Cold Start Problem

[tlovidiu]

Hello,
I've got a C200 1999 TDCI.

When it got cold, I got problems starting it.

1) I put the key, wait 60 seconds, try to turn it on...
2) It starts stays 1 second and dies (even If I press the gas pedal)
3) I wait other 60 seconds, try to start, with a long key about 10 seconds and it wont start or it would start (thirt key usually).

If the water indicator stays over 40°C it starts without problems.

What could It be?

[8=Anonymous=8]

I'm guessing it's too cold or your glow plugs isn't working
Don't have a diesel myself so I'm not quite sure

[nelius]

off topic but OP are you Romanian? I saw the name ovidiu and I thought "ba asta ii roman"

[tlovidiu]

yes I am, any other ideas?

[tlovidiu]

The glow plugs are new :)

[tlovidiu]

By the way, I've changed only 2 glow plugs of 4, because the Mercedes Tester told me that.
Did I have to change them all?

[8=Anonymous=8]

usually changing it all is a better choice

[strictlyspeakin]

I loved my diesel: 190D 2.2.

The glow plug relay or a pair of failed glow plugs. Do you have a glow plug indicator on the dash? It should be lit telling you how long to wait before starting the car. It was an interesting circuit.

[tlovidiu]

I have an indicator, It stays on 5 sec and then stops.
By the way, I've changed the 2nd and the 3rd glow plugs...

[strictlyspeakin]

The time of the indicator should vary inversely with temperature. The lower the temp, the longer the indicator. 5 seconds seems short so something is not correct.

You can leave the key on, but the relay controls how long voltage is sent to the glow plugs regardless of key position. They did this to prevent the plugs from melting. There is also a hard coded max duration.

Can I ask why you picked the 2nd and 3rd?
If it were a pair, I'd would suspect that either the (1st and 3rd) or the (2nd and 4th) are bad. I seem to recall the 190 compared the values in parallel rather than series. Pull the other 2 and see what they look like. An ohmmeter can help determine if they are good. Compare values to a new one.

Based on your description the relay is not operating long enough for the current temp. Voltmeter to see how long 12V at the plug should confirm this.

[tlovidiu]

The mercedes tester told me that the 2nd and 3rd are bad.
I will check what you told me.

Thanks.

[strictlyspeakin]

keep me posted.

[tlovidiu]

I went to the mechanic today... He told me he checked the glow plugs, and he told me that they are ok.

I don't know what to say...

Today it was very cold, I was able to hear and feel the pistons going but without it starting.

Could it be the High Pressure Pump?

[tlovidiu]

today.. i put thw key on... let it 3seconds,so the glow plyg light goes off, then i did this again for five times without yurning on the car.... and it magically started without problems. lol

[strictlyspeakin]

I pulled out my 190D manuals. I'm still leaning toward that relay. There is an ambient temperature in the preglow time relay. It determines length time the circuit is energized. Safety limit (max time) is temperature + 20-35 seconds. On the 190 the high pressure pump is driven by the rotation of the engine. I really doubt it is bad. If there were a leak and air in the high pressure lines, it would be hard to start, but I think you'd notice. The rubberized return lines used to leak, you'd see that they looked wet. You're not really seeing that.
Most of the test procedures are for when the indicator light is not lighting up.
The primary test for a complaint involving the lamp lighting up, but engine fires poorly after indicator light goes out, is for the glow plugs. How many amps they each draw and whether or not there is resistance on each line. Measuring resistance from the engine block back to the coupling near the relay. I don't know what the mechanic did to test the plugs, but presuming that he knows what he's doing, there is one more test to try. It is possible that the indicator lamp indicates a fault (does not turn on) only after a failure of 2 glow plugs in cylinders 2-4. To make sure that the fault indication in the preglow time relay is not defective, disconnect 2 glow plugs in cylinders 2-4. If the indicator lamp is not not lighting up, the relay is working.

temperature in degrees C = preglow indicator light on duration
80 = 2 seconds
60 = 3 seconds
30 = 4 seconds
10 = 5 seconds
00 = 7 seconds
-10 = 11 seconds
-20 = 18 seconds
-30 = 30 seconds
I think my real world experiences added a couple of seconds to each but this is what is in the book.

[tlovidiu]

Thanks for this info.

But now I think another is the problem.

I heard a strange noise near the rear left wheel when the car is on.(Even if it's not moving)

Could be a problem with the fuel pump that is on the back of the car?

[tlovidiu]

Yeah, I looked on the old mercedes tester's results and it says clearly: Heater Booster (No flames has formed after repeated attemps starting)

Should I buy a new one? Or repair it somehow?

[strictlyspeakin]

Did you try the test I described above (disconnecting 2 to see if the light doesn't work)?

The fuel pump for gas engine cars is located near the rear wheel (it's on the right for my US C220) and it can be heard it as long as the key is on. Maybe that's what you hear? Is the high pressure pump still mounted on the side of the engine like it was in the 190?

[tlovidiu]

i couldnt try that yet. but the trick i used doesnt work anymore :( i really think it's the fuel pump. would the tester tell me this?

[tlovidiu]

Well,

I removed the caps of my 2nd and 4th glow plugs. I started, and it died(but not as it dies usually in the morning). The glow plug light didn't do anything. He was the same as if there would be all 4 connected.
I've done the same with the 1st and 3rd.

Now I gonna change the relay, because I can have them for free, my uncle works for the factory that makes them for mercedes. I hope it's this the shit, but I think the fuel pump is. :(

[strictlyspeakin]

With 2 disconnected the expectation would be that the glow plug light would not come on. So that part is working.
I'm confused by your statement "He was the same as if there would be all 4 connected". I thought you said the light did come on when all 4 were connected. The car starts and then stalls? I missed that point if you said it earlier. Yeah, I'd be chasing fuel and not the glow plug circuit.

A diesel really only needs 3 things to run: air, compression and fuel. The glow plug circuit only make the car easier to start. If it has failed, the car will still eventually start with enough cranking and those 3 present.

What weird noise did you hear from the rear? Where is your high pressure fuel pump located?

[tlovidiu]

Well,

When I disconnected the 2 glow plugs, the glow plug light turned on for 2 seconds(like when all 4 are connected)
Just to test, my friend disconnected the parking brake sensor (that's what he told me) and the parking brake light did not turn on.

I hear a strange noise, near the rear left wheel. I think it's that that makes the strange noise.

Look this:
http://www.mybenz.org/zoopp/html/uploads/img4beebecd0a211.jpg

Next morning I will try to record an usual cold start and post the video.

P.S.: When I start the car, at the first attempt, it works perfectly, but it dies after 2 seconds, and I feel like no fuel is getting to it.
When I disconnected the glow plugs, It couldn't start and it made a different sound when dying.