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1993 300SEL (Sold) 2007 X5
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Discussion Starter #1 (Edited)
Hi guys,

I've starting having this weird problem with my W140. Basicly the symptoms are as follows:

Car sits for about a week as I'm not driving it much.

Start car takes a while to start but not really that long a few cranks at most.

Drive car to supermarket to do shopping (about 5 mins or so @50km/h) All is normal AC, radio lights etc all on.

Park car and go shopping return about an hour later.

Car takes a long time to crank and fire (about 3-4 secs) car idles fine.

Place car in reverse start moving off and car dies with battery light on dash. I should say I see no dimming in the headlights nor any of the electrical systems in the car itself.

Try cranking again (once again about 3-4 secs) car starts put into reverse and dies.

I have a powerpack/jumpstarter in the boot so I grab that and use the "test buttton" shows my very new and very large battery is at almost full charge.

With the powerpack connected I start the car it starts although faster than before not as fast as one would think it should.

Use the test button again and it shows car is charging at about 14V amps or whatever the unit of charging the car is. Not too accurate but is well within the "charging" section of the meter.

Remove clips and drive car home car runs fine with lights stereo etc.

Arrive home turn car off then try and start it again this time the car starts instantly I mean pretty much just flick the key and there is life the first time.

Unpack the shopping and return 10 mins later car starts well again turn off start again and it's fine....

I know there is a thread like this already but my symptoms are different. My only thought is that it's a bad battery connection or something but I can't see any signs of corrosion.

Battery new (had charging system checked at shop said it was good)
Spark plugs about 12 months old same with dist cap
New leads about 3-4 months ago
Wiring harness is good
ETA? Don't know
Injectors? Don't know

Any ideas guys?

Thanks.
 

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F250 7.3TD Mercedes Benz W140 S600 1996 119k k's(sold), MB W124 300E 1989 261k k's(sold)
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464 Posts
Hi NZ. Is your big new battery anchored down well? Could there be a little bit of movement which is interrupting the current from the battery? Has the big battery chaffed the earthing lead? I'd suggest removing the battery, checking the high tension lead and earth, dismantle , clean and reassemble with electrolyte gel on the connections.
If the battery connections are good, I'd check the lead to the starter motor - remember our Norwegian member had starting problems because the high tension lead to the starter motor decomposed.
 

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W220 S320 CDI 2005; W140 S280 1994 (Sold Nov. 2012)
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867 Posts
Hi NZ,

I would say that, if your battery is cranking the engine OK - and it sounds as though it is - then there's probably not much wrong with the battery or the connections.

I would think it more likely that the engine is not getting a rich enough mixture while it's cold. I don't know how warm the engine gets after your 5 minute run but maybe, when you come out and restart it, it is still requiring a richer mixture and/or higher idling speed but not getting it. You engage reverse and the transmission drag stalls it.

I would start by checking the engine temperature sensor since the signal from this is used by the engine management to decide on mixture enrichment and raising the idling speed. If it's reading high then the mixture won't be enhanced sufficiently. The sensor actually contains two independent thermistors connected to different inputs on the engine management. I believe that fault code 27 for the diagnostic module indicates whether there is a significant deviation between the temperature indications from these two thermistors. For what it's worth, that's where I would look.

Good luck,

Mike
 

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1993 300SEL (Sold) 2007 X5
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Discussion Starter #4
Hmm, both interesting suggestions guys. I don't think I'll be able to get the car down to the mechanics this week as we're getting into exams at university right now but it's good to know what direction we're heading in.

Simon I'll check the battery when I have a spare moment. As far as the starter goes I'm not sure if it's that as when the car does fire up it works perfectly infact better than it ever has with this new battery.

Mike thanks for the info. Is the sensor a part thats hard to get to or anything like that? I'm thinking that if I try and start the car again and the car fails to start and if I apply the throttle and the car comes to life that will be the sign that something is wrong the mixture as the car should apply that itself?

Considering the temp is getting down to about 0'C here at night at the moment and this was at night the engine would have been pretty cold.

Thanks guys.
 

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Current 1992 - 500SEL, W124 - 1989 230E (sold)
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OK i dont think this has anything to do with your battery/starter or charging. I had nearly identical problem with mine when not driven for week or more, it would nearly stall (kinda stumble) and it would run on like 7 cylinders (or what felt like 5 somtimes) also it didnt matter if i put it in D or R it would stumble same way for either gears selected, at some point car was running so bad that i couldnt even get up small hill(only the second restart after beeing parked up tho), so i have replaced all the filters(air,fuel) and plugs and it got way better but still not perfect, what was strange is that when started in a garage it would be fine but when shut of after 5-10 minutes and restarted it would do that(kinda same as yours)......However recently i have replaced my harness and so far (fingers crossed) it seems to have gone....
Few questions, if its parked for a week and you for long drive (no just 5 minutes down the shop) does it still do that? (mine didnt it was the only short trip that caused issues)

