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Garage => Mechanicals => Topic started by: 13B on 23 March 2008, 03:04 AM

Title: My 450SE d-jet is running poorly again - ignition questions
Post by: 13B on 23 March 2008, 03:04 AM
Hi guys, my 450SE is running poorly again... well lets be specific and say its stopped running.  It also fouls plugs easy and generally is a bit fumey.

I'm suspecting in the distributor, and wanted some opinions on whether I'm on the mark or not...

The wire from the points runs to the green wire outside the distributor to the amplifier on the inner-guard o the car.

There is another smaller wire which runs from the distributor floor to the base-plate (the plate connected to the vacuum advancer). 

I have 2 distributors and both have a condensor sitting there connected to nothing... whats the point of it and should it be connected to something or not?

I think've lost TDC with all my distributor removing/re-installing and I can't see the marker easily on the font fo the engine with the suspension pump in the way.  Is there any way to get a good reading on the timing marker or is it best to remove the radiator, fan, degrease and then I should get a good view that way?

I.
Title: Re: My 450SE d-jet is running poorly again - ignition questions
Post by: carl888 on 24 March 2008, 04:21 AM
Hi guys, my 450SE is running poorly again... well lets be specific and say its stopped running.  It also fouls plugs easy and generally is a bit fumey.

I'm suspecting in the distributor, and wanted some opinions on whether I'm on the mark or not...

The wire from the points runs to the green wire outside the distributor to the amplifier on the inner-guard o the car.

There is another smaller wire which runs from the distributor floor to the base-plate (the plate connected to the vacuum advancer). 

I have 2 distributors and both have a condensor sitting there connected to nothing... whats the point of it and should it be connected to something or not?

I think've lost TDC with all my distributor removing/re-installing and I can't see the marker easily on the font fo the engine with the suspension pump in the way.  Is there any way to get a good reading on the timing marker or is it best to remove the radiator, fan, degrease and then I should get a good view that way?

I.


Hi Ian,

I would just check the timing at idle first, should be around TDC or a tad before and it will run right (You can tweak it later but this is a good starting value) and if its fouling plugs, I suspect the cold start enrichment is stuck on.

The purpose of the condenser is to eliminiate pitting of the points through spark erosion.  The car will run without it, but the life of the points will be significantly reduced.

You should be able to see TDC on the crank pulley with a good clean.  Remember, engines have two TDC's, so you'll need to know what the valve train is doing if you have lost TDC.   (This is because there are two revolutions of the crank for every one revolution of the camshafts and distributor)

Regards,

Carl.



Title: Re: My 450SE d-jet is running poorly again - ignition questions
Post by: 13B on 24 March 2008, 04:50 AM
Quote
You should be able to see TDC on the crank pulley with a good clean.  Remember, engines have two TDC's, so you'll need to know what the valve train is doing if you have lost TDC.   (This is because there are two revolutions of the crank for every one revolution of the camshafts and distributor)

Wait a minute - is this true for all V8 engines or just MB ones?  Surprised the Haynes manual doesn't make mention of this but maybe its so obvious to all who have ever worked on engines no one mentions it anymore....

... my backgrounds in wankels, which as we know are two stroke so TDC on the pully is TDC on every revolution, not every 2nd one.

This morning was spent pulling out the distributor, checking the trigger and breaker points (they all worked as they should), removing the condensor (which isn't connected to anything on either of the two distributors I have), checked the advancing mechanisms worked and when I was happy with my work proceeded to find TDC...

By rapidly flicking the key I could turn the engine a few degrees, clean the marks and found the TDC marker.  Re-installed the dizzy with the rotor pointing at #1 terminal.  Nothing.  Now I get occasional pops thru the intake (only 2, then I gave up) and the odd pop out the exhaust...  tell me I've got the dizzy out by 360 degrees please???

I.
Title: Re: My 450SE d-jet is running poorly again - ignition questions
Post by: carl888 on 24 March 2008, 05:08 AM
Hi Ian,

Yes, ALL 4 stroke engines spin the crank 720 degrees for every 360 degrees of the cam(s),the distributor and the injection pump if sequential like a diesel or L-Jet.

As for your last paragraph, I reckon 360 degrees is the key here  ;D

Regards,

Carl.


