Help with checking Timing on 280s needed please

[MajorBenz]

Hi guys,
After a long sabatical I'm doing some work on my 280s again.
Looking for some definitve answer on the timing settings, as I'm finding the various technical manuals either confusing or contradictory.
This is a 1969 280s, with the M130 engine.

Let's start with "Dwell Angle":

I'm pretty sure my coil is the non-transistor type.
As per the Merc workshop manual:
"Identification marks of the transistor ignition are: blue..coil, blue dot on vacuum"
My coil / vacuum don't have these colors / marks.
Here is a pic:

IMG_1465.JPG

IMG_1466.JPG

So...what is the dwell setting I'm aiming for?
Workshop manual: 35° (+4-2)
Chilton's: 37-41°
Chilton's other manual: 41° (+- 1)

I guess somewhere around 37° ?

Any input/advice appreciated.
More questions to follow...

[Chai]

It's possible that a previous owner changed the high-tension (HT) coil with a generic unit. I also notice the spark plug leads are non-MB.

Whether the ignition is transistor-based can be determined by tracing the wire to the HT coil (the other is to ground). If that wire runs to the breaker points in the distributor, it's non-transistor. If it leads to a 'box', that's the transistor unit.
Working back, the transistor ignition has a wire that leads to the breaker points in the distributor.

The blue HT coil matches the (weak) output from transistor ignition. The number of internal windings differ from the non-transistor HT coils - the blue unit accepts a smaller voltage/current (from the transistor ignition system) to produce the required spark voltage.

Using a non-blue coil with the original MB transistor ignition system means a 'weaker' spark.

Sorry, I don't know the dwell settings for your engine.

[CraigB]

So if you are asking about dwell, I take it you have conventional points in the distributor (which is how you adjust dwell). My dwell meter is not that precise, so anywhere in that range from the manuals, I would be hard pressed to set precisely and I doubt would have any real effect on its running. Chiltons is US, which tend to have more emissions stuff, so I would go with factory.

Is there a problem with the car or you are just asking for tuning purposes? If your car is standard, then it should have a wire to the plus on the coil that will get power when the ignition switch goes on and the minus will have a wire to the points, as indicated by Chai. I agree with Chai that the leads look like a silicon lead and not the original solid core lead with metal resistor ends. Depending on quality, the silicon tend to break down and need changing, the originals last much much longer and less likely to cause problems and have you chasing misfires etc.

[Bartman4800]

Also,

If you still have the original breaker points in the dizzy, you need to make sure the HT leads are all copper.

This ignition does NOT work properly with more modern carbon HT leads which have an internal resistance.

Also ensure you run NON resistance plugs, the best ones to use are NGK BP6ES or BP5ES (without an R in the code for resistance)

The dwell angle is not super critical, somewhere between those specs is fine. Make sure the breaker points are not pitted and are clean. Run a nail file in between if necessary.

When in doubt replace them, and also replace the capacitor/condensor. They are cheap and still available at the stealership.

Once the engine is running, set the spark timing at 8 deg BTDC, with the vacuum disconnected and plugged

Bart

[MajorBenz]

Thanks for your replies guys.

I will try the dwell angle in the workshop manual.

To answer some your questions:

Current state of car:
It starts and stays on, but it is running rough.

Why am I playing with the timing?
I just put one of the carbs back in after rebuilding it. (Both carbs done now. Only took me 3 years!)
I want to follow the workshop manual procedures for adjusting and balancing carbs - the first thing it says to do is make sure the dwell angle and timing are set correctly.

Coil - transistor or not?
There is a wire running from the negative terminal on the coil, to the distributor.
When it gets there, it splits with one branch going to the points, and the other to the condensor.
Like this:

IMG_1470.JPG

Does this establish that the coil is definitely NON TRANSISTOR?
(The other wire, from the positive coil terminal, disapears down under radiator resovoir.)

Regular points/distributor?
Here are the points and distributor - look pretty regular to me. What do you reckon?

IMG_1469.JPG

(Bit suprised by the amount of greasy muck in there. I know people sometimes put a drop on the shaft - but looks like previous owner may have been bit over zealous? Might give it a clean up...)

Plugs:
I have NGK BP6ES installed.

