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Momentary Power Loss

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chris18

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Joined
Aug 22, 2007
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11
Not sure if this should be posted here or under engine problems.

I have a 1996 C200 Elegance Auto Petrol chassis number: WDB2020202F426553

During the last two weeks I have begun to get sudden power loss when trying to accelerate hard. For example if I put my foot down as I would to get kick down the power drops but as soon as I take my foot of the accelerator the power returns.

If I allow the speed to build sedately then everything is fine and you wouldn't know there was a problem, the car runs like a dream.

Sometimes the fault clears on it's own and I get full kick down for a time.

The fuel pump pressure is fine (4.0 BAR) but was told it could be the Air Mass centre (Meter) but a mechanic friend of mine, who is head mechanic at a local non MB dealership, came to take a look and said he could find it where he would normally expect i.e in the air intake so assumes there isn't one fitted. Which is strange because I got a quote for the part from the local MB dealer when I quoted my chassis number.

Was also told there could a switch under the accelerator pedal which triggers kick down but can't find anything all I can see are two black what look like throttle stop fittings.

Since I bought the car 4 years ago from Simpsons in Maidstone I have a number of problems. Radiator, head gasket, ECU (repaired but failed after 12 months and repaired again under the repair warranty).

Given this and the value of the car (£1500-1800) and also that I was told on the last MOT that the silencer was beginning to breakdown so will need replacing in the not too distant future, I am seriously considering disposing of the car rather than chase good money after bad.

I could probably part-exchange the car to a dealer provided they don't do a full road test but it would obviously be better if I could get it running 100%. I couldn't in all concious sell it privately and pass the problem onto someone else.

I believe if I decide to destroy the car then under the End of Life Vehicle (ELV) Directive I can contact MB who will put in touch with their authorised treatment facility (ATF), where a Certificate of Destruction (CoD) will be issued and the car destroyed at no cost to me.

Does anyone know if this is true and how the system works?

Have even though about selling it to a breaker for spares but don't know if it's worth the hassle.

If anyone car offer any help as to what the problem might be, and also where the Air Mass Centre is located I would be very grateful.
.
Thanks
 
Thanks
According to the log book the first digits of my engine number are 111941 so it doesn't look like it had an MAF fitted. Out of curiousity what are the differences between the 111941 and 941945 engines?

My daughter was driving the car, she had borrowed it for a couple of weeks, when it first happened and eventually she had it relayed back to me end of last week as she thought it would fail. The breakdown engineer said he had tested the fuel pump pressure and that was OK but still thought it was a fuel related problem.

The "off the cuff" diagnosis of my mechanic friend, who has looked after the car since I bought it was that if the fuel pump pressure was OK then all the symptoms pointed to a faulty MAF which was why he was confused when he couldn't find one, especially as like me he had been quoted the part by a local dealer based on the VIN number.

Having looked at the car and road tested it he thinks it is some sort of electronics breakdown. He doesn't have specialist diagnostics equipment so can't go any further and the guy he uses, who dealt with my faulty ECU, is on holiday.

He did say I could take it to the local MB dealer and have them run a test but thought this would probably cost about £100 which for obvious reasons I'm not to keen to pay out.

Having come across the forum whilst browsing I was hoping that perhaps someone could give me some pointers as to the likely cause so that I could pass these on to him and he could investigate.

Don't know if this is signifcant but when I started it up this morning it wouldn't tick over initially. My mechanic friend had slowed the revs down last night as he thought they were a bit fast and might have been adjusted by the breakdown mechanic. In the end I had to set the revs in Parked to about 1800 which gave me about 900 in Drive and it was OK. I'm going to try it again tomorrow as my friend has suggested I drive it and see how I get on.
 
May be a FUEL PUMP RELAY which also has a "kickdown " function if your age of car still has one? Usually found behind the battery beside the ECU marked kickdown and 4 zyl on the top.
 
grober said:
May be a FUEL PUMP RELAY which also has a "kickdown " function if your age of car still has one? Usually found behind the battery beside the ECU marked kickdown and 4 zyl on the top.
Click to expand...

All MBs, no kick down = fuel pump relay goes open circuit on on of the PCB tracks, just bridge with wire and solder up
 
Thanks for the replies.

grober

Will take a look and see if I can locate the fuel pump relay as you describe. My battery is in the boot by the way nowhere near the ECU. Where is the best place to look boot or ECU??

television

If this is the fault am I right to assume the open circuit is on the PCB is in the relay itself? Does it need specialist equipment to identify which track needs bridging and to access the relay innards?

