3.2 starting issues

[Dieselman]

Have you got a spark tester. It's unlikely all would go down together but not impossible depending on the cause.

I take it this is electrical injection (Motronic), if so a set of node lights for the injectors would tell you if they are triggering. Maybe you could make some using LED and resistors.

 

[Mark300SL]

Have you got a spark tester. It's unlikely all would go down together but not impossible depending on the cause.

Very close

It has the infamous engine harness issue - but only to to the coilpacks ??
I know ECU damage is likely, as well as coilpack damage but for now I need to rebuild the harness to the coilpacks.
3 " away from the head the harness is absolutely perfect, all the injector wiring is flexible and healthy as are the other conenctions, however where the coilpack wiring enters the head it has disintegrated. I sliced open the point rubber where it