Cold Start Problem 300TE
 

I purchased an 88 300 TE with 272 k miles on it in August and its been fine for me until recently with the cold weather. It won't start but gives every impression it wants to. Plenty of crank and a sounds like its ready but won't hold the rpm s. When I was finally able to get it going the temperature outside had risen significantly but the car felt like it was running on 3 cylinders. My mechanic, who's not a big Mercedes guy, seems to think that a block heater should resolve the problem but that assumes I plug it in at every stop. I noticed that a cold start valve is an available part but don't have a clue. Maybe just a tune up? Any thoughts would be greatly appreciated. By the way, it will remain cold in these parts of Idaho until April.

A block heater is not necessary and would be a PITA. You really need to seek out a mechanic who understands the Bosch CIS fuel systems. You could have a cold start valve problem, but I rather doubt it. The failure rate on that circuit is very low. Wilthout having the car in front of me, I'm suspecting a faulty signal from a temp sensor or the car isn't operating off of the computer for some reason. I'm sure your mech has taken care of your other cars, but it isn't fair for either one of you to ask him to diagnose this car.

Post Script: Thank you very muck for posting exactly the year, make, and model of the car you are asking about. One of the pet peeves of the professionals on this site which sometimes means no answer to the question is yahoos who insist on keeping that information a closely guarded secret. One of the pros here always asks:" Is this A Ford or A Chevy."

Thanks for the feedback. Appears I may have found a local familiar with these systems. We'll see next week when he gets to it.

Good luck, and it would be nice if you post the answer.

Peter

Still haven't gotten it to the mechanic he's very busy. So I've been making an attempt to look under the hood and noted that the Breather Hose to the air filter is barely attached to the manifold and the thin hard plastic tubing (vacume hose?) which attaches to the bottom of the Breather Hose is broken and brittle. Last but not least, the Air Intake Hose is split in half. Think any of this may have an impact on the car's inabilty to start?

By the way, where does that thin hard plastic tubing go? I've been tempted to pull the entire air filter housing to see but until it stops snowing or I tow it to the mechanic I think working on it under the current scenario seems a bit masochistic.

Any thoughts would be greatly appreciated.

Air intake hose makes no difference, but hoses to valve cover are quite important. See
http://www.peachparts.com/shopforum/1029163-post2.html

Still waiting on a spot for the mechanic to look at the car, but was curious about the location of the air temp sensor or better yet, is there somewhere I can look at a diagram of the air and fuel injection system with part numbers or descriptions? I've was told that the CD manual is not a very good source but are there any other alternatives?

Check the Water Temp Sensor. It tells the CIS-E controller the Engine Temp and is what tells the CIS to fire the Cold Start Valve and also to regulate idle, to raise, for proper warm up. When that sensor fails the CIS system thinks the engine is warmer than it is and thus does not provide enough fuel or idle control.

Do you have a part number for that Water Temp Sensor? I've been getting info that there is more than one.

Thanks for the info

Click on the "FAST LANE" tab at the top of this page. Enter your year/make... then selech your model. The _Catagory_ is "+Fuel Injection" and the part is called... "Water Temp. Sensor"
or just click this link :)
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1OH0MY2181OH0MYQHF&year=1988&make=MB&model=300-TE-001&category=C&part=Water+Temp.+Sensor&appEngines=_any
Your existing sensor should be tested for proper resistance before it is replaced (no need to throw dollars [though not too many in this case] away unnesessarily)
Should test as follows:
Ohm's range from the temp chart in the /Engine Manual-Combustion Manual-07.3 Mechanical/electronic gasoline injection system (KE injection)-121 Testing electrical components of KE injection system. page 60

Temperature °C........Resistance kΩ
-20........................15.7
-10.........................9.2
0............................5.9
10...........................3.7
20...........................2.5
30...........................1.7
40...........................1.18
50...........................0.84
60...........................0.60
70...........................0.435
80...........................0.325
90...........................0.247
Same resistance values apply to KE intake air temp sensor.
I think this chart applies to these 2 sensors for all KE systems but don't know for sure.

Invaluable

Thank you

Back to it

I'm not sure what year we are dealing with??

Has the engine been tuned-up lately? Maybe check the spark plug wire resistance, replace plugs, inspect rotor/distributor might be in order.

These engines are quite reliable, but on a 20 year old car may need some diagnosis to get it sorted out. I'd start with the temp sensor, then you can check the function of the cold start valve, OPV relay, fuel pressures and try and work things out.

