Slow cranking

Discussion in 'Domestics' started by Friday, Apr 13, 2017.

  1. billr

    billr wrench Staff Member

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    It is a similar test, but not the same. From the battery positive to the starter tests the usually-red power cable. From the battery negative to the starter case tests the ground path; which includes ground cables, conductivity between the engine and starter, etc. Both readings should be "near-zero" while cranking (well, always actually). Your battery is at 9.8V while cranking, but voltage from the starter "power in" terminal to the starter case is only 6V, correct. Let's find out if that 3.8V loss is in the + or in the ground, then you know which one to focus on. Worst case... both have a couple of volts loss.
     
  2. Friday

    Friday Hero Member

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    Okay. I did the positive battery post and main terminal on starter test. I hadn't read your post, and was in a hurry, it was starting to sprinkle. While cranking it would show around 1V. When the truck started it would jump to around 12, then slowly go down and stop around 3V. I can do the ground path test tomorrow.
     
  3. billr

    billr wrench Staff Member

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    Just to be sure, the starter terminal you are probing is the large one that the battery cable connects to, not the large terminal that connects to the starter innards via a short cable/strap? The results you last posted don't make sense to me, but let's wait until you check the grounding before I hit you with questions.
     
  4. Friday

    Friday Hero Member

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    Bill:
    I'll redo the test and make sure it is on the correct terminal. Then I'll do the grounding test. This time I will disconnect the fuel pump relay so the truck never starts.
     
  5. Friday

    Friday Hero Member

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    Bill:
    Rain finally stopped and ground dried up enough to crawl under the truck. Positive side reads + 1.4 while cranking. Negative side reads -0.6 while cranking. Also, I'm attaching a sound file of what the truck sounds like when I start. Listen to it and tell me if you think it should spin up faster.
     

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  6. Friday

    Friday Hero Member

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    Does it sound anything like this?
     

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  7. billr

    billr wrench Staff Member

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    I have a comparable vehicle, the '97 Chevy van with a 350; it doesn't crank slow...

    Do you have live-data, can you check what cranking rpm is? (spark or fuel disabled so you can crank it for few seconds and get a reading)

    It sounds like you have accounted for 2V of drop in the cabling. What about the other 1.8V? I'm trying to make the arithmetic come out right.

    Sorry, I can't listen to that file. MP3 is not something I have ever used.
     
  8. Friday

    Friday Hero Member

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    I'm assuming you're not talking about watching the tach while cranking? Something more sophisticated?
     
  9. Friday

    Friday Hero Member

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    Can you play any sound files? I can convert this one into something else.
     
  10. billr

    billr wrench Staff Member

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    The tach may work, but I'm looking for something in the 150-250 rpm range, resolution and accuracy down there will be poor unless your tach is digital. Do you have a scanner that shows live-data? That's what I would use. (I think it should crank at 200-225 rpm)

    If you don't have live-data available... STOP! Let's get you talking to "nickb2" about ELM327 and inexpensive ways to get live-data.

    I am so much a non-user of digital audio/video that I don't know what I can use. If it is a link that I can click on, fine. On yours, doing that took me to a TWAIN thing, then an app store (another unknown to me), then some music pics that had nothing to do with your cranking. You are dealing here with a guy that doesn't have a cell-phone and has never used an ATM...
     
  11. Friday

    Friday Hero Member

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    Let me check my scanner when I get home. I'm out shopping with my granddaughter for a graduation dress.
     
  12. billr

    billr wrench Staff Member

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    Ha, that's another thing I have no skills with; choosing the right dress.
     
  13. Mobile Dan

    Mobile Dan wrench

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    Bill, does your computer have sound card, speakers of any kind? Does it beep when you turn it on?
     
  14. Friday

    Friday Hero Member

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    LOL! I was just the driver. My wife and granddaughter did the picking out. I think I may have paid for the two dresses, as well. I tried to send you the sound file in a different format, but this site does not allow WAV files or WMA files. I'm going to go check my scanner now.
     
  15. Friday

    Friday Hero Member

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    Dan, I tried to upload both a WAV file and a WMA file and the site doesn't allow either. I'm going to try an MPG. The site allows this file type. Don't know if Bill's computer will play it.
     

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