Hildegard is a very nice 93' 280TE Auto with M104 engine (HFM) and just 98K on the clock. She is quite temperamental and now has became rather reluctant to get started in the mornings.
This happens at random and does not correlate well with outside temp. (It can be quite difficult even at mild temperatures). You have to crank the engine for ages and then splutters into life with a tremendous smell of unburnt petrol (reminds me of an engine of old times flooded by inappropriate use of the manual choke). There is no problem at all with hot starts.
Another issue is a ticking noise in the engine on starting up. It usually disappears within a few seconds, although a couple of days ago persisted for a long while and was really loud: ?hydraulic valve lifters, ?Timing chain.
What do you think?.
Any suggestions will be highly appreciated.
How long has it been since the spark plugs/wires have been replaced?
I would address the ticking noise by replacing the oil /filter with Mobil 1 0W-40. It works miracles...
Could be a bad fuel pressure regulator. Pull off the vacuum hose and see if you smell gas, if so it's bad. It's located on the front top right of the engine.
Thank you very much to jrs2000, Sergio and Deanyel for your suggestions.
I think this car has three coils but I would not know how you check them. The spark plugs are MB items and were renewed around a year or so. At the time the spark plug wires seemed to be in very good condition.
The oil I use is Total Quartz 7000 10w40 (semisynthetic). I change it (along with oil filter) every 3500 to 4000 miles.
I will definitely check the fuel regulator and get back to you.
I very much appreciate your input.
The Independent Specialist I took the car to can't find anything wrong at all. Since there is plenty of unburnt fuel he reckons the problem must be related to ignition rather than fuel supply. He said the crank position sensor could be showing an intermitent fault but he can't be sure and I am reluctant to start putting new parts without evidence of them being faulty. He could not find any stored codes.
I am increasingly concerned as repeated failure to start could ruin the very expensive cat
The Independent Specialist I took the car to can't find anything wrong at all. Since there is plenty of unburnt fuel he reckons the problem must be related to ignition rather than fuel supply. He said the crank position sensor could be showing an intermitent fault but he can't be sure and I am reluctant to start putting new parts without evidence of them being faulty. He could not find any stored codes.
I am increasingly concerned as repeated failure to start could ruin the very expensive cat
In other words: HELP!
Thank you in advance
RUN, DON't WALK TO ANOTHER SPECIALIST OR TAKE IT TO A MERC DEALER
The crank position sensor can be check with an ohm meter and an oscilliscope.
He must be seeing your "symptoms", but gives you a "nothing wrong" answer because his ability to diagnose is limited !!!
The next specialist needs to check/diagnose everything from the O2 loop to the starting cycle, complete fuel supply and ignition system before he starts to replace what will be expensive parts.
You don't need a specialist who replaces parts one by one to see if it corrects the problem !!!
Hi RBYCC
What you say makes sense to me.
I will have to search for a place where they can undertake this type of diagnostic issues.
Thank you very much.
Have you built the LED code reader? If not, you might want to consider building one,as it is very simple and will tell you a lot about your engine. Do a seach on this forum for "code reader" and you will get links to the schematics and instructions on use as well as the code key.
Cold start problems M104 engine with HFM
. Since there is plenty of unburnt fuel he reckons the problem must be related to ignition rather than fuel supply. He said the crank position sensor could be showing an intermitent fault but he can't be sure and I am reluctant to start putting new parts without evidence of them being faulty. He could not find any stored codes.
Linear Mode