HT leads
I replaced what it came with, because they were in bad shape.
I got these at repco I think - it says "Repco Hi Temp. Silicon Supression" on them.
Can't remember the model.
Considering they are fairly new, and the car isn't going anywhere (unregistered) - can I get by with them for tuning purposes?
If not - where can I procure these Original copper ones?
Cursory search found these - https://www.pelicanparts.com/catalog/Su ... .htm#item0 - but there is no mention of what they are made of...

[Bartman4800]

Yes it looks like you have the original points setup.
Check whether you have a lot of slop in the shaft.

Replace any of the 12V leads that look dodgy. Also, there should be a ballast resistor across the coil (a rectangular ceramic block)

Here is an option for a set of HT leads:

https://www.dbdepot.de/ignition-cable-s ... s-Oldtimer

But try your stealership as well.

Just a hunch, but did you check whether the HT leads are in the correct sequence (Zundfolge)?

Regards, Bart

[CraigB]

That all looks good and just the standard set up. So just rough running. My most likely candidates for that would be ignition and/or carbies...... so you've got that all covered! For a quick check, if you pulled your plug leads one at a time at idle and see what the response is of the engine. If pulling front three or back three gives a consistent response, then that's hinting carby balance, if just one has little drop in revs then its hinting at a dodgy lead, but as pointed out by Bart, if they are silicon leads then its making it hard for the system, but happens all the time. Worst situation is when people get a new car and do the first thing you might with a ford or holden and just put a new set of leads on, throwing out perfectly good solid core leads and replacing with something that is going to break down and cause problems.

But sounds like your on the right track but it will be hard to set that balance in your carbs if you have a bad lead. Also have you done a compression test? valves adjusted? That will all make things hard. Compression test I always use as step one. If valves, rings etc worn and uneven, you will never get it all running right. But if it was running right before the carbs started giving you grief, then it is most likely fine and just needing tuning.

And going back to the original question before we created all these worries!...... checking dwell is really saying, check your points are in good condition and adjusted properly - if that's dodgy, then dwell would be way out.

[MajorBenz]

Hey Bart,

Thanks for your suggestions.

"Also, there should be a ballast resistor across the coil (a rectangular ceramic block)"
I don't think I have one of those, but will look it up.

"but did you check whether the HT leads are in the correct sequence (Zundfolge)?"
I'm guessing that means "are the th plugs connected to the correct spot on the distributor"?
I think so. I was pretty careful when I changed the leads - marked the numbers on cap.

Back on it tomoz, will update thread with progress.

[MajorBenz]

That all looks good and just the standard set up. So just rough running. My most likely candidates for that would be ignition and/or carbies...... so you've got that all covered! For a quick check, if you pulled your plug leads one at a time at idle and see what the response is of the engine. If pulling front three or back three gives a consistent response, then that's hinting carby balance, if just one has little drop in revs then its hinting at a dodgy lead, but as pointed out by Bart, if they are silicon leads then its making it hard for the system, but happens all the time. Worst situation is when people get a new car and do the first thing you might with a ford or holden and just put a new set of leads on, throwing out perfectly good solid core leads and replacing with something that is going to break down and cause problems.

But sounds like your on the right track but it will be hard to set that balance in your carbs if you have a bad lead. Also have you done a compression test? valves adjusted? That will all make things hard. Compression test I always use as step one. If valves, rings etc worn and uneven, you will never get it all running right. But if it was running right before the carbs started giving you grief, then it is most likely fine and just needing tuning.

And going back to the original question before we created all these worries!...... checking dwell is really saying, check your points are in good condition and adjusted properly - if that's dodgy, then dwell would be way out.

Hey Craig,

Thanks for your suggestions.

I don't have a compression tester unfortunately.
I do have test results from when I bought the car. Will have to dig them up.

I'm moving house, and the car has to go I'm afraid.
Just trying to get it going as well as possible before offering for sale.

[Chai]

Can someone please confirm if there should be a ballast resistor for a non-transistorised ignition system?
My impression is that the ballast resistor only exists when a transistor ignition system is installed, so should not exist for this engine.

This is what the ballast resistors looks like.

Blue ignition coil and the ballast resistor.jpg

The transistor ignition module.

