Help...Misfiring

[Bearcat]

I have a 280SL 1970 and I have a big problem. The car is misfiring on one cylinder and having driven it hard .  I thought it might have been points, so I changed the points, the distrib cap , condenser,plugs and leads and all to no avail. I also reset the timing to 8 degress tdc as per the book Its now pointing towards fuel. could i have a bad injector or worse again the mech fuel injection? any ideas folks as I am getting frustrated.

When i took the old plugs out they were very black and sooty. ....this points to worn piston rings but the car doesnt burn oil or belch any blue smoke

280SL 1970

[ja17]

Hello Bearcat,
We could use a little more information. How is the idle? Is the miss on one cylinder or random? If it is on one cylinder find out which one it is by removing one wire at a time until you find it. Next take a compression check of that cylinder to make sure it is ok. If the compression is ok the problem would most likely be electrical or fuel.
You can trouble shoot a stuck or dirty injector by cracking the fitting at each injector one at a time while the engine is idling. You should be able to notice a rpm decrease each time.


Joe Alexander
Blacklick, Ohio

[Bearcat]

Joe, the idle ok but the second you step on the gas, she is down on power and down on a cylinder upto 3000rpm. Tomorrow we do a compression test. I fear it is a gas issue as against electrical. Maybe a blocked fuel injector....then we look at the pump. Any other ideas come to mind let me know.



David

[Cees Klumper]

You seem to indicate the problem started after having driven the car 'hard'. Could it have anything to do with the head gasket?

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[ja17]

Hello Bearcat,
A compression drop will make itself noticable at idle, so you are probably ok here. You may have some kind of unusual ignition problem. So anyway, after 3,000 rpm does the engine run ok?

Joe Alexander
Blacklick, Ohio

[Ben]

Hey Bearcat.........sorry I didn't call I only switched my phone on this morning !

I didn't hear you mentioning the rotor itself, however first thing is to do what Joe suggested and locate which cylinder isn't firing !

Could also be a vacuum leak.........check the vacuum advance pipe and the various fittings on the inlet manifold particularly the brake servo !

Call me if you want today .......

Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor

[mulrik]

Had a similar problem look under the post" another ignition problem". See there what I did.

I would also investigate the fuel injection. Take of the fuel lead at the nozzle and see if fuel comes out when cranking. Otherwise clean the nozzles, there is a post somewhere on that.

'67 250 SL Papyrus White 113043-10-000023

[Bearcat]

folks i have solved the problem having re done the electrics but it was actually fuel and a faulty injector and a cracked breather pipe?. I left it with my garage man and the car has never run better. thank you for all you help as i could at least give a few pointers to my mechanic. My engine bay loks neat though with all the new wiring! thanks again