W126 Engine Pinking Noise/Fuel Smell

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Arthur Daley

Active Member
Oct 9, 2009
My W126 engine still pinks on hard acceleration (280SE model) even though the car has just had a good service and the timing set. Now when starting the car after it's been standing there has always been a slight smell of fuel through the heater which goes after a few seconds. I have never really worried too much about this as most of the old cars I have owned have been the same.........however....in a bit to get rid of the pinking I changed fuel from Morrisons to Shell V Power.

The result is that the pinking has got a lot better but the smell of fuel on starting is much stronger!!!!

Anyone else had these problems/know any solutions?
Your car's ignition timing was designed for a new engine running on the correct grade of fuel which in your car might well have originally been leaded =higher octane petrol=98RON. Which equates to the improvement you got by moving to Shell V power = 99 RON. Superimposed on this "idealised " situation is a possible increase in compression ratio due to deposits on the piston crowns or combustion chambers or if the the head has been skimmed during the renewal of the cylinder head gasket for example . I would try retarding the ignition a couple of degrees at a time to see if that helps.
You may find the increased smell is due to a change in composition of the fuel rather than any increased leakage. I think 99 RON fuel uses more aromatic hydrocarbons in its composition to achieve a better octane rating and it may be these you are smelling.
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Cheers the new fuel seems to have done it...........will try different fuels to find one that doesn't make the car pink and doesn't smell too bad on start up!!
Your car has been set up to run on the lowest ron unleaded fuel from day one, so if you're getting pinking i suspect a sensor is faulty. You shouldn't have to be playing around with ignition timing etc just to get the car to run on normal unleaded fuel.

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