive a CMP signal.

Fuel System
Test 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 malfunctioning check valve in the fuel feed rear pipe allows the fuel in the lines to drain back to the tank after the engine stops. To test for this condition, 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.
Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
Test for a restricted fuel filter. Refer to Fuel System Diagnosis .
Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Ignition System
Test for proper ignition voltage output with spark tester J 26792 . Refer to Electronic Ignition (EI) System Diagnosis .
Remove the spark plugs and inspect for the following conditions:
Correct heat range; refer to Spark Plug Usage in Engine Electrical.
Wet plugs; refer to Spark Plug Visual Diagnosis in Engine Electrical.
Cracks; refer to Spark Plug Visual Diagnosis in Engine Electrical.
Wear; refer to Spark Plug Visual Diagnosis in Engine Electrical.
Improper gap; refer to Spark Plug Replacement in Engine Electrical.
Burned electrodes; refer to Spark Plug Visual Diagnosis in Engine Electrical.
Heavy deposits; refer to Spark Plug Visual Diagnosis 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 Fuel Trim System Rich Bank 1 or DTC P0175 Fuel Trim System Rich Bank 2 for diagnosis of the rich condition. Refer to Spark Plug Visual Diagnosis in Engine Electrical for diagnosis of coolant or oil fouled spark plugs.
Inspect for bare or shorted ignition wires. Refer to Spark Plug Wires Not Operating Properly in Engine Electrical.
Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis .

Engine Mechanical
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:
The cylinder heads
The camshaft
The pistons, etc.
Refer to Engine Mechanical.