R129 300SL 24v - Stalling & Misfiring

[DanMorgan]

Hi,

I've been having issues with my 300 24v SL recently, it would run fine on startup and then stall or misfire once warmed up. I changed the distributor cap and it seemed to sort it out, which did work, but ive now bought it out again and it has started to play up again. However, now it wont start at all and there was no spark from the plugs.

I have changed the following:

• Distributor Cap
• MAS Sensor
• OVP Relay

I have ordered a new coilpack to fit tomorrow, could this be the problem? The car also has a Clifford Concept 650 alarm, which may be causing some sort of issue.


Does anyone have any suggestions or advice?



Thanks,
Dan

 

[neilrr]

Is the EZL good?

 

[DanMorgan]

Is the EZL good?

Is there anyway I can see if its any good?

 

[neilrr]

I suppose you could test for a spark at the end of each lead, but TBH I think if it's an EZL prob it would be there all the time.

 

[DanMorgan]

I suppose you could test for a spark at the end of each lead, but TBH I think if it's an EZL prob it would be there all the time.

Yeah, this is the first time now it just wont start, normally it wouldnt for a while then it would, but now its literally dead. Im going to change the coilpack tomorrow and hope for the best. The EZL isnt cheap so im hoping its not that

 

[neilrr]

I have several -24v EZLs if you find you need one.

I don't think they are available from MB anymore.

 

[ray_hennig]

I have changed the following:

• Distributor Cap
• MAS Sensor
• OVP Relay

I don't see the rotor arm on your list. That would be the first item for me, given your symptoms.

Genuine MB part or Beru/Bosch second best.

RayH

 

[grober]

but ive now bought it out again and it has started to play up again.
From this I assume the car has been sitting for some time??? you might simply have damp in the distributor- dry it out thoroghly with a hair dryer.
ps as per Ray's tip only use MB or BERU/BOSCH HT ignition components-- cheap substitutes tend to work for a short time then develop faults.

 

[DanMorgan]

It had only been sitting for around a month, it was an intermittent problem, but now the car wont start at all. I fitted a new ignition coil and still nothing. In around an hour, im fitting a new bosch CPS, fingers crossed!

 

[DanMorgan]

Strangely, after I replaced all the things, it decided it still didn't want to work. Therefore, I swapped the new rotor arm for the old one, and it decided to fire up? Very odd - has anyone experienced similar?

 

[grober]

Had a similar problem once on a boat with a inboard 6 cylinder Ford engine. Breakdown of insulation from rotor arm metal contacts to the distributor drive spindle leaking HT away. Perhaps an illustration that when replacing components on the HT system it often a good idea to replace them one at time even if you intend to change several parts ---I know you are going to ask which one first---- I don't think there's a definitive answer to that one--- sorry

 

[ray_hennig]

, I swapped the new rotor arm for the old one, and it decided to fire up? Very odd - has anyone experienced similar?

Yes, on a 300CE-24. The new rotor was a Bremi and I put back the original 17 year old rotor. I now have a spanking new MB rotor arm.

RayH

 

[Will]

Yes, on a 300CE-24. The new rotor was a Bremi and I put back the original 17 year old rotor. I now have a spanking new MB rotor arm.

RayH

Yep - had that once years ago on an old Rover V8. Relieved when it finally worked!

 

[rorf]

As Grober said, use only the best original ignition components.

 

[ray_hennig]

As Grober said, use only the best original ignition components.

I think I said that first!!

In fact, I've been whingeing on about that ever since I had the rotor problem. It's about the only solid advice I ever give to these forums. Oh, aside from clearing codes on 5 speed auto box controllers. I whinge about that too.

Any old way, back to the vin blanc and best of everything to everyone.

RayH

 

[jonthetourist]

Just resuscitating this thread because I took out my 300-24 this morning and got the usual misfire after around 6 miles.

Parked up and took off the distributor cap, which had loads of moisture inside. I had been away for a fortnight so was half expecting this. Cleaned it out and everything was fine again.

It's annoying because this is my third cap and there seems no way to prevent moisture getting in there if the car is unused. On the other hand, it's the only thing that has gone wrong so far, and fixing it is within my level of competence, which would not be true of most other jobs. So I guess I can live with it.

Jon

 

[Sp!ke]

Is the seal at the bottom of the distributor cap intact or could it be missing?

 

[E270 Owner]

The alarm system should only cut the starter circuit unless they have purposely wired it in to the ignition system for whatever reason.

Might be worth getting the alarms immobilizer relays checked, they should be external from the main unit (cat1/2 dependent) if its installed to Thatcham Specification.

 

[219]

I had the same problems when I had my 300TE , 300TE-24 and 190E 2.6 - see the connection ?

I also went through distributor caps ( sometimes they can be very short lived ) , rotor arms and leads , can't say with certainty they made much difference .

What I found seemed to make more difference than anything else was a new set of spark plugs !

After experimentation , I found that NGK seemed to last the course better than the Bosch or Beru ones I had used for years ! BP6 ES if memory serves ?

 

[macker64]

I have my 300ce 24v for nearly 2 yrs now and during that time I have replaced various ignition components to rectify mis-firing issues.

Firstly, make sure the car is running with the standard merc copper core plugs. This particular engine will not run correctly if fitted with any other type of plug.

Mercedes plug part no. A0031596703.

Also, when you remove the dizzy cap you should see a circular orange/red coloured backplate which should have a sealing rubber oring around its circumference.

This oring, if still in place, will have deteriorated due to the extreme heat generated by the engine.

This oring is used to seal the dizzy cap and must be replaced.

Mercedes part no. A0149975848

These coupes are fantastic cars and were built to a standard that is sadly not the norm today.