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Thread: Slow Crank

  1. #1

    Default Slow Crank

    Hello again,

    1985 GT 5.0 newly rebuilt motor installed last month. Thought everything was good to go but the starter was really slow to crank. Took the spark plugs out and somewhat faster but not near enough to start engine (especially with in). Tested the battery (tried another one as well), tested starter, bought new starter and installed only to have the same slow crank. All connections are clean, new solenoid, new positive cable. Unbolted the starter but left positive lead on and used jumper cable to ground starter to frame. Seemed to me it spun like it did on the bench test at the parts house. Lights dim and pulsate when turning over as if there is a major drain going on somewhere. Checked grounding strap connection too. Turned the crankshaft with torque wrench and takes *maybe* 20-25ftlbs to turn, so clutch binding doesn't seem likely. My thinking is electrical/grounding but I'm running out of options of known things to try.

    To add: I have used jumper from installed starter to frame and also bypassed grounding strap with cables. Any help/suggestions would be appreciated. Surely someone out there has seen this before. TIA

  2. #2

    Default

    Valves adjusted correctly?

    Distributer 180 degrees out?
    '79 Indy pace car T-top
    '81 Cobra
    '81 Cobra T-top
    '82 Mustang GT T-top
    '87 Corvette
    '10 Mustang GT Convertible
    '17 F250
    '17 Landrover Discovery Sport

  3. #3

    Default

    At this point, I'd have to consider it a possibility but would that make a difference with spark plugs removed?

  4. #4

    Default

    It should crank quick with the plugs out.

    How many CCA is the battery? Does it make a difference if you also jump it with another battery?

    If not then you are down to an electric issue. Probably a connection. Take a picture of your battery and solenoid area and post it.
    '79 Indy pace car T-top
    '81 Cobra
    '81 Cobra T-top
    '82 Mustang GT T-top
    '87 Corvette
    '10 Mustang GT Convertible
    '17 F250
    '17 Landrover Discovery Sport

  5. #5

    Default

    One is 580 CCA and the other is 650. Haven't tried to jump it w/ another battery. However, I did hook up 50amp charger/starter w/ same results. Tried to post pics but says invalid file type. I'll try again later today.
    Attached Images Attached Images  

  6. #6

    Default

    Oh well, it posted after all...

  7. #7

    Default

    What kind of starter?... because I have seen this, slow cranking, with GM starters with their (heat soaked) on board solenoid...
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  8. #8

    Default

    Looks like it is wired OK. The blue negative wire on the battery should go to a clean ground on the block. Try bypassing the solenoid and power the starter directly.
    '79 Indy pace car T-top
    '81 Cobra
    '81 Cobra T-top
    '82 Mustang GT T-top
    '87 Corvette
    '10 Mustang GT Convertible
    '17 F250
    '17 Landrover Discovery Sport

  9. #9

    Default

    Tried bypassing the solenoid and still the same. Ground point is paint-free. Getting closer to the point of pulling engine ��������

  10. #10
    FEP Power Member Ourobos's Avatar
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    Default

    Put a 15/16 socket on the damper bolt and see how it feels turning it over by hand.
    1986 CHP SSP Coupe

  11. #11

    Default

    Quote Originally Posted by Ourobos View Post
    Put a 15/16 socket on the damper bolt and see how it feels turning it over by hand.
    Turns easily with about 20-25ftlbs on torque wrench. I thought if it were binding somehow then it would take much more force to turn.

  12. #12

    Default

    Cam off causing valves not to open when they should?

    Still should crank normally with plugs out though.
    '79 Indy pace car T-top
    '81 Cobra
    '81 Cobra T-top
    '82 Mustang GT T-top
    '87 Corvette
    '10 Mustang GT Convertible
    '17 F250
    '17 Landrover Discovery Sport

  13. #13

    Default

    Oil level too high? Carb dumping fuel in the cyls ? Starter binding on the flywheel?

    Just throwing out idea's.
    '79 Indy pace car T-top
    '81 Cobra
    '81 Cobra T-top
    '82 Mustang GT T-top
    '87 Corvette
    '10 Mustang GT Convertible
    '17 F250
    '17 Landrover Discovery Sport

  14. #14
    FEP Power Member Ourobos's Avatar
    Join Date
    Apr 2008
    Location
    Waikoloa , Hawaii
    Posts
    1,879

    Default

    So the fact it turns properly by hand tells me it's an electrical or grounding issue. I have had the exact problem in some Broncos, I always ran an additional 4 gauge wire from the starter bolt to the frame, and it solved it. I see you tried a similar solution with a set of jumper cables, I'm thinking it may not have been 'grounded' well enough though. I would try that first.

    Also, what is your battery voltage on a meter? What does the voltage do when you crank it (on a meter)?
    1986 CHP SSP Coupe

  15. #15

    Default

    I'm with ^^^ Ourobos, the simplest explanation is that this is electrical, and a few simple measurements
    with a digital meter will prove it one way or another. If a starter is slow, it's because it wants more volts
    than it is getting. That doesn't necessarily mean it's a voltage problem, though, because the starter can
    be wanting to pull too much current.

