2005 MERCEDES (W220) S320CDI HARD STARTING ISSUE??

Hybrid_Singh

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2005 Mercedes S320cdi (W220)
I am based in the UK and the weather has changed dramatically over the past week. I purchased a 2005 model S320cdi Mercedes S class for my daily highway commute. (80 miles) This is a well looked after example only done 80k miles and I bought her 3 months ago and has been a fantastic car to drive and very comfy and has a full service record.
My issue started 4 weeks ago where it took 2 attempts to start one day and then would be fine all day. Then gradually got more regular 2xs b4 it would fire up. No codes were displayed so was a little puzzled so on advice of diesel technician replaced glow plug relay from euro car parts (Hitachi £42 unit) it still took starts before it fired up after fitting, however next day fired up first kick. Then it went back to 2 crank start and then yesterday it was worse, 5 cranks and then coolant light visit workshop came on? Later I did my 40 miles highway run and its drives superb, 4 hrs after parking up really hard start, 8 cranks b4 it came to life. Although once it's warm it fires up everytime. The only message on Cluster which appears is Coolant light visit workshop everytime this occurs and then dissappears when I recycle the ignition again. No other codes recorded.

I have also replaced glow plugs, injector rail, quantity control valve and also had the injectors tested and they are perfect. Strangely if I leave the car parked for a few days it starts up.perfectly fine and then gets worse after 2 days of my daily commute.

I am posting today's rail pressure live test result screen shots from my Diagnostic tool, first one is whilst car is stationery from cold to see levels and the second one is cranking whilst it is not firing up. It is clear on this that rail pressure is very low, but once its fires up it goes to 250-360 bar pressure.

Any advice would be great as im not ready to give up on this beauty just yet.

Thanks in advance, BTW fuel filter was replaced in February.
 

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Hybrid_Singh

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I am based in the UK and the weather has changed dramatically over the past few weeks. I purchased a 2005 model S320cdi Mercedes for my daily highway commute. (80 miles) This is a well looked after 80k mile example and I bought her 3 months ago and has been a fantastic car to drive and very comfy and has a full service record.

My issue started 4 weeks ago where it took 2 attempts to start one day and then would be fine all day. Then gradually got more regular 2xs b4 it would fire up. No codes were displayed so was a little puzzled so on advice of diesel technician replaced glow plug relay from euro car parts (Hitachi £42 unit) it still took starts before it fired up after fitting, however next day fired up first kick. Then it went back to 2 crank start and then yesterday it was worse, 5 cranks and then coolant light visit workshop came on? Later I did my 40 miles highway run and its drives superb, 4 hrs after parking up really hard start, 8 cranks b4 it came to life. Although once it's warm it fires up everytime.

Following all the above I have replaced all the Glow plugs, fuel pressure rail, quantity control valve. Injectors have been tested and are working perfectly fine.

I am posting screen shots of cold start done today using live testing on my Diagnostic tool. First picture is car ignition on cold, second picture is trying to crank the car and you will notice fuel pressure is very low. However after 6th crank it comes to life and pressure goes to 250-340 bar.

If car is left for a couple of days it fires up immediately but then after running for a couple days on my daily commute it begins to fault as above and gradually gets worse everyday.

Thanks in advance, BTW fuel filter was replaced in February.
 

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mioba

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Is your mechanic a merc specialist?

Whats the battery voltage first thing before you start up.
 

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Sounds like you might have air getting into the system. Check all the plastic pipe connectors and O rings.
 
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Hybrid_Singh

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Hi Battery Voltage is fine as it sounds very strong when attempting to start.

Please see following link which opens upto a video clip I took yesterday of vehicle starting after 6 attempts.


This video displays the stats using Diagnostic tool, clearly showing little fuel pressure. However amazingly the car fired up perfectly today all day?

Also view attached screenshots, first ignition on from.cold and second one attempting to start.

Any advice would be appreciated. No codes have been stored.

Thanks
 

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supernoodle

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If that first screen was the first start, why are engine and fuel temps 50 plus?

There is an electric pre supply pump. That should give you fuel under pressure (5 bar) at the high pressure pump inlet. Check that you're getting a good supply of air free fuel there. It should prime for a short time after key on, so you can check without cranking.
 
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Hybrid_Singh

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Hi,

Apologies just to clarify that start wasn't first morning start it was after car was left for 2 hrs from driving it. I wanted to see if I could monitor results on live feed. See the YouTube video I attached.


Thanks
 
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Hybrid_Singh

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Also please can you confirm where to find the electric pre supply pump you mention in your thread. Should I remove fuel pipe going into high pressure pump to check fuel supply without crank?
 

supernoodle

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The pump is in the tank, combined with the level sensor.

You turn the pump on and off with a diag tool too (at least on CR max you can) when sitting in the car you can hear it.

Yes, check pump inlet, that's ultimately where it needs to be.
 

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mioba

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Have you considered the fuel filter being blocked, full of water
 
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Hybrid_Singh

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Yes someone else mentioned this, but what threw me was I bought the car in September and the paperwork supplied with the car had details of service done in February stating fuel filter change. Although car is due service in 1100 miles I'm going to change the filter this week to rule it out.

As I mentioned before if I leave for a couple of days it starts first crank however after 1 or 1 days of my motor way commute it begins to behave bad and gets worse, but then sometimes I expect it not to start and it cranks first time. Also when I drove it is perfect on boost and acceleration, just embarrassing when it let's me down on starting as posted in my YouTube video.

Otherwise it's a great car.

Thanks
 
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Hybrid_Singh

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Not yet.

Do you suggest I check full fuel pipes or at any particular section?

Thanks
 

Doug1234

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My thought is find the low pressure fuel pump relay and replace it or there are usually some on the car exactly the same that do different functions like air conditioning etc and swap one of them in and see if that helps.
 

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Not yet.

Do you suggest I check full fuel pipes or at any particular section?

Thanks
Why keep looking for other faults when you haven’t checked the basics?
Check ALL the pipes with this end, small o ring goes hard and square.
If still poor starting, check injector leak off.
 

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supernoodle

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Sorry, just realised you've probably got the old engine with the engine driven pre supply pump. That should have a clear section of hose on the outlet where you can see if you have air in the fuel.

Check the seals on the inlet/outlet and the big seal behind the front plate of the pump body. Then work backward.


IMG_20220117_210156.jpg
 
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Hybrid_Singh

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Thanks mate.

This is great I will check this week. Can I get replacement pipes and seals from.anywhere or is it dealer part only?
 
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Hybrid_Singh

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My thought is find the low pressure fuel pump relay and replace it or there are usually some on the car exactly the same that do different functions like air conditioning etc and swap one of them in and see if that helps.
Where is this relay normally located?
 

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Do you have the earlier clear fuel pipes. As suggested these are prone to 'o' ring ingress.
The later fuel pipes aren't clear, so less likely to have issue.

The fuel filter may still have an 'o' ring on the fuel pipe/s, unless they're a push on instead of a push in.

It might help us if we know which style of fuel pipes you have
 

mersum1es

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Sorry, just realised you've probably got the old engine with the engine driven pre supply pump. That should have a clear section of hose on the outlet where you can see if you have air in the fuel.

Check the seals on the inlet/outlet and the big seal behind the front plate of the pump body. Then work backward.


View attachment 73972

2005 MY W220 has OM648. So aux pump in tank an no o-ring issues
 


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