Title: Re: My 450SE d-jet is running poorly again - ignition questions
Post by: koan on 24 March 2008, 01:05 PM

By rapidly flicking the key I could  Re-installed the dizzy with the rotor pointing at #1 terminal.  Nothing.  Now I get occasional pops thru the intake (only 2, then I gave up) and the odd pop out the exhaust...  tell me I've got the dizzy out by 360 degrees please???


My distributor has a mark to help in reinstalling. With the cap removed there is there is a small grove in the top edge of the of the distributor body. With the engine at TDC (number 1 cylinder, firing stroke) the rotor arm should point to this mark. This assumes that the plugs leads are in their correct positions in the distributor cap, number 1 plug goes to the goes to hole marked number 1 on the cap.

Assorted pops and backfires in the inlet manifold could be caused by a mix up in what lead goes to what plug.

Every cylinder has a TDC, the one marked on the pulley is number 1's TDC. Both valves of number 1 cylinder will be closed at TDC of the correct revolution which is no use if you cant see the valves and rockers but if you put a finger on number 1 cylinder as you or a helper turns the engine clockwise towards the TDC mark you will feel the compression against your finger. 

koan
Title: Re: My 450SE d-jet is running poorly again - ignition questions
Post by: oscar on 26 March 2008, 01:57 AM
After thinking I'd lost TDC once I read about turning the crank with a 27mm socket and putting your finger in the spark plug hole to #1 cylinder.  When approaching TDC, #1 is on its compression stroke and both valves will be closed and the compression escaping past your finger obvious.  It may not be necessary but I had to remove the fan with an 8mm spanner when I've attached a 27mm socket to the crank in the past.  See if you can work out the compression stroke of #1 with someone else clicking over the starter perhaps.

Re TDC markings; Viewing the timing marks during timing adjustment is difficult for M116 and M117 with suspension pumps.  If that suspension pump is gone, timing adjustment would become so much easier IMO.  The haynes manual's pics are very poor and IMO the photo is taken from underneath the engine which they don't admit to.  But it's the only way you can get a good photo of the timing marks (pre phonecams).  There should also be a blue painted dot indicating the factory timing mark which will be in line with the markings but not painted on them.

Re the condenser.  I'm not 100% sure but I understood they weren't really needed because these points don't carry the full spark and therefore dont become pitted anyway.  They merely carry a signal rather than many volts or amps.  I don't have a condensor and the points have a black/white striped wire.  There's mention in parts catalogues that the  black/white points are the ones to use over originals if no condensor is used.  Don't know what's the difference.

And lastly that second wire to the baseplate, again, not 100%, but I thought that was merely an earthing strap.  Mines just that, non insulated and braided copper.

Title: Re: My 450SE d-jet is running poorly again - ignition questions
Post by: 13B on 29 March 2008, 03:44 AM
Well I got the old girl running again, turns out I was 360 degrees out on the TDC like you guys said and now its back up and running.  Still not really 100% happy but its getting better the more I fiddle with it...

Since I remove the points of the dizzy I put them back in and adjusted them via sight and got them pretty close on the dewll meter - 29 degrees.  Checking our online manuals I see to increase the dwell you make the point gap smaller, but twice I made the gap smaller and each time the dwell got smaller (the inverse of what should be happening) so I put it back the the largest gap (again by sight) I dared and again got a dwell angle of 29 degrees so I think that is where its going to stay.

As far as timing is concerned since the car is running its "in the ballpark" but I still can't find the optimum angle to put the timing light on to get an accurate reading and adjust as necessary.  The pointer and marker and perfectly clean and legible with the dizzy out, its just when its in that its hard (impossible) to read the timing markers.

Bring on the rear spring/shock conversion which will get rid of that pesky SLS system forever - I'll at least be able to see my timing markers.  Even moreso with the A/C compressor gone.  Another thing I'll be doing soon is relocating the battery to the boot, which with the other mods just mentioned, should give me good clean access on either side of the V8 engine.

I.
Title: Re: My 450SE d-jet is running poorly again - ignition questions
Post by: scraf on 29 March 2008, 03:55 AM
... just as an aside, known of a few instances where a ( non-Mercedes ) car has started to run roughly at around the 50 - 60 kmh mark, replacing the condenser was the quick and easy fix.