M113 V8 hot start woes

[rgv250ads]

Symptoms:
car starts and runs fine fron cold. No issue with battery or alternator.
once upto temp, if turned off and left for anytine, say filling up with fuel, it wont start.
Leave it to cool for an hour or so, it will start but very laboured. No engine management light or any clues.

so.......
classic symptoms of crank position sensor. Changed that......... great,
but alas no, went for a drive drive today, parked up, returned to car after 20 mins, wont start, turns once but nothing.
Battery fine, roof operates, all good. Leave for a further 2 hours to cool down, fires up no problem.

I am now thinking camshaft sensor, just replace it as part of process of elimination.

Do you think it coild be anything else. Alternator and battery all fine.
Adam.

[rgv250ads]

Mike.T said:

Are there no fault codes? Definitely worth trying a camshaft sensor if there aren't. I've changed one for this fault after initiallly changing the camshaft sensor.

Hi Mike
Dont have a code reader and am yet to take the car to my MB Indy..... Interesting that you changed both. assume the issue went away after changing both...?

[rgv250ads]

Murph7355 said:

Starter motor/solenoid?

Hi Murph, if it was either item, wouldn't this be prevalent upon starting everytime not just hot starting? i am curious to learn if a hot starter motor and or a hot solenoid would cause the symptoms i'm having.

[rgv250ads]

Just spoke to my MB Indy - He said if it was a downed Crank or Cam sensor the typical symptom is continuous cranking but will not fire into life. I dont have that, what i have is when hot, it wont even crank over, akin to the caterham description above. I get one turn of the motor then Klunk, wont even crank when hot.

So i'm thinking Starter Solenoid and or Starter Motor itself.

Any other thoughts?

Thanks for the input so far. It's going into the Indy on Saturday for full diagnosis while hooked into STAR. Then it'll definitely be resolved one hopes!

[rgv250ads]

Yea but to rule out the battery & alternator i went for a drive after it started, put everything on and i mean everything, full chat (heated seats, air scarf, heated rear screen, headlights) then got home, turned it off, operated the roof multiple times, basically putting huge drain on the battery and alternator.

Would not start (as was hot) so thought okay if this is battery/alternator related it'll be dead in 5 hours or so when all cool. But alas no, fired straight up and even when switched off immediately, still powered the roof and seats etc without any complaints.

I am convinced it is Starter Motor/solenoid/starter wires, that sort of thing.

Really appreciate the comments on this thread tho. Doesn't it just boil you piss when you have intermittent faults!

[rgv250ads]

r129sl said:

Assuming the replacement CPS is not a bad one (never heard of that before), it does sound starter motor-related. I have had two cars on which either the starter motor has failed or the wiring to the starter motor—specifically the earth strap—has become disconnected and in both cases the failure was at first intermittent. I did not notice a temperature correlation, however, but nor did I rule that out. I guess the temperature could be significant if there is a very fine or partial break in any part of the wiring. I would look to the wiring first. My m113 engine has 260k on it and the starter is fine; I have another Mercedes on 350k and the starter is becoming noisy (and will be replaced this Friday) but is still the original.

Valuable Info. Thanks for replying.

[rgv250ads]

Mike.T said:

Sorry, I read your first comment as it would only start when it cooled down after cranking for a while. Until recently I worked in Mercedes for 11 years and this was a common problem but the car would not normally even bring up a fault code for the crank sensor so if there was no fault code rather than spending more of the customers money hunting around it was cheaper considering the price of the sensor to just replace it. One time it didn't rectify the fault and after a bit of hunting I found the cam sensor wasnt picking up the reading off the cam so I replaced it and rectified the fault. However if it's not cranking at all it is possibly the starter motor even though I'd never experienced an issue with them when they get warm. Let me know what fixes it, I'm curious to find out.

Mike thanks for your reply. I will report back once fixed!

[rgv250ads]

Key Start.

[rgv250ads]

MB Indy has reported back it's a Dying Battery.
seems after loading and once hot (in engine bay) this is when the battery is at its weakest

Dead cells in it.

Dated 2005 so original fitment.
So strange, as it's on a CTEK charger with green lights and what not. So seems to hold a charge and maintain one, yet that is the source of the problem.

Anyway, new battery going on (MB part) and we'll see how it goes. Maybe putting it on a CTEK was disguising the issue but it's been on the CTEK since i got the car in 2014.

I guess 10 years is a decent stretch from the Battery.

[rgv250ads]

1st world problem i know, but resetting all the Audio and what not after the battery has been swapped will be a right PITA ! however, being stranded at random locations is somewhat more annoying . . . .

My Indy says the MB Genuine ones are a cut above quality wise, and only 10% more than Varta (he gets OEM and decent discounts from a Merc dealer as spending some £30k a month with them on parts).

I am happy to follow his guidance as he knows his stuff and i trust his judgement. Plus if we move on to Sensor style failures later (as i suspected this time) then we know a MB battery went on it and he fitted it.

Least I got a new Crank Position Sensor fitted (knuckles still bleeding TBH) so i know that has been done, as it was likely to start giving up the ghost sometime now anyway, lucky to have got 10 years out of it reading Internet stories on CPS on the M113.

Adam.