C220 W202 won't start

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mike18hc

Active Member
Joined
Jul 26, 2006
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99
Can anyone help me resolve the starting problem that's just happened with my 1995 c220 W202 petrol saloon?
The car's always been a good starter but 2 days ago I turned the key and, for a second, the engine fired. It then died. No indicators in the instrument panel had changed from normal (SRS still turns off after a few seconds) and all the noises expected when the car's ignition's on were there as usual.
I checked the fuel pump and its relay by jumpering and a test meter and both worked. The tank's 3/4 full and I released the vapour pressure.
I checked the fuses in the main fuse box and the ones on relays underneath it. The aux fan relay one was burned out so I replaced it.
The fuses in the boot were all OK.
For no particular reason I put the car in N and turned the key. The engine fired for a few seconds and died.
Today, having left it overnight, it fired immediately but died seconds later.
The OVP fuse is OK and tapping the relay makes no difference.
I read that the fuel injection can turn off for safety reasons if the car doesn't start and there is no smell of fuel from the exhaust.
The car's got a 38-pin diagnostic socket with 8 pins...for 2 power supplies, ground, Hot film fuel injection, the ignition speed signal, the A/C, central locking and air bag control unit.
Since the car can actually start, it doesn't look like anything testable will be related to the problem but I will make a tester for it.
For the same reason it doesn't look like the immobiliser can be the cause either.
Has anyone had this sort of problem and cured it?
 
Did you disconnect the battery at any time?
Is there an alarm , any alarm stickers or odd looking keys with the car?

Dec
 
There is an alarm and it continues to work OK. There is a separate unit with a key that enables/disables the horn when the alarm works.
I disconnected the battery to allow everything to reset in case I hadn't noticed something. I haven't yet resynched the roof/windows key closing.
 
Do you have Red & Green lights on mirror like in the video linked below, if so, do the flash alternately when you try to start the car?

The alarm is integrated with the immobiliser in the video below , do you have that set up in the passenger foot well under the foot rest?

It all does sound a bit like an immobiliser problem, if you disable the alarm siren/horn with the key will it still not start


https://www.youtube.com/watch?v=81jOSKzpaas


Dec
 
The red mirror and door handle lights go on and off when locking and the green lights operate when opening. They do not work alternately or go on together.
I just checked what they did when trying to start the engine and the answer is...nothing.
However, the engine fired for a second and then died.
Also, the interior front lights come on for 20 seconds when the doors are unlocked and I'd never noticed that before.
I'd originally thought about the immobilizer but discounted it when the engine fired, albeit for a few seconds, as the immobilizer wouldn't let that happen even for a second. Would it?
I'll have to check there's fuel going to the engine as even when I operated the pump by jumpering it the engine still failed to start.
O
 
The red mirror and door handle lights go on and off when locking and the green lights operate when opening. They do not work alternately or go on together.
I just checked what they did when trying to start the engine and the answer is...nothing.
However, the engine fired for a second and then died.
Also, the interior front lights come on for 20 seconds when the doors are unlocked and I'd never noticed that before.
I'd originally thought about the immobilizer but discounted it when the engine fired, albeit for a few seconds, as the immobilizer wouldn't let that happen even for a second. Would it?
I'll have to check there's fuel going to the engine as even when I operated the pump by jumpering it the engine still failed to start.
 
There's petrol getting to the high pressure line but it looks like the injection system's turned off as I checked the plugs again and they are good but no smell of petrol.
I wonder if an injector's leaking a bit giving enough petrol to ignite, but I doubt it as when it fires there seems to be a complete firing sequence in all pots.
When I'd refitted the plugs I left off the air ducting completely with the sensors out and it started again for a second, but a bit more weakly this time.
I checked under the passenger foot panel and saw a mercedes-marked unit, 0 350 01 021 that had 2 sockets, one with 3 wires and one with a lot of wires. It looked like what I have read to be an immobilizer but the number's strange. There are 2 added-on fuses feeding an additional unit which may be the second immobilizer many people have mentioned.
 
Interior front lights come on for 20 seconds is normal when unlocking.

The black box at the top of picture is the immobiliser.
The hand is holding a Scorpion alarm control box.
Is that what you describe?
You are in the UK, aren’t you?

Dec

maxresdefault.jpg
 
Hi,
The starting and dying is exactly what my C230K did when the immobiliser was faulty.I believe the supply to the fuel pump relay is fed from a different place when cranking the engine once running the fuel pump relay is fed from the ecu (I think), hence why that it stops as soon as it fires.
It does it this way so in an accident and the engine stops the fuel is cut off and doesn't continue to pump.
 
The box being held is the one I gave the p/n of incorrectly. It starts with a Q and not a 0, so it is the alarm control unit. I'll now look for the immobilizer, but what I can do when I find it is anyone's guess.
I am in the UK.
 