What year is this car?????????

Michael

kirk333 is one of the few new posters to include year, model, and location in his request for help. Now the old posters just need to take time to read the info provided.:D

Damm- missed it in the first sentence!

Sorry about that!

Again thanks for the feedback. Hopefully I'll have an answer to this by next week sometime.

I can't understand how someone could attempt to seek advice in this arena without providing year make and model. Are Mercedes that similar between years and models?

I think it stems from a faliure to realize that automotive systems change periodically... and that car is not like all others.

Shoveled the foot of snow off the car Friday anticipating a tow to the Mechanic today but decided yesterday morning to drag it home with the help of my son in law. Put it in the garage with a small heater blowing under the front of the car and decided to give it a try at 5 PM last night. The car fired up with no problem and ran fine (just like the old days). Drove it around the block and put it back in the garage. Cold temperatures still prevail.

Because I've purchased numerous parts, I changed the plugs and breather hose(they were easy to locate). Car again runs fine. I'm not sure but think that my old problem may arise soon and thought I'd test the situation by replacing the Air Temp Sensor first and see if this could be the culprit HOWEVER I CAN'T LOCATE IT. I pulled the Air Filter housing thinking I might see it underneath but am now at a loss.

Any assistance would be greatly appreciated.

Oh by the way, it appears that the broken thin hard plastic vacume line from the Breather Hose previously mentioned goes to the Fuel Pressure Regulator. Think this might be an issue for cold starts?

Refering to my inabilty to locate the Air Temp Sensor, I now believe it should be attached to the Air Intake Hose to the air filter.

This gets interesting. The new Air Intake Hose (which I purchased) allows for the Air Temp Sensor (which I purchased) to attach via a hole on the side of the Air Intake Hose. The old Air Intake Hose has a round plug snapped into the hole where the Air Temp Sensor should go.

Where would the Air Temp Sensor be if its not where it should be?
What would the Air Temp Sensor connect to in this odd scenario?

The Water Temp Sensor is on the block. It is easy to test and takes a whopping 5 minutes and is a <$50 part. Takes less than 20 minutes to replace as well. So go test that. It should be on the right hand front side of the block in the sensor array. It is either a 2 wire or 4 wire sensor.

http://img.eautopartscatalog.com/live/C602012903BOS.JPG

http://img.eautopartscatalog.com/live/C602012373FEB.JPG

Test that first using the table on the first page of this Thread.

The reason you have a plug in your air intake is because the M103 engine didn't use that sensor until 1990. If that sensor is defective or unplugged on a 90 or newer, it will trigger a CEL or MIL. The temp sensor I would concentrate on is located at the rear left side of the block. It has 4 terminals and 2 or 4 connevtors depending on model year. You can swap the connectors to test, because the 2 sensors in the unit are exactly the same. Good luck.

OK Have to recap. I checked my books and discovered that the 4 pole sensor is Ca only. If you have a 49 State car, you have a 2 pole sensor in the same location. Let me determine a test procedure for that sensor.

I left the car out all day yesterday(high 23 low 5)and started it twice and let it get up to temperature. Turned it off and left it alone for 10 minutes and then restarted it with no problem. Drove it up the road a few miles last night to see how acceleration felt and it drove fine until I was pulled over by a County Sheriff for exceeding the speed limit by 10 (65 in a 55).

I explained that I was only a quarter mile from home and this had been the maiden voyage since the cold weather had started. He was quite nice and wanted to know if the temperature readout on the dash was accurate (showing 3 degrees at 6:30 Pm). No ticket just a warning.

Left the car out last night (high 5 low -6) and started it up with no problem this morning. Drove it to work and just restarted it after letting it sit for 20 minutes (showing 14 degrees).

And thats where we are. Plugs have been changed, new breather hose, new vacume line from the breather hose to the fuel pressure regulator, new air intake hose to the air filter and a new Air Temp Sensor temporarily filling the hole where it would be if it were a 1990.

The breather hose/vacuum line are what fixed it. Can't have vacuum leaks and expect good cold starting.

Thanks much Kent for the early advice. Lets see how long this lasts. No problems at all today multiple cold and warm starts. Supposed to get to about 15 below tonight and I'm leaving the car out to see how it'll respond in the morning. I think tomorro may be my last post on this subject. Hope so.

Immediate start this morning, no issues, low last night -8, current temp +3.

Thank you all. This is an excellent forum. Saved myself a bundle and started learning a new car.

Looking forward using this group again.

Happy Holidays!!!