W124 engine cutting out/no starting - possible OVP relay ?

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Max_London

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Oct 29, 2012
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Hello everybody !

my name is Max , please to meet you all
I found the forum very interesting , with a lot of people with great knowledge and experience !
I was trying to do some research , but I couldn't find the answers that I need to understand the problem with my car
I hope maybe some of you can help me .. and I apologize in advance if some topics has been discussed previously

I have a W124 TE200 1992 .. and I have problems starting the car , actually it doesn't start anymore :wallbash: .. and last time I've used after it took me 5 minutes to start , eventually was stalling/cutting off badly … at the beginning only at low revs .. and after that the cutting increased .. so I just parked the car somewhere safe and that's it

after my research on here I have found some possible issue with that ..

wiring loom ?
OVP relay ?
Distributor cap ?

the wiring loom looks quite good to me .. but obviously this things need a bit of time involved and a proper check .. I only looked superficially ..
also .. I found always here , that the problem with the wiring loom affected mainly the models with the multi-coil set up on later M104 engines
" apparently " earlier models with M102 , M103 shouldn't have this problem
(my one is a M102)
is it that possible ?

OVP relay then seem to me a good explanation .. if only could I find it ! .. where is it on my model ? definitely not near the battery ..
or at least it doesn't looks similar to this … which is the one found it on google image

2009-11-13_223147_ovp_relay.PNG



I've checked, just behind the fuse box , there is another compartment with something that looks like it .. but I'm not sure which is which ..
I found this one .. which it may be a multi-relay ? .. perhaps something to do with this ?


photo31xpp.jpg


photo31xpp.jpg



Distributor cap has been replaced 3 years ago , but a friend of mine said to check that out as well .. you never know .. :cool:

any suggestions ?

thanks in advance

Max
 
Overvoltage relay is by the battery it is the silver relay with a fuse in the top.was the abs light staying on.? If it was then the Overvoltage relay is at fault check the fuse in the top of it dist cap could also be at fault
 
Overvoltage relay is by the battery it is the silver relay with a fuse in the top.was the abs light staying on.?

Honestly .. I couldn't find it near the battery :confused: ... I will give it another try tomorrow .. I don't remember the ABS light .. need to check that as well ..

thanks anyway .. I will keep updated
 
Remove the black plastic cover behind the battery, the ovp relay is on the right by the inner wing.
 
Ok ... I will definitely try that tomorrow ..

thanks for your help

Max
 
IT WILL NOT BE THE WIRING LOOM as you correctly surmised. 2 things stop a car from running fuel supply and/or ignition problems. First port of call for me would the fuel pump relay- which supplies power to the fuel pump - if its faulty the engine will get no fuel. Second would be ignition This could be the HT [ high voltage] part of system= distributor cap /rotor arm/ coil or the LT low voltage section= the transistorised ignition bit--- the EZL ignition unit--- the ignition switch-- and indirectly the ENGINE ECU powered via the OVP [ OVERVOLTAGE PROTECTION RELAY]
First make sure the car's battery is charged up and the engine is turning over briskly on the starter. Then check for a strong smell of petrol and the sound of the fuel pump running---- both things positive--- fuel system possibly OK and its an ignition fault. then remove one of the spark plugs and lay it on a good metal earth on the engine- [don't do this by disconnecting the HT LEAD keep the plug in circuit as a load for the ignition] look for a strong fat spark. this should help you where to look next?
 
Can you hear the fuel pump running? Distributor caps frequently fail. Well worth getting the MB original if it has gone. The OVP relay is involved in all sorts of things including the fuel pump. Certainly worth checking if you can here the buzz from it before cranking the engine. There is a fuel pump relay and both it and the OVP relay need to be in good order for it to start
 
Hey guys ... thank you very much ..

I really appreciated your help

I didn't listen the fuel pump relay because unfortunately , all the time I turn the ignition , I have the bloody antenna of my radio going up automatically , so I didn't pay to much attention .. that's what I should have done !
probably best thing I would do tomorrow , I open the bonnet , turn the key on , and I'll go close to the relay to see if I can hear anything .. or maybe I'll ask a friend to come over and turn the key ..
I think may that be gone as you said .. because normally you would hear that wouldn't you ? .. no matter the antenna ..
I bought the car recently and I haven't really used that much .. so I don't remember really if I could hear it before ..

I'm glad to exclude the wiring loom anyway .. :rolleyes:
 
The fuel pump is at the rear. Best to listen at the drivers side rear wheel. If its not running its more likely to be one of the relays than the pump itself.
Also check the distributor cap very carefully. Tiny cracks or moisture can cause it not to start.
 
Thanks guys !

I had a quick look just now ..

I couldn't hear the fuel pump (was quite clear to me , but then again ... need double check with a friend seated at the back .. hopefully tomorrow) ..the ABS light remains on , I found the OVP relay .. and after disconnecting it I check the fuse but seems ok ..
obviously I think replacing it is probably the best thing to do ..

I don't think will be able to look at it again before tomorrow .. but then I will check the distributor cap as well ..

thanks for now

Max
 
The relays can look fine but have dodgy joints inside. Our 280 needed both the OVP and fuel pump relays changing. They deteriorate over time Im afraid.
 
Ok .. looking at the positive side of it , even if I replace them both + the distributor cap , it will be still cheaper than the wiring loom .. which was my initial worry !

and also I can do it myself easily with no big time involved ..
let's see how it goes ..

cheers

Max
 
Ok .. looking at the positive side of it , even if I replace them both + the distributor cap , it will be still cheaper than the wiring loom .. which was my initial worry !

and also I can do it myself easily with no big time involved ..
let's see how it goes ..

cheers

Max

If you have a conventional distributor cap, I would guess you have the KE Jetronic injection and those, to my knowledge, never suffered the degrading wiring loom.

Just a thought.

R
 

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