1985 MB 280SL does not start when the weather is cold. Yet when the sun is shining and the weather is warm, it starts first time. Can any one diagnose the problem/issue

Asked by Jun 20, 2016 at 07:57 PM about the 1985 Mercedes-Benz SL-Class 280SL

Question type: Maintenance & Repair

4 Answers


I complete though engine "tune" and sensors check is needed 30+ years old. Even if it starts easier in warm temperatures its far from running correctly a few diagnostic tests would demonstrate this very quickly. Regards

Thanks for yr guidance. What sort of tests did you have in mind. Will be grateful for an answer. If u r resident of uk, perhaps u can recommend a garage that can carry out these tests.


First test is AF mixture the early MFI injection system seem to always run rich, check the exhaust pipe does it have a carbon, fluffy shoot deposit? I use a handheld modern gas analyzer to read HC, CO, N0x, C02 for tuning, It is the standard in 2016. NEXT, the ignition system.. point wear and corresponding dwell time needs to checked and set, along with the distributor tested for bearing wear so there is no variation of dwell, I use a dwell meter and tachometer to check this function I set dwell with the engine in dynamic rotation. Ignition wires (should be replaced), but can be checked prior for Ohms of resistance with a multi meter such a Fluke or quilty meter. A leakdown test on the engine gives a very good indication of overall sealing and efficiency of the "Hardware", piston rings, cylinder walls, valves and seats.. etc. A good double platinum spark plug(s) 6, should be used in service. Finally all senders / sensors..coil etc. be tested / checked with an oscilloscope I favor a Laptop based PICO, or at least a mulitmeter not as desirable. There is more to check.. though this is a good overview after having this done the 280SL will behave as a different vehicle REALLY... I'm in the U.S. my niece currently resides in Kensington · London Coordinates: 51°30′00″N 0°11′24″W Sorry, I'm presently NOT (yet, possibly the future?) connected to a service facility there therefore can't recommend one. Click on my image or name for some additional Info..Cheers

1 people found this helpful.

Thanks Mark. Helpful. Most HT leads, spark plugs etc were changed last year by a mechanic, the coil was replaced last week. I am not sure if the mechanic checked the mixture? I do not know much about car mechanics, but would a rich mixture prevent starting in marginally cold weather? Is checking the mixture on a fuel injected engine relatively easy to check? Thanks once again

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