W163 Saga, new chapter.. engine will not start (most of the times)

[DexterML]

Hi all

The car has been fine for about a month and a half or so. New Crank shaft and Cam shaft sensors, new fuel lines and it worked fine. Can't complain, when it works, it works.
About a week ago, it begun not starting up when hot. I.e. you start it up, drive around, turn off, try to turn on again and it would just crank. It took 3 or 4 tries to get it to start. No air in the fuel lines. I checked.
It got progressively worse and it now sometimes won't start when cold. If it manages to start, it will go on for hours, no problem. But if you turn off.... you're screwed.
So far the highest it has gotten is 8 tries to start. And it cranks for quite a while. Sometimes it fires and dies immediately.

Took the covers off and looked at the injectors. One of them seems a little bit 'wetter' around its seating, like I sprayed it with wd40 or something. But nothing like the leaky injectors you see on photos online.

Any thoughts anyone ?

 

[Wearsthefoxhat]

Problems when hot often point to a failing CPS. I notice that you have replaced it, was it a good one, MB or Bosch ?

 

[DexterML]

Problems when hot often point to a failing CPS. I notice that you have replaced it, was it a good one, MB or Bosch ?

Hello
You mean cam shaft sensor right? The one at the top of the engine, not the one at the bottom (crankshaft)?
But don't CPSs cause the car to die while you drive it as well? So far this hasn't happened.

Did not check to be honest, ordered from a German site online though with the actual part number. I still got the original one that came with the car, don't think that was the issue ( I suspect the leaky fuel lines caused the initial problems). I can put that back and check.

 

[Jobsworth]

The camshaft sensor is only used when cranking, to identify whether the number 1 cylinder is on its firing stroke or exhaust stroke. Failure isn’t massively common, but I’ve done a few. Crankshaft sensor can also give hot start problems, and this is very common. They rarely store a fault code, and very occasionally give cutting out while running, but that’s also rare.
You need to check the rail pressure live value when it’s failing to start. That will give you the biggest clue. Or give it a whiff of easy start when it’s failed.

 

[DexterML]

You need to check the rail pressure live value when it’s failing to start. That will give you the biggest clue.

Hello
Thanks for that. I presume you mean check it with a scanner, right?

Or give it a whiff of easy start when it’s failed.

That has gone right over my head. If you don't mind can you elaborate a bit?

 

[Jobsworth]

If you spray some easy start, just a little - don’t go mad with it, and it fires up and runs it’s going to be rail pressure isn’t coming up high enough cranking. When it fires and speeds up it’ll usually overcome any leakage or air that’s stopping it. That means the pipes, pump, rail, injectors need further looking at.
If it fires on the easy start but then stops again when it’s been used up the fault more likely lies with the electronics

 

[DexterML]

If you spray some easy start, just a little - don’t go mad with it, and it fires up and runs it’s going to be rail pressure isn’t coming up high enough cranking. When it fires and speeds up it’ll usually overcome any leakage or air that’s stopping it. That means the pipes, pump, rail, injectors need further looking at.
If it fires on the easy start but then stops again when it’s been used up the fault more likely lies with the electronics

Thanks for that, I understand now.

This car will drive me crazy. It wouldn't start from cold this morning:

1st attempt: Just crank
2nd attempt: fire and die
3rd attempt: fire and die
Waited 30 secs
4th attempt: Fired up

drove it for 30 minutes on the clock, let it stand idling another 5, turned off and immediately on again without removing key from ignition, started up twice in a row with not a cough !!!!

I have a tiny little OBD2 bluetooth thing, I think that reads fuel pressure. I'll see if it can show anything as well.

 

[ALFAitalia]

Excessive leak back from the injectors? Had that issue with similar effects on my Grand Cherokee...which had exactly the same 270 5 cylinder Merc engine. One of the injectors was leaking back about 5 times what the other four were resulting in low rail pressure. One new injector (recon to be honest) sorted it.

 

[DexterML]

Excessive leak back from the injectors? Had that issue with similar effects on my Grand Cherokee...which had exactly the same 270 5 cylinder Merc engine. One of the injectors was leaking back about 5 times what the other four were resulting in low rail pressure. One new injector (recon to be honest) sorted it.

Is there a way to verify this visually? I ran the engine with the cover off and I couldn't see anything around the injectors...I suppose the problem could be minute still and not manifesting so much..

I've ordered some easy start to try what jobsworth suggested.

 

[ALFAitalia]

You need to disconnect the leak off pipes and route them to five little jars whilst blocking off the return tube and running the engine. You can buy them....but I made my own for about three quid with fish tank air pipe and 5 of those little plastic jars designed for fluid in hand luggage on plane.!! Each jar will slowly collect derv and should be at a similar rate. One of mine was filling up much faster than the rest proving it to be the worn out injector and the one affecting rail pressure and starting.

This is my thread from the Jeep forum I made about it back in 2011!

Testing leak back on WJ CRD 2.7 (Pics)

www.jeepforum.com

 

[DexterML]

You need to disconnect the leak off pipes and route them to five little jars whilst blocking off the return tube and running the engine. You can buy them....but I made my own for about three quid with fish tank air pipe and 5 of those little plastic jars designed for fluid in hand luggage on plane.!! Each jar will slowly collect derv and should be at a similar rate. One of mine was filling up much faster than the rest proving it to be the worn out injector and the one affecting rail pressure and starting.

This is my thread from the Jeep forum I made about it back in 2011!

Testing leak back on WJ CRD 2.7 (Pics)

www.jeepforum.com

Thank you !!

I'll be trying this as soon as possible.

 

[Kerabo]

My 220 CDI was just the same.
it would fire but not start . Maybe 1 in 30 attempts it would start.

I know you have changed it but try another Camshaft sensor.
It needs this to tell the engine what stroke it’s on.. The Crank sensor when running will take over but to start it needs the Cam sensor.
very easy to change.
I did eventually find a fault code.