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Thread: Spark plug leads and other question

  1. #1
    Join Date
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    Spark plug leads and other questions

    Hello all,
    I just became the proud owner of yet another project, a 1983 733I. Naturally bought in non running condition for cheap.... I'll throw up some pictures and an official "this is how I got it thread" but before all of that, I have a couple quick questions.

    1) I need to buy sone new spark plug leads for it, but the sets online seem to be broken into two categories, those that say they are for cars with ignition upgrade, and those that are for cars without, how do I tell which ones I need?

    2) Whoever worked\hacked on this car last seemed to be having some electrical fun and I need to piece it back together\trouble shoot it. I found the 733I service manual online but it doesn't seem to have any wiring diagrams or electrical troubleshooting guides. Is there a like anyone can give me to either one?

    -thanks

  2. #2
    Join Date
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    E21/early e23/e34
    Depending on which plug wires you have the sparkplugs will have to match- think it's resistor or non resistor- basically the top "head" either spins off or not- plugs can't be interchanged to fit wires, wires have to fit plugs- Or... just change them all out to match.

  3. #3
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    I'm looking on rock auto and the distributer caps are labeled the same (upgrade or without) so I don't know that its resistor related. At6 least I've never seen a cat with a cap that was different between resistor plugs or leeds....

  4. #4
    Join Date
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    '86 635CSi, etc.
    The electrical troubleshooting manuals are all posted here:
    http://wedophones.com/BMWManualsLead.htm
    Here's a great site for troubleshooting the early Motronics:
    http://hiperformancestore.com/Motronic.htm

    Your car should have the really early Motronic, any 633 or 533 should have a very similar setup.

    I think the resistors are the same, at least for all the Motronic units I've seen. There are two different distributor caps. AFAIK the early pre-upgrade version always has the push-on rotor and a cap with skinny coil 'towers'. The upgrade has a bolt-on rotor and thicker dist cap coil towers set a little further apart. The fatter upgrade plug wires won't fit on the early dist cap. The caps are not interchangeable either, since the two types of rotors are different depths and the caps have rotor button towers to match. To make things even more confusing, BMW also had cam adapters so techs could upgrade the early systems. I've only seen them for the late-model Motronic cam snout but I'm told there are also adapters for the early cams.

    The plug wires have to match the dist cap. The skinny ones usually point straight up from the cap, the upgrade always has 90deg terminals.

    The late model cap & rotor fits all kinds of BMWs, including the M20s and M70 V12s.

  5. #5
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    Thanks! I don't suppose you could rustle up a picture of the two types for me?I really don't want to order the wrong wires... and if I can avoid removing the cap I'd love that tools from what I've read its a bit of a bear to get off...
    Last edited by dude99; 02-14-2018 at 08:04 PM.

  6. #6
    Join Date
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    1985 Mercedes 300SD
    Are the upgraded caps always red in colour?
    1983 BMW 733i My current project (or at least one of them)
    2003 Volvo V70 5 Speed Current Daily Driver
    1993 300TE 4Matic Project wagon -sold
    1997 E290 Turbo Diesel Wagon -traded for above, an amazingly comfortable car to drive, great drivetrain, but the rust, oh my god the rust

    1992 BMW 525i -traded in
    1990 Silver 300TE -Sold Loved the wagon, hated the M103
    1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
    1979 Silver 300D "The Silver Slug" -Sold

  7. #7
    Join Date
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    1985 745i, 1986 735i
    this is what the upgrade ignition cap and wires should look like (ignore the cobwebs)

    2000 BMW M5 Evolve tune, UUC Short Throw Shifter
    1985 BMW 745i 18" Style 37's, Team745i Chip, Getrag 265/6, Clutchmasters FX-300, UUC Short Throw Shifter, Strut Tower Bar, Bilstein HD's ("Build" Thread)
    1986 BMW 735i Getrag 265/6 Swap, Strut Tower Bar, Bilstein HD's, Euro F/R Conversion, 3.46 L/S Diff (Scrapped)

    2016 Ford Mustang GT Performance Pack Stock
    2004 Mercury Marauder
    Eaton M112, 3.4 Billetflow upper, Accufab SBTB + Plenum, 4.10's, Stainless Works LT's, 2.5" Exhaust, Borla Stingers, FX-R projectors, Addco F/R swaybars
    2003 Mercury Marauder JLT CAI, SCT Xcal4, Stainless Works LT's, SW 2.5" Catback
    1996 Ford Bronco
    4" lift, 35" BFG A/T's, MH1 projectors

  8. #8
    Join Date
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    1983/84/85 745i

    Thumbs up

    I bet mine has more cobwebs.

    Post a picture of your current cap/rotor/wires... and your 300SD. I have owned my '85 since 2002 or so.
    I sell Motronic 013 ECU boost cut delete chips and drop in Tial conversions.
    07/1983 745i One owner car!
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
    10/1984 745i
    11/1984 745i
    IH, Ford, MB, Volvo, and GM round out the pack.



