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Engine cranks, sputters, backfires, no start

Tiny
JOHN CLARK8
  • MEMBER
  • 2005 JEEP GRAND CHEROKEE
  • 3.7L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 257,000 MILES
When I turn the key engine crank tries to start sputters then backfires no start.
Wednesday, January 6th, 2021 AT 8:03 AM

20 Replies

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

I would start with a compression test to be sure the timing chain has not failed. Backfiring usually has to do with timing.

https://www.2carpros.com/articles/engine-backfires-while-running

https://www.2carpros.com/articles/how-to-test-engine-compression

https://www.2carpros.com/articles/how-a-timing-belt-works

Roy
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Wednesday, January 6th, 2021 AT 8:36 AM
Tiny
JOHN CLARK8
  • MEMBER
  • 17 POSTS
I would but vehicle does not start as mentioned above.
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Wednesday, January 6th, 2021 AT 11:32 AM
Tiny
JOHN CLARK8
  • MEMBER
  • 17 POSTS
The vehicle was running before but when it got hot I would get traction not enable and vehicle would just shake. Turn it off wait then restart engine light flashes 10 times.
Put on scanner code for crankshaft replace and replaced plugs.
Clear codes rescan code comes up for camshaft. Replaced now no codes.
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Wednesday, January 6th, 2021 AT 11:51 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
It does not need to run for a compression test at all. It is done by cranking only.

The fact you have cam and crank sensor codes tells me it may be timing.

Roy
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Wednesday, January 6th, 2021 AT 12:16 PM
Tiny
JOHN CLARK8
  • MEMBER
  • 17 POSTS
The cam sensor came up when I took it out by accident and when I put in old one that's when the code came up. The wire was not connected tight so I reconnected after no codes and would I have not notice if timing was off.
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Wednesday, January 6th, 2021 AT 12:53 PM
Tiny
ASEMASTER6371
  • MECHANIC
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Let me know the results of the compression test.

Roy
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Wednesday, January 6th, 2021 AT 12:59 PM
Tiny
JOHN CLARK8
  • MEMBER
  • 17 POSTS
Also video for checking timing and compression is not available.
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+1
Wednesday, January 6th, 2021 AT 1:04 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
You can rent a tester at a parts store and the guide I sent you shows you how to perform the test.

Roy
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Wednesday, January 6th, 2021 AT 1:10 PM
Tiny
JOHN CLARK8
  • MEMBER
  • 17 POSTS
I am in Canada and not sure if they rent tools here. But you said if I just want you to know if I had compression by using paper towel.
Also if timing is off how is this fixed? Also the engine lights flashes 10 times.
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Wednesday, January 6th, 2021 AT 1:38 PM
Tiny
ASEMASTER6371
  • MECHANIC
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You need a gauge to test. You need 140-160 pounds in each cylinder. The paper towel is not a valid test.

If it is off, then the front of the motor has to be torn down to find out what failed in the timing system.

I attached a youtube video of the procedure for you to follow.

https://www.youtube.com/watch?v=0bHxW0qU4WQ&t=4s

Roy
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Wednesday, January 6th, 2021 AT 1:46 PM
Tiny
JOHN CLARK8
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  • 17 POSTS
If that the issue then what's the next step?
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Wednesday, January 6th, 2021 AT 2:08 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
If the compression is low, then you need to insert shop air into each cylinder that is low to see where the compression leak is located.

It will either come out the exhaust, the air filter, or the oil fill cap.

You need to determine this prior to tearing down the motor.

Roy
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Wednesday, January 6th, 2021 AT 2:17 PM
Tiny
JOHN CLARK8
  • MEMBER
  • 17 POSTS
No if there is no compression issue what's next?
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Wednesday, January 6th, 2021 AT 2:30 PM
Tiny
ASEMASTER6371
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As I stated in my last response, shop air is inserted into the cylinders to determine where the compression leak is located.

Roy
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Wednesday, January 6th, 2021 AT 2:43 PM
Tiny
JOHN CLARK8
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  • 17 POSTS
I will reword it if the compression is okay, what would be the step?
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Wednesday, January 6th, 2021 AT 4:57 PM
Tiny
ASEMASTER6371
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One step at a time. Keep me updated on the compression test.

Roy
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Wednesday, January 6th, 2021 AT 5:01 PM
Tiny
JOHN CLARK8
  • MEMBER
  • 17 POSTS
Cannot rent tools COVID. Any other way to test?
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Thursday, January 7th, 2021 AT 9:41 AM
Tiny
ASEMASTER6371
  • MECHANIC
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Nope, you need to buy a cheap one. Do you have any Harbor Freights around you? They have some cheap test equipment.

Roy
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Thursday, January 7th, 2021 AT 9:53 AM
Tiny
JOHN CLARK8
  • MEMBER
  • 17 POSTS
No, I am in Ontario Canada lock down until 28th.
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Thursday, January 7th, 2021 AT 10:37 AM
Tiny
ASEMASTER6371
  • MECHANIC
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Okay, you will have to wait until you can get the tool.

Roy
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Thursday, January 7th, 2021 AT 10:49 AM

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