R107 1989 300SL - Cold starting problem

[Pie-Man]

Over and above the niggling electrical gremlins I have with my "new" 107 is a cold starting problem.

The car does not fire unless so turn it over for about 10-20 seconds whilst giving it a little throttle (sorry ... been racing bikes for too long!). It then runs very unevenly and will stall unless you keep the revs up. After about a couple of minutes it settles down and you can let it idle.

Once the engine is warm, there is no issue whatsoever.

The car was just been serviced by a pukka MB dealer who if anything made the problem worse! It's going back in for a second try ... but I thought I'd ask the real experts! Could it be a fuel pressure issue? Or am I barking up the wrong tree? I want to make sure that I'm not charged for unnecessary stuff by the dealer!

Cheers,

Tim

 

[Myros]

Tim

it sounds pretty much like an cold start injector problem. This is meant to richen the mixture and thin it out as the engine warms up. It could be the relay, temp sender, injector itself. Hopefully Malcolm is on song today and will be able to help.

 

[Pie-Man]

Hi again guys!

Urgent help required if possible!?! :!:

Hughes of Beaconsfield have our car at present and are attempting to resolve the cold starting issue. They "think" that the issue is related to the "fuel distributor". They are to receive a loan part today to fit and then test. This part is £900!! they say!!

The car runs excellently when warm and starts without a problem.
The only issue relates to cold starting and rough idling until the engine is warm enough to run comfortably.

I am sceptical about their choice of component ... I can't see how this could resolve the cold starting issue?

Any advice or comments?

Thanks!!!

 

[television]

I cant see it being that, as it has nothing to do with cold starting. the cold starting device comes on with the starter, too little time right now.

Malcolm

 

[Pie-Man]

Thanks malcolm - Pie Man's feminine side responding with a little more info (guesswork) from the garage.

" it appears that the fuel distributor is leaking causing fuel to accumulate when left overnight. As the engine is turned over on starter this clears allowing the car to fire up"

This would not seem to explain the need to blip the throttle until the engine is warm to prevent stopping IMHO!

Thanks Jo

 

[Pie-Man]

Boing! Help please!

 

[wscheffer]

It's your cold start valve that is at fault. The cold start valve richens the mixture and as stated above thins out the mixture as the vehicle warms up...

 

[Pie-Man]

Thanks guys for your help ... the car is still at the dealer, so I'll update the saga later today! :!:

 

[Pie-Man]

Surprise, surprise ... replacing the fuel distributor didn't improve the situation! Car is still at the dealer and they're going to try again Monday!!!

 

[Pie-Man]

Update ... car is STILL at the dealers!

They've just about changed every component, pressure tested it, etc.

Methinks they don't know what they're doing? They've almost admitted as much as they quote ... "can't just plug it in and auto-diagnose it" ... makes you worry about the capability of MB mechanics doesn't it?! :?

 

[Myros]

I hope you aren't paying for all this hit and miss

you'll be skint by the time they fix it.

 

[Pie-Man]

Nope ... or so they tell me?!

But it is becoming quite ridiculous!

 

[television]

Some more things need to be established, are the electrics OK, the crankshaft sensor could do this. without knowing whats been checked and how makes it very hard to know what to say

 

[Pie-Man]

without knowing whats been checked and how makes it very hard to know what to say

That's my problem too!
Can't get any sense out of the dealer ... all I can confirm is that they tried a new fuel distributor, cold start injector, all other injectors and have performed an overnight fuel pressure test ... ... no problems found ...

(they used "loan" parts for these tests!!!)

 

[dandpl]

Pie Man

What was the answer do you know yet...........best of luck

you are a Mercedes star!

dandpl

 

[Pie-Man]

Ah ... good timing! I've just spoken to the dealer and they think it may be the "throttle actuator" which sits under the fuel distributor? They suggest that the fuel-air mix wasn't being adjusted correctly on cold start?

Does this sound right? The replacement part is £700?!

 

[television]

Cant see it being that as the throttle actuator does not know or care if it is hot or cold. unless I am missing something here

 

[Pie-Man]

Cant see it being that as the throttle actuator does not know or care if it is hot or cold. unless I am missing something here

I'm obviously getting this data second hand thru the service guy sitting behind a desk ... but he referred to "enrichment settings" which basically control the mix ... I'm hoping to either pick the car up or at least pop in on Saturday to try and understand this better! However, surely an actuator such as this is simply a butterfly & solenoid arrangement? Therefore this either needs resetting or the solenoid needs replacing ... I can't for the life of me see such a part costing £700!?

Interestingly the dealer has been most apologetic ... "we've lost all our skilled technicians and that's why it's taken so long ... everything now is electronically diagnosed"

 

[television]

For a start your car does not have a throttle actuator as such, you have a mixture control unit that is part of the air flow sensor, this device has a C02 setting and thats all, fuel enrichment is done before this. You have engine temperature sensors, air temperature sensor that allow the fuel enrichment to operate as needed.

I do have the complete set up and service for your car,but it is in a huge fat book that will go under mt copier.

 

[Pie-Man]

For a start your car does not have a throttle actuator as such ... ...

Excellent information Malcolm! Thanks!

I'm seriously concerned that they are unable to ascertain the root cause of the concern and at the same time may present me a huge bill for a replacement component I don't actually need!?! :?

I'm expecting an update some time soon; I'm also going to ask to talk to the responsible engineer to get a more structured technical breakdown.

To what the service guy was referring to when he mentioned throttle actuator I don't really know? Hmmmm ...

Thanks again Malcolm ... ... if you don't mind I might have to rely on your technical interpretation again this afternoon?!

Tim