MbTransistorIgnitionSwitchingUnit05.JPG

[Bartman4800]

Here is an explanation for the reasons of a ballast resistor.

https://www.youtube.com/watch?v=V8M-07nluAE

When I installed a fully electronic 123 ignition system in my finny (a completely new dizzy, not an add-on), I did away with the ballast resistor after consulting with a 123 company specialist. I also purchased a new Beru coil from them.



Regards, Bart

[MajorBenz]

Some delays due to bad weather and bad moods, but back at it now...

A few discoveries:

1.) Found the ballast resistor!

IMG_1489.JPG

2.) There is no slack in the distributor shaft. Yay!

3.) Points were filthy. Took 'em out, cleaned, and sanded contact area with 1600grit. Wiped out intereior of distributor which was pretty mucky. Can anyone tell me what this thing that is circled is? I put my little mirror down next to it - looks pretty grotty. Only way to clean would be to bend that tab back - should I bother?

IMG_1496.jpg

Going to order some new points.
Looked around at the online suppliers, but many of the prescribed options have a male connector, when mine definitely needs a female.
Anybody know what the part no. is for points like these?

IMG_1495.JPG

[Christo C]

That little tab has a ball bearing underneath - it is spring steel - DO NOT bend it! It keeps a small pressure on the plate underneath as it rotates a little for the vacuum advance/retard.

[Bartman4800]

I think I said before, that the stealership can supply the points for a few bucks.
And while you replace them, also replace the capacitor! Otherwise your new points might only last a month.

I thought cable is not part of the points, it should come away with a screw on the points itself.
But if that is the only problem, just crimp on a new male connector.


Regards, Bart

[CraigB]

Same thought - points don't have wire - So if you can remove from your points can probably re attach to new. Those wires can break inside, so a multimeter on resistance mode and wiggling it around woul let you know if any breaks. I thought they were something like GB6 and same as a volksy - but could be different distributors.

[MajorBenz]

That little tab has a ball bearing underneath - it is spring steel - DO NOT bend it! It keeps a small pressure on the plate underneath as it rotates a little for the vacuum advance/retard.

No bending - got it.
Thanks for explaining.

[MajorBenz]

I think I said before, that the stealership can supply the points for a few bucks.
And while you replace them, also replace the capacitor! Otherwise your new points might only last a month.

I thought cable is not part of the points, it should come away with a screw on the points itself.
But if that is the only problem, just crimp on a new male connector.


Regards, Bart

Lol - right you are Bart - the wire clips in.
Only working with half a brain today, good to have you guys to pick up the slack.

Am I putting a dab of something on the distibutor shaft where the rubber heel rides? Regular grease?

[Bartman4800]

Just a dab of wheel bearing grease on the rotor lobes should be sufficient.
Not too much, just a coating.

Regards, Bart

[MajorBenz]

Just a dab of wheel bearing grease on the rotor lobes should be sufficient.
Not too much, just a coating.

Regards, Bart

cheers mate.
:)

[MajorBenz]

Yes it looks like you have the original points setup.
Check whether you have a lot of slop in the shaft.

Replace any of the 12V leads that look dodgy. Also, there should be a ballast resistor across the coil (a rectangular ceramic block)

Here is an option for a set of HT leads:

https://www.dbdepot.de/ignition-cable-s ... s-Oldtimer

But try your stealership as well.

Just a hunch, but did you check whether the HT leads are in the correct sequence (Zundfolge)?

Regards, Bart

Hi Bart,

Just looking at the arrangement of the HT leads and thought of your post.

There is a notch in the distributor housing - which I belive is meant to indicate where the rotor will be when cylinder 1 is at TDC?

The lead that is above this spot is going to cylinder 6. Does this seem right?

Here are a couple of pics:

IMG_1540.JPG

IMG_1541.JPG

Maybe I screwed up when I replaced the leads...


And just to confirm, this IS the location of the cylinders on the engine yes?

IMG_1539.JPG

[Christo C]

Ahem, I think cylinders are normally numbered from Front to Rear, in which case the Rotor is pointing at the correct mark

[MajorBenz]

Ahem, I think cylinders are normally numbered from Front to Rear, in which case the Rotor is pointing at the correct mark

Can someone else confirm this?
Not sure why I thought cylinders 1 was nearest the firewall...checking...

