Misbehaving Merc

MinorMe

I recently bought a 1973 450 SL :cool: which runs like a dog in damp or wet weather (not enough revs to move when drive is engaged) and runs sluggishly otherwise:eek: :eek: . I have been advised to change the plug leads and put a lead additive through the petrol. However I note from previous threads that these older mercs were built with hardened valve seats and would not require additives. She currently idles at 2000 rpm, which is the only way to guarantee that she will start in this weather. Before I go changing too much, has anyone encountered similar ???

franksm

Try WD40 on the plug leads and distributor cap ?

Sounds maybe like one of the carbs isn't working at all (assuming multiple carbs) or out of sync. Hard to judge without seeing it.

If the car is new to you, I'd change the easy stuff as a matter of course: plugs, leads, distributor cap, rotor arm. That might account for a lot of it.

If something's misfiring on a V8, you don't necessarily notice it as a misfire other than the engine being sluggish, not idling properly, or rattling etc

Oshbosh

Plug leads are probably a good idea, my 1982 230CE never had a problem with unleaded and my mechanic said not to worry. I've no idea why you've no power but with regard to starting in damp weather try putting a plastic bag over the distributor cap ( yes it is ridiculous). My first MG always had problems starting in the rain. I tried that plastic seal spray stuff, and didn't work. Put a plastic bag in and never ever had a problem again. In fact when i sold it to a friend of mine he called me after a week and said it wouldn't start. I asked if it had been raining, which it had, and then asked if the bag was still there, he said he'd removed it as he didn't know what it was for , put the bag back says i and everything will be okay, he did and it was.

MercMad

You dont need any additive !

I would change the Rotor Arm and Cap. If the leads look ropey then change them too ! Its good insurance !

Why is it idling at 2000RPM ? Did someone set it that way to compensate and prevent stalling ?

The idle valve and vacuum pipes at the very front of the engine perish and give these exact syptoms. Check all rubber pipes in this area, they are easy to replace !

mike65

Should be injected, bosch D

http://www.w116.org/library/M117

Mike.

MinorMe

Thanks for all the advice. I have been away for the last week but will try some of these suggestions at the weekend and report back with a progress report !!

8~)

Second the advice re: plugs, rotor and leads. Always start with the basics.

trev44

you have me curious now. let me know how you get on.. is there very black smoke coming out the back.