SO this brings me to a another question, is all your harnesses nice and pretty or did you just check the visible parts (like just temp sensor cables etc)? Also good time to do plugs and filters... and see how it behaves after that (it was very noticable improvement for me)
 

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1993 300SEL (Sold) 2007 X5
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Discussion Starter #6
OK i dont think this has anything to do with your battery/starter or charging. I had nearly identical problem with mine when not driven for week or more, it would nearly stall (kinda stumble) and it would run on like 7 cylinders (or what felt like 5 somtimes) also it didnt matter if i put it in D or R it would stumble same way for either gears selected, at some point car was running so bad that i couldnt even get up small hill(only the second restart after beeing parked up tho), so i have replaced all the filters(air,fuel) and plugs and it got way better but still not perfect, what was strange is that when started in a garage it would be fine but when shut of after 5-10 minutes and restarted it would do that(kinda same as yours)......However recently i have replaced my harness and so far (fingers crossed) it seems to have gone....
Few questions, if its parked for a week and you for long drive (no just 5 minutes down the shop) does it still do that? (mine didnt it was the only short trip that caused issues)

SO this brings me to a another question, is all your harnesses nice and pretty or did you just check the visible parts (like just temp sensor cables etc)? Also good time to do plugs and filters... and see how it behaves after that (it was very noticable improvement for me)
The harness appears fine, when I purchased the car in late 2005 the shop whom I had carry out the PPI knew about the harness issues on the W140 and commented that it looked almost new to them. Coming from Singapore I wasn't suprised to find that it was most likely replaced earlier. All the visible parts look really nice but like you said I don't know whats under it. Still though most wiring harness issues I've seen come about when the harness is pretty obvious. One thing though I had the radiator replaced over the summer...do you think the harness or temp sensor could have been damaged or not put back on properly when that was done?

As far as plugs and filters go the car was serviced in Feb and also at the start of 2007 I had all the plugs and fuel filter changed it's done about 35000km's since then are they ready for a change again?

Thanks for the info.
 

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Current 1992 - 500SEL, W124 - 1989 230E (sold)
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They shouldnt have touched any plugs to replace the radiator, its not in a way of anything, however have a poke around anyway, check all the plugs and Vacuum lines. By any chance do you know what spark plugs went in? Some dont last very long (30000kms is normal service interval).... if you gonna do them make sure you get BOSCH F8DC4 or F8DC0($4 at super cheap auto ...no NGK platinums or similar rubish)
Air filter wont cause any issues at all, but could possibly be fuel filter, pressure regulator etc....
All i know is that mine was realy bad i did plugs and fuelfilter and it was almost gone and harness made it perfect (car runs fine even when i waterblast engine now so it was definately moisture getting into old harness when car was parked up)
so since you have new harness i would start with cheap basics....
 

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1987 560SL - 1994 S420 - 2005 S55 AMG
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NZ Benz, have you replaced the fuel regulator? I had problems with starting (had to crank 5-10 seconds) after short trips. Might be worth a check.
 

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1993 300SEL (Sold) 2007 X5
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Discussion Starter #9
NZ Benz, have you replaced the fuel regulator? I had problems with starting (had to crank 5-10 seconds) after short trips. Might be worth a check.
I guess that could also effect the mixture also then right? That and spark plugs will be worth a try then.

Thanks.
 

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Current 1992 - 500SEL, W124 - 1989 230E (sold)
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yeh the regulator is here: (so you know what it looks like an how much it should cost)

Your Parts Search Returned 0 Part(s)

you might as well do the filter and plugs tho....
i dont think its worth gettin any codes pulled for this yet as it only happens sometimes
it might be bit of and trial/error so it would be good to start with cheap and obvious stuff....
 

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1993 300SEL (Sold) 2007 X5
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Discussion Starter #11
yeh the regulator is here: (so you know what it looks like an how much it should cost)

Your Parts Search Returned 0 Part(s)

you might as well do the filter and plugs tho....
i dont think its worth gettin any codes pulled for this yet as it only happens sometimes
it might be bit of and trial/error so it would be good to start with cheap and obvious stuff....
What I was thinking would be a good idea also is to get a couple of those "damp-rid" cans and shoving them in the engine bay for a few days. That would hopefully that will remove any dampness that may be causing a malfunction within the harness. That will then allow me to know if it's moisture or not. If that makes no change then I'll start replacing different components. Does that sound like a good place to start?
 

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1993 300SEL (Sold) 2007 X5
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Discussion Starter #12
Just another point about plugs when I had all my components like plugs and dist cap fuel filter changed I noticed a big difference the car still runs really well and is smooth not like when they needed to be changed I'd think to cause that type of problem (the one I have now) would mean a plug would have to be pretty badly fouled so bad infact that it would cause the problem all the time not just sometimes.
 

