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Garage => Mechanicals => Topic started by: stillmatic on 10 December 2018, 03:16 AM

Title: 280SE correct ignition timing
Post by: stillmatic on 10 December 2018, 03:16 AM
Can anyone help me figure out the correct ignition timing for my 280SE? I'm getting different info from the engine manual vs Chilton's and most posts I found here are referencing timing for V8's.
Title: Re: 280SE correct ignition timing
Post by: Max-NL on 10 December 2018, 06:31 AM
Attached is the german manual for the w116. Assuming you have the 116.985 engine you'd want the super unverbleit version (super unleaded). So about 26 degrees at 3000 rpm without vacuum.
Title: Re: 280SE correct ignition timing
Post by: stillmatic on 10 December 2018, 06:51 AM
Thank you Max, this is great info! For idle, is that also 4 degrees before TDC?
Title: Re: 280SE correct ignition timing
Post by: stillmatic on 10 December 2018, 06:59 AM
Also, how much would you recommend retarding it for 95 octane?
Title: Re: 280SE correct ignition timing
Post by: UTn_boy on 11 December 2018, 12:00 PM
Michael, see pictures below out of the book.  They should answer all of your questions, including the questions about octane rating verses timing.  However, do not skip the timing checks at the 1,500, 3,000, and 4,500 RPM increments.  Setting the timing at idle only may not yield the correct timing at higher rpm's.  These timing checks at various rpm's wasn't an optional thing for convenience.  They're put in the service literature for good reason. 


Title: Re: 280SE correct ignition timing
Post by: Justin280s on 11 December 2018, 12:33 PM
Great post.  I was about to ask about this.  Love this forum.
Title: Re: 280SE correct ignition timing
Post by: revilla on 15 May 2019, 06:50 AM
Hello everyone,

Coming back to what it seems an elusive subject, hard for consensus.

According to the spec (the one posted by Aaron above) for a 110.985 engine ignt timing should be:
- 32° @3000RPMs both vacuum lines disconnected (VERY clear, no issues)
- TDC +/- 3° @ Idle speed

Question: is the TDC +/- 3° @ idle with or without vacuum lines?

I ask because on the cell it reads literally "TDC +/- 3° with" BUT in the title of that column it states "Test values ignition timing without vacuum".  Thus, confusion at least for me!  Does that "with" in the idling cell mean with vacuum despite the indication of without in the column title?

Thanks in advance for your inputs.

Robert

Title: Re: 280SE correct ignition timing
Post by: revilla on 15 May 2019, 07:05 AM
And then we have this to add even more confusion...

So?
With or without vacuum lines at Idle?
30° or 32° @3000RPMs?


Can anyone clarify please?

Gracias :)

Robert

(http://C:\TEMP\Ignition Timing 280SE 110 Engine German.JPG)
Title: Re: 280SE correct ignition timing
Post by: ptashek on 16 May 2019, 03:01 AM
Idle with vacuum, 1500 and 3000rpm without.

For fuel below 98RON, retard by 1° per octane (at 3000rpm, no vacuum).
Title: Re: 280SE correct ignition timing
Post by: revilla on 16 May 2019, 03:57 AM
Perfect, thanks Lucas.

It remains the 2nd mystery...

@3000 RPMs 32° (English spec) or 30° (German spec)?

Or maybe 2° don't make a difference really (???)

Thanks in advance

Title: Re: 280SE correct ignition timing
Post by: ptashek on 16 May 2019, 07:24 AM
Perfect, thanks Lucas.

It remains the 2nd mystery...

@3000 RPMs 32° (English spec) or 30° (German spec)?

Or maybe 2° don't make a difference really (???)

Thanks in advance

French market engines would be high compression versions, same as for the German market, in which case 30° is the correct value.

There's some differences between federal/California engines us euro folks can happily ignore ;)
Title: Re: 280SE correct ignition timing
Post by: revilla on 17 May 2019, 02:24 AM
VERY CLEAR !!! Thanks again. :)

I found a problem while doing the adjustment.  I must be doing something wrong.  When I set up the advance @3000RPMs 30° it's impossible later to get the spec value at TDC +/- 3° for idle.

I followed these steps when adjusting the timing:

Start engine
Disconnect both vacuum lines
Accelerate speed to 3000
Rotate distributor until advance reaches 30°
Back to idle
Reconnect both vacuum lines
But reading @ idle = 22°
Restart
Left both vacuum lines connected
Rotate distributor until reaching TDC = engine not happy
Stop

So I can’t get TDC at idle, not even close, after setting 30° at 3000.