[Christo C]

Only numbered the way you think in Electric cars.

[MajorBenz]

Ahem, I think cylinders are normally numbered from Front to Rear, in which case the Rotor is pointing at the correct mark

Ok, false alarm, I figured it out. A year ago, when I replaced the HT leads I think I just numbered the cylinders arbitrarily from back to front, and then followed the cables back to the distributor and marked the numbers there too. Amateur hour, but got the leads replaced correctly.
So just to be sure this the actual numbering order of the cylinders?

IMG_1542.JPG

Which would mean when my distributor rotor passes the notch it's firing 1, followed by 5, 3 ,6, 2, 4.

Which seems correct.
Would have been pretty weird if they were all messed up but the engine still ran.

[Bartman4800]

That seems correct.

Wow, you have a cockpit in your vehicle?

Bart

[MajorBenz]

That seems correct.

Wow, you have a cockpit in your vehicle?

Bart

Well, I can definitely be a bit of a cock sometimes...
;)

Making progress:
Points back in.
One x adjustment.
Now reading 32 degrees dwell @ 850rpm.
Sounding smoother already.
If weather holds in morning will get on to timing and then balancing the carbs.

[tsharkey]

Which would mean when my distributor rotor passes the notch it's firing 1, followed by 5, 3 ,6, 2, 4.

Firing Order.JPG

[MajorBenz]

Which would mean when my distributor rotor passes the notch it's firing 1, followed by 5, 3 ,6, 2, 4.

Firing Order.JPG

Lol - right in front of my face.

[Bartman4800]

Funny thing:

A few months ago a guy had a BMW for sale on Gumtree, and he claimed it had the famous "Zundfolge Engine" installed....
Weird thing, all BMW engines are Zundfolge engines. Hey wait: Mercedes too???

Years ago, Opel changed engine design from CIH (cam in head) to OHC (Overhead Camshaft)

A guy I worked with was convinced the OHC engines came out of the OHC factory in Germany....

Then I told him I had an Alfa at home with a DOHC engine

[Christo C]

Zundfolge = Ignition Sequence / Firing Order

[Bartman4800]

Yes it looks like you have the original points setup.
Check whether you have a lot of slop in the shaft.

Replace any of the 12V leads that look dodgy. Also, there should be a ballast resistor across the coil (a rectangular ceramic block)

Here is an option for a set of HT leads:

https://www.dbdepot.de/ignition-cable-s ... s-Oldtimer

But try your stealership as well.

Just a hunch, but did you check whether the HT leads are in the correct sequence (Zundfolge)?

Regards, Bart

[CraigB]

I have a feeling there isn't a standard way of numbering cylinders, but however your manufacturers number it you need to match to the firing order they state. Reason i say that is that i think in my past I had a car that did number from the firewall in the workshop manual and I am pretty sure landrover have a different way of numbering cylinders, odds on one side - evens on other....... so i did a google on Mercedes V8 firing order in images...... and they show both numbering for V8. I think the firing order on my rocker covers is 1 to 4 on one side and 5 to 8 on other. But there is some logic to the odds and evens, being the order on the crankshaft - and pretty sure the original marks on the rods is 1 to 8 down the crank.

But i'm sure as stated here it is 1 to 6 inline starting from the front of the car.

[Christo C]

Looking carefully at your pictures of the Distributor there appears to be two Condensers fitted - that is odd - are they both connected?
(The part # 1 237 330 318 next to the points thru-connection at the side is a Bosch Condenser)

[Bartman4800]

One capacitor is most likely a suppressor, to stop interference with the radio...

[MajorBenz]

One capacitor is most likely a suppressor, to stop interference with the radio...

Only one is hooked up. Was like that when bought.

[MajorBenz]

Also,

If you still have the original breaker points in the dizzy, you need to make sure the HT leads are all copper.

This ignition does NOT work properly with more modern carbon HT leads which have an internal resistance.

Also ensure you run NON resistance plugs, the best ones to use are NGK BP6ES or BP5ES (without an R in the code for resistance)

The dwell angle is not super critical, somewhere between those specs is fine. Make sure the breaker points are not pitted and are clean. Run a nail file in between if necessary.

When in doubt replace them, and also replace the capacitor/condensor. They are cheap and still available at the stealership.

