C250CDI W204 Starting Issues - Help

[MarkII]

Hi all, need some help/advice - are there any known issues with the C250CDI regarding starting?

Went to take SWMBO for a nice day out walking on the Long Mynd only to find 'Gerta' wouldn't fire up as normal - engine spinning nicely but absolutely no combustion, not even a hint of it catching.

The car is a 2010 plate C250CDI Sport Auto, just turned 50K, complete MBSH and had a full B service including all filters, new water pump and EGR seal (both for water leaks) less than 2K ago and I always use premium (GTL) type fuel.

After three attempts she caught and ran like a bag of bolts for a few seconds with a clear mis-fire until all settled down. Initially I put it down to the fact the car hadn't been used for a few weeks but it's happened three more times during the day and doesn't seem to matter whether it's hot or cold - the same issue with starting and rough running, plus (and I may be imagining this) the car sounds more 'diesel like' between 1,600 and 2,000RPM.

Any thoughts/known issues re starting problems with this engine?

 

[MarkII]

PS: No check engine light showing.

 

[MarkII]

Update: The car started OK twice today but the third time took two attempts, so clearly an intermittent fault.

It's now booked at Mercedes for Tuesday, so I hope to know more then.

I'm wondering if it could be the crank position sensor

 

[MarkII]

Local MB dealer has just been in touch: Basically, there are no fault codes showing but they think the Fuel Rail Pressure Sensor might be at fault.

The engine seems to start OK provided the accelerator is depressed slightly but won't start without the accelerator depressed and they've checked the pedal unit and that checks out ok.

Anyway, I'm pretty depressed now as fixing it via MB is gonna cost almost £700 in total and Mercedes won't help towards the cost. I'm told Mercedes will only supply the entire fuel rail, including the sensor and the cost for that is £550

Seems pretty poor MB won't supply just the sensor (which surely ought to be £100 or so) and won't contribute something towards the extortionate cost of the fuel rail, esp as the car has a full MBSH and has only covered 51K miles.....

I wouldn't mind sporting some money to substitute a part and give it a try but when there's no guarantee it is the FRPS, £700 isn't a gamble I fancy taking.

Any thoughts on the matter would be appreciated.

 

[DieselPete]

Try and find one from breakers or ebay just to see if it works. Can you get to the sensor and google the numbers on it you may bd able to buy one from the internet. Its an easy job to replace as long as its easy to get to. I think its madness that you have to buy a complete rail.

 

[Ted]

Sounds like an air leak into the fuel lines. If they are transparent, can you see bubbles?
Definitely worth a trip to an indy for a second opinion.

 

[MarkII]

Thanks Gents

Pete - I totally agree, it's madness to remove and replace the entire rail when it could just be the sensor that's faulty and esp when there isn't a fault code and they can't be certain.

I'd be happy to give it a go myself and have plenty of experience working on engines but nearly all of it with petrol units - very little working diesel experience. My main concern would be safety regarding the high pressure on the fuel rail.

Do you know, does the fuel rail retain high pressure even when the engine is stationary?

Would the replacement of the Fuel Pressure Sensor require bleeding of the system?

I've taken a picture to show the rail and what I believe to be the FRPS - looks like a Delphi rail, so I'm assuming it will be a Delphi sensor??



Thanks, Mark

 

[a111r]

Find an Indie who know what they're doing, can interpret codes.

Surely cdi rail pressure variation can be identified diagnostically? It's a key issue to starting, EPC error message.

 

[MarkII]

Find an Indie who know what they're doing, can interpret codes.

Surely cdi rail pressure variation can be identified diagnostically? It's a key issue to starting, EPC error message.

Thanks but as I mentioned previously, according to the Mercedes dealer the problem isn't throwing up any codes. If it were then it should be giving P0193 or P0194 for the Fuel Rail Pressure Sensor but it isn't so the FRPS is somewhat of a best guess.

The MB dealer told me they had done a pressure test and that when the fault occurs and there is no throttle applied (as it would be normally for starting), there is no pressure but when the throttle is opened , pressure in the rail is normal. I asked if they had checked out the throttle control unit (to rule that out) and they say it's working fine.

Difficult to track down really and under the circumstances it might be less expensive to fit/have a FRPS fitted than keep paying diagnostics charges.

Intermittant faults on electronics

 

[vijilants]

When mine had issues the dealership replaced just about everything under the bonnet until they cleared the fault including the ECU. Luckily it was covered under an external warranty.

You are better off with a good indie.

What you must understand is with the majority of dealers, if Star doesn't throw up any clues, they are clueless and then go in to replacing components all over the place till the fault clears and you pay the bill.

They are not mechanics, they are code readers. You need a mechanic who understands these systems to look at this and mechanically work out and diagnose the issue.

Also I'm afraid they are under no obligation to chip in on any of the costs regardless of service history.

