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Random no starts and stalls

Tiny
DANIEL R. BIRDSEY
  • MEMBER
  • 1999 FORD TAURUS
  • 3.0L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 165,000 MILES
Any weather, any time, all totally random as far as I can tell. Engine cranks fine, but wont fire. Or if it does fire, will run fine for a day, or two or ten, then will stall randomly. Wont start again after that stall, for another five minutes to seven days. Checked spark, it is good. We have put in a new fuel pump, new fuel filter, new crankshaft position sensor. Because it happens on both hot/cold and dry/wet days, I am running out of ideas. Please! Any thoughts?

engine code U, single OHC
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Saturday, June 25th, 2016 AT 2:21 PM

6 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
How long since a tune-up? Any applicable trouble codes. If there was a code, what was the number? I need more than just U-code?

Usually if it cranks good but wont start, have a helper crank it while you visually check for spark at the spark plugs, if spark everywhere, use a gauge and check proper fuel pressure and fuel injector pulse, engine cranking.
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Wednesday, May 3rd, 2017 AT 11:40 AM
Tiny
DANIEL R. BIRDSEY
  • MEMBER
  • 4 POSTS
Fuel pressure was checked, good. No dtc codes. Spark has been checked, all good. Tune up within last 10,000 miles.
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Wednesday, May 3rd, 2017 AT 11:40 AM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
In your post, you mentioned a U code, I thought?

If you have proper amounts of air--fuel--spark--compression at the proper time, I am not sure why it wont start? If you can check to see if system is running rich or lean, when problem is ongoing, that might point us in the right direction?
I usually want to check MAF sensor, but, I cannot guarantee anything? Do not replace anything unless your testing points in that direction.
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Wednesday, May 3rd, 2017 AT 11:40 AM
Tiny
DANIEL R. BIRDSEY
  • MEMBER
  • 4 POSTS
Engine code U is the VIN number for that particular engine. Unfortunately, problem appears to be absolutely random. Have not yet tested MAF sensor. Planning to check that and camshaft position sensor next weekend. I know it is for top be electrical, competitive input related somehow. I mean, combustion is based on fuel, air, spark, and compression. And I have got those. Even when it acts like it does not want to fire and start, I can test and still see spark on all cylinders, good fuel pressure. Granted, I have never tested compression on this, but when it does run, it runs great. So compression, by logic, should not be the issue. I'll research MAF and camshaft position sensor and definitely test those next weekend. Otherwise, I am lost on this one. Just does not make sense.
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Wednesday, May 3rd, 2017 AT 11:40 AM
Tiny
DANIEL R. BIRDSEY
  • MEMBER
  • 4 POSTS
Holy typos. Sorry. I meant to say "electrical, computer input"
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Wednesday, May 3rd, 2017 AT 11:40 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
The next step would be to check injector pulse, here is a guide to help you see how to do it.

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

Please let us know what you find

Best, Ken
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Wednesday, May 3rd, 2017 AT 11:40 AM

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