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  #1  
Old 03-13-2007, 03:18 PM
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75 450 SL No spark

Hi-

Newbie to Mercedes, pardon the ignorance. Recently acquired a 75 450 SE with no spark- coil tests ok, but no ignition. Trigger points are new- any tips or suggestions?


Thanks for your time and help.


Last edited by addwestern; 03-15-2007 at 03:05 PM.
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  #2  
Old 03-13-2007, 05:09 PM
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More Details

75 450 SL No spark-picture2-897.jpg

75 450 SL No spark-picture2-896.jpg

So the first things I notice are strange- there is not 12v going to the positive side of the coil-and there is no condensor inside the distributor. Is this normal? If so, where does it connect? Also, there is this green wire with a plug coming out of the harness that is by the coil. See Attached.
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Old 03-13-2007, 05:17 PM
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Bad transistor box, get a Pertronix or Crane breakerless ignition.

Also check the ignition resistors to make sure they aren't broken -- you have no power to the switchbox that way, and no ignition. The green wire is the trigger wire to the transistor switching box that actually fires the coil.

Peter
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  #4  
Old 03-13-2007, 06:28 PM
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I have to ask: have you tried plugging the green wire into the transistor box?
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'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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Old 03-13-2007, 06:36 PM
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After looking at everyone's description- it would seem that the transistor box is missing- I am going to swing by a parts yard to see if i can aquire one. I appreciate everyone's help thus far.
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  #6  
Old 03-13-2007, 06:43 PM
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Well, that explains the lack of spark .

Since you already have a blue coil, you are 'way better of with Peter's suggestion to go with a Pertronix.
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #7  
Old 03-13-2007, 07:36 PM
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I've got the switchgear box I pulled from my '72 280SEL 4.5. I'm not sure if the part is the same or not but suspect it is. If you want mine for $50 plus shipping I will even throw in the blue coil and a new spare set of point and condensor.
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  #8  
Old 03-15-2007, 03:05 PM
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Does anyone know if the condensor is in the distributor on that model?
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  #9  
Old 03-15-2007, 05:00 PM
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No condensor with the transistor box (or Pertronix).
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #10  
Old 03-15-2007, 05:30 PM
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One last question- I appreciate the help. It seems that the distributor was out of the car when it was acquired. what is the best way of getting it in the correct position- I think it may be 1-2 teeth off.
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  #11  
Old 03-15-2007, 06:32 PM
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Add:

Remove the cam cover so you can observe the valves for #1 cylinder. Using a 27mm socket, rotate the crankshaft until the TDC mark on the balancer aligns with the pointer on the timing case. (Ensure you rotate the crank in the normal direction of rotation. Do not run the crankshaft backward.) Verify that both valves on #1 cylinder are fully closed and the cam lobes are on their base circle. This is TDC on the compression stroke. (If you are in doubt, simply rotate the crank through a full cycle, two full revolutions, to confirm. If the exhaust valve opens next after you pass TDC on the power stroke, you were on TDC, so just continue rotating until you get back to where you were.) Now, at TDC check the distributor rotor to verify it aligns directly with the #1 spark plug terminal in the distributor cap. If not, adjust the distributor accordingly by removing the distributor and rotating the shaft to the appropriate position. Reinstall the distributor and confirm it points directly at the #1 terminal in the cap. It helps to mark the position of the distributor clamping bolt in the adjustment slot so you can do your verification of position from a consistent reference point. Remember, the distributor gear is helical cut so the distributor shaft will rotate slightly as you remove the distributor to reposition it one or two teeth.

Also, before you reposition the distributor, check to see whether simply moving the wires one position left or right will solve the problem. The previous owner may have wired the cap wrong if the wires were replaced. Your distributor rotor should point at the #1 terminal with the clamping bolt about midway in its adjustment slot.

230/8

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