Hard Cold Starting

[Dbrindle]

I have a 92 300 TE wagon with about 120K miles - Great car. Now am having a cold start problem that is getting progressively worse. The car starts and runs fine when after the first time it is started - but starts in the morning can require cranking the engine for 5 or 10 minutes to get it to go. After that the next time it starts immediately. The car runs better than it ever has otherwise.

When the problem first started I put in a can of Berryman's in the tank to clean out the injection system that that had no effect. I have also tried parking it at different angles thinking that there may be an air leak into the injection system. I had that problem on the 190D I owned.

One shop changed the voltage regulator and charged $236 - that did not fix the problem - The car cranked fine and the battery was charging fine before the repair.

Now the local agency has spent four hours trouble shooting the problem and they claim the coil and spark plugs are the problem. I have not heard of a coil causing a cold start problem - but this could be unique to the 300 TE? They want $563 to change the coil and for the time in diagnostics. I am tempted to go this route and let them own the problem until it is really fixed.

I have a strong background in mechanics and have owned shops in the past but am not up to date on the injection system on the 300 TE. Someone told me it was the last of the CIS systems - but some how that did not sound right.

Does the car have a cold start injector - where is it and how is it powered??

I was also told that there is a by pass circuit to the coil that gives it a boost while starting for a hotter spark. Is the 300 TE coil special or is it just the standard Bosch coil??

I am open to suggestions either what to look for or for a good shop in the San Francisco Bay area to take it too.

Thanks a bunch

Dan

['79 Super Turtle]

I just wanted to say that the partshop fastlane at this website lists a Bosch cold start valve for a 1992 300TE for $89.00, so you must have one.

I won't offer any advice, but if you have this valve, did the shop ever test it for resistance, spray pattern, or whether the temp. sensor was activating the valve?

I ask this because on my '88 Land Cruiser I had the exact same problem, and it turned out that the wiring connection to the cold start injector was corroded, or loose.

I'm sure someone else here will be able to give some advice.

[dacia]

I had the same problem with my 300E. There is a coolant temperature sensor at the end of the engineblock (at the firewall) with a two-pole connector on top of it. One wire is going to the computer (behind the battery), the other leads to the EZL controlunit on the left front fender.
It is a resistor changing its resistance according to the coolant temperature. If I am not mistaken the warmer the engine the lower the resistance (I don't have the manual with me but it list the actual values.)All you need is an ohm-meter to test it. Check the resistance to ground on both poles. The value should be same for both. If it is infinite there is your problem. The sensor is under $100.00 and easy to change. By the way, the shop that changed the voltage regulator, stay far away from those kind of people. That regulator should be somewhere around $50.00 and takes about 10 minutes to change on the 103 engine and the alternator stays in place. I am just wondering how they came to the conclusion that the cold-starting problem is caused by a bad voltage regulator?? The cold start injector is at the middle of the block (between the 3rd and 4th injector) with an electric connector and a fuelline attached to it, but you have to remove the airfilter-housing to access it. When I had the starting problem I simply supplied battery voltage to it and I could hear it spraying fuel so it was OK. By the way the Partsshop sells the manual on CD. I think it is worth the investment if you are a do-it-yourself type.
The ignition-coil is the same for the 4 and the 6 cylinder engine so you can put in a used one from a 190 as well (this is according to my Mercedes engine manual). I got mine for $40.00 off of a 190 last year and it is working like a charm. I don't think your engine will start if you have a bad coil. Mine didn't anyway. And the engine manual walks you through the procedure to check that coil.
Good luck.

Alex

[Edited by dacia on 03-15-2001 at 05:48 PM]

[jeffsr]

Your car has a cold start valve (injector). it is located between the front and rear intake mainfold runners (between 3 and 4) as previously mentioned. it is controlled by a vacuum thermo valve and the temp sensor. It's only function is to provide a rich mixture under cold start conditions. A lot of the time the thermo valve will break and lose vacuum. Check all of the connectors, etc, along the driver's side of the head.

I'm not a Mercedes tech so this is just a thought...

I believe that all of the fuel injected engines require a check valve to hold fuel pressure. In my 420SEL it is located at the fuel pump between the pump and the fuel hose. They are only around $20.00 USD.

On cold start my 450SEL starts right up - it's 6 years older. With a bad fuel check valve the 420SEL had to crank for several seconds. (It would not take 10-15 minutes - I was hoping you were exagerating there) The fuel pump even without the check valve should bring the pressure up within 5 to 15 seconds.

It's worth a try - cheap anyway... Good luck!

[JimF]

Dan,

check the cold start valve. Had the same problem due to a LEAKING cold start valve. It would drip, drip and it basically flood the engine.

Also the ECT is another good place to check. Should measure as follows:
temp ohms
20 2500
30 1700
40 1170
50 830

Judge from there.

[Dbrindle]

Thanks every one for all of the help. I decided to have the agency repair the car per their diagnosis - ignition coil and plugs. That they would own the problem for a year. This seems to have fixed the problem. It has not been real cold lately, but the car was not starting at all when I had it towed to the agency. Now it starts every time - first try and does not stall when putting it in gear.

The diagnosis did not sound right to me - but it fixed the problem - go figure.

Now the next question. I put some new NGK plugs in the car a year back - could the plugs somehow have dragged down the coil???

Thanks again - I now have the manual on CD so the next problem I am armed and ready.

Dan

[crhenkel]

I found a thread on the coil problems with 190's and 300's nor really having a strong spark. ( neither here not there for arguement) what I am saying is, I had an old coil and a suspected ignition/coil problem. I followed the threads advice and got a Accel universal Hi output coil from mail order. Installed it in about an hour in original location and just replaces coil lead end. This not only fixed idle and start prob. but the engine runs better, uses less gas, and the coil with shipping cost under $60. I can supple the info I gathered in the installation on request. It has been in the car for 5000 miles and no problems whatsoever with compatability. Same with the o2 sensor swap I learned about on the site. 1990 Ford mustang sensor is the same output and input information...sensor costs only $37! Direct replace MB part. Works for 190 and 300, maybe more