W220 Intermittent hot start problem

[Eddie01]

After some feed back for hot start problem,

2002 S320 CDI (W220)
Recent work in past 1000 miles
A service with additional work (Prestige Car Service )
High pressure fuel pump
Fuel return lines (All replaced)
2x injectors re-seated (new seals)

Symptoms, “Intermittent”
NOTE, currently only a hot start issue not cold start;
Shut down engine after a run (full operating temperature)
Leave standing for approximately 10 minutes
Cranks but doesn’t fire
No malfunction alarms displayed on dash (although I think the excessive cranking would have been logged)

After searching for possibilities (Google is your friend )
Crank Shaft Position Sensor
Low fuel pressure due to air ingress (Injector not closing or leaking line)

I’ve found plenty of documented reports with above fix recommendation but not accompanied with post result fix?

Next is diagnostics analyser to recall faults

I’m open to suggestion of things I may have overlooked?

Eddie

 

[Dieselman]

The crank sensor is the No1 hit for this. You can meter it with a voltmeter to see if it's working when cranking.

Just replace it anyway, if it isn't failed it will do sometime.

 

[momomo]

Yup i agree with Dieselman, these go all the time...

 

[BlackC55]

Not on 320 CDI's they don't!

 

[momomo]

Not on 320 CDI's they don't!

Of course not very common CDI's! I meant in general they go all the time on Mercedes. Its funny actually a while ago the dealership told us we needed to change the one on our 320 CDI when in for some warranty work, when the car was running perfect as it should.

 

[AllanE]

I don't know how this ECU works, but most I have dabbled with only need a crank sensor signal to keep fuelling after the starter has stopped cranking (meaning: Cut fuel if engine stops).
If the symptom has only started after the work was done, I'd check for leaks first.
Do diseasels have fuel pressure regulators? If so, that may be worth a check.
You could remove the fuel rail just after a run (careful, things will be hot!) and see if there is any sign of an injector leaking.
Has the fuel filter been changed? If not, this could be blocked enough to stop the car starting - I presume diseasels need a 'rich' misture to start like petrols...

 

[alexander patie]

nope, this is typical crank sensor issue, and not unheard of on the 320cdi.

 

[Eddie01]

Thanks for the input guys, much appreciated.
Car had new fuel filter, high pressure pump, fuel lines and injectors re-seated, been perfectly behaved for the past couple of thousand miles.
Decided to pop back to Prestige Car Service and have him take a look, I'm sure there must be a code stored that will point in the general direction.
When diagnosed and fixed I'll post up for future reference, should help people.

Eddie

 

[Mark300SL]

Eddie was round mine today and I witnessed this for the first time

After getting to me (1hr drove) and leaving the car for 15/20 mins it didn't want to start
Tried again 10 mins later and it "caught" and the end of a very long crank. After letting it run for 60 seconds and assuming any fuel pressure issues would have been eradicated I got him to switch it of and try again - Again it cranked for about 20 odd seconds before firing and then idling as normal


Ed is hopefully going to be able to take it to Ollys next week and hopefully we will at least see if its stored a code

 

[BlackC55]

I feel this is an injector fault. We will see though.

 

[alexander patie]

why not the obvious crank sensor olly? if it has not been changed yet i think it needs careful thought...

 

[BlackC55]

Sure I will check it i always do on these type of faults.

 

[alexander patie]

fair enough, difficult with intermittent faults isn't it? i always prefer one that arrives on the back of a truck and refuses to start, the car that is ok for two months then plays up for 1/2 hr is often impossible to find by testing.

 

[jonnyboy]

fair enough, difficult with intermittent faults isn't it? i always prefer one that arrives on the back of a truck and refuses to start, the car that is ok for two months then plays up for 1/2 hr is often impossible to find by testing.

Like so many things - we had a boiler intermittent problem - I ended up camcordering the fault to help the engineer - sorted.
Also I'm having intermittent breathing problems - the consultant is soooo frustrated its never been present when I've seen him......

But then again, getting to the bottom of a PITA is alway much more satisfying than rectifying run-of-the-mill things. Its probably why I do tend to take on jobs other contractors price themselves out of.....

 

[alexander patie]

But then again, getting to the bottom of a PITA is alway much more satisfying than rectifying run-of-the-mill things. ....

absolutely, but not getting to the bottom of a PITA is tiring and soul destroying! not that i ever fail of course .

had a fun one last week, w210 with failing cruise control, works up to 50 mph then not above. no esp faults, checked all usual issues like tyre sizes/pressures and scanned all modules etc etc. the only 'problem' i could find was an excessive variation in front wheel speeds at a steady speed - at 90 k/h they both varied up and down by >5 k/h. i suspected poor signals from the front and the output was only around 0.2mv (ac) both sides when spinning the wheels at 60rpm - should be >0.5mv. the customer took it upon himself to jump the gun and buy 2x front sensors which we fitted for him, no change. we then inspected the front hubs as i had suggested and lo and behold the exciter teeth were badly rusted! 2x new hubs later and all is well, shame he wasted the money on those front sensors though! a very happy ending for us, and vindication of the thorough and methodical approach.

 

[jonnyboy]

trigger-happy customer, eh ?
yes, i get them too !

got a couple of packs of bricks sitting at sites unused as the wrong ones..........

that reminds me, when I change my truck, get one with a HIAB for the freebie collections!!!!

 

[Eddie01]

I'm booked in to see Olly tomorrow morning, car will be up to operating temperature by the time I arrive so I can let it sit for a while and the problem will replicate.
As per opening post, my initial thoughts were CPS but it wasn't, what I term classic symptoms hence the post.
Anyway, hopefully Olly can get to the bottom of this

Eddie

 

[alexander patie]

i am sure olly is the man, he gets constantly good reviews on the forums.

 

[BlackC55]

Got the car in now.

What do you all think it was?

 

[Mark300SL]

I think I have an idea



Mark