    Taking voltage measurements at the battery while cranking, and also at the starter while cranking, will tell
    you what's happening, then it's just a matter of interpreting why. Do the same with the ground side.

    Just 'cause the starter spins OK on the bench doesn't mean it's good. Starters typically have two sets of
    brushes, kinda like having two motors on a common shaft. If one set is not in play, the remaining set will
    try to do all the work on it's own, and the starter will try to draw a LOT more current. That same starter
    will bench test just fine, because it's not pulling a load.

    I wouldn't think the starter gear would be binding on a Ford, UNLESS you left out the starter index plate
    (also sometimes called a block plate). The purpose of that plate is to set the proper starter clearance to
    the ring gear. It's why you never have to shim Ford starters (or anyone else's except GM, for that matter).
    Cheers,
    Jeff Cook

    '85 GT Hatch, 5-speed T-Top, Eibachs, Konis, & ARE 5-Spokes ... '85 GT Vert, CFI/AOD, all factory...
    '79 Fairmont StaWag, 5.0, 62K original miles ... '04 Azure Blue 40th Anny Mach 1, 37K original miles...
    2012 F150 S-Crew 4x4 5.0 "Blue Coyote"... 65 coupe, 289 auto, Pony interior ... '67 coupe 6-cyl 4-speed ...
    '68 Vert, Mexican block 307 4-speed... '71 Datsun 510 ...
    And a 1-of-328 Deep Blue Pearl 2003 Marauder 4.6 DOHC, J-Mod, 4.10s and Lidio tune

  16. #16

    Default

    I️ haven’t tried testing for voltage drop while starting. Also, bought a new starter, installed it and did the exact same thing. Took it back the next day and reinstalled the original one. The grounding cables are the same as they were before engine was pulled. Then again, the starter was turning a 230k mi original motor.

  17. #17

    Default

    If you get a 3/8 offset flywheel and a 5/8" offset starter, it won't disenguage. It will still start though, or at least my car did.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  18. #18

    Default

    It could be a number of things.

    What starter are you using?
    The original big hulking mess. Or, the new smaller hi-torque starter, with a re-wire?
    Starters, especially the original big ones, get damaged by the high heat from the headers. Over time, they will take more current, and turn the engine over slower.

    Also, how's the wire going from the starter relay to the starter?

    Last, I don't like the low-cost way that Ford attached the ground wire on these cars. Note, that these cars are over 30 years old, and only some have had problems. So, it wasn't horrible, just not ideal.
    Ford attached the ground to the timing cover. The path for the electrical current is horrible, and is begging to cause electrolysis in the stud, timing cover, and block.

    I attached my ground to the AC bracket, and did a notch of the power steering bracket.













    Good luck!

  19. #19

    Default

    Why would attaching the ground to the aluminum a.c. bracket be preferable to the aluminum timing chain cover if electrolysis is a problem?
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  20. #20

    Default

    Quote Originally Posted by Haystack View Post
    Why would attaching the ground to the aluminum a.c. bracket be preferable to the aluminum timing chain cover if electrolysis is a problem?
    Connecting the negative cable to the AC bracket provides a shorter, and better electrical connection to the block.

    With the timing cover, if you look at that mess electrically, there's only electrical conduction between the studs where they go into the block, and then the stud-to-washer to timing-cover. The timing cover and the piece behind that have an electrically isolation gasket between them and then the cast iron block.

    As I said, it "still works" fine "most of the time".

    However, the biggest concern is when the electrolysis does happen in the stock setup (and it will - it's just a matter of amount), it can do some/all of the following:
    a) "Fuse"/"Merge"/"Weld" the stud to the block.
    Add in some seeping water, and you get the very common problem of the stud breaking in the block. Then being a massive pain to drill out.

    b) Weakening the stud, causing the stud to break/snap, when trying to be removed.

    c) There will be electrolysis and corrosion between all of the different types of metal. With the studs and the block and timing cover, as the electrolysis and corrosion increases, the resistance increases. This causes even more current, which causes even more electrolysis and corrosion. And, the vicious cycle starts.

    Again, the stock setup does not "suck". As long as someone isn't trying to remove a timing cover stud, and the electrolysis and corrosion don't get too bad.
    For people that live in dry temperate weather locations, they are probably saying "WTF" is he talking about. For the vast majority of Americans and the World, wet (rain snow), and snow/winter conditions make the electrolysis and corrosion increases VASTLY worst.

    Look at any new daily driver car after a full year in New England. I show you rust in plenty of places. After 5 years, it's much worse. After 10 years, the Southern California and "desert climate" people would look at the under carriage of a New England car, and would swear that they were somehow transported a zillion billion years in the future.

    Hope the above helps.

  21. #21

    Default

    Theoretically, the most direct point and shortest connection for the highest loads would be right to the starter.

    The corrosion happens any time two different types of metal share electrons with each other, theoretically at least. Acids and detergents definitely do speed this up, but the real problem is power shared through different types of metal.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  22. #22

    Default

    Finally...got some good oil pressure with another battery and charger/starter on it. Guess that made all the difference. Thanks for all the replies and suggestions!

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