I am having issues with my 300E starting & running on a cold engine.

Symptons:
1. If the car has been sitting or cold (North Carolina cold - 50 degrees and under) for more than just a few hours the car has a hard time starting. The starter runs fine, but the engine does not seem to catch. Sometimes the engine sounds like it is firing but it just will not catch..stop turning the key the engine stops firing. If it is really cold (30 or so) and the car has been sitting for overnight or a day, the car will not start on the first series of tries. I have to go out in the morning, try to start for a few minutes, leave the car and come back about 5 min or more and try again. Usually when I come back it will start with a little hesitation. To make it a little weirder, sometimes it starts w/o too much trouble (two turns of the key for 5 seconds) even when it is cold..40-50 degrees. It can take 15 min. on a really bad day to get it to go.

2. When it finally does start it does not want to go.. No power. I push the gas, the car moves forward about 1 foot and it then jerks and tries to cut off. Even if I floor it in neutral, the car shutters and grumbles and will cut off. Once the engine reaches about 80 degrees the car acts better. The first few hundred yards lacks power and it may shutter once or twice and loose all horsepower for about 5 seconds. After that, the car drive perfectly. This seems to happen at air temps below 65-70. After the engine reaches 80 and it is driven a bit - no problems, even if i park it for an hour or 3.

All of these problems started just a little bit at the end of last winter.. Just about a dozen times. Once spring hit, no reoccurrence. This year is much worse.

I keep it well serviced and took it to my local MB expert. They kept it for a week and saw the same issues. They replaced a few things, replaced a $500 part (relay?) no help, and took it back off. They could not figure it out. Their only hope was to keep it another few days and replace 2-3 other $500 components to see if any of those would help.

One other confession... I did run it out of gas last year on accident..not absolutely out. I ran out as I drove into the gas station; sputtering the last 50 yrs and barely making it to the pump. It took a minutes to get the car to start after I filled the tank.. sputtering for the first 1 minute or so. Did I clog the fuel lines with tank crud? But why would it only be a problem in the cold?

Any ideas... I love my MB.

David

 

Three elements typically cause these symptoms...engine temp sensor, cold start valve and fuel pump relay.

You said they replaced a relay....what relay did they replace?

 

They replaced the thermostat in Dec., set the fuel mixture, and swapped the overload protection relay.. The relay did nothing to solve the issues, so they out the old one back to save me $$.

 

Have them check the fuel pump relay which is located next to the OVP relay.
The fuel pump relay controls the cold start valve, which in essence is the fuel enrichment device for starting in below 50 degree weather.

Ed A.

 

My car actually has the fuel pump relay inside of the MAS Control Unit. I don't know if it's because my car is a 24 valve or not, but if you have something that looks like this near your OVP relay and battery, then you have the MAS Control unit.

http://img.eautopartscatalog.com/live/P209770430OES.JPG

Cross your fingers and hope you don't. I had to replace this whole damn thing just to fix the fuel pump relay in my car. Note that my cold start symptoms were the same as yours, although once I could get my car to start it would run fine.

 

Yeah MAS unit troubles -_- For the loss. I just got mine installed (ordered it used from Germany, 76$ US Shipped), and it appears to have fixed my issues. I have the 24v 300ce as well.

 

I've had a cold morning and it took 15 min. to start.. Urr. I will have my mechanic try those 2 things.

I noticed this morning that there seemed to be a strong fuel smell once I started the car (and walked behind it as it warmed up).

Thanks guys. I'll let you know.

D

 

I agree with the temp sensor and possibly cold start valve.

 

Your car is a 92 300E with the M103 engine, right? And KE-Jetronic injection..

It´s always good to rule out the basics. Plugs, rotor and cap might need inspection. I´d also investigate how old your fuel filter is, but perhaps your mechanic has checked these things out?
-The metal plate in the mechanical air flow sensor also sometimes goes out of alignment, so that it does not rest correctly in its place inside the housing. That causes hard starting since incorrect amount of fuel is thus delivered while starting. In that case you need to loosen the 10mm bolt in the centre of the plate and arrange it so it rests correctly. Seen it happen on a few occasions. - Just a thought.

Cheers,

 

Alder, did you replace the MAS and if you did, was the problem fixed? I have the same issue and would like to know if this fixes the issue

 

I have problems with cold start. I replaced cold start valve, temp. sensor (with 4 pins) and MAS. I am only getting 6 volts at the cold start. I had the cold start valve out, turned around and hooked up with the fuel line and supplied 12 volts from the battery. With ignition on (fuel pump on) the cold valve sprayed fuel, so the valve is good. The temp sensor and MAS are new. But only 6 volts are reaching the cold start valve when cranking instead of 10-12 volts.. Any ideas?

 

Bad CSV relay. I will look at the wiring diagram later if I get time.

 

There doesn't seem to be a CSV relay. In fact, I can't even find the CSV mentioned in the drawings. It must not exist. I would start by checking connections at the CIS control unit. It probably originates there. There is a 12 volt wire from start into the CIS unit.

 

I found the diagram. It looks like if the CSV doesn't get 12 volts, it could be that your OVP is not supplying full voltage to Z7, terminal 2 of the CSV. Check voltage between terminal #2 on the CSV and Ground during cold cranking and you should get full voltage. If not, your OVP is suspect. If you do, then something is wrong with that transistor inside the CIS unit.

At least that's the way I see it.

 

Here is what finally worked:

1. Replaced spark plugs with factory - Did not better the issue.
2. Replaced Fuel Governer Valve (E.H.A Valve) and replaced it with used part. It ran much better but still sluggish at dead stop.
3. Replaced Coolant temp sensor (used by the fuel injection system) and reset the fuel mix....and now it runs perfect!

Now for the windshield wiper pump.. stopped working again.. 1 yr after replacing the pump.. time for a Lexus!

D

 

You're going to settle for a Lexus because of a $15.00 DIY washer pump? I took mine apart 3 times before I finally fixed it so it stopped leaking washer fluid all over my garage floor. It's a very easy fix.