 

[DieselPete]

If im replacing a fuel rail sensor i slacken off an injector pipe first this will release any pressure in the rail. I would also back probe the sensor on an occilascope, this will show if its working correctly

 

[MarkII]

Thanks Pete

I'll see if I can replicate the fault and see what voltage readings I get from the back of the sensor and take it from there.

Unfortunately (as Vigilants suggested above) the MB agent didn't seem interested in doing more indepth testing, so looks like it's down to yours truly or a local indie...

Mark

 

[Yugguy]

You could call Mercland Nuneaton, see if they can swap the sensor alone. Sometimes indys will do stuff main dealers cant be bothered with or may not even know how to do.

 

[MarkII]

You could call Mercland Nuneaton, see if they can swap the sensor alone. Sometimes indys will do stuff main dealers cant be bothered with or may not even know how to do.

Thanks Guy,

Mercland is where I bought the car from but they're some distance away and if I need to there are people closer to me.

To be honest, I'd prefer to give it a shot myself - I trained in Automotive Engineering many moons ago but that was back in the days when most injection was still mechanical and although I've kept my passion and (up until recently) my 'hand in' modifying and servicing cars, I've never done much work with diesel engines (beyond ecu reflash and basic stuff). Also my health hasn't been up to much the last few years, which is why recently I've left things to the local MB dealer but it is frustrating when you think 'I could probably sort that' and they don't seem prepared to look at anything that doesn't involve straight replacement at £££'s

If I don't feel up to it myself then I know a few good people locally but my nearest proper Mercedes specialist is probably Tim Stear at Monarch in Lichfield.

Mark

 

[Yugguy]

No worries - I got mine from Mercland too, just a week ago. Bought the 2 year warranty though.

Aye, why not have a look yourself? Just cos Merc want to flog you the whole unit doesnt mean you have to.

On my old Focus if the rear suspension bushes went Ford would only supply, and main dealers would only fit, the whole arm itself. But it was possible, and relatively easy, just to split the bushes out and replace them.

 

[MarkII]

No worries - I got mine from Mercland too, just a week ago.

Small world eh...

Just cos Merc want to flog you the whole unit doesnt mean you have to.

Agreed and I've now found a supplier who says they can supply a new sensor at c£130-150 delivered - if it all goes to plan then I'll post up their contact details as it could save other owners £££'s too.

Aye, why not have a look yourself?

Do I detect a Scottish accent there Guy?
If so, where do you hail from originally?

 

[Yugguy]

No I'm a Lancashire lad but my wife and daughter can trace back to Rob Roy Macgregor.

Funnily enough tho my first car was also a Marina. 1.8tc. Leafsprings and all. I loved it though, first independence, 1987. Back when you really had to drive cars.

 

[MarkII]

No I'm a Lancashire lad but my wife and daughter can trace back to Rob Roy Macgregor.

Well you've bought a 'Stirling' motor anyway......sorry, 'I'll get me coat'

Funnily enough tho my first car was also a Marina. 1.8tc. Leafsprings and all. I loved it though, first independence, 1987. Back when you really had to drive cars.

Ah yes, the good old days: I'm a bit older than your good self, so I spent many a happy hour back in 1982 tuning, modifying and driving mine: A white 1.8, 4dr saloon, with white Weller 8 spokes, 175 tyres, rebuilt suspension with Monroe shocks at the rear and a slightly breathed on engine (ported/flowed head, rebuilt/balanced carbs, pancake filters, electronic ignition and a custom fabricated twin outlet exhaust) - to everyone else it was just a tarted up Marina, to me it was the next entry in the RAC Rally and drifting it in the snow was a great lesson in car control

 

[MarkII]

Quick update: More starting problems over the weekend, so I took the car to a friendly local garage to ask if they could check for a code.

Thankfully the engine failed to start whilst I was there and on two occasions gave a P0193 code (faulty Fuel Rail Pressure Sensor), so I'm more confident now that this is the source of the starting problems.

After some care moving the wiring loom aside, I've now got the part numbers of the current sensor (which is a Delphi unit) and have ordered one from a supplier who say they can provide a matching Delphi sensor - also the price is a quarter of what Mercedes quoted for the fuel rail & sensor (unnecessary).

The Delphi Part Numbers are shown below: 9307Z521A and 55PP22-01





If all goes to plan, I should have the new sensor by Friday and will post up the suppliers contact details.

HTH Mark

 

[Yugguy]

I'd have loved to have seen your old Marina. Mine died of water pump failure, water would pour out when idling but not when at speed so I ended up dreading traffic lights. I had neither the money nor the skill to fix it.

Not as bad as the Yugo 45 I had as a student. At the end of its life it couldn't go faster than 50 and the cabin would fill slowly with smoke.

Great days.