Engine cranks but does not start

QUIET STORM

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2005 CHEVROLET COLORADO
3.5L
5 CYL
4WD
AUTOMATIC
200,000 MILES

My truck is not starting on its own. To make this easy, I've changed fuel pump, crank sensor, Cam sensor, fuel regulator, serviced the vehicle, because of starting related reasons. Now when I attempt to start the truck it will not. Before it would have started on the second or third crank but nothing anymore. So, I've checked sensor connections, the grounds on the fenders and also the relays in the engine and everything same to be working. So, I put my computer on the truck and got Crankshaft position (CKP) -Exhaust camshaft position correlation, Camshaft Position Sensor Circuit, and Camshaft Position Sensor Performance. Even though they were just changed. Now when I clear all codes, the truck starts right up, If I disconnect the battery and wait for a minute and put the terminals on then the truck starts right up and runs like a dream without any issues. But when I turn the truck off, for about 3 minutes then I will have to clear codes on the computer or disconnect the terminals again to get the truck to restart. Do we believe the truck computer? I really need help, also just to let you know the passcode lock isn't flashing either.

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,732 POSTS

Hi,

We need to narrow it down. When it won't restart, what is lost, fuel, or spark to the plugs? I need you to try something. Using starting fluid, see if it will start for a couple of seconds and then stall. I'm trying to narrow things down. If it does start and then stall, I will know its fuel related. If there is no change, I need you to reconfirm there is a good hot blue snapping spark. Here is a link showing how to test:

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

Let me know what you find or if you have other questions. Also, let me know the specific codes you are getting.

Take care,

Joe

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Monday, February 14th, 2022 AT 6:17 PM

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3 POSTS

Hey Joe,

Thanks for the response and sorry I didn't get back sooner. So, this is what I did: I went to the shop and purchased a new Intake and Exhaust Cam sensor. I replace both when starting, I only get the engine to crank. So, I cleared the computer, still only cranking. I take the new exhaust sensor out and place the old one back in and reset the computer and the truck starts on one crank. However, when I turn it off, I will have to reset the computer for the vehicle to start again. This is weird, I first thought that the sensor was faulty, so I went and purchased another exhaust cam sensor only for the same thing to happen. Different name brand, purchase from different stores. What do you think?
Thanks in advance.

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Monday, February 21st, 2022 AT 2:28 PM

JACOBANDNICKOLAS

MECHANIC
109,732 POSTS

Hi,

That's an interesting one. By chance, are you getting any diagnostic trouble codes when it won't restart? Also, how are you resetting the computer?

Let me know.

Joe

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Monday, February 21st, 2022 AT 7:36 PM

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3 POSTS

Yes, it is very interesting. The two photos show the diagnostic codes I am getting. This first one is when I am using the old Exhaust Sensor, and the second one is when I use the new Exhaust Sensor. I use the diagnostic scanner to reset, or I disconnect the battery for about ten seconds. Both will allow me to restart the vehicle with the old sensor, however if I use the new sensor in the vehicle none of the resetting methods will start the vehicle. I know if I take to the shop, they will tell me to change the sensors according to the reading they will get but all have been changed. Again, Exhaust and Intake Cam sensors, Crank Sensor, Fuel regulator, Fuel Pump. Once the truck is started, it runs great, but it just needs to get started. I thought about the timing chain, but I figured that can't be the issue as it starts the old sensor. It just won't restart once It's turned off. Will have to do a reset and who wants to be in the hood for every time.

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Tuesday, February 22nd, 2022 AT 5:07 AM

JACOBANDNICKOLAS

MECHANIC
109,732 POSTS

If you disconnect the battery, try this. Disconnect both terminals from the battery and then zip tie them together for approximately 30 minutes. This will drain any capacitors in the system and hopefully, if this is a permanent fault, it should eliminate it.

Let me know if that makes any difference. Also, after doing this, see if there are any codes stored prior to starting it.

Let me know.

Joe