Hi all!

I've got a '82 380SL.

Initially, car starts and runs perfectly, and will run all day as long as you never shut it off. Initially there is ZERO hesitation. Once it gets warm, there is SLIGHT hesitation, but nothing I would spend any time on.

However: if you turn car off and restart it right away AFTER IT has gotten hot:
- Starts right up and idles fine but lacks power.
- ECON needle sits at about 40% to the right while idling in D (normal = about 10%).
- Slow taking off and sluggish until you can maintain above 1500RPM,
- ECON needle goes to 100% quicker than normal when accelerating, but maybe just because you have to push pedal farther.
- Can floor it and get it up > 2000RPM and it will accelerate close or = to full power and will get up to high speeds then cruise along with ECON needle about normal.
- My impression is that as you drive more miles, it gets a little better, but NEVER really like when started up cold, particularly at low speeds.

If cold-started then shutoff after 10 seconds and restarted:
- NORMAL.
If shutoff after 30 seconds and restarted:
- Horrible; extremely hard to get up to 1500 RPM, until driven about 15 minutes, then like above.

If warmed up then shutoff and left for more than a few minutes then restarted:
- Not quite horrible at first, then gets back to bad when warmed back up.
If left for 3-4-5 hours and restarted:
- Horrible.

FURTHER:
- Fuel economy seems pretty bad but since odometer is broken it's hard to tell, and since I'm on full throttle a lot to get RPMs up, may explain, but seems like around 12-15 max.
- Doesn't belch smoke and doesn't stink when idling once it fully warmed up.
- The car does have a 'brand-x' ignition module; replaced about 10 years ago and this problem started 4-5 years ago.

What I've done:
- I replaced fuel accumulator and pump and filter. No change.
- Squirting starting fluid around vacuum hoses/connections has no effect on idle speed.
- The coil, dist cap/rotor, plugs are newish. The plug wires have proper resistance.
- I jumpered the fuel pump relay so it ran continuously and no change.
---- therefore not the relay itself.
- The filter screen on the input side of the WUR appears clean and I put a few drops of penetrating oil down there in case there was crud. No change. I can't get the screen(s) out, at least not without taking the WUR out.
- the fuel system does hold significant pressure for at least a few minutes: when unscrewing WUR input, liquid gas sprayed out.
- I've unplugged every wire connected to a sensor/etc. that I could find and no change.
- Running injector cleaner for 3rd time, just because everyone says, it's the injectors...
-

Very puzzling why some condition could occur 30 seconds (but not 10 seconds) after initial startup.
- happens before anything gets really hot, but then stays broken for hours (I don't think it's OK until it's completely cold like overnight or literally all day).
- also since most of the normal power is available at >2000RPM that proves that a lot of things are working right when it's hot (plenty of fuel and spark).

I took to a place that specializes in classic MB, Jag, etc. and he told me he couldn't diagnose it without draining my wallet. No MB dealers around, but I'm pretty sure they WOULD drain me... One other guy and he said that type of problem is 'always injectors', but I don't think he listened to what all I was saying and I think I stated reasons why it can't be injectors alone (if not, I'd like to understand why before I spend $$$ and dig that deep into).

I've read hundreds of forum threads and none were this problem, although a few were similar.

I do have the manual "CD" on my computer but don't have everything I need to do all the tests and honestly get lost on some of it...

I would really appreciate any and all suggestions, comments and questions that might help get me on a path towards fixing. I like driving the car but have resorted to leaving it running in store parking lots which is not always a viable solution. Frustrating not being able to take the car much of anywhere for fear of it becoming even more un-drivable far away from home...

Thanks,

Mike

 

Hi, a few more points to clarify.

1. I did recently replace the O2 sensor. I forgot to say that before. No change.
2. Yesterday, I did a little bit more specific test: started up and ran, shutting off every 15 seconds or so, driving in-between. Problem didn't happen until about the 3 minute mark this time. It was a much cooler day than when I did before though. Then I parked it and started up every hour numerous times: after about 7 hours, it still was crappy. Overnight it starts up and runs great again...

 

Long story but replacing the OVP relay did the trick. See BENZWORLD.ORG.

 

See BENZWORLD.ORG

Replaced OVP relay.

 

What is the OVP relay? Where is it located?

 

Over Voltage Protection relay. It is the one with the red top. Found these pictures on BenzWorld. You can see the fuse in the second one.