Once the engine is running, set the spark timing at 8 deg BTDC, with the vacuum disconnected and plugged

Bart

On to the timing now - have a few questions:

1.) Timing light has "2 cycle" and "4 cycle" mode. I assume mercedes engine is a 4 stroke?

2.) I think the reading I am getting is 8˚ ATDC @ idling speed (845rpm)
Here is drawing of what I'm seeing:

IMG_1654.JPG

Am I reading this correctly? Seems to be a long way off the desired value.

3.) Just to double check - you reckon 8˚BTDC is the sweet spot? My workshop manual says "3-12˚":

IMG_1655.JPG

4.) When we say "with vacuum disconnected and plugged" - am I plugging the tube coming from the carb? Or the hole on the distributor? Both?


I'll probably make better progress when I stop trying to start the engine with either the dizzy rotor missing, or a breaker bar still connected from hand turning the engine.

[Bartman4800]

1. Yes, your Mercedes has a 4-stroke or 4-cycle engine. In the 2-cycle mode, it would expect one spark per revolution, instead of one spark per 2. It would only make a difference for the Rev counter on your timing light.

2. You are spot on. Your timing pulley rotates clockwise, so everything on the right side of the 0-line is BTDC

3. Yes, 8 deg is the sweet spot, you could go to 10 deg if it does not ping. You can also go to 3 deg, but you might find your engine does not pull as well.

4. You only have to plug the hose coming from the carb to avoid any potential vacuum leaks, just to keep the engine idling better. There is no vacuum generated in your distributor, this hole can remain open. Reconnect after you are done obviously.

[MajorBenz]

1. Yes, your Mercedes has a 4-stroke or 4-cycle engine

2. You are spot on. Your timing pulley rotates clockwise, so everything on the right side of the 0-line is BTDC

3. Yes, 8 deg is the sweet spot, you could go to 10 deg if it does not ping. You can also go to 3 deg, but you might find your engine does not pull as well.

4. You only have to plug the hose coming from the carb to avoid any potential vacuum leaks, just to keep the engine idling better. There is no vacuum generated in your distributor, this hole can remain open. Reconnect after you are done obviously.

Thanks for your detailed reply Bart.
Seems my timing is actually dead on then?
I was reading the marks left to right and had my ATDC and BTDC the wrong way around.
It does make sense if you follow the wheel in it's rotation - the marks to the right reach the pointer BEFORE Top dead centre.

Not going to worry about the advance readings for the moment as car ain't going anywhere.
Next up is balancing the carbs, but in the meantime I think I hear a new intermittant buzzing noise coming from somewhere on the right side of engine. Here is a link to video footage:

https://flic.kr/p/2kAjkrv

Any idea what that may be? Can't find anything loose. Wondering if maybe distributor shaft does not have enough grease...

[MajorBenz]

Oh - I'm meant to check the spark plug gap too.
Nothing in my owner's manual.
Chilton's says 0.6mm.
Correct?

[Bartman4800]

0.6 mm sounds about right, but NGK's come gapped in the box (that's what the cardboard tube protects)
That buzzing noise could come from your power steering pump.
Or a bad bearing inside the distributor...

Can you post a video on boobtube so we can listen?

Try with a stethoscope, or a screwdriver held against your ear to determine where it comes from.

Bart

[MajorBenz]

0.6 mm sounds about right, but NGK's come gapped in the box (that's what the cardboard tube protects)
That buzzing noise could come from your power steering pump.
Or a bad bearing inside the distributor...

Can you post a video on boobtube so we can listen?

Try with a stethoscope, or a screwdriver held against your ear to determine where it comes from.

Bart

Link should go to a video with sound. Does it not work? play?
I like that screwdriver stethoscope hack.

[Bartman4800]

It worked now.
First I would check the fluid level in that power steering reservoir.
It sounds like cavitation. Does it get worse when you turn the steering wheel?

Bart

[CraigB]

Not sure about the noise but if it is power steering related it should change if you steer while the car is stationary.

Couldn't help noticing the range of colours and rubber ends on leads. They are no doubt silicon core leads. It sounds like its running smooth enough, but if you are investing in new leads at some stage, good to put back the proper 1 ohm resistance solid core leads - they will last forever and never have to worry about if that is your misfire reason.