1985 MB 380SL ~ hot starting issues & rough/rich idle

[detox2181]

I am asking for support on a 1985 380SL. During these summer months my vehicle has become harder to start on the hotter days after the engine has already been warmed up. \
First thing in the morning there is little to no hesitation when starting. Only when the day warms up and the engine is warm does the car not seem to want to start. First attempts usually will only continuously turn over and over again as if there is no fuel even if I ease on the accelerator. After a few seconds of tturning over I wait a minute then try again and it will start up after about 3-5 seconds of cranking.
Once started it has a rough idle and the exhaust gasses smell a bit rich.
I've recently replaced the plugs and wires and that is when the problem began to occur. I brought it to a mechanic who replaced the valve seals and valve cover gaskets. But there were no error codes coming up which would explain these problems. Tested the battery about 13.84 volt and the alternator is putting out about 13.84 volts. I am at a loss.
Please any advice would be appreciated. I have found it difficult to find much talk about this vehicle. Thank you

 

[burmanut]

hot start problem 1982 380sl

I'm having exactly the same hot start problem with my 1982 380SL, i.e. starts fine when cold but requires prolonged cranking when hot which is about 8 hours after it is parked. It will start fine when hot if the engine is only off a few minutes as when running a quick errand. Leave it 5 minutes and it is very hard to start. Did you find a solution to your problem? I'm located in an isolated area without much in the way of MB mechanics so any guidance would be appreciated.

DJ

 

[shayes]

Can I add my name to the list of people experiencing this problem and worse?
Car is 85 500SEL.
It's been behaivng similar to what you mention, ie OK to start from cold and runs beautifully, but when an attempt to start it after its been parked after a run, it becomes very spluttery and irregular for the first (30?) seconds.

Ultimate indignity only yesterday, in that the car did for the second time when having been driven only half a mile, die on me.
I had replaced a Relay to see if this was the problem. and of course forgot to put the old one in the car, so had to leg it home to get it, just in case this was the cause.
Fact is, that it still would not start. Battery was not the problem. (It had died on me a few weeks back at virtually same spot, but after concerted effort to start it, it eventually did irregularly kick into life and smoothed out. Petrol this time half full, last time quarter full.

AA guy turned up and took off Plug lead and said bags of spark. Linked second battery but still no go. Took off Air Filter and squirted Aviation Fuel (or whatever ) and not even a kick from one cylinder. Towed back to the House - and this the Car that Michael Caine drove in that appalling Film Shadow Run. (not his car, though it was up for sale on e-bay last week or I would not have known about it!) The Car was the Star!!

Today, took out three of plugs and they are virtually new, no tarnish on the rim edge at all and only a small amount of soot on the firing pin.Slightly Wet with the squirty stuff which he told me he put in half a Can!!

Charged battery on trickle and this evening turned over car just once - no sign of life. Decided not to do anything further until tomorrow.

So what the h*** is causing this new misery, having only a week ago resolved my high idle problem with a replacement ICU.

Is there a problem and diagnosis section on the Merc CD' where I can troubleshoot this particular quirk?

 

[shirubaby]

Could this be a leaky injector problem? I'm only going on what other people have said about it on the forums.

Hi Mike,

I would have the balance of fuel delivery cheked on a machine, i.e. are all injectors delivering equal supply to the cylinders.

If your mileage is excess of 70k, then it may be that one or two injectors are blocked or even leaky. Which would cause starting problems hot and cold. Leaky injectors would cause loss of fuel pressure leading to hot start problems. Blocked injectors would mean you're not firing on all cylinders, hence a cold start problem.

I think it's a good idea to replace injectors that have seen more than 70k miles.

But have the fuel system components, i.e. distributor and injectors tested on a machine before replacnig anything.


Talbir

 

[RonH]

Had similar problem with ,86 190E.Difficult starting only after stopping for short time,i.e. refueling at garage etc.Replaced 5th injector (cold start ) with substitute I had in garage.....cured my problem.Hope this may help.

 

[shayes]

So, concensus seems to be either OVP Relay (I took apart the s/hand replacement and found blistering and corrosion aplenty in the circuit board sandwich) or possibly a duff Injector or injectors.

I have purchased a new OVP Relay for £44.17 which is now a different number being as per a 190E model and will fit tomorrow.
Note that it has an extra pin but this is what the Merc main dealers assured me is the one.

For a while I have been suprised that I don't seem to hear the petrol pump clicking as I did in the SEC. Told this could be a fault in the Kickdown Relay and may be my problem. Tried an alternative s/hand one on the day of my ordeal but no go. Opened this s/hand one up and found corrosion to the pins to plates connectors. Probably both at the end of their life. Not tried the bridging of number 8 pin to earth as per CD Manual as not certain which is number 8. Wary of making a mistake and making matters worse..

Will plough on

 

[BIGSTEVE]

Bad Hot Starting And Cutting Out When Hot

Hi Guys, I Had A Similar Problem With A V8, Starts Fine When Cold And After A Run It Would Cut Out Or Fail To Start After Switching Off, It Turned Out To Be The Fuel Pump Relay Over Heating, As Soon As It Cooled Down It Was Ok, If This Matches Your Fault, Try Bridging The Supply To The Fuel Pump Direct At The Relay Socket, It Drives The Pump Direct This Will Eliminate The Relay, Hope This Helps, Regards Steve @spr Autos.

 

[shayes]

I will try a new relay I brought recently. See if this does the trick. No point in leaving it in the glove compartment. Having got the Car back GOING again, I had forgotten which of the Relays out of the handful that I have acquired, is actually in the Car!

Thanks

 

[television]

Don't forget you guys, fuel pumps have a limited life, as they get clogged up inside they slow down, this increases the current load through the relay.

What they do in the USA is to take them off and run them backwards putting in diesel to clean them (it disolves the crud)

Malcolm

 

[shayes]

I think you must be right Malcolm unless its the Injectors. Just tested the new Relay and same problem after forty minutes - sluggish firing for about eight seconds.
May feed through some STP Injector cleaner beofr reverse deiseling a Petrol Pump - sounds simpler.