I have vacuum in both lines.  There’s vacuum at idle in the hose going behind the pod.  There’s vacuum at the other hose going on front of the pod when at 3000.

I tested the pod and there’s no air leak.  The arm moves freely when vacuum is applied and it holds it long term meaning no leaks. 

What's interesting is that when I accelerate from idle to 3000RPMs and back, there's no noticeable changes in the advance figure.  It barely fluctuates around 30° no matter the RPMs.  Then when I reconnected the lines it goes down to 22° but never lower towards the aim of TDC +/- 3°

So I left it at 22° idle (30° 3000) where the engines seems stable and happy with no misfiring.

Anybody had the same problem?
Am I doing something wrong? 

Title: Re: 280SE correct ignition timing
Post by: rumb on 17 May 2019, 04:56 AM
Assuming your vac lines are connected correctly I think this indicates your mechanical advance does not work.
Title: Re: 280SE correct ignition timing
Post by: revilla on 17 May 2019, 05:03 AM
Thanks Rumb

what does that mean?
possible root cause?
where/what should I look at?

Help is appreciated
Robert


Title: Re: 280SE correct ignition timing
Post by: revilla on 19 May 2019, 01:47 PM
Thanks for your PMs
You’re the best!!!

As we say around here, Voilà Voilà !

Problem found and resolved. There was a deformed spring and broken plastic slider that was causing the advance adjustment mechanism to misbehave. I replaced them using an old distributor I had. I imagine these minuscule parts are either hard to find or NLA.  Once root cause killed I arrived at TDC idle and 30° @ 3000.  Eureka!

And what a DIFFERENCE in performance that makes!!! Wow!!! I expect also a positive impact in fuel consumption... that we’ll see....

BTW, thanks Rueda1 for your great post about overhauling the distributor. Excellent to say the least. I took advantage to clean things up while in there. Contributors like you make this forum the great resource it is. Bravo!

What I love the most is the learning process we go through when “playing” with a system first time. Knowing how it technically works is essential to fix it. Then the intellectual effort pays off when the solution is securely in place. The reward is to better know, repair, improve and preserve these wonders.

Thank you all. Have a good day.
Title: Re: 280SE correct ignition timing
Post by: irvine on 20 May 2019, 02:56 AM
Is that the distributor you took apart, is it d-jet or k-jet.

I recently cleaned mine and the funk that came out was disgusting.

Neil.
Title: Re: 280SE correct ignition timing
Post by: revilla on 20 May 2019, 02:31 PM
Hi Neil,

K-jet.  Dist PN 0237 302 005 as stamped on the body.

Robert

Title: Re: 280SE correct ignition timing
Post by: Big Tiny on 04 September 2020, 07:37 PM
Sorry to dig up an old thread.

But I almost have the same issue as above.

Advance at idle is ~ 12-14 deg.

3000 rpm or thereabouts is close to 30 deg.

No change in advance with or without vacuum. No what I do I'm not getting anywhere near 3 deg BTDC at idle.

Its a 1984 280se. M110 989.

I think I will pull dizzy off and have a look at the advance mechanism. Any hints on getting new parts if needed would be of great help.

BT
Title: Re: 280SE correct ignition timing
Post by: Big Tiny on 04 September 2020, 10:00 PM
Just pulled mine off and had a look. Same issue here, looks like someone has done some work on it before, as there looks to be two types of springs fitted to the mechanism. little piece of black plastic fell out when opened, one side of the mechanism missing that black 'arm' and not loading properly.

Title: Re: 280SE correct ignition timing
Post by: Big Tiny on 05 September 2020, 08:13 PM
From the manual.


My car has the ( 0237 304 021 ) ignition distributor

What I'm confused about is that the Aus delivered cars run 2 deg ATDC at idle ? all other values are the same. No chance my car achieve that with full retard at the dizzy.

For reference prior to removing Dizzy, it was aroun 12 deg BTDC at idle and 30 deg at 3k rpm. So looks like it was on point with the Japanese delivered cars.

Title: Re: 280SE correct ignition timing
Post by: Big Tiny on 06 September 2020, 04:13 AM
Distributor all cleaned and repaired. It was a little bit dirty inside and some sticky old grease, I'm assuming that's enough to screw with the advance mechanism.

I will refit tomorrow and see what it reads on the timing light.

If anyone has anymore insight into the timing specs above ? would be great. What I don't understand is how can the base timing at idle be
2 deg ATDC but still achieve the same advance at 1500/3500 where the Jap spec engine is 10 deg BTDC ?
Clearly I'm missing something here.