Miss firing 380 SL

Isdyldan

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Hi - could someone help me cure my running problem please? I have an '81 380SL which I acquired as a non runner. I messed around with the timing but eventually found it had the wrong coil on it. I bought a standard looking second hand blue coil from Mercman and it started up fine. After starting & stopping a number of times to get in & out of the garage to work on it, she is now only running on about half the cylinders, and when I remove the plugs they are wet with fuel. The car has ballast resitstors on it - could it be that I still have the wrong coil please, or does this sound like the timing maybe? I have no idea how to statically time this engine as I couldn't get a voltage to drop across the coil as I twisted the dirtributer - is there a technique to static time this engine please? last week it ran fine again for 10 minutes or so but is now lumpy again! Any ideas would be more than welcome.
Thanks
 

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more info required

is it one bank of cylinders out, or a mixture on both sides. It's unlikely the coil is going to miss one bank out completely if it is the culprit, more likely to miss out cylinders at random. Wearing a thick glove you can test for the missing ones while running bu pulling off the HT leads from the cap. Don't do this for long though, as it's not good to have all that energy going nowhere.
Does she fire up fine, then go rough, or fire up rough and stay that way.
Is it after the warm-up phase is over?
Sorry to send you back with a to-do list, but if you can describe it a bit better, then we all have a chance of locking on to the cause more quickly.
 

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Wear in the top bearing on the distributor could cause only half the plugs to fire.

Another well known fault is dampness in the dizzy cap and rotor arm.

Plug leads can go completely open circuit
 
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Isdyldan

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Hi - thanks for your swift replies. She seems to start quite lumpy now, and seems to be 'choking' as if I rev shortly after starting there seems to be flooding going on. I've never really got her up to temperature properly. The plugs are new and gaped properly. I'll try the HT lead removal exercise tomorrow and see which & how many are missing. Really odd as she was running fantastically well a few weeks ago & nothing has been altered. Being kept in a dry garage too, so can't see damp being an issue.
Thanks again.
 

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Then test the HT leads if you have an ohm meter, though if the engine has not been up to running temp, then the condensation levels could be high inside the dizzy cap
 
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Isdyldan

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Very strange things are happening. I started her up - running lumpy - and started removing plug leads from the distributer and a couple made no apparent difference. I went to get some paper to make a note of which ones and found it ticking over fine when I got back, and after removing leads again, found all to be firing! However, I got in the car to give a rev, and found that the dash had all gone wonky - rev counter & fuel gauge not working, and oil pressure gauge up at full. The oil gauge fell back on switch off ignition, but went straight back to full on switch ignition on again (without engine running). What is going on?? Could this be related to the running issue?
 

Myros

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the oil pressure guage

will record whatever the pressure is, engine on or off. If i come back to mine after a few hours, it still registers a few bar, but overnight dies down to zero until I fire her up again.
The wonky dials are indicative of some funny electricals going on. the rev counter is a notoriously good indicator of electrical health, and will go all over the shop if your battery/ electrics are not sound. It does sound as though your battery is ok, but maybe a test of the battery and charging system is in order. The ABS light should come on and stay on if your voltage falls to 10v or below and stays there ( or if your ABS is faulty) if it's working.
Re the lumpy running, it could be from moisture building up in the dizzy and then drying off as the engine warms up. Or it could be from an iffy feed to the coil. Or it could be the coil being affected by low voltage, or moisture, or something else that I can't figure out now.
Start with the basics, and clean everything up and check the charging voltage and battery condition, and if they all pan out, we'll get wiggy with a test meter.
 

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The ignition switch could also have poor contacts
 

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If the ignition module was messing abou that would affect the rev counter(but not the fuel guage).
However,as you said that you've not had it up to temperature properly yet,pull the dipstick out & have a sniff of the oil on it.If it smells 'petroly',change the oil & filter & the plugs,then take it out for 4 or 5 miles.
You may have an issue with the fuel pressure regulator though,as in its' relaxed state this increases the fuel pressure for the period of the warm-up cycle.
 
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Isdyldan

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Great - I charged the battery right up & now the rev counter & oil pressure gauge are working fine. Fuel gauge still intermittent but probably to do with the sender. There have never been any working ignition lights (battery or oil), so not sure what that could be. I've checked fuses. The hand brake light does work though.
She is quite hard to restart once warmed up - do you think this could be to do with timing please? That is the only thing I have messed about with.
Regards, Dylan
 

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ignition lights

could be blown bulbs. You can get at some of them by removing the rhs loudspeaker, but not all. it's steering wheel off and cluster out to get at the rest.
The timing could well be the culprit, as you'll be lean when warm, and therefore more sensitive to sparking. I've got some info in a data book at home. Post up the chassis and engine number if you have them, and I'll see what i can find out. Give me a day or tow though.
 