  9. #9
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    Here's two pics of my cap, forgive the crappy cell phone pics
    246.jpg247.jpg
    Last edited by dude99; 02-15-2018 at 08:44 PM.
    1983 BMW 733i My current project (or at least one of them)
    2003 Volvo V70 5 Speed Current Daily Driver
    1993 300TE 4Matic Project wagon -sold
    1997 E290 Turbo Diesel Wagon -traded for above, an amazingly comfortable car to drive, great drivetrain, but the rust, oh my god the rust

    1992 BMW 525i -traded in
    1990 Silver 300TE -Sold Loved the wagon, hated the M103
    1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
    1979 Silver 300D "The Silver Slug" -Sold

  10. #10
    Join Date
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    My Cars
    1985 Mercedes 300SD
    And as requested, my 300SD... *Sigh* I regret selling this one...
    DSC000491111.jpgDSC00050.jpgDSC00055.jpg
    1983 BMW 733i My current project (or at least one of them)
    2003 Volvo V70 5 Speed Current Daily Driver
    1993 300TE 4Matic Project wagon -sold
    1997 E290 Turbo Diesel Wagon -traded for above, an amazingly comfortable car to drive, great drivetrain, but the rust, oh my god the rust

    1992 BMW 525i -traded in
    1990 Silver 300TE -Sold Loved the wagon, hated the M103
    1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
    1979 Silver 300D "The Silver Slug" -Sold

  11. #11
    Join Date
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    1983/84/85 745i

    Thumbs up

    I bet you could just slap a later cap/rotor on it with later wires and get on with life.



    SD looks awesome, my paint (Astral Silver) is baked to no end. I just redid the interior, looks great inside now and I have a Sanden conversion.
    I sell Motronic 013 ECU boost cut delete chips and drop in Tial conversions.
    07/1983 745i One owner car!
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
    10/1984 745i
    11/1984 745i
    IH, Ford, MB, Volvo, and GM round out the pack.



  12. #12
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    So mine is the early non upgrade cap right?

  13. #13
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    TX
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    1983/84/85 745i
    Looked at a cap from a car here, it has the male points in the cap and female in the wire set.
    I sell Motronic 013 ECU boost cut delete chips and drop in Tial conversions.
    07/1983 745i One owner car!
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
    10/1984 745i
    11/1984 745i
    IH, Ford, MB, Volvo, and GM round out the pack.



  14. #14
    Join Date
    Jan 2012
    Location
    Vancouver, BC Canada
    Posts
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    My Cars
    1985 Mercedes 300SD
    So just to beat the dead horse, the old style has the male pin in the cap?
    1983 BMW 733i My current project (or at least one of them)
    2003 Volvo V70 5 Speed Current Daily Driver
    1993 300TE 4Matic Project wagon -sold
    1997 E290 Turbo Diesel Wagon -traded for above, an amazingly comfortable car to drive, great drivetrain, but the rust, oh my god the rust

    1992 BMW 525i -traded in
    1990 Silver 300TE -Sold Loved the wagon, hated the M103
    1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
    1979 Silver 300D "The Silver Slug" -Sold

  15. #15
    Join Date
    Jan 2012
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    Vancouver, BC Canada
    Posts
    50
    My Cars
    1985 Mercedes 300SD
    On the rock auto pics it looks like both types have male pins in the cap... mine looks to be the old style cap... conformation with my pics above would be great before I order through
    1983 BMW 733i My current project (or at least one of them)
    2003 Volvo V70 5 Speed Current Daily Driver
    1993 300TE 4Matic Project wagon -sold
    1997 E290 Turbo Diesel Wagon -traded for above, an amazingly comfortable car to drive, great drivetrain, but the rust, oh my god the rust

    1992 BMW 525i -traded in
    1990 Silver 300TE -Sold Loved the wagon, hated the M103
    1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
    1979 Silver 300D "The Silver Slug" -Sold

  16. #16
    Join Date
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    Pittsburgh, PA
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    '86 635CSi, etc.
    Quote Originally Posted by dude99 View Post
    On the rock auto pics it looks like both types have male pins in the cap... mine looks to be the old style cap... conformation with my pics above would be great before I order through
    You definintely have the early cap. Both caps have all male pins, I thought? Here's a few pics for your reference:
    IMG_20180216_223633.jpg
    Upgrade on left. Note much larger spacing on the plug towers.
    IMG_20180216_223623.jpg
    Upgrade on left, note taller central pin. The caps are not interchangeable...although it's possible to mod the later cap to fit it onto an early rotor in an emergency.
    Here's the rotors, upgrade on left:
    IMG_20180216_223926.jpg IMG_20180216_224132.jpg

  17. #17
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    1985 Mercedes 300SD
    Thanks!

  18. #18
    Join Date
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    TX
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    1983/84/85 745i

    Thumbs up

    Sweet, I learned something too.

    The car I looked at here for a reference is an 06/83 745i if it helps.
    I sell Motronic 013 ECU boost cut delete chips and drop in Tial conversions.
    07/1983 745i One owner car!
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
    10/1984 745i
    11/1984 745i
    IH, Ford, MB, Volvo, and GM round out the pack.



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