After bridging does it just mean that the kickdown function isn't available but the engine will run as normal that apart? Can you still accelerate quickly if you need to get out of trouble?

How much of a job is it to replace the relay and any idea of cost?

What were the two differences between the two engines as mentioned in your earlier reply.

Thanks
 
Last edited:
The relays are easy to open and in most cases the breaks in the track can be seen.

Its a waste of money to buy a new one, if you are unsure of this type of work, any TV repair guy that works from home can do it in minutes, including a blanket solder. (re solder all connections)
 
The location of the fuel pump relay varies according to the age of the car. In the early cars its located in a holder beside the auxiliary fuse box beside the battery in the boot. The other relay locations are
1. in the relay compartment behind the fuse box located beside the brake servo. remove the lid of the fuse box held on with clips first then remove the 3 screws holding on the fuse box surround this then allows access to the relay compartment.
2. other relays may be in the module box (if present) at the opposite side of the engine compartment --again at the rear of the engine compartment near the bulkhead.
 
Thanks for the replies & info.

As soon as it stops raining I'll see if I can locate the relay. From your reply grober it's probably in the boot with the battery.

Been out in the car this morning and it ran OK until I tried kick down.

At the moment the tick over is fast because I had to do that last night when it wouldn't idle initially.

Would a defective fuel pump relay affect the idling?

If it is the relay then my mechanic friend would be more than capable of doing the repair.

Thanks
 
An intermitant fracture on a PCB can right its self or go faulty when ever it pleases

The biggest problem with them is 2 dry joints, solder them up and you can discount that component.

Always start with basics, as basics are still responsable for most car faults
 
Just had a thought. What actually triggers the kick down? I assume there must be some switch that activates the fuel pump relay in a special way to provide kick down when the accelerator is fully depressed?

Dry solder joints are always a problem, as are PCB fractures, as I've found to my cost when doing model railways and building other types of modelling circuit boards. They can also be a devil to find if intermittent.

Want to give as much info as I can to my mechanic friend from suggestions given here in the hope that he can do an easy fix to the problem.
 
chris18 said:
Thanks for the replies & info.

As soon as it stops raining I'll see if I can locate the relay. From your reply grober it's probably in the boot with the battery.

Been out in the car this morning and it ran OK until I tried kick down.

At the moment the tick over is fast because I had to do that last night when it wouldn't idle initially.

Would a defective fuel pump relay affect the idling?

If it is the relay then my mechanic friend would be more than capable of doing the repair.

Thanks
Click to expand...

Hi Chris, sorry to hijack your post, I also have no kick-down and erratic idle!

Just been out to look for the relay in question & I'm b*ggered if I can find it. Not in the main fuse box or the other main electrical box on the other side of the engine (or at least as far as I can see).

Mine is a 210 2.3 Petrol 1996, battery under the rear seat.

Also searched WIS, but to no avail.

Any ideas where to look, anyone?

Cheers
 
Hi Westy

No problem feel free, perhaps between us we can crack both problems.

Malcolm

Not to worry perhaps someone will be able to tell me. Looking at things logically if Westy has the same sort of problem on his car then no kick down and irratic idling would seem to be linked, perhaps to the fuel pump relay??
 
Last edited:
Westy said:
Hi Chris, sorry to hijack your post, I also have no kick-down and erratic idle!

Just been out to look for the relay in question & I'm b*ggered if I can find it. Not in the main fuse box or the other main electrical box on the other side of the engine (or at least as far as I can see).

Mine is a 210 2.3 Petrol 1996, battery under the rear seat.

Also searched WIS, but to no avail.

Any ideas where to look, anyone?

Cheers
Click to expand...

Not familiar with your model but maybe here? http://w210.pietrzyk.net/electrical_contmod.htm
 
chris18 said:
Hi Westy

No problem feel free, perhaps between us we can crack both problems.

Malcolm

Not to worry perhaps someone will be able to tell me. Looking at things logically if Westy has the same sort of problem on his car then no kick down and irratic idling would seem to be linked, perhaps to the fuel pump relay??
Click to expand...

Thanks Chris, much obliged.

I'm not sure if the erratic idling and lack of kickdown are linked, but it's certainly something worth investigating.
 
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