W124 Engine bay wiring looms

[coupe addict]

american sourced wiring looms

I'm still struggling with my US version wiring loom. These are widely available on eBay at around £250, so there is a compelling reason to try to make it work.

The lhd issue hasn't been a problem - the MAF connector has to be rerouted because its a little shorter, and the main loom has some excess length to find a home for, but that all works OK.

The big problem is with the ETA wiring, which is not present on the american loom at all - presumable being a seperate item. I have spliced in my old ETA connector (with much added insulation - it really was awful), and the car starts on the button and runs apparently perfectly - BUT - I cannot get it to idle. Presumably either I have messed up on splicing in the ETA wiring: or I've omitted a sensor: or I've generated a new fault by, eg, breaking a vacuum pipe.

Diagnosis would be much helped if I knew more (!): particularly if I knew how the ETA acquired its information about idle speed - is there a specific sensor for this?

My only known anomaly with the loom at this stage is that I have an extra connector at the very front of the engine block for which I can't find a sensor. I had imagined this to be for the EGA - which my 94 E320 coupe does not have, I think. Am I wrong about this? Is there a lurking, idle speed related, sensor that I have failed to spot?

Any help would be appreciated: if this can be cracked, not only will I get my beloved coupe back on the road, but also I will be able to show how to use the much cheaper US component in this country.

 

[susan.david62]

I'm trying to replace the loom on my (adored) e320 coupe, 1994, but without getting a mortgage. I bought a loom for a U.S. model 94 coupe which seems to be identical in all respects except that it has no wiring for the throttle actuator.
I anticipate that this could cause some problems driving the car so I'm thinking of grafting the 8 pin ETA wiring from my old loom onto the new one, which seems to have 8 less pins utilised on the ECU multiway connector which might (in a simpler world) correspond.
For this I would need to know the pinout for the connector, and also how to enter the sealed connector without destroying it.
Any information would be gratefully received.
coupe addict is offline Report Post
I'm surprised the loom is similar, because the battery and ECU is different side of engine compartment to our UK models, but the engine is same layout.

I guess you will just have lots of slack in the cables near the bulkhead.

I find your post confusing, as I cannot imagine a missing set of wires to the plug which attaches to the throttle under the inlet manifold. Are you suggesting the US models have a seperate set of wires (a mini loom) for the throttle ?

 

[coupe deville]

. Are you suggesting the US models have a seperate set of wires (a mini loom) for the throttle ?

Not just the US models, my coupe has a separate loom for the throttle body, see post number 111, the 104 loom shenanigans is a complex nightmare because nothing is straight forward. Before I changed my loom I had a fault code for an injector short circuit although the car appeared to be running ok, clearly it wasn't as it is now running much better, so good in fact that I think it has too much engine for the chassis [new steering components and new front springs and bilsteins all round, nothing wrong with the chassis ] and I need a supply of brave pills to keep the right foot planted on the twisty bits.

Coupe Addict I think you have a connector that you don't need and I wouldn't worry about that PeachPartsWiki: W124 Engine Wiring Harness Replacement, see the pic halfway down.
I would clear the codes with a blink tester, then run the engine, go for a drive if thats possible and then check codes. If you still can't sort it you need to meet up with a friendly Cornish coupe owner where you can stick your head under his bonnet to try and get some ideas. Failing that, a good indie, wish I could help but I'm 250+ miles away, good luck with it, you must be tearing your hair out.

 

[coupe addict]

US loom a cheaper option

I finally cracked this (thank you to Grober and Coupe de Ville for help and encouragement) but I can't make a post long enough to describe how without being timed out by the forum. PM me if you want the details - it worked and cost about £400 including rewiring the ETA, so its a big saving.
Steve

 

[Pigpen]

If you could find the time to type it out in notepad then cut n paste into the forum I'd be really grateful.

PP

 

[coupe deville]

I finally cracked this


Glad to hear it, well done

 

[coupe addict]

I spoke too soon - the Eta wiring also failed and now I have an ECU problem arising from failure of the ETA wiring. However, in principle I can see how to make it work - once its done I will write it all up and post it here - I owe that to the members who've helped, especially Grober and Coupe de Ville -tks.

 

[DanSL]

SL 500 - R129 V8 Loom

Has anybody had one of these pack-up on a 92-95 model or have any of you indy's had a car in needing a repalcement?

I have recently spoken to a guy at a respected indy who is admant that these are not a problem on the V8 R129's and I also read this on a yank forum if I remember correctly.

 

[Doodle]

Pffft. That's crap.

Here's an example of a 1995 wiring loom from my car

 

[DanSL]

Much as I thought - guess the guy wasn't upon R129's.

Doodle; take it you've replaced yours - did you do it for good measure or was the car playing up and what did it set you back please?

 

[Doodle]

Preventative - knew it was bad and didn't want it to get any worse and cause damage.

It was around £600-700, I don't remember exactly.

 

[DanSL]

Could I please get some advice as to the simplest way to check out the loom on an SL 500.

Thanks

 

[Doodle]

I'm sure it's been mentioned before on the thread, but pop the airbox off and have a look at the state of the wiring loom insulation, especially near connectors and where it's exposed.

If it looks like the ones above, crunchy insulation and exposed wires, the loom has had it and needs replacing.

 

[jackafrica]

I've just picked up my 3/95 E280 with the M104 and removed the cam valley cover, the ECU cover and checked all the sensors I can see which would be part of the wiring loom, as well as the injector plugs and I cannot see any degradation of the insulation, in the areas where it is exposed. No brittle insulation, or even moving the wires I can see has cracked the insulation.

The car has a MB dealer service history for 15 years perhaps it has been replaced.
My inspection draws me toward this conclusion.
I've looked carefully at the loom from the engine ECU to the side cover holding the injector wires as well as in the valley cover and cannot find an identification tag.
From the dust in the engine bay, the loom not been disturbed recently.

Is there a definite method or way of determining whether the loom is a replacement or the earlier fragile jobbie?

Cheers
Richard

 

[jackafrica]

Well I am still unable to find an identification tag on the loom.
It is definitely a replacement, the wire insulation material is flexible and exhibits none of the degradable qualities obvious as those shown in this thread.

There is a grommet missing, which is would be located on the sub-firewall (for want of a better description) near where the loom enters and exits the engine ECU on the left side.

As others have alluded, removal of spark plugs and disturbing the loom generally, IF IT IS A BAD ONE, will usually result in some sort of fault.

Surely, after the number of years that have passed nearly all the affected cars would've been rectified.

I'd be interested to know if anyone has had a loom replaced more than once for the same fault of the brittle insulation.

 

[coupe addict]

loom label

There should be a small paper label on the loom just inside the battery/ecu compartment, immediately behind what you call the sub-firewall or even hidden by it. This will have the part number and crucially the date of manufacture. If <1999 , if >1999.

Steve

 

[RichCC]

Hi

Just joined the club.

I have the dreaded harness decompostition problem and have found this thread fascinating.

I'm looking for a donor loom (willing to pay) so I can make up a new one to replace the dusty problem I have

Martyn n mentioned one in post 37 - - - is it still available ????

I plan to try and make a tutorial with all the information I have gathered and getting a donor loom will be the last part before I start

Cheers

 

[Martyn_n]

Sorry Rich I've thown mine away. Welcome to the forum and good luck with the rewire.

 

[coupe deville]

I still have the old loom, doesn't have the throttle body plug, see post 111

 

[RichCC]

Thanks Martyn. Never mind

Dave do you want to get rid of it, I'm happy to pay

As a newbie I can't pm so my email is [email protected]

Cheers

Richard