Myros

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info as given for TSZ ignition

all 116.962, 963 and 117.962,963 engines with Bosch distributor 0237401010.
set the dizzy to , no vacuum, 3000 rpm, 25 degrees before top dead centre + or - 1 degree.
Check values are at idle , no vacuum, 13-19 degrees advance,
at 1500 rpm, no vacuum, 11-15 degrees advance.
With vacuum connected, 3000 rpm ,15-17 degrees before top dead centre. No retard settings, (after TDC) recorded.

117.963 with distributor B237480114, set at 5000 rpm, 26 degrees btdc vacuum off,
Check values 12-18 deg at idle, 6-10 degrees at 1500rpm, 17-23 degrees 3000rpm. all vacuum off. 15-17 degrees advance btdc vacuum on

that's the best i can make of it from the german. the first value is Einstellwert, whic I take as setting value, and the other figures are Prufwerte, which I take as check values.
TDC marks should be on the crank pulley and somewhere on the dizzy mounting bit.
Haven't got that info to hand. Maybe Malcolm can help?
 
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television

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When setting with a strobe lamp the vacuum is normally disconnected as you say Myros. The timing marks are easy to see with a strobe.

See what info I have later in the day
 
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Isdyldan

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Hi - Thanks for your time.

I have an odd thing again - there seems to be two different chassis numbers! The one on the vin plate is 107 045 22003565, but stamped on the cross member in large figures is WDB107 045 22003312.

Other numbers on the Vin plate are:

70 7183900 72
881H 881H M-
320 440 467 583 592

The 881H I think is the colour code which is as it should be, Thistle Green, but in other paint outlets (for example Halfords) comes up as some sort of silver!

Is one of the above numbers the engine number please, or is that stamped on the engine itself ?

Thanks, Dylan
 

Myros

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as your is an 107.045 ( 380 SL)

it's unlikely to have an 117.963 engine, as I think that's a late series 500. Mines a 117.962.

yours is going to be a 116.962 or 963. use the data for that.
 
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Isdyldan

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Hi again - It seems I am not out of the woods with this one. I have discovered after now having the car on the road a couple of days that the battery is not charging. I removed the alternator and took it to an auto electrician who tested it and said it was working fine. I told him how I had put a volt meter across the battery with engine running and only got 9 volts (flat battery - started car with booster pack). He asked me if the ignition/battery dash light was working - 'Er, no'. He said that if the dash lamp was blown then the charging circuit would not work! Has anyone heard this before?
My question now then please:- My Haynes manual is actually for a SL350/450 and not a 380, but is the cluster removal the same procedure please? This book says it will just pop out, but it feels like something may break.
Many thanks again for your time - any assistance/comments most welcome.
Regards, Dylan
 

Myros

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it's abit fiddly

you'll need either a 14 or 18mm socket ( get surface drive) or a 10mm hex key/sump key.
You'll work it out by pulling the pad off the horn and seeing what lies beneath.
You'll need a hefty mate, or some rope to tie the wheel off so it doesn't turn while you undo the nut/bolt. A pair of pulling hooks from your ever-lovin' dealer won't go amiss either.
Once you have the cluster out, you can disconnect the wiring and then just pop the bulbs out, noting what goes where and replace the lot with new ones.
Have a search on here for cluster removal, I'm sure you'll find something as i remember posting years ago.
Your tightening torque for the steering wheel is 80nm.
http://www.sternzeit-107.de/modules.php?name=News&file=article&sid=392&mode=&order=0&thold=0 this is interesting if you can handle the german.
 
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Isdyldan

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Thanks Myros - got the wheel off with a 10mm hex key socket and some rope - it was VERY tight! Instrument pod came out easily, and the lamp was not blown. Put it back in and all worked - thought it must have been a corroded contact. Pod back in, wheel on, started the engine & got 14.2 volts across the battery. I was very happy until I noticed that oil pressure, fuel, and temp gauges were all not working now!
I feel I am narrowing down the cause of my problems to bad connections to the instrument pod, so thanks for everyones input. I'll clean & check everything tomorrow.
 

Myros

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I had all this fun when i replaced a blown bulb

and on reassembly, the speedo didn't work. You'll find the wires are old and tired and you might have to resolder or splice new bits in. The connectors were fine on my speedo, but a bit of detective work found the green wire was dead about 1cm back from the end. When opened it up, the copper had corroded away. An easy fix that time, but I'm prepared for more of it .
Keep up the good work Dan. I nearly came to work in mine this morning, but the wind and rain put me off getting it out of the garage. Not like me at all, I must be sickening for something......

I've not heard that one about the bulb and the circuit. I confess to not understanding electronics at all. Maybe Malcolm can enlighten us. If only he had designed the electrics in these Mercs.....
 

television

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The bulb in the dash is on the exciter side of the reg pack, if the bulb has blown or is making a poor contact then it cannot charge. This was a common problem 30 years ago but hardly hear of it now.

Must say that I have enjoyed reading you post Myros, very few can do that timing work these days. There was so much satisfaction to be got from setting up an engine by hand, these days all you can do is to look at it
 

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