Hi Andy.
The Haynes manual shows something they call a Main Relay controlling the Petrol Injection unit and the fuel pump. Right now I'm trying to find out what that relay is and where it is. The manual schematic shows 12V coming from the injection control to what it refers to a "passenger fusebox" and from there to the injectors. I can't locate that either but I can see 12V coming out of the PI unit at the right place!
 
Did you view this video here… https://www.youtube.com/watch?v=81jOSKzpaas
When you find the immobiliser, you could see if any wires have been modified as illustrated in above vidio.
You could also open the immobiliser to inspect the PCB for any kind of damaged soldering.

Dec

b4f1ip.jpg

szk11g.jpg
 
I looked at the video but assumed since the indicators worked correctly on mine that this fix wouldn't work for me.
I'll get down to investigate this further tomorrow.
If I got another immobilizer with the same part number would it work or is there further coding to differentiate between models?
Did what was done in the video cut the immobilizer out of the circuit? If it did that would be the ultimate test!
 
Got spark at all four plugs? Ecu is a common failure on our car loses 2 cylinders
Collapsed fuel filter? I have had this before.
Does the pump run?
 
What you could try is to unplug Plug A, the Red & Green should flash alternately when you turn ignition on, this tells you that the immobiliser hasn’t disarmed… because it’s unplugged.

The Scorpion alarm is an add on, the Mercedes immobiliser doesn’t know the alarm is wired into the system, so, when you unlock the car, with the remote, you also disarm the Mercedes immobiliser, but, the Scorpion alarm may also have an immobiliser which has in some way become defective, the only way to test if this is the case is to remove the Alarm from the immobiliser wiring just as was done in the video.

What was done in the video didn’t cut the Mercedes immobiliser out of the circuit; it cut the Scorpion alarm out of the circuit, so, doing what was done in video might solve the problem, that is, if indeed your alarm is wired into the Mercedes immobiliser and the alarm is responsible for the fault because its faulty.

The use to sell the remote fob part without key blade and the immobiliser, from the same car, on ebay, but no idea if this actually works or not. Example below.

t014s6.jpg


We don’t know what the problem is, it could be fuel or some other fault so all you can do is eliminate things like the alarm system, these alarms were known to be faulty and did cause starting faults like yours.

Dec
 
I probed the 38-pin diag socket but there were no errors in the PI or Central locking memories.
The wiring is not identical to the situation in the video but is worryingly similar! A Purple/Black and a Yellow/Red wire coming from the large alarm plug are cut off in one harness. A White/Black wire and a Green/Black wire from the same plug have, respectively, been soldered onto a White wire and a Green wire coming from the small multi-wire plug in the immobilizer.
There's just a green and a white wire in the other immobilizers plug and they go off into the car's bodywork with no sign of any changes.
I guess I'll have to bite the bullet and cut the 2 alarm wires. I can resolder them if it makes no improvement.
 
Cutting the wires made no difference except the side indicators stopped working. Soldered them back in.
I changed the fuel filter. No difference. Jumpered the pump again. Slight squirt when I opened the fuel rail schrader valve. Is that right?
If the immobilizer cuts out the ignition and pump how could it ever start as it has done from time to time?
If the immobilizer indicates it's armed by both red and green lights flashing, which they don't in this case, does that mean it can't be the immobilizer?
 
Do you have a picture of the seen and what wires you were cutting?
If the Red & Green flash when you turn on ignition then that means the immobiliser is armed and car won’t start.
If Red & Green don’t flash when you turn on ignition then the immobiliser is disarmed and car should start.
Did you open the immobiliser to have a look at the PCB?

Were eitherof the two wires coming from Plug A cut or spliced into?

b4f1ip.jpg


Dec
 
Plug A had the Green and White wires untouched but a green and a white wire going to plug B had been spliced into 2 wires going to the alarm's large socket.
I will take some pictures.
Sorry about the wording! The red and green never go on together or alternately. They just go green for open and red for closed. No lights appear when turning the ignition on, ...but the car won't start! It set me wondering if the immobilizer's a red herring as I don't think I've read about a problem of non-starting that hasn't has red/green flashing lights mentioned...
 
The Green and White wires untouched means the alarm plays no part in immobilising the car.
The green and a white wire going to plug B, being spliced, is to tell the alarm the car has been unlocked or locked so it can be armed or disarmed.
Unless there is something wrong inside the Mercedes immobiliser then you can rule out the immobiliser.
As you can see in the video, compared to your car, there was a different approach on how these alarms were wired into the car by alarm the installers.

There is a K40 unit in the ECU box on passenger side, take a look inside it. It has a black relay on it which is the starter relay located below the left Red arrow in picture.

2eg8uxe.jpg



Example… https://www.youtube.com/watch?v=eB0iCiIeH9k


Dec
 

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