kostas86

Have a '91 300e 3.0 with 98k miles. Noticed car began to misfire and once in awhile would get a really sluggish off the line in first gear (almost as if I wasn't pressing gas pedal at all). Again this happened very rarely but when it did occur, it would only do it in 1st gear from a dead stop and then would shift and accelerate normal after that. Recently did new fuel filter and fuel line connection, followed by spark plugs, wires, cap and rotor. Shortly after the tune up, on the first drive, car smoothly and quietly dies while driving (didn't even notice until I went to hit gas pedal and noticed no acceleration and all dash lights on. Replaced ignition coil, swapped out crank sensors and ignition control module but still no spark at the coil. When cranking rpm needle jumps to about 500rpm. Checked for fuel by disconnecting the connection at CIS unit and it has fuel and fuel pump works.
I am stumped, anyone know what this can be?
Thanks!

kostas86

Also, the one wire/cable that connects into ignition control module and runs towards the fuse box and then across to CIS-E unit behind battery, can't get a read out on resistance for that one.

optimusprime m1

Do you have voltage at the coil ? Also do you have an immobiliser on your car and can it be turned off ,as some have a key in dash board to do this. My car had no spark it was the alrm and or immobiliser.

kostas86

No immobilizer which I am aware of and no aftermarket alarms.
Coil has 12v on both terminal and ground. The coil output has no spark but power going to the coil wires that are connected to it.

optimusprime m1

Kostas this is a check on your coil
1 Check the ingnition coil primary coil resistance by connecting an ohmeter between the + pssitive [black wire] and negative - [green wire ] terminals on the coil the resistance should be 0.4 ohm to 0.6 ohm
2 Check the ingnition coil secondaty coil resistance by connecting an ohmeter between the coil output terminal [king leed] and ingnition coil negative terminal the resistance should be 5.000 to 7,200 ohms Set meter to suit . Due to the time gap from uk, to you i will be going to bed as your getting up .

kostas86

Ohmed out within spec, appears to have no signal to ignition coil.

optimusprime m1

I wpnt give up, to find your problem out. The EZL is looking to be the suspect .The cps sends it the mesage to fire. Did you check all the earth points out on the engine side ,just in case you have one thats not making contact .And look at the fuses in the fuse box.

optimusprime m1

Look at you PM i sent you a manual link. Reading about this on google .Your revs are high on no start .You said 500 rpm .I read that the flywheel is creating to much voltage to EZL .Should only just see the revcounter move ,so it said. His problem was sticky flywheel .As it moved it made more voltage than normal .the EZL thinks its started up and cuts out .He had to clean of the grease and re spray it with chain lub. Might be worth remembering this... As the firring cycle is sent from the EZL this is what i think is the problem. To much voltage and the ezl thinks its running ,so wont fire the coil up ..

kostas86

What were the chances that the new Bosch rotor that was installed was bad? I knew it had to be something with tune up parts because it was running fine before tune up. Swapped out another new Bosch rotor and started up! *fingers crossed* I still have some start up issues though, car doesn't always start on first try, usually on second try. I am assuming this might be fuel pressure issue. Let the car sit, I am going to prime pump (which works) 3 to 4 times before first crank and see if that helps.

QVHK

Your problem seems to resemble that of another buddy here: see thread below:
https://mbworld.org/forums/e-class-w...yone-know.html
Is there a common problem with the new Bosch rotor?

kostas86

Wow, looks like pretty much same exact situation and all! There must be a batch of faulty Bosch rotors out there.

optimusprime m1

I thought you said you had no spark at the coil. You must have had spark at the coil to get it to start .

kostas86

Would the rotor be part of the signal to the coil that would initiate the spark? The coil had no output but power going to the coil wires that are connected to it. So I decided to install another new Bosch rotor and car fired up. The car was running before the tune up so I knew something occurred with the parts installed.
Now to chase down what appears to be a potential fuel pressure issue. Almost every time I try to start car when it's been sitting for awhile, no luck on the first try, it'll start up but die within 5 seconds. But on the 2nd or 3rd attempt it'll be start up. If I have been driving, shut down car and then go to start it after say 15 or 30 minutes, car will start up. Also, I've noticed when initially started up especially when sitting for awhile, it runs rough for about 5 seconds or until a few accelerations and then smooths out and okay for rest of driving. Very similar feel to bad misfire.

QVHK

Other possibilities of the start on second or third attempt even when engine was warm, and start-and-die symptoms are: bad fuel pump relay, fuel pumps (there are two), or fuel pressure regulator, or a badly blocked fuel filter.

optimusprime m1

The coil gets nothing only voltage of 12 volts ,thats till the ezl sends the message to it to energise and fire .So you must have another problem .You could have put a spark tester in the king lead to see if you had a spark if so the centre lead was faulty. Anyway your up and running now.

kostas86

I installed new fuel filter when I installed a new "J" fuel line connection that attaches to filter (original one rusted).
So not sure if coincidence, but been priming system 4x before start up and so far been helping car start up on first try. This leads me to believe it's the Fuel Pressure Regulator?

Thanks again for all the knowledge

optimusprime m1

Fuel pressure regulator is under the air box.. You will need to remove air box to get in to remove the pipe from the end of it .Keep some cloth handy in case it leaks ..Start the engine .Now let it run ,do you see any fuel from the regulator .Now dont get mixed up with the fuel accumulator that sits next to the fuel filter by the pettrol pump.If you have fuel come out when its running , its shot. Realy after this check you need a check on fuel pressure.

kostas86

Thanks, I am hoping I can get to it by this weekend.