Intermittent crank/no-start?

DBOGARDE

MEMBER
2014 VOLKSWAGEN JETTA
2.0L
4 CYL
2WD
MANUAL
81,000 MILES

My son's base model car listed above has an intermittent (1x every 2 weeks) crank no-start problem. Brand new battery, alternator good, starter good. Reads 12.5v when trying to start. The temporary solution has been to disconnect the battery for a couple hours, reconnect, and the car starts right up! May be coincidental and resting may contribute to the start. Good for 2 weeks, then it happens again. This has been consistent at least 5 times. VW dealer had it for 9 days and could not replicate the problem, so could not fix it (they never drove it - just tried to start it daily and it started right up). I got it to fail last week and VCDS showed No engine fault codes. It eventually started later. It's intermittent so I need this fixed before I give it back to him.

Sunday, April 16th, 2023 AT 7:29 PM

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
51,615 POSTS

Intermittent problems are the most difficult to repair. When it doesn't start, can you turn the key on without cranking the engine to hear the fuel pump run in the tank for about 5 seconds? Also, when it doesn't start will the engine run on starting fluid? If not when it won't start let's check for spark.

Here are guides to help us get started:

https://www.2carpros.com/articles/how-to-check-for-ignition-spark

This way we can narrow down which system is failing. Also, when you say no codes was this done as a CAN scan? If not, I would try it to see if anything comes up. You can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Here is one for about $99.00 if you need it:

https://amzn.to/3ZixY4v

Please go over these guides and report back.

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Monday, April 17th, 2023 AT 12:19 PM

DBOGARDE

MEMBER
2 POSTS

I appreciate the suggestions. Yes, the codes were pulled using my VAGCOM software over CAN. When it failed, I didn't pay attention to the fuel pump priming in the on position, but have been listening for it ever since, and every time it starts, I can hear it prime for a few seconds. I did notice the RPM bouncing around 200rpm when it failed so kind of ruling out the crank position sensor. Since then, I picked up an in-line spark tester, Noid injector tester, and fuel pressure test kit, and the laptop all sitting in my trunk ready for the next time it fails. Fuel pressure at the rail is 50PSI after priming, and 59PSI running - so there is the baseline I'm working from. Is there anything else I should look for next time it fails on me? What would potentially cause a crank/no-start and not register an engine fault code? I guess it's a waiting game at this point as I can't really do anything but drive the hell out of it and hope it breaks down so I can do more diagnosing - as messed up as that is.

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Monday, April 17th, 2023 AT 12:36 PM

KEN L

MASTER CERTIFIED MECHANIC
51,615 POSTS

Sometimes it's all you can do, I have seen a breakout box that can be installed which monitors the system and can give clues to the system that is breaking down, both methods work.

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Tuesday, April 18th, 2023 AT 9:00 AM