M103 no start

[92-2.6]

Hopefully someone can point me in the right direction. I've searched through the archives, and found several leads, but no answers.

I have a '92 190e 2.6 with just shy of 250K. The car had been running normally, but on a drive several weeks ago it began to stumble when I came to a stop at an intersection. Thankfully I was able to go the additional two blocks to my destination without any problem. I came out to start the car 10-15 minutes later and it would not start. The engine turned over as normal, but it would not start. I left the car and came back 4-5 hours later. It started as normal and I drove it home (7 miles away) without any problem.

Once home I tried to restart the car after it sat for a few minutes and once again it would not start.

I pulled the cap and rotor which are about a year old. There are signs of carbon tracking, but not too bad. The plugs are about the same age, and appear to be in ok shape, but it appears the car has been running a bit on the rich side as they were all a bit black. I cleaned them as best I could with some brake cleaner and reinstalled.

A day later I started the car without any problem, but it died after about a mile and would not start. I came back later that day started the car and drove it home again. Since I've had the car back home it now will not start.

Initially I thought it might be the coolant temp sensor. They're fairly cheap so I replaced it, but that caused no change.

It appears to have a weak yellow spark at the plugs. I swapped in a used coil and get the same quality of spark. It acts as if it wants to start, but almost seems as if the timing is way off as it has backfired while trying to start. Voltage at the coil is just shy of 12v. I read 11.8v which might be due to the battery getting slightly drained by all the attempts to start the engine.

I tried spraying carb cleaner down the throttle plate to see if the problem is fuel, but this had no effect.

I pulled the connector for the crank position sensor from the ignition module. Not really knowing how to test it I just used an ohm meter to see if there was any change when the engine was cranked. It does fluctuate, so I'm assuming that's okay.

I've seen many threads talking about cracked vacuum lines in M103 engines. I am not finding anything obvious here either.

Any other suggestions are greatly appreciated.

Thanks,
Dean

[lee polowczuk]

Originally Posted by 92-2.6

Hopefully someone can point me in the right direction. I've searched through the archives, and found several leads, but no answers.

I have a '92 190e 2.6 with just shy of 250K. The car had been running normally, but on a drive several weeks ago it began to stumble when I came to a stop at an intersection. Thankfully I was able to go the additional two blocks to my destination without any problem. I came out to start the car 10-15 minutes later and it would not start. The engine turned over as normal, but it would not start. I left the car and came back 4-5 hours later. It started as normal and I drove it home (7 miles away) without any problem.

Once home I tried to restart the car after it sat for a few minutes and once again it would not start.

I pulled the cap and rotor which are about a year old. There are signs of carbon tracking, but not too bad. The plugs are about the same age, and appear to be in ok shape, but it appears the car has been running a bit on the rich side as they were all a bit black. I cleaned them as best I could with some brake cleaner and reinstalled.

A day later I started the car without any problem, but it died after about a mile and would not start. I came back later that day started the car and drove it home again. Since I've had the car back home it now will not start.

Initially I thought it might be the coolant temp sensor. They're fairly cheap so I replaced it, but that caused no change.

It appears to have a weak yellow spark at the plugs. I swapped in a used coil and get the same quality of spark. It acts as if it wants to start, but almost seems as if the timing is way off as it has backfired while trying to start. Voltage at the coil is just shy of 12v. I read 11.8v which might be due to the battery getting slightly drained by all the attempts to start the engine.

I tried spraying carb cleaner down the throttle plate to see if the problem is fuel, but this had no effect.

I pulled the connector for the crank position sensor from the ignition module. Not really knowing how to test it I just used an ohm meter to see if there was any change when the engine was cranked. It does fluctuate, so I'm assuming that's okay.

I've seen many threads talking about cracked vacuum lines in M103 engines. I am not finding anything obvious here either.

Any other suggestions are greatly appreciated.

Thanks,
Dean

when i had this problem once... it was the cps.... when i had it again.... it was the distributor cap which appeared to be fine.... i just had weak spark... pull a spark plug and test spark... if it's not strong blue... its probably the cap...

i did what you did had a spare coil.... not the issue... went to a junk yard and got a spare ecm....not the issue...

i was kind of shocked when it was the cap...but then i looked at my records and noticed i had replaced the rotor....but not the cap... so i spent the 50 dollars for the cap...and it started right up....

i have a spare cps.... if you want to try it.... my symptoms for the cps... is that it would start when cold... you could drive the car for a long time... but eventually it would stall out and not restart hot.... after reading... i got a new cps... problem disappeared...

i know i did this trial and error... and some say don't throw parts at the car...but the truth is... parts are so cheap... and one diagnosis would cost me the same as a cps and cap

[92-2.6]

Hi Lee,

I'd like to borrow your CPS to see if that resolves the problem. See your PM.

Thanks,
Dean

[S-Class Guru]

Yeah, I'd bet on the CPS. It hasn't happened to me, but a friends '02 had the exact same symptoms you described, and a new CPS fixed it right up.

dG

[lee polowczuk]

you can borrow it... no problem... it does come from a 3.0 engine rather than 2.6... darn thing looks the same for both engines.... although they have a different part number for each

[92-2.6]

Turns out that on my car that the OVP seemed to be the issue keeping the car from running properly. I believe there were several issues including the cap and rotor, and possibly the fuel filter that were contributing factors.

In the end I noticed the SRS light would stay on when the car would start, but not actually idle well, or drive. In searching back through various threads I found this to be a problem related to the OVP. I borrowed a good OVP, swapped it in, and the car has run well ever since.

I have been using the cheaper Bosch branded caps and rotors, and it seems like those are good for maybe two years before they need to be replaced. I don't know if the factory parts have better longevity, but as a maintenance item it seems good to calendar replacement of these about every 24 months.

I did the wrong thing by throwing parts at the car, and came very close to calling it quits.

-Dean