PeachParts Mercedes-Benz Forum - 103 Stalling and not starting when warm...

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My vehicle only has ONE pump.

It was replaced once a while back. It could be the problem. I just have to find the time to test it. Hopefully this weekend.

Thanks!

Quote:

Originally Posted by J.HIDALGO (Post 2115980)

It was replaced once a while back. It could be the problem. I just have to find the time to test it. Hopefully this weekend.

Thanks!

nmake sure its not leaking, which a fuel pressure test will show

J.Hidalgo: My guess is the CPS---same thing happened to me. This is my experience from an earlier post:

Quote:

I recently had intermittent ignition problems with my 91 300TE (245K miles). The car first started missing intermittently when warm and then after 50 total miles of operation since the intermittent missing began refused to start warm (it had the audacity to leave me stranded for the first time in the 130K miles I have owned it. After the car cooled down it started and ran fine a couple of times until it finally wouldn't start cold. When attempting to start the car at this point the engine locked up (I wondered if the timing chain had slipped a tooth or two) and backfired through the intake manifold (indicating improper ignition timing) before it finally wouldn't "fire" anymore. Although I could hear the fuel pumps operating, I sprayed starting fluid into the air cleaner and cranked the car to make sure it was getting fuel. It didn't fire once. Next, I cranked the car with the coil wire disconnected from the distributor and observed a healthy spark firing at what seemed to be the appropriate intervals. I checked the distributor rotor and since the resistance of the rotor appeared too high I replaced it with a new rotor I had available. Still no start. I suspected the CPS or the EZL was the culprit. Since it was easy to check the status of the CPS, I measured the resistance (800 Ohms) and the cranking voltage (.4V AC) and found all to be within specs. Although I am not in the habit of throwing parts at a problem, since I needed to make sure the car was operable within a very short time period, I ordered a coil and CPS from an online source and purchased a used EZL from ebay. I installed the ignition coil first (the easiest to do) and the car wouldn't start. Next, I installed the used EZL (next easiest to install) and the car wouldn't start. Finally, I installed the CPS and the car started without problem. When I removed the old CPS I noticed that the seal around the wires at the sensor itself had failed and moisture/oil had penetrated the area. It is a mystery to me why the voltage and resistance measurements of the old CPS were within spec and the system appeared to have good spark but I guess that happens sometimes. Because of the backfires I did try to use my timing light to get an idea of the timing situation but because the light was not bright enough at cranking speed, I could not confirm that the timing was off (although I know it was due to the backfiring). I pose this question to the experts like stevebfl, etc.---How could a defective CPS presumably retard ignition timing to where the engine won't run yet still seemingly operate the EZL/ignition coil properly?

I am located in Jacksonville and can lend you a used good coil and EZL unit to try but my bet is still the CPS. Mark

I guess I will have to get a CPS. So far, everything I measured is within limits...including the CPS. I even got an used coil from a junk yard. No luck!
Right now, I can hear the fuel pumps powering up, the car will star but, it will die within 5 seconds like if the engine was choking.
Did you access the CPS from the bottom and did you have to remove the oil filter?

I accessed the bolt from the top but you do have to get underneath to determine where the cable is attached to the intake manifold and release the cable from these clips. I believe I did remove the oil filter to be able to see the attachment bolt but you can determine that as you go. A very bright flashlight will help you locate the bolt. IIRC it takes a 5mm allen socket, universal joint with a very long extension. Be sure to gunk the area well before removal---very greasy---and to clean out the allen head so you don't strip the the head and create a real nightmare:eek: Let us know how it goes. Mark

I will probably try it. What part of Jax are you in...? I am in Orange park...

I am on the Westside---Lake Shore Blvd. Mark

Quote:

PM sent.

Got it. Mark

The coolant temp sensor is a likely candidate as well, especially since the symptoms changed when you disconnected it. In a thread here somewhere, I posted the temperature/resistance curve chart. You can see if your coolant temp sensor is out of spec with an ohmmeter and this chart.

A really off temp sensor will make the car die, ask me how I know.....

-tp

I already ordered the CPS.

The sensor may be next...

Good news and bad news...

The good news, I replaced the CPS succesfully.
The bad news, I did not fix the problem.
Replacing the CPS is not that bad. Access to the 5 mm allen bolt is tight and hard to reach but, I did it from the top without removing the oil filter. For reference, you can shine a flashlight (from the drivers side) down between the oil filter and the fire wall and you should be able to see the allen bolt. It is located below and to the right of the oil filter. The old CPS a resistance of
.849 k and the new one .829 k. Both well within specs. However, the old one had a very small piece of insulation missing between the sensor side and the wire. I took some pictures and I will post in the future.
I also measured the resistance between the two pins of the coolant temperature sensor: 4.67k at 62 F or 14 C
It starts all the time but, it dies right away.

What do you guys think...?

I'm not sure it's your entire problem, but that reading is out of spec. At 14 degrees Celsius, your reading should be right around 3K.

4.7K corresponds to roughly 5 degrees C. Your car thinks the engine is colder than it actually is..... This would in theory lead to a rich condition.

Are you checking the right sensor? There should be TWO elements in your temp sensor if you are checking the right one. The single element temp sensor is for your temp gauge ONLY. The dual element sensor is the one that matters as far as how your engine runs. You need to check the value of both elements, and they both need to be in spec.

Even if it's not what's killing your car, an out of spec temp sensor will cause havoc with your MPG and performance.

-tp

Here's the thread where I posted the chart.....

http://www.peachparts.com/shopforum/tech-help/239276-hard-start-when-warm.html

-tp

I am sure it is the right sensor...

I am measuring the resistance between the two elements. A picture of the sensor is attached.

I also suspect two diffferent problems...Hopefully, the CPS resolved one of the problems. Now, if I could only start the car...