W124 200 carburettor sometimes hard to start when hot

[robbomerc]

Hi guys . I have recently bought a low mileage 200 . It is a 1989 carb model low mileage 53000 miles . It is lovely . Originally from the UAE . It is base spec manual but with AC . I love it , it is pretty mint and the little things that need doing I am going through . It occasionally is hard to start when hot . Always first turn of the key starts when cold . If I park up for 20 minutes it can take a while to fire up . I had a W123 200 which used to be the same . No EFI 224’s I have owned have done it . Could it be fuel evaporation being a carb in a hot engine bay ? The car runs well and does 38mpg . I think it is a mechanical pump on these carb versions? As I say it runs well otherwise and no smell of fuel . Any ideas ? Thanks in advance

 

[mioba]

Sounds like a vac leak somewhere. Had similar on my W124 many many many years agoz

 

[DREAMER NO2]

A very nice looking car .. How long ago was it when you last changed spark plugs,.,, distributor cap.. along with the rotor and ht leads .80% of all problems are electrical . I start at the battery ,,,clean the posts and lub them with copper grease or silicone and refit . Once this is done and you still have problems then go on to the mechanical side . Might very well be the cold start device in the carb is sticking on check vacuum pipes . Something on the carb is not working as it should .And finding information on the internet is very hard for the 200 but i bet you have found this out by now.

 

[robbomerc]

A very nice looking car .. How long ago was it when you last changed spark plugs,.,, distributor cap.. along with the rotor and ht leads .80% of all problems are electrical . I start at the battery ,,,clean the posts and lub them with copper grease or silicone and refit . Once this is done and you still have problems then go on to the mechanical side . Might very well be the cold start device in the carb is sticking on check vacuum pipes . Something on the carb is not working as it should .And finding information on the internet is very hard for the 200 but i bet you have found this out by now.

Thanks . Yes full service recently , carb service plugs but no new distributor cap or leads . will check for leaks but all looks good

 

[DREAMER NO2]

Did you find out what fuel pump is on the car ? i though they were all 12 volts under rear passengers side floor .It might be that the fuel is draining back through the none return valve on fuel pump when its hot .Or blocked fuel filter . And i would try another coil . They tend to go out when hot .

 

[robbomerc]

Did you find out what fuel pump is on the car ? i though they were all 12 volts under rear passengers side floor .It might be that the fuel is draining back through the none return valve on fuel pump when its hot .Or blocked fuel filter . And i would try another coil . They tend to go out when hot .

I don't hear the buzz of an electric pump on turning the key so assume it is mechanical as carboretored . It starts well cold and runs really well so I am thinking fuel starved or vapourised by hot engine bay / weak non return valve

 

[DREAMER NO2]

You do have electric fuel pump , because no W124 have cam driven fuel pumps . Look under the car passengers side rear .

 

[robbomerc]

You do have electric fuel pump , because no W124 have cam driven fuel pumps . Look under the car passengers side rear .

Ok many thanks . Maybe my previous 124's have had noisier pumps . Will check it tonight

 

[DREAMER NO2]

Check all fuses first . And your fuel pump relay will have a fuse on the top .check that.

 

[ajlsl600]

Fuel evaporation very possible

 

[Fessel]

I have a '87 200T carb model and had similar problems towards the end of last year. Finally tracked it down to an almost invisible split in one of the vac hoses that was ok when cold but when engine bay was hot seemed to allow air in. Unusual problem and we found the cause more or less by accident having eliminated everything else we could think of. Maybe worth you checking it out.
Fessel.

 

[DREAMER NO2]

On par with mine .

 

[robbomerc]

I have a '87 200T carb model and had similar problems towards the end of last year. Finally tracked it down to an almost invisible split in one of the vac hoses that was ok when cold but when engine bay was hot seemed to allow air in. Unusual problem and we found the cause more or less by accident having eliminated everything else we could think of. Maybe worth you checking it out.
Fessel.

Thanks for that . Where was the vaccum hose located ? Sounds right .

 

[Fessel]

I haven't got that car handy right now to pinpoint the leak with a photo, a mate has got it over in Killarney taking a weeks holiday with his wife and kids. All legal, He's a named driver on my multiple car classic insurance ;o) From memory tho' it was a pipe that was feeding the multiple vac pipes in engine compartment drivers by the fuse boxes. If you are still having problems I can post a pic after next weekend when I get the car back

 

[robbomerc]

I haven't got that car handy right now to pinpoint the leak with a photo, a mate has got it over in Killarney taking a weeks holiday with his wife and kids. All legal, He's a named driver on my multiple car classic insurance ;o) From memory tho' it was a pipe that was feeding the multiple vac pipes in engine compartment drivers by the fuse boxes. If you are still having problems I can post a pic after next weekend when I get the car back

brilliant many thanks

 

[robbomerc]

Blimey ! Ongoing Saga took it to my Mercedes dealer as local specialist waiting list is 9 months ! They looked at it and for £200 told me it needed a carb specialist to look at it !!
Looks like the vacuum diaphragm is old and not holding the vacuum . Managed to order a kit from Southern carburetors and other bit from Classic Mercedes in Poole . Both very helpful. i hope this will help

 

[DREAMER NO2]

Thats good, my classic insurance will only take my name on the policy with no other driver but me ,,if is a classic car the insures look at it that you dont let others use it .

 

[robbomerc]

Could not get it fixed so I sold it as a non runner . Shame But no one was willing to look at it . Shame but seems the knowledge of older Mercedes is dying , especially if it involves a carburettor

 

[DREAMER NO2]

Yes it is a shame i bet it goes to the scrap yard if its not looked after

 

[DREAMER NO2]

Thats good, my classic insurance will only take my name on the policy with no other driver but me ,,if is a classic car the insures look at it that you dont let others use it .

Dont know what insurance had to do with this post must have had a senior moment lol