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Starts but will not stay running?

Tiny
1998Z71
  • MEMBER
  • 1998 CHEVROLET TRUCK
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 185,000 MILES
Truck was running fine with a small misfire then I decided to check the codes with an obd2 scanner. Well, it pulled up the same ones it had last year. Now keep in mind I had the truck running to see if it would pull any new codes and it didn’t so, I tried to clear the old codes and as soon as I did the truck shut off and it will not stay running anymore. It will start and run for about 2 seconds then it shtus off. Security light is on, but it has been on for about 2 weeks with no issue.
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Saturday, July 15th, 2023 AT 4:24 PM

9 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,942 POSTS
What are the codes? It sounds like the fuel pump has gone out, if you turn the ignition on without cranking the engine over can you hear the fuel pump run in the tank for about 5 seconds? If not let's see if the engine will run on starting fluid. Here is a guide to help us get started and I have included how to change the dual pump out in case you need it. If the security light is not flashing the system is not enabled.

https://www.2carpros.com/articles/car-not-running-advanced

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Sunday, July 16th, 2023 AT 10:33 AM
Tiny
1998Z71
  • MEMBER
  • 6 POSTS
Yes, I can hear the pump running when I turn the key on. But I can also keep the truck running with carb cleaner if I have somebody spray it when I start the truck. And the check valve on the fuel line has enough pressure that the gas will spray the bottom of the hood when I press it but I don’t have a don’t have a tester to actually test the fuel pressure.
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Sunday, July 16th, 2023 AT 1:23 PM
Tiny
1998Z71
  • MEMBER
  • 6 POSTS
P1345 and p1153.
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Sunday, July 16th, 2023 AT 3:30 PM
Tiny
1998Z71
  • MEMBER
  • 6 POSTS
I have already replaced camshaft and crankshaft sensor last year, but the code was stored in the memory. That’s why I tried to erase them and when I did it shut off the truck and now it won’t stay running. It starts for about 2 seconds then shuts off.
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Sunday, July 16th, 2023 AT 3:33 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,942 POSTS
So, the P1345 code is for the crankshaft sensor so you may have a defective part. Is the security light flashing?

Here is more information on the codes:

P1345: This code refers to a problem with the crankshaft position sensor (CKP) or its correlation with the camshaft position sensor (CMP). It typically indicates a fault in the timing of the engine. Possible causes include a faulty CKP sensor, CMP sensor, or a timing chain/belt issue.

P1153: This code is related to the oxygen sensor (O2 sensor) on Bank 2, Sensor 1. It indicates a problem with the O2 sensor's response time or its ability to accurately measure the oxygen content in the exhaust gas. This could be caused by a faulty O2 sensor, an exhaust leak, or a problem with the engine's air/fuel mixture.

Also, the crankshaft sensor needs to be relearned when changing it out:

Crankshaft Position System Variation Learn

1. Install the scan tool.
2. Apply the vehicle's parking brake.
3. Block the drive wheels.
4. Close the hood.
5. Place the vehicle's transmission in Park (AT) or Neutral (MT).
6. Idle the engine until the coolant temperature reaches 65 C (150 F).
7. Turn OFF all the accessories.

Important: If the CKP System Variation Learn Procedure cannot be completed successfully, refer to DTC P1336 Crankshaft Position (CKP) System Variation Not Learned for additional diagnostic information. See: A L L Diagnostic Trouble Codes (DTC) > P Code Charts

8. Enable the Crankshaft Position System Variation Learn Procedure with the scan tool.

Important: After the ignition switch is turned to the Crank position, the VCM must see a change in the state of brake switch (Released to Applied) to run the learn procedure. Also, the service brakes and the parking brake must be held throughout the duration of the learn procedure.

9. Apply and hold the service brakes.

Important: While the learn procedure is in progress, release the throttle immediately when the engine starts to decelerate. The engine control is returned to the operator and the engine will respond to throttle position after the learn procedure is complete.

10. Slowly raise the engine speed to 4,000 RPM.
11. Immediately release the throttle when the engine speed decreases.
12. Turn OFF the ignition for 15 seconds after the learn procedure is completed successfully.

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Monday, July 17th, 2023 AT 10:34 AM
Tiny
1998Z71
  • MEMBER
  • 6 POSTS
This issue I’m having is to do with fuel I have already fixed the crankshaft sensor problem. I had to replace the timing chain cover cause the sensor kept pushing out under load. The problem I’m having now I believe the computer is shutting off the fuel pump right after start up. I can keep the truck running with choke cleaner, but it shuts off as soon as I stop spraying.
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Monday, July 17th, 2023 AT 12:55 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Is the security light flashing? Also, I would check the fuse for the PCM. Does this truck have two fuel tanks?
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Tuesday, July 18th, 2023 AT 10:07 AM
Tiny
1998Z71
  • MEMBER
  • 6 POSTS
Okay, I got the truck running. I had a friend with a good scan tool to check and clear the computer. But I have a question about my air conditioner. Last year it worked fine and now this year I can’t get the compressor to engage unless I run a hot wire straight to the green wire on the compressor. But then it doesn’t cycle, just stays engaged.
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Tuesday, July 18th, 2023 AT 7:39 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,942 POSTS
Glad you could get it fixed, thanks for letting us know. Please use 2CarPros anytime we are here to help.

Sorry we only handle one problem per thread, please post your new question here, you must be logged in.

https://www.2carpros.com/questions/new

Cheers, Ken
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Thursday, July 20th, 2023 AT 10:12 AM

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