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Discussion Starter #1
Hi - I have a 1986 560SL and just replaced the Spark Plug wires, Distributor Cap and Rotor (due to a rough idle). After doing this the car now won't start. I verified that the wire numbering, etc. were all correct and checked that a spark was indeed getting to one of the spark plugs - but still no go. From reading around I've seen a lot of posts regarding the rotor position may potentially be an issue.

Any advice or guidance would be appreciated. Thanks.
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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Rotor position? It is keyed so that it can only be installed in one position. The same position you took it off.

You should triple check your firing order / wire positions. If it worked before you touched it then, in theory, it should work after.

Also check that you didn't dislodge anything else whilst doing your tune up. Or tune down....as it were. :)
 

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Discussion Starter #3
Thanks - I understand the rotor only goes on in one position but I was reading some suggestions that it need to be 'rotated' so that it was pointing at the '#1' position? We did triple check the firing order/positions (does anyone have a diagram of the proper positions so I can make sure I got that right: 1-4 on passenger side, 5-8 on driver side)?
I've also looked around and made sure I didn't mess anything else up while making this 'update' and can't find anything obvious. Based on these symptoms are there particular things/areas I should be looking?
Thanks again!.
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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Everything needs ( or needed ) to go back on exactly the way it came off. That's it.
 

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Discussion Starter #6
thanks - took everything off and put them back on as indicated in this photo and it started. Now when I put it in 'Drive' it stalls out? Runs fine when in Park, Reverse. but if I give it gas in Drive it stalls out.
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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Make sure that every wire connection has positive contact. In other words....make sure the boots are firmly pushed down onto the sparkplugs and the cap.
 

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Discussion Starter #8
thanks - did that, but now won't even start again. Seems like a timing issue but I triple checked the plugs, put the old distributor cap back in, validated the rotor was in the right position. Not sure what the hell I did but just cranks now.
 

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Discussion Starter #9
Also, getting backfire out of the intake when I try to start it, if that helps diagnose the issue any further.
 

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Discussion Starter #11
I did not only the distributor cap and rotor in addition to plugs and wires (also changed the caskets on the spark plug casing.

One other thing, just got it started again (seems like it starts cold) and was able to get it in Drive consistently, it only dies when I give it gas in Drive. If I idle in Drive it runs fine?
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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I did not only the distributor cap and rotor in addition to plugs and wires (also changed the caskets on the spark plug casing.

One other thing, just got it started again (seems like it starts cold) and was able to get it in Drive consistently, it only dies when I give it gas in Drive. If I idle in Drive it runs fine?
I assume you mean gaskets but I have no idea what spark plug casings are.
 

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Since it starts now, will it start and run normally with the old distributor cap and rotor? If so, then maybe swap in just the new rotor, then the distributor cap to see if one of those items is causing the fault under gas. If it still doesn't run with the old cap and rotor on, you may have bumped something and accidentally unplugged a wire or vacuum hose somewhere.
If it starts and runs with the old gear, and still doesn't want to accelerate with the new gear, my guess is timing.
 

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Discussion Starter #17
Thanks - we did swap back to the old distributor cap and rotor and have the same symptoms:
  • starts cold and sounds like it is running well can move rpms up with no problems in park/neutral
  • when we put it in Drive and try to give it gas it dies
  • try and start again and it has a lot of difficulty - will eventually start after multiple tries
  • sometimes backfires when trying to start after it has warmed up
We did find a loose hose from the idle control and replaced it but exactly the same symptoms.

When we put on the new rotor we took pictures and made sure the rotor position was exactly the same. We feel like it is a timing issue as well but we did nothing that should have impacted the timing? Is there a way to validate the timing is or is not the issue?
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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You may have disturbed the crank position sensor at the left rear of the engine when changing gasket.. It is the input timing which is not really adjustable on the 560SL. You can check timing with a timing light. Di you unplug the EHD valve on the fuel distributor? If so check the connection.
 
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