No Start in Rain
 

Every time it rains my '87 560SL won't start. It cranks but won't start. We've had a week of rain and more if forecast here in east Texas. So, my SL sits and sits. HELP! I haven't tried starter fluid. Should I? I was advised by my local supplier that starter fluid can dry out the cylinders if not used very sparingly. How can I fix my rainy starting problem permanently?

you don't need starter fluid, you need a mechanic. I havn't had that issue to chase so any more information that you can share would be really helpful.
Bill

Damp No Start
 

Check your distributor cap for cracks and/or carbon tracking. Examine closely as it can sometimes be hard to see.

Often manifests itself as hard/no start when high humidity.

Get back to us either way so we can add to the data base.

Ditto on the cap. Pop it off and look for wetness inside. If it's wet, spray it with WD-40 (among other things, it's a water displacement agent), wipe out the excess and see if she'll start.

Check your air filter, too. I don't know how water would get in there, but if the element gets wet, no air will pass.

Oh, and your cylinders get oiled every time they move up and down...

Thanks for all your tips. I'll look at the distributor later today, and let you know what happens

It would also be a good idea to check the coil and the coil wire. If they're bad wet conditions can cause a short and no start.

can also be ignition wires.run engine in the dark and look to see sparks[arking electric] around ig wires...wd 40 will help temporary on wires.

This is a good idea and the cap ideas also. About 15 years ago I learned that I could scrape the crud off of the cap electrodes inside and have a new cap. Works great. If you have carbon tracks then I would toss it. I have only seen those once in my life.

My VW was plagued with this issue a long time ago. Traced the problem to corrosion on the coil wire end.

Replace the distributor cap, rotor and O-ring. If the ignition wires look dry and cracked replace them with new Beru wires. Remove all the spark plugs and inspect them. It's likely they need to be replaced also. Be sure to use non-resistor spark plugs, gapped as specified in your Owner's Manual.

Before you break out the "parts shotgun" and start firing away, does your car actually sit out in the rain or is it in a garage and won't start on days when it rains?

Fabulous saying - Parts Shotgun!!

Try a spare sparkplug in a plug wire when it doesn't start - fire or not? Dribble a little gas down the intake - start or not??

Fabulous saying, but a horrible repair technique.

It's cheaper to identify & verify the problem (and then fix it) than it is to keep swapping out parts and crossing your fingers.

Thanks for all your tips. I didn't get on the job, today. DHJenkins. . . No garage, it sits outdoor under an all-weather cover. However, the last few days it was in our carport which is, of course, open, though there has been not direct rain hitting the car.

I am normally COMPLETELY AGAINST replacing parts without diagnosis. In this case, however, I learned almost 40 years ago when working in the truck shop that when a customer called and said it wouldn't start and the weather had recently gotten damp, that there was no need to do ANYTHING except get a new distributor cap and go replace it. This fixed it EVERY SINGLE TIME!

Just replace the distributor cap and be happy.