560 SEL - Mis-fire then zero

[Ron McCubbin]

My apologies for the length of this,but I'm at the end of my tether.I work in Saudi and have recently bought a M-B 560 SEL,Last week the problem started,going to work in the morning the car was running fine but in the afternoon it starts to misfire,this rapidly went from a misfire to no ignition at all.
I have changed the fuel filter,air filter,8 plugs,dizzy cap and rotor arm.(dizzy cap and rotor arm are 2nd hand as new spares hard to come by in this neck of the woods)
There is a spark at each plug and fuel is present at the metering unit,injector lines and injectors.The only time there is a hint of ignition is when I connect the 'coil' directly to a plug using a spare H/T lead,crank the engine and the fuel/air mix ignites.The rotor arm rotates
so I assume the dizzy drive is good,cam shafts turn so I presume drive chains/belts haven't broken.
Has any one had this problem before.Any info would be most welcome,ideal spark plug gap,injector opening pressure,timing settings degress BTDC/ATDC,
Are there any sensors in the system for fuel pressure?
Are there any "safety breaks" in the ign system where by you can turn the engine over but it will not fire-up.
After changing the plugs and fuel filter the car started and didn't have a misfire although it did sound a bit flat,although this was without the airfilter box being attached, after I turned it off it hasn't started since.
Is there any need to prime the injectors,if so,in which order?
  Any or all ideas and suggestions will be appreciated enormously.
The car is a 1986 model,203,000 kms on the clock,has been regularly serviced and is in superb condition for it's age.

 

[Andy]

560 SEL

Hi Ron,

If your sure there is no high ressistance in the coil lead and the coil is ok. I would try another ignition pack. These can fail. But for some reason don't on the 6cylinder engines.
If possible try another one off a V8. 420 upwards should start it.

Regards

Andy@ www.mercedesservicing.com

 

[Ron McCubbin]

560 SEL

Thanks for you swift reply to my problem,but can you give me some idea as to where it is located on a 560,
bearing in mind it's left hand drive and sometimes differ to right hand drive models.A description would be real handy,how many plugs/sockets it has,size and if poss a M-B part number.Our local M-B shop doesn't have a great deal in stock,but if they don't have it I can possibly get it sent from Jeddah or Riyadh.Failing that I'll order one from the UK.
  Many thanks once again.

 

[Ron McCubbin]

560 SEL

Thanks for you swift reply to my problem,but can you give me some idea as to where it is located on a 560,
bearing in mind it's left hand drive and sometimes differ to right hand drive models.A description would be real handy,how many plugs/sockets it has,size and if poss a M-B part number.Our local M-B shop doesn't have a great deal in stock,but if they don't have it I can possibly get it sent from Jeddah or Riyadh.Failing that I'll order one from the UK.
  Many thanks once again.

 

[Anonymous]

560 SEL

This sounds like the coil is duff and not giving a high enough votage for a spark when under compression.  Check the timing with a strobe light, anything in the region before TDC will start the car, ansd check the coil output.

 

[Andy]

560 SEL

Hi Ron,

The coil should be self explanatery. But if not it is situated on the left hand side of the car just below the rocker cover on the flitch side. The ignition pack is on the same side in the area of the head lamp just below on the flitch. Has a green or black lead going to it. There are from memory 3 thicker plugs on it. Before you replace see if you can borrow one of somebody to check it out. These items are expensive.

Regards

Andy @ www.mercedesservicing.com