No crank no start on Mercedes A-Class

Mercedes A-Class W169 A190 automatic petrol 2004.

No previous problems starting.

Several weeks ago, after refuelling, the engine started normally, but stalled after about 100 yards and I rolled to the edge of the road. On turning the key, no start no crank. All symbols on the dashboard illuminated. All lights working. After about 10 minuets, the car restarted but stalled when Drive engaged, apparently lacking power. This procedure continued until I had to abandon the car.

One peculiarity, whenever I tried to start the car, the electric cooling fan attached to the radiator would start and became incredibly noisy when the ignition was switched on. I noticed a similar problem on one of the scannerdanner youtube videos.

Next day I installed a new fully charged battery but no start, no crank. Again all engine symbols illuminated and all lights operational. Checked all fuses and relays and all appear ok. However, the starter motor cut-out relay is incorporated into the starter motor and I have not been able to check. However, the starter motor turns if power is applied from the battery.

The OBD code reader cannot communicate with car, although on previous occasions there was no problem.

A day later I checked the cabling to the Control Module box, behind the screen washer liquid container under the bonnet, but all seemed ok.

The next day I was amazed that the car started first time and appeared to drive a short distance normally in both Drive and Reverse. However, the instrument panel gave the warnings “BAS ESP” and “ABS”

A day later I returned to the car intending to drive home, however the no start, no crank situation was back again and remained for about a week.

After again rechecking all the cables the car started and I was able to engage Reverse and Drive, and managed to drive about a quarter of a mile before the car stalled again and the whole scenario started again.

I noticed on one of the scannerdanner videos the use of a “short and open circuit finder” so I decided to make the investment. The system appears to put a frequency down a cable, which can be followed by a detecting device, complete with bending aerial, until a break is found. I await with hope the arrival of this device.

I have found several references to this problem on the same model of Mercedes, but no solutions.

About a week before this problem started, both front suspension systems (combined shock absorber and spring) were replaced.

This has been a great little car for a lot of years so any help getting her back on her wheels would be greatly appreciated.

Many thanks,

Peter FD

Hello Peter in the Alpes-

"The OBD code reader cannot communicate with car, although on previous occasions there was no problem"

Im no master mechanic, but before you start looking at this and that and maybe this is the issue type stuff- Check your DLC (Data Link Connector) wires and make sure they are in one piece. Once you have verified that the DLC wires are good, then hook up the code reader or scanner to see what it says.

What scanner do you have?

Hi MrMike
Many thanks for your responce.
I have a very basic OBD reader which has previously given engine information on this car but after the no crank no start problem cannot communicate. The wires to the plug on the car appear to be in good condition, and the OBD reader works when connected to a different car.
I appear to have a break in a cable, or corroded contact, or bad earth somewhere in the system.
The fact that the car will sometimes start (although rarely), and runs perfectly normally for a short distance suggests that all the modules are working correctly.
Unfortunately, on the two occcasions I managed to get the car to start I didn't have the OBD reader with me, although I doubt any useful information would have been gathered.
I appear to have a break in a curcuit somewhere which occasionally closes, permitting the car to start normally, however as the car warms-up the break re-opens and the engine stalls. When the engine stalls, I can usually restart the engine a couple of times (starter motor working correctly), however the engine is unstable and lacks power - and any attempt to engage Drive results in stalling.
After this, I have a no crank no start which can last for days.
The symptoms appear to be quite specific and I have the feeling something is staring me in the face and I just can't see it.
The car starts first time and I can drive away. Shortly after this, the engine stalls. At this point I can restart the car but the engine is unstable, lacking power and continually stalls. After a couple of unstable restarts, I have the no crank no start - even though the battery is good, all the instrument panel lights are on, and headlights etc work fine.
On a cold start, after a few minuets in Drive, something cuts the engine but permits a couple of restarts with the starter motor working fine, although the engine is unstable, then the situation progresses as something cuts the starter motor. There must be a relationship which would permit the problem to be identified.

