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Cranks but will not start or if it does not for long

Tiny
SPYNTRAK
  • MEMBER
  • 2007 JEEP COMPASS
  • 2.4L
  • 4 CYL
  • 150,000 MILES
Hi, I am working on the vehicle listed above, the problem is it was making this rumbling, choking type sound when turning the ignition key, and when it did start up it has a really really bad noise and shaking idle, just for a few seconds then it shuts off. The owner had took it to two shops and could not have figured out the problem. I checked the spark plugs (owner had changed them 3 months ago) had a lot of carbon, I clean them, I check a vacuum lines, replaced crankshaft position sensor, clean all connectors, changed the drive belt, oil change, checked all fuses and relays. I even used starting fluid to help it start up. What can it be?
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Wednesday, April 1st, 2020 AT 10:06 AM

10 Replies

Tiny
AL514
  • MECHANIC
  • 4,793 POSTS
Hello, are you hearing any mechanical type noises when it's running? I've seen on these Compass's the rock arms popping of, due to build up in the hydraulic lifters, did you do a leak down test yet to see if any cylinders are sealing correctly. I guess these are prone to this happening due to lack of oil changes. If you pop the valve cover off you may find a couple rocker arms loose or popped of completely.
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Wednesday, April 1st, 2020 AT 1:08 PM
Tiny
SPYNTRAK
  • MEMBER
  • 36 POSTS
No I haven't done the leak down test yet, that was gonna be my next move. Did you see and hear the engine running on the video I sent? If so that's all the engine does sounds smooth but then in seconds you hear it rev up n down for another couple more seconds then just shuts off just like in the video. Actually I was working on removing the valve cover but seeing that it's hasn't been moved since he bought it and it's made out of plastic I didn't want to crack it because it's really stuck on there.
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Wednesday, April 1st, 2020 AT 4:37 PM
Tiny
AL514
  • MECHANIC
  • 4,793 POSTS
Yeah, it sounds like it's hunting for the correct idle, so I would suspect a vacuum leak for the idle, but that abrupt shut off is of concern. But the starting fluid keeps it running? Sounds like the fuel pump isn't keeping up. May be very weak and on its way out. If you have an amp clamp, fuel pumps usually run 6-9amps. See if it's dropping out. You may be dealing with a vacuum leak as well.
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Thursday, April 2nd, 2020 AT 11:50 AM
Tiny
SPYNTRAK
  • MEMBER
  • 36 POSTS
Okay, so now I have gotten it to sun smoothly, two things are still left one the car takes a little more time then usual to start up. What can cause that?Second when I put it on drive it sort of makes this quick jerk when pressing the gas pedal and also takes off slow like has no power. The rpm was at reading 4 thousand and speedometer was just starting to move upward. Can that be the speed sensor lack of power?
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Monday, April 13th, 2020 AT 11:38 AM
Tiny
SPYNTRAK
  • MEMBER
  • 36 POSTS
Oh, and on the scanner it's reading o2 senor bank.
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Monday, April 13th, 2020 AT 11:39 AM
Tiny
SPYNTRAK
  • MEMBER
  • 36 POSTS
Okay, so now I have gotten it to run smoothly, two things are still left one the car takes a little more time then usual to start up what can cause that?Second when I put it on drive it sort of makes this quick jerk when pressing the gas pedal and also takes off slow like has no power. The rpm was at reading 4 thousand and speedometer was just starting to move upward. Can that be the speed sensor lack of power?
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Tuesday, April 14th, 2020 AT 11:28 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

An extended crank before starting is usually the result of one of two things, fuel pressure drop off or worn spark plugs. I need you to try something. Follow this simple test when starting.

1) Turn the key from off to the run position (engine off) and count to 5.
2) Turn the key off and repeat step 1, three more times.
3) On the last time, see if it starts quickly.

Let me know the results of that. Or, here is a link that explains how to test fuel pump pressure and pressure drop off:

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

Now for the 4,000 RPM's and the speedometer just starting to move sounds like the transmission is slipping. Is the transmission fluid clean and full?

Let us know.

Joe
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Thursday, April 16th, 2020 AT 9:09 PM
Tiny
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  • MEMBER
  • 36 POSTS
I tried the key trick and still same results takes a while to turn over. Am not sure about the trans fluid there's not a way to check. It's a CVT transmission.
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Saturday, April 18th, 2020 AT 4:12 PM
Tiny
SPYNTRAK
  • MEMBER
  • 36 POSTS
I also noticed the traction light stays on when in idle.
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Saturday, April 18th, 2020 AT 4:13 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

The ATF can be checked, but requires a special dipstick. If you look, you'll find the dipstick tube which is capped off. That gets removed and then a dipstick can be used.

If you decide to check it and can get your hands on a dipstick from a dealer, make sure if it is low only to add Mopar(R) CVTF+4 (Automatic Transmission Fluid) or equal.

Now the delayed start. Has the vehicle been tuned up recently? Have you checked engine compression? Is fuel pressure within spec?

Let me know.
Joe
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Saturday, April 18th, 2020 AT 8:04 PM

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