to all shade tree mechanics

My 500SL (1985) starts great, idles fine at first, then seems to develop an irregular idle, and has occasionally cut off, but restarts ok. Recently replaced the plugs, checked the distributor cap and rotor... all seems ok here. Can't hear or see any arcing around the cables. Any suggestions...and as usual...

[Pete S]

Ricky,
I had a similar experience w/my 107 (an Aug. 1989 300SL in the UK - sadly never supplied to the US market). Try replacing the gas pump relay (a black box with connectors) which is situated behind a pop-off cover inside and at the back of the glove box. They're expensive and my MB dealer let me switch it over at the dealership, in case it didn't work. Et Voila! it's been as good as gold since. One word of advice; MB "moved" these relays around from model to model and sometimes year-to-year (so I was told!) but start looking in that place first. Let me know how you get on.
Good luck!
Pete S

300 SL
230 TE
E320

Pete... Thanks for the info. I was afraid that I wasn't going to get a response from anyone. Thought I had offended members by asking for "shade tree mechanics!" I should have known that the "SL Forum" only has one "shade tree mechanic"...(me).

As for the part, I think I know where I may be able to get it used... I found a place were there is a wrecked SL. I'll try that first before I go spending the big $$ buying it new.

Thanks again,

[G-Benz]

Actually, there a lot of "shade-tree" mechanics out here...that is why we have this forum...we come here to ask questions about our cars, and sometimes get advice from the pros.

I consider myself a "shade-garage" mechanic though...

[Steve Gutman]

I spent quite a bit of time on a siimilar problem that got increasingly worse. I went through fuel pump relay, OVP relay, idle speed control module, air slide valve, plugs, cap and rotor, coil wire, plug ends and it turned out to be a bad Ignition Control Unit. Let me know if I can help.

Steve
1985 500 SL Euro

Steve, I've been trying to answer you for the last several days now, but seem to be having problems with my e-mail and logging in. So will attempt to just let you know why I haven't responded to your replies. Going to send this and see what happens. I'm getting ready to get off work now so if this makes it through I talk at you on Monday. CU RickyD

[Steve Gutman]

Hello rickyd,

Is your problem intermittent? If so, these problems can be hard to diagnose and expensive to repair.

If it happens every time a good MB mechanic should be able to diagnose and repair it but in some cases the testing of a component can cost as much as it’s replacement (if you do it yourself and scrounge for parts).

Check to see if the ICU is loose. It is on the driver’s side fender behind the headlight area and has a wire that goes to the coil. Mine was loose and hot. My friend has a 1985 500SEL and his was loose as well. Both his and mine had only 2 of the 3 mounting holes with clips and bolts. Actually, I borrowed his for a few days to confirm that my ICU was bad.

My 500SL still runs rough below 2000 RPM but at over 100,000 miles it could probably use fuel injectors and plug wires. I want to change them to improve the idle (and exercise my limited mechanical ability). But I think I will have it put on a scope first. I have heard from more than one source that these motors do not idle well but I think they just need to be well maintained.

Let me know if I can help.

Steve
1985 500SL Euro

Rickyd

Check the overload protection relay, I am not sure if it is a relay but it has a blade fuse on top. Check the fuse.

zeromax