I have a 1987 560 SL that seems to run extremely well; very smooth acceleration and idle. After changing the plugs, I noticed that some seemed to indicate a lean condition (very white insulator). The rest had the normal greyish-brown color. Would this be indication of a problem with the fuel distributor? IF not, what else could cause this problem. As I said, the car runs great otherwise.

Max

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M. Sandler

1986 560SEC: 150,000 miles, runs great, but I've got to sell it (too many cars for one man)
1987 560SL: 122,000 miles, used to run poorly, now (thanks to forum), runs great!
1997 GMC Jimmy: Turned out to be a turkey.
1989 T-Bird Super Coupe: 150,000 miles, still runs great. Ford got it right.

Sounds like you have a good running SL!

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Bad fuel distribultor very rarely results in uneven fuel delivery between injectors, but bad injectors surely will! So will leaking injector seals.

However, since you don't have any running problems (lumpy idle, hesitation on takeoff, etc), I would leave well enough alone until a problem develops.

If you do get symptoms of vacuum leaks or plugged injectors, change injectors, seals, and the seals between the manifold halves.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Thanks for everyone's replies. The injectors were replaced about a year ago along with the seals, so I don't think that is the problem. The cylinders that appeared to be running lean were the first and last on each bank. I'm starting to believe that I better leave well enough alone, and wait for some other REAL problem to surface!

Max

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M. Sandler

1986 560SEC: 150,000 miles, runs great, but I've got to sell it (too many cars for one man)
1987 560SL: 122,000 miles, used to run poorly, now (thanks to forum), runs great!
1997 GMC Jimmy: Turned out to be a turkey.
1989 T-Bird Super Coupe: 150,000 miles, still runs great. Ford got it right.

Sounds like a great car; if it were just the rear banks, or just #8, I'd say your heads had blocked EGR ports (#8 normally plugs up last -- very common); however, first and last cylinders is probably normal, or possible slightly leaky cold start injector, as the idle air bypass w/ cold start injector start at each banks middle cylinders and work towards the outside of them. Could also possibly be a leaky fuel distributor; you can verify this by checking out the lower fuel distributor housing (push down the airflow meter and see if you detect any "wetness" on the boot or around the throttle valve). There are more even remote possibilities, but you can check these if you like.

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Don't ask me, I'm a shop-owner by default

BenzRepair, it's interesting that you mention 'wetness' on the boot or around the throttle plate. I have a 1991 300CE with CIS-E fuel injection and have those very symptoms. Does a 1987 500SL have the same fuel injection system? How do you confirm a leaky fuel distributor and if so, repair it?

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Fred Hoelzle