wet engine 560sl--1987 - PeachParts Mercedes-Benz Forum

560slsteve · #1 08-14-2008, 05:17 PM

I have been noticing lately that my SL wouldnt start readily after a good wash job, especially when i do an engine clean and spray the hose around in the engine compartment a bit. I do try to keep the spray off the alternator and the coils, etc., but have never had a problem before with any of my other cars, and not with the SL until recently.

once after washing the engine, i had to wait several hours and spray WD40 to displace the water before she would start--it ran rough at first and then settled out. Now for the current crisis---

yesterday was a real frog strangler here on the east coast--first time in a long time where it rained all day long with virtually no let up. the car sat in the yard after running 4 hours on an interstate the day before. It ran great!!

I tried to start the car about mid day yesterday, and she wouldnt hit. It turned over well with plenty of battery power, but no ignition. so i figure it's wet somewhere. I try today, and its no go, even with spraying down the engine compartment. now, at the end of the day, its trying to start, and is beginning to hit on a few cylinders, but hasnt started yet. hopefully it wil start tomorrow with a little extra drying time.

So my question is, wonder where this water is effecting this car? i have sprayed well around the ignition module and coil, and all the plug wires (which are new and the correct ones). its definitely ignition because all the spark plugs were wet with gas earlier when i checked them. it sounds like it wants to start now, but acts like its flooded. the only water i have seen standing in the engine compartment is in a small area under the front fender under the ignition module, and at the same place inside the right fender, which i have dried.

Any suggestions about where to look would be appreciated. i have checked under the distributor cap and it was dry there---no carbon tracks and the rotor button end looked good.

I definitely have to trace this one down, or I will be stuck somewhere after a rain unless i am driving in it. i guess the engine heat keeps it dried up enuf to run.

Thanks

tecqboy · #2 08-14-2008, 06:21 PM

I don't know what other's may think, but I wouldn't spray WD-40 into contacts or on electrical stuff. It doesn't evaporate totally without a residue. Clean compressed air is best if you have it. If you ever get it started, look at the engine in a totally dark garage and watch for signs of electrical arcing. You have a high voltage breakdown and the classic signs of water in the wires, boots or coils.

560slsteve · #3 08-14-2008, 08:19 PM

thanks tec,

i really didnt realize that wd40 could possibly harm the electronics. wonder if a can of contact cleaner onthose parts would cut it off and do no harm? at least it would evaporate quickly.

i tried to start it htis evening, and now its trying to start but no go. hopefully tomorrow will be a better day and if it starts i will definitley look for archs under the hood.

i'll let you know if i find anything.

thank you much.

abe g · #4 08-15-2008, 12:13 PM

If it dries quickly could be DANGEROUS ! I cant help with start but suggest drilling drain area where water collects. Good luck Abe G

560slsteve · #5 08-15-2008, 01:11 PM

hi all,

well, this morning she began to hit on a few cylinders and then started. choked out all the old gas from trying to start yesterday, and then ran as normal. I let it run for a while to make sure the battery was charging, and she was ok. i do have a slight miss at idle and was diagnosed by a master merc mech that #8 cylinder was missing at idle and i needed a new fuel distributor. I havent sprung for that yet. i did do the new injectors and seals , and again traced the missed back to #8 and even changed the FD lines and made the problem move, so i believe the mech had the proper diagnosis on that problem.

But, since she is running ok now, there has to have been something that was wet. this was the first time it got wet while raining. I was thinking that if my coil was weak, it wouldnt take a lot of water to zap it of enuf voltage to possibly prevent a start. i dont know how to test one and havent done the research to try it yet. i know that previous trouble on my other older cars always involved a new coil, and they never seemed to make much of a difference. And i am sure that mercedes is also proud of their coils.....

thanks for the replies and further advice. i am definitely going to drill a hole to drain those little catch wells in the front frame under the ignition controller to eliminate that water.
might not help but couldnt hurt. cant find where mercedes had one in there that could have been clogged, so i will make my own.

thanks.

Richard Wooldridge · #6 08-16-2008, 01:19 AM

There are drain holes at every low spot that water might collect, so try clearing them before drilling any holes, any drilled holes are sure to be points that will start to rust later on.

I would use silicon grease on all the spark plug and distributor boots as a first step in diagnosing the ignition problem, it makes the wires much easier to remove and install. A point to consider is the insulation at the coil... if it is dirty, and you haven't used silicon grease on the boot, it probably would have a low resistance path to the coil cover through the dirt on the insulation.

560slsteve · #7 08-16-2008, 10:18 AM

thanks Richard.

I am going to look the car over well today and apply the silicon grease to the boots. i will look over the coil insulation as well. everything is very clean under there, but the coil cover doesnt seem to fit very well. i will have to check on that as well, but still dont see how water could get to that area withthe hood down.

supposed to rain again this weekend, so maybe your suggestions will help.

thanks for the response.

560slsteve · #8 08-16-2008, 02:03 PM

Today I took the coil off to check it out---where the wires are grounded to the mounting ears of the coil against the body of the car I found substantial pitting. i am guessing that this is an ignition grounding point.

maybe thats where moisture causes a bad ground so i lose voltage from the coil. it started fine when i reassembled the job after cleaning the contact spots really well. hopefully this will greatly help--i will know after the next rain!!!! IT might be a good place to check if anyone suspects ignition problems in the future due to a bad ground.

thanks