Engine cranks but does not start?

Tiny
JEREMY0507
  • MEMBER
  • 1996 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 133,000 MILES
So I changed both my downstream O2 sensors and my EGR valve and now the truck will not start. It does crank over and acts like it wants to but wont. There are also no codes. Only ones were from the O2 sensors the the EGR valve went so I replaced all of them. Any suggestions would be helpful. Thanks.

PS: The truck did run after the O2 sensors but not after the EGR valve was replaced.
Sunday, August 2nd, 2020 AT 10:09 AM

9 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

Can you give me the code numbers? Codes rarely identify bad parts, just failed systems.

https://www.2carpros.com/articles/car-cranks-but-wont-start

Can you hear the fuel pump run when you turn on the key? You need to test the actual pressure to be sure sufficient fuel is being delivered to the rail.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

When you crank it, does the tachometer move up a little showing RPM? That will tell me if the crank sensor is ending a signal.

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

https://www.2carpros.com/articles/how-to-test-an-ignition-system

Roy
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Sunday, August 2nd, 2020 AT 10:36 AM
Tiny
JEREMY0507
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The codes were; P0137 and P0157. For the 02 sensors. The fuel pressure is 60 PSI and I can hear the pump kicking on. The tachometer gauge goes a little under 1/2 RPM when cranking it over.
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Sunday, August 2nd, 2020 AT 10:58 AM
Tiny
ASEMASTER6371
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The downstream O2 have nothing to do with it not starting. Those sensors have 1 function and that is to monitor the catalytic converters.

Fuel pressure is good.

Can you spray some carburetor cleaner into the air filter ans see if it starts and stalls?

Did you check for spark to one of the plugs while cranking?

I attached a wiring diagram for you. Check the voltage to the pink wire at the sensor for power with the key on.

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Roy

153,154

CIRCUIT DESCRIPTION
The Vehicle Control Module (VCM) supplies a voltage of approximately 0.45 volt (450 mV) between the HO2S High and the HO2S Low circuits.

If this voltage is measured using a 10 megohm digital voltmeter, the voltage may read as low as 0.32 volt. The Heated Oxygen Sensor (HO2S) varies the voltage within a range of about 1.0 volt (1000 mV) if the exhaust is rich to as low as 0.10 volt (100 mV) if the exhaust is lean. The VCM monitors the Heated Oxygen Sensor (HO2S) activity for 100 seconds after a Closed Loop. During the monitor period, the VCM counts the number of times that the HO2S switches from rich to lean and from lean to rich and adds the amount of time it took to complete all switches. With this information, the VCM determines an average time for all switches. If the average time to switch is too slow, a DTC P0153 sets.

When HO2S temperature is below 360°C (600°F), the sensor will not produce any voltage. The sensor will behave like an open circuit. This will result in an Open Loop operation.

The HO2S heater provides for a faster sensor warm-up which allows the sensor to become active in a shorter period of time and remain active during a long extended idle. The DTC P0153 determines if the HO2S is functioning properly by checking its response time. This DTC is a type B DTC.

CONDITIONS FOR SETTING THE DTC
The following conditions will set the DTC:

No Throttle Position (TP) sensor DTCs.
No Evaporative Emissions (EVAP) DTCs.
No Intake Air Temperature (IAT) sensor DTCs.
No Manifold Absolute Pressure (MAP) sensor DTCs.
No Engine Coolant Temperature (ECT) sensor DTCs.
No Mass Air Flow (MAF) sensor DTCs.
No intrusive test in progress.
No device controls active.
System voltage measures at least 9.0 volts.
The HO2S (Bank 2, Sensor 1) average transition time from Lean to Rich is greater than 85 milliseconds.
The HO2S (Bank 2, Sensor 1) average transition time from Rich to Lean is greater than 85 milliseconds.

Response Test Enable

DTCs P0151, P0152, P0154, and P0155 are not present.
A Closed Loop.
The Engine Coolant Temperature (ECT) is greater than 57°C.
The engine run time is greater than 75 seconds.
Engine speed is at least 1100 RPM but no more than 3000 RPM.
The MAF is at least 15 grams per seconds but no more than 55 grams per second.
The EVAP canister purge duty cycle is greater than 0%.
The above conditions are present for more than 2 seconds.
The HO2S (Bank 2, Sensor 1) voltage remains between 0.300 volts and 0.600 volts.

ACTION TAKEN WHEN DTC SETS
The VCM turns on the Malfunction Indicator Lamp (MIL) after the second test failure.

CONDITIONS FOR CLEARING THE MIL/DTC
The VCM turns the MIL off after 3 consecutive driving trips without a fault condition present. A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 40°F from the start-up coolant temperature and the engine coolant temperature exceeds 160°F during that same ignition cycle) or the scan tool clearing feature has been used.

DIAGNOSTIC AIDS
Check the HO2S heater operation.

NOTE: Never solder the HO2S wires. For proper wire and connector repairs, refer to Wiring Repairs.

TEST DESCRIPTION
The numbers below refer to the step numbers in the diagnostic table.

4. This step checks for physical damage to the engine components and the converter.
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Sunday, August 2nd, 2020 AT 11:16 AM
Tiny
JEREMY0507
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  • 27 POSTS
There is spark at the coil but not the plugs.
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Sunday, August 2nd, 2020 AT 1:24 PM
Tiny
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Check your cap and rotor to be sure they are not damaged.

Look for a burn mark on the rotor.

Check the wire at the distributor cap and see if spark is going into the cap.

Also, make sure the distributor is turning.

Roy
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Sunday, August 2nd, 2020 AT 1:30 PM
Tiny
JEREMY0507
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So the rotor does turn, but there is crust residue on all the leads inside the cap. Here is a picture:
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Sunday, August 2nd, 2020 AT 2:24 PM
Tiny
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Replace the cap and rotor.

Did you check for spark to the coil to be sure the wire is good?

Roy
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Sunday, August 2nd, 2020 AT 2:32 PM
Tiny
JEREMY0507
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I checked the coil wire, it's. Good.I will get a cap an rotor. Hopefully that’s it. Thanks I appreciate the help.
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Sunday, August 2nd, 2020 AT 2:37 PM
Tiny
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You are welcome.

Always glad to help.

Roy
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Sunday, August 2nd, 2020 AT 2:41 PM

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