W124 Cold Start ok- Hot start turns over a long time

Blazer

Member
Joined
Oct 20, 2017
Messages
48
Location
UK
Car
Mercedes
Hello All

My W124 300E 1992 starts fine from cold, one spin and it fires into life. When starting from hot or even warm, it is reluctant to start and has to turn over multiple times before eventually starting. Any ideas what could be the cause ?

Thanks
 

optimusprime

MB Enthusiast
SUPPORTER
Joined
Dec 29, 2013
Messages
4,012
Location
Kidderminster Worcestershire UK
Car
Mercedes W124 260E M103
Blazer this is a problem i have had from day one of owning a W124 with the M103 engine ,. And to help you i am going to say , get a fuel pressure test first . dont spend a anything in parts yet .. Why i know this is i have replaced everything on my car you can think of . And i still have the nasty hot start .But as yet i have not changed the fuel pumps . I have an idea my car is running on one fuel pump, and not two. Also in the pump end is a check valve that can cause a problem if faulty So a pressure test will tell you if it is a fuel problem or not. My car is covered up for the winter , so its my next project in the spring .So many pressure test kits on Ebay for around £25 .
 

neilrr

MB Enthusiast
Joined
Jul 20, 2004
Messages
6,656
Car
Various.
If you always or nearly always buy petrol from one vendor (a supermarket chain, perhaps?) try a different brand. Years ago I sold a nice 190E 2.6 to a bloke who complained of your issue. He bought his petrol from a supermarket. It went away when he started buying Shell or BP or Texaco. Dunno why but I noticed the car pinked a lot on Esso so I know the car ran differently on different brands of fuel.
 
OP
OP
Blazer

Blazer

Member
Joined
Oct 20, 2017
Messages
48
Location
UK
Car
Mercedes
Blazer this is a problem i have had from day one of owning a W124 with the M103 engine ,. And to help you i am going to say , get a fuel pressure test first . dont spend a anything in parts yet .. Why i know this is i have replaced everything on my car you can think of . And i still have the nasty hot start .But as yet i have not changed the fuel pumps . I have an idea my car is running on one fuel pump, and not two. Also in the pump end is a check valve that can cause a problem if faulty So a pressure test will tell you if it is a fuel problem or not. My car is covered up for the winter , so its my next project in the spring .So many pressure test kits on Ebay for around £25 .
Hi Optimusprime Thank you for your reply . I will look into checking the fuel pressure... Are you suggesting testing / monitoring the fuel pressure on cold and hot starts?

I have had a quick look at the fuel pump, fuel filter and check value under the car at the rear end - us a visual to see the set-up and part numbers, I have one pump.

BTW the car runs great once started....
 
OP
OP
Blazer

Blazer

Member
Joined
Oct 20, 2017
Messages
48
Location
UK
Car
Mercedes
If you always or nearly always buy petrol from one vendor (a supermarket chain, perhaps?) try a different brand. Years ago I sold a nice 190E 2.6 to a bloke who complained of your issue. He bought his petrol from a supermarket. It went away when he started buying Shell or BP or Texaco. Dunno why but I noticed the car pinked a lot on Esso so I know the car ran differently on different brands of fuel.
Hi Neilrr, I buy my fuel form various sources including Shell, BP, Esso etc.... makes no difference to the starting issue.

Thanks
 

optimusprime

MB Enthusiast
SUPPORTER
Joined
Dec 29, 2013
Messages
4,012
Location
Kidderminster Worcestershire UK
Car
Mercedes W124 260E M103
Neilerr Thanks And i only use one gas station for my fuel . And i never ever use any supermarket brand . And the tank is full right now and the way i use it it will take 6 months to run it all off .So its worth a try for me to use another brand of fuel for a change .
 

190

MB Enthusiast
Joined
Mar 4, 2015
Messages
3,787
Location
Cheshire
Car
2009 W204 C180K
Logically it's either too little fuel - fuel pressure ?
or
too much fuel - cold start injector operating when it shouldn't or for too long ?

A simple test for the cold start injector would be to unplug it to see if the hot start problem goes away.
 
OP
OP
Blazer

Blazer

Member
Joined
Oct 20, 2017
Messages
48
Location
UK
Car
Mercedes
Logically it's either too little fuel - fuel pressure ?
or
too much fuel - cold start injector operating when it shouldn't or for too long ?

A simple test for the cold start injector would be to unplug it to see if the hot start problem goes away.
Thanks for the suggestion
 

ray_hennig

Active Member
Joined
Dec 1, 2008
Messages
737
Location
France
Car
MB 300CE-24 Sportline
Hello All

My W124 300E 1992 starts fine from cold, one spin and it fires into life. When starting from hot or even warm, it is reluctant to start and has to turn over multiple times before eventually starting. Any ideas what could be the cause ?

Thanks
Mine would always start warm but misfire for 30 seconds until up to speed.

New injectors and seals cured it. AN expensive (500€) fix but very satisfying.

Rayh
 
OP
OP
Blazer

Blazer

Member
Joined
Oct 20, 2017
Messages
48
Location
UK
Car
Mercedes
Mine would always start warm but misfire for 30 seconds until up to speed.

New injectors and seals cured it. AN expensive (500€) fix but very satisfying.

Rayh
Thanks - New injectors and seals.... An expensive (500€) fix :oops:
 

optimusprime

MB Enthusiast
SUPPORTER
Joined
Dec 29, 2013
Messages
4,012
Location
Kidderminster Worcestershire UK
Car
Mercedes W124 260E M103
As for my hot start .Everything i can replace i have done , all new Bosch injectors and seals .So now i am going to replacing both fuel pumps with a pair of Bosch . New fuel filter and accumulator fitted last year . Replaced all the ht side plugs leads rotor distributor cap all Bosch.. but Beru leads .Nothing left now but to replace fuel pumps . Reason i am changing the fuel pump is, i think its only running on one pump.And to buy a fuel presure tester it would cost me more money when i know there is a problem up the back end. The pumps are 31 y/o now so they do need changing . It could be the none return valves ,But these come new on the new pumps that i have . You could try this , on the next hot start,, remove the tank cap before you try to start the hot engine. See if it helps, and if it as then its another problem you have.
 
OP
OP
Blazer

Blazer

Member
Joined
Oct 20, 2017
Messages
48
Location
UK
Car
Mercedes
Very true but it worked wonders.

Sadly, as these cars pass 30 years, replacing worn parts becomes ever more costly. And don't I know it!!!

R
We run and maintain these old cars for the love... :cool:
 

Users who are viewing this thread

Top Bottom