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Current 1992 - 500SEL, W124 - 1989 230E (sold)
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yeh it does look like some other part but since it only occurs when car has been sitting for while, it does bring me to the whole moisture idea as it pretty wet/cold where you come from :)
 

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W220 S320 CDI 2005; W140 S280 1994 (Sold Nov. 2012)
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Hi NZ,

The coolant temperature sensor is easily accessible. It's located on the side of the water pump casting (upper part), just back from the power steering fluid reservoir. It has a round plug connected to it. Rather than pull the codes, it occurred to me that you could simply remove the plug and measure the resistances of the two thermistors with a multimeter. If they were significantly different then that would point to a problem with one of them.

I tried to check this out on my engine (2.8 l) only to find that my sensor has only 2 pins not 4 - I guess you get what you pay for! All the detailed technical info I have relates to the vehicles for the US market and so doesn't cover the 2.8 per se, but should be correct for yours, I guess.

Have you checked the idling speed when you start the car from cold? The figures I have are as follows:

Coolant temp (degC) ____ P or N selected (rpm) ____ Gear selected (rpm)

___ <0 _____________________ 800-950 ____________ 700-900
___ >0 <=40 ________________ 750-900 ____________ 650-800
___ >40 ____________________ 600-750 ____________ 500-650

Hope this helps,

Mike
 

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Discussion Starter #15
Ok guys I went and gone some "damp-rid" from the supermarket I'm leaning more and more towards the damp being the problem. As a test of how damp it is under there I opened up the fuse box and felt the card fuse diagram that's in there...dampish. So I've stashed two of these things under the bonnet (just must not forget to remove when I drive) and will see in a day or two what the deal will be. The weather down here is a bit better now atleast.
 

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Discussion Starter #16
Ok update:

Seems to have worked! I'm pretty suprised. Since my last post the car has sat. The weather has been a bit drier but I'fe also had those damprids in there and when I turned the key (car was cold and it's about 4'C here) there was instant life :) Moved the car down the road and came back. Turned key off. Turned car on whilst still running electrical sytems such as lights and stereo and once again instant life.

Although thats only half the problem solved...you should be able to keep a car on the street without having to put damprid under the bonnet.

I'm now thinking it might be the wiring harness as the fact that removing the damp caused it to run fine seems to exclude alot of the other things.

I'd be interested in your thoughts.

Thanks for the input guys.
 

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Current 1992 - 500SEL, W124 - 1989 230E (sold)
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Umm solution to you problem = garage :)

No realy... there are other harnesses apart from the one for injectors/temp sensor/cam solenoid (the actual engine harness)... it would be good to check condition of those(they run over the engine in that skiny tray). Since it seems to be just moisture causing issues i doubt it will be much else. Otherwise things like sparkplug cables, quality of fuel come to mind ...you know it sits for week, water condenses inside the tank and then you go for drive by the time you get to shops you have used up the fuel in hoses and fuel filter and upon restart you suck in bit of water.....i know nice story but could be possible, you could try to fill up(get pre-approved for bank loan first :D) and put in some fuel stabiliser and see if it runs ok after week with no moisture absorbing thingies...

In the end...
I know this wont be much of a solution but it has been said many times that W140 just doesnt like to sit.... (i had mine parked up now for almost a week, just want to realy test out if the new engine harness solved that problem, if it doesnt work then i think i will be in pretty much same boat as you, will let you know....)
 

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Ok, this is going a bit off topic, I’m sure I've read somewhere else that the W140 doesn’t like to sit, mine sat in a container for almost two months and started fine/ran fine, then another month or so, same thing, and again no problems. when i gave the engine a wash, i hosed it down good an' proper, i mean i really sprayed water all over the place, tried to start her and she wasn’t happy at all, eventually found the spark plug 'wells' were full of water, so i got out the compressor, blew out the water and left the hood/bonnet open overnight, the following morning, started, idle wouldn’t settle and engine would cut out, left bank had a weird consistent whine, like a servo or something that wouldn’t shut down or close a valve (dunno), then a LOUD metallic ping, i thought something expensive just broke, but immediately after that, she settled into a nice butter smooth purr and ran fine.

Like I said, it’s a bit off topic, but since we’re talking about moisture and idle…. Anybody have any suggestions what the LOUD ping might have been?
 

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1995 S420 19" giovanna's, tint, in-dash tv.1986 mustang LX supercharged 4 eyed pride~
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the loud Ping was from the guy teeing off on #9.
 

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1989 560sl, 2016 G63
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Not that this helps...

...you out, Conky, but I was told years ago when I bought my first W140 to never, ever, ever pressure wash under the bonnet. In fact, I wouldn't permit it to be done on any car. With all the electronics in modern automobiles, they are designed to accept a bit of water coming up from the bottom, but not a high pressure blast from above. I hand clean my motor with toothbrushes, small rags and simple green, being careful to avoid electrical components.

When I had my S-500 resprayed last November the muppets at the paint garage pressure washed the motor after I asked them specifically not to. Result, loads of electrical faults, faulty indicators and damaged grounds. I passed along the repair bill to them which they refused, of course.

I would take your W140 to your favorite mechanic and have him run a diagnostic to located the faults. Short of that you may have endless issues with water invasion already having done the damage.

Best of luck with it.

Cheers,

R.
 
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