Difficult start when cold?

The first thing that comes to my mind is the fuel damper.

Over the fuel pumps.

Regards,
aam.

 

Great, will take a look.

Replace and see, right?

 

My preferred method is to do a pressure system test, for that you need a fuel manifold.

That will also tell if the check valves, etc are leaking.
But 70% of hard cold start is the damper/accumulator.

Another way to test it is by removing it, put a hose on the pressure side, pump it to about 5- 80 psi if the other side leaks...

It is nothing more then a can, rubber diaphragm, that's what leaks, and a spring.

Note.
Some late years and engines, do not have an accumulator.

Regards,
aam.

 

You have the air temp sensor and water temp sensor, the air one is the one to check, this one can call up the cold start device. Pulling the connector or the air temp and water temp will tell the engine that it is very cold.

 

Great - where are these located? Any pictures?

 

My M103 had a cold start injector - if you have an M104 it probably has one

 

Yes I'm having the same problem, I have changed the water temp sensor and the air temp sensor, didn't solve the problem. I haven't changed the fuel damper so I will try that. Also AAM is the fuel damper the fuel accumulator? or is it a different thing entirely?

 

Yes is the same.

Also like Jim said the cold start valve works very little.
We are talking seconds.

Just so we have meeting of the minds.

If we are talking sensors....
It is the four pin sensor that two pins go to the ECU controlling the mixtures.
The other two pins are for the A/C.

You do have a water temp. sensor, but it's for the temp. gauge.
The air sensor, located at the left snorkel by the headlight.

Right?

Regards,
aam.

 

poor cold starting

Unless it's very cold, the cold start injector is never really used, you could unplug it and 99% of the time you would never know the difference.

The KE-Jetronic does have a default running program if the electronics fail. Many years ago I remember looking at a 190E with a similar problem, the fuse on top of the OVP relay had blown, a new one sorted it.

 

Unless it's very cold, the cold start injector is never really used, you could unplug it and 99% of the time you would never know the difference.

The KE-Jetronic does have a default running program if the electronics fail. Many years ago I remember looking at a 190E with a similar problem, the fuse on top of the OVP relay had blown, a new one sorted it.

Yes, I know of the OVP - check the fuse and it is ok.

Unless the relay is blown? Any way to know if the relay is the problem?

 

Yep, I changed both water sensors the 4 pin and the 2 pin (my gauge was finicky), then I changed the one that goes into the pipe that's closer to the air box little opening for it. didn't reduce the time of a cold start, I think you are correct on the dampener, it does need to be changed and also sometimes it starts then shuts off after starting and I have to start it again, which points to a fuel issue.

 

Do you mean one of these?

 

Do you happen to know the part number from Bosch or MB?

Thank you

 

There you go...

Bosch # 0438170055 $104

If you have questions, it will help you, if you fill your avatar.

Those who know me know, that if you make it easy, I answer....
You get 15 seconds.

OK,OK,

If is a joke, a little longer. Lol.

Regards,
aam.

 

Air temp sensor is 26. The pressure regulator is another that could cause lots of cranking first start of the day

 

Got - thank you.

The car also feel quite "weak" - and in hot condition, while it does start, it doesnt start right away.

I know these engine have variable cam timing, could that also be the problem?

 

Isn't this the accumulator?

Another question: What are these switches near the OVP?

Thanks

 

They are NOT switches they are modules/ MAS module.
It controls the fuel pumps among other things.

The picture with the arrow is your fuel pressure regulator.

Regards,
aam.

 

I may be completely off base here - if my old 300E is to be compared - but if I recall correctly the accumulator on that car was near the fuel pump underneath and it could indeed be the cause of cold start difficulty. Its job is to maintain the pressure of the FI system and if it looses pressure while sitting overnight you have to crank the engine a bit to get the pressure back up and the car starting.

 

Yes - I have checked, but I believe my diagnosis was wrong - the doesnt drive well when warm either - very weak.

 

accumulator

The accumulator is really only there to hold pressure for hot starting, it can't hold it overnight. If the car is poor from cold and also when warm it must be a lack of pressure or volume of fuel, you probably need to get the pressures and volumes checked.A good fuel pump should be able to pump vastly more than the engine could ever use , hence the need for a fuel pressure regulator. You can check it's output by finding the return line to the tank and putting it into a jug(you might need to make up hoses/adaptors)a good pump should give you one and a half to two pints in 30 seconds, if its noticeably less than this you need to check the fuel filter firstly.

 

Ok - thank you.

I will take the gamble and replace the OVP..

 

Found this

http://www.benzworld.org/forums/w124-e-ce-d-td-class/1572015-ovp-basic-function-test.html

 

Hello, I finally received the 300SL I purchased from the US and started using it last week. The engine has difficulties starting when cold - when warm it starts right up and drives perfect. Does this engine have a cold start valve and it's own independent temp sensor? Any ideas? Thanks

I took out the k jet tronic 3 10mm bolts and of course the fuel lines top and sides there was a hose below with 2 ports going into side of engine below cold start valve hose that was split in the middle i ordered hoping this may be the cause my 1991 300sl will never start cold unless i put fuel in bowl be careful the curved s hose that cold start valve goes into gets very brittle also and hard as heck to find only Vaico had 50 bucks!

 

my 1991 300sl will never start cold

I assume you have either the M103 or M104 engine, yes?

My M104 starts very promptly in the coldest weather; the other day, -8C. Like you, we are aware that the hoses around the intake need to be perfect. All ours were replaced, including the big boot under the air meter. And the seals around the injectors must be good.

Check the 4-pin engine temperature sensor. And the air intake sensor.

And measure the Duty Cycle at the diagnostics socket (the round one - Pins 2 & 3). I have some procedures (for the M104 - attached - and possibly others) if you need them but, basically, you should measure with ignition on engine off, engine idling below 70C, then above 80C, then at 2500 rpm.

When those things are verified as OK, it's probably time to measure fuel pressures.

And also, the engines demand the best HT components.

Good hunting.

RayH

 

Has your fuel been sitting a long time? My car wouldn’t run after the fuel went bad until I put Heet in it that turned that water in the tank into alcohol.

I have the M104 and cold start was really bad (>15 seconds) until I replaced the ECU. Now it’s in spec at <5 seconds, no matter the temp.

 

Now it’s in spec at <5 seconds, no matter the temp.

5 seconds? I'd expect 0.5 seconds. After a month maybe 1 second. Fuel pressures?

R

 

Spec is 5 seconds... from CIS KE-Jet documentation. Usually starts faster. Usually two or three seconds.

 

As Ray said, a correctly set up Mercedes CIS-e KE should fire up on first crank within 0.5 sec from cold.
You can open or download a short 10 sec video from the Onedrive link below and see for yourself.
engine-cold start-0.5 sec

Proof is seeing.

 

I'm starting to believe it might be the ECM I get just a steady light on socket 3 socket 8 10 blinks and no check engine light ever lights up before starting

 

EBay’s your friend. Just get same p/n as yours.

 

Just hoping that's what it is does part number 011-545-09 32 (02) correct for the ECM that's what number I have I'm hoping I'm on the correct module thanks thanks

 

Watch MMWA on YouTube where he replaces the caps in his M104.980 ECU. Likely that’s the problem, in these.