Any suggestions gratefully recieved.

Many thanks,

Peter

Hey Pete-

Them DLC wires might look good at the DLC but you really need to break out a meter and do continuity checks to know for sure. Hopefully you have a decent wiring diagram that you can use to find out where each DLC wire goes. Disconnect the wire(s) one at a time where they end and check continuity from start to ending point of wire(s). Remember, no power on circuit. Your looking for a reading of 5 Ohms or below- anything over 5 Ohms and your wire is more than likely bad. Have you had a chance to measure power and ground at your sensors yet? Meaning KOEO (Key On Engine Off)- Using a wiring diagram, start pulling sensor connectors off and check your 5V Ref wires for a constant 5 Volts. Also check sensor ground wires- (Multimeter (-) lead attached to Battery (-) post and meter (+) lead to sensor ground socket on connection), you want to see NO MORE than 0.01V.

Have you replaced anything recently? These are just some easy things that you can do to rule out your wiring. Let me know what you find-

MrMike

On at least two occasions you wiggled the wiring and got the engine to run. Concentrate on those areas again. Look for contact points where wires rub, are near heat or are stressed. You're not likely to find the problem but getting the engine running is the point. Once running go to those same wiring areas and touch systematically watching for the engine to stall or stumble. It's a cat and mouse game which takes patiences.

One more thing-

Check your grounds- all grounds- engine, chassis and any grounds that may be hidden under the dash. A bad ground can wreak some havoc on alot of stuff.

Hi again everyone.
I purchased a workshop manual online (appears to be a copy of the original Mercedes workshop manual), however there's no wiring diagram.
I've searched the internet without success.
Could someone point me in the right direction?
It's a Mercedes A-Class W168 A190 automatic petrol 2004.
Does the Scannerdanner Premium subscription give access to wiring diagrams?
Many thanks,
Peter

Pete-

Im sure someone in this forum can get access to it

Hi MrMike
Many thanks for the response.
If someone has access to a copy that would be a great help.
In the meantime, I contacted the internet site I purchased the workshop manual from and I recently recieved a huge iso file that must burned onto a usb key. I then need to download an ETMViewer to try and find the wiring diagram which may or may not be there! - talk about leaving the edge of the known world!!
However perhaps I'll get lucky with the forum of the iso file - or both.
Thanks again

FYI-

I have a 2010 Dodge Ram 1500 and initially bought a Chilton repair manual for it. The manual is not bad for the DIYer person not working full time in an auto shop repair facility, but the wiring diagrams are just basic. I went to the Mitchell web site and purchased a 1 year subscription for the repair/wiring diagrams for my truck, my wifes truck and our car. What a difference they are from the standard diagrams. I live out in the woods in middle of WV and all I have is a good multimeter, computer safe test light and a few other tools which Ive found work. I would highly recommend purchasing the Mitchell diagrams and get a copy of the Scanner Danner book. The book can be a little confusing in areas if you have never used a scope or have thousands of dollars worth of diagnosing test equipment at your ready, but thats when you ask the questions when you dont understand something.
What Ive been doing is making a reference binder with all basic testing methods and I think by the time I get done with it, I will have pretty much everything I need in this one binder as my "go to" reference. Ive thought about signing up for the Scanner Danner premium stuff, but my internet really sucks here and I dont think it would work because of the crappy internet.
Their is a small garage in town about 12 miles away from my house- its one of about 3 small shops in the entire county and you dont want to take a car there because they known for just throwing parts at stuff and rigging stuff to work. I was in there one time just to drop off used engine oil and I seen them trying to get a rotor off by hitting it with a hammer? Who does that? Amazing-
The point for me is that if I can learn something new everyday and learn how to apply it, then its all good.

Hii Peter
I would like to know if you have found the problem on the Mercedes because I have one giving me the same problem.
I've checked the wires