1982 380sl not starting

[spkunkle]

Hello,
I have a 1982 380sl that I am having trouble starting, if I hold down the throttle plate just a little it starts and runs fine. I removed and cleaned the idle control valve, checked that it is getting power, it hums and clicks when the key is turned, so I am guessing it is working. does adjusting the tower screw open that throttle plate?

the previous owner said the idle was to high so he had a mechanic adjust it, when I got it it was already warmed up and running and worked fine for the 20 minute drive back.

any help would be appreciated,
thanks, Sean

[Frank Reiner]

Originally Posted by spkunkle

Hello,
I have a 1982 380sl that I am having trouble starting, if I hold down the throttle plate just a little it starts and runs fine. I removed and cleaned the idle control valve, checked that it is getting power, it hums and clicks when the key is turned, so I am guessing it is working. does adjusting the tower screw open that throttle plate?

the previous owner said the idle was to high so he had a mechanic adjust it, when I got it it was already warmed up and running and worked fine for the 20 minute drive back.

any help would be appreciated,
thanks, Sean

The "throttle plate" is not the throttle plate!! It is the air flow sensor plate, and moves not via the throttle linkage, but in response to air flow into the engine. When you depressed it you also moved the fuel metering plunger in the fuel distributor (FD) in the rich direction. In the event that the PO's "mechanic" turned the tower screw in the lean direction, it may have had the effect of reducing the idle speed (due to leanness), but it also made the basic mixture so lean as to inhibit cold starting.

Have you explored how the tower screw works? The upper section is spring loaded upwards, and must be depressed and slightly turned to engage with the lower screw, which is the actual adjuster. CW is richer, and changes should be limited to 1/8 turn increments with a total of four.
After that, if starting difficulties remain, a reevaluation of more components is in order.

[mespe]

Originally Posted by spkunkle

Hello,
the previous owner said the idle was to high so he had a mechanic adjust it,

That says it all. The adjustments are out of whack. And to make things worse, you don't know which adjustments are incorrect. Best thing to do is to set it up as per factory spec. Probably in the manual,,,

This high idle could be a leaking cold start valve (if the 380 has one,,, only seen one 380)

[spkunkle]

Thanks, the information was great, turns out in addition, the wire to the idle control valve was broke, I fixed that and readjusted the tower screw (I'm glad you told me how that screw works) and it fired right up. it took all four 1/8 turns! runs great now! the previous owners mechanic missed the broken wire and tried to make up for it with the mixture screw. probably just to get it sold to me!

I really appreciate the help,

Sean

[spkunkle]

I guess I spoke too soon, now that the weather is nice I took the car for a ride and after about 5 miles the car started sputtering and barely made it back, couldn't get it over 10 mph. after it sits for a bit it will start up and run fine again, ran some lucas through it thinking I had some dirt in fuel, but tried again today, and it ran fine at first, but after a short ride it started to run terrible again, I found if I push down on the air flow sensor plate slightly it will smooth out.
so to sum up, runs fine cold, terrible hot.
any help would be appreciated,
thanks,
Sean

[rayhennig]

Originally Posted by spkunkle

I guess I spoke too soon, now that the weather is nice I took the car for a ride and after about 5 miles the car started sputtering and barely made it back, couldn't get it over 10 mph. after it sits for a bit it will start up and run fine again, ran some lucas through it thinking I had some dirt in fuel, but tried again today, and it ran fine at first, but after a short ride it started to run terrible again, I found if I push down on the air flow sensor plate slightly it will smooth out.
so to sum up, runs fine cold, terrible hot.
any help would be appreciated,
thanks,
Sean

First thing is to make sure that all HT components are 100%, using only MB original parts or Beru/Bosch as second best.

RayH