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Thread: Hard Crank and Power Loss

  1. #1
    Join Date
    Feb 2019
    Location
    Ohio
    Posts
    3

    Hard Crank and Power Loss

    I just purchased a beautiful '89 SC, Silver, Manual.

    I don't have much history on this car, they guy I bought it from didn't have it very long and it was a trade to him.

    The car starts just fine cold. After driving for about 15 minutes or so it will start acting up. The RPM gauge stops working, on acceleration the car lunges (almost like it's only firing every other throw). If I shut the car off, wait a few seconds until everything shuts off, and after about three or four hard cranks it will fire up and run like nothing has happened. The hard crank is almost like the battery is dying. I have had the battery and alternator checked and both are good (alternator is on the low end of the OK), I bought an OBD-1 reader but haven't figured out how to use it.

    I am more of a driver/oil changer type mechanic. If it doesn't require any specific skills I can normally do it if the instructions are clear (that seems to be the hardest part about wrenching).

  2. #2
    Join Date
    Dec 2007
    Location
    Salem OR
    Posts
    7,173
    Until you learn how to read codes, you run the risk of firing the part$ cannon at it, but....those symptoms are typical of harness and component issues, specifically the front harness that connects to the cam & crank sensors, DIS & coil, and.... the cam sensor itself. There may be other issues, of course.

    Inspect the harness for damage & oil soaking. Read the codes to confirm the cam sensor. See this page [ http://www.njtacc.com/tech/eec_codes.html] for a code list that includes those specific to the SC. In your case, I'd suspect at least a 19. What happens if you disconnect the cam sensor and run it that way? Cam sensor is below the supercharger snout, next to the pass. side head, on the timing cover. Be careful with all harness connectors...given their age, the clips tend to break easily.



    https://www.autozone.com/engine-mana...nsor/31289_0_0

    If you pull it, check for green corrosion on the pins and confirm it is using only one internal red rubber gasket.

    Feel free to search here for previous threads on bouncing or dancing tach or cam sensor symptoms. This is one you should read: http://www.sccoa.com/forums/showthre...t=dancing+tach

    Warm/hot start issues can also be the result of vacuum leaks. Tons of those on the SC, not just hoses, but the intercooler tube flanges as well.

    Be aware that the SC has complex electronics that can be tricky to troubleshoot without basic diagnostic equipment and patience. Ground connections are critical as well. Besides the code reader in general you'll want the EVTM to help w/wiring issues. eBay is a good source for the EVTM & factory repair and diagnosis manuals.
    Last edited by KMT; 03-21-2019 at 06:30 PM. Reason: Added cam sensor image and link

  3. #3
    Join Date
    Jul 2002
    Location
    Roanoke, Virginia
    Posts
    3,348
    Quote Originally Posted by Popeye1am View Post
    I just purchased a beautiful '89 SC, Silver, Manual.

    I don't have much history on this car, they guy I bought it from didn't have it very long and it was a trade to him.

    The car starts just fine cold. After driving for about 15 minutes or so it will start acting up. The RPM gauge stops working, on acceleration the car lunges (almost like it's only firing every other throw). If I shut the car off, wait a few seconds until everything shuts off, and after about three or four hard cranks it will fire up and run like nothing has happened. The hard crank is almost like the battery is dying. I have had the battery and alternator checked and both are good (alternator is on the low end of the OK), I bought an OBD-1 reader but haven't figured out how to use it.

    I am more of a driver/oil changer type mechanic. If it doesn't require any specific skills I can normally do it if the instructions are clear (that seems to be the hardest part about wrenching).
    What you've described is the common symptoms of a bad Cam Sensor. The Cam sensor can be found underneath the front snout of the Supercharger on the passenger side. Looks like a black hockey puck. The sensor is relatively cheap ($16-$35 on Rockauto).

    Before you spend money - if you want to test it as the issue. Unplug the sensor. The car will start after 3 or 4 hard cranks like you mention and run off the ECU.

    -Tim
    Current Collection
    1994 Thunderbird SC - Auto converted to 5spd

    1995 Thunderbird SC - Auto

    1994 Thunderbird SC - 5spd
    1989 Thunderbird SC - 5spd - Daily Driver
    1990 Thunder/Cougar XR7 - 5spd
    1994 Thunderbird SC - 3v Project

  4. #4
    Join Date
    Nov 2012
    Location
    Canton, GA
    Posts
    265
    In December 2017, I had a similar issue with my 1990 SC 5-speed. The car ran ok for 10-15 minutes, then it would run rough and the tach went dead (or bounced like crazy). I remember replacing my sparkplugs, air filter, DIS module, battery, and Camshaft sensor (the last one fixed my tach problem). So, a little troubleshooting is a good idea before replacing all the things.

    However, my harmonic balancer was also shot and it had actually snapped off two of the bolts (which made removal difficult). My dad thought the harmonic balancer was the reason my car shook and vibrated so hard, but now I wonder if my camshaft sensor caused the car to shake and prematurely wear out the harmonic balancer. Iím not an expert like the other guys, but I thought I would say something since I had a similar issue.

  5. #5
    Join Date
    Feb 2019
    Location
    Ohio
    Posts
    3

    Fixed

    So I ran the codes (112) and replaced the Air Temp Sensor. I also replaced the cam sensor and the problem appears to be fixed.

    Thank you to each of you for the help.

  6. #6
    Join Date
    Dec 2007
    Location
    Salem OR
    Posts
    7,173
    Glad you sorted it out, thanks for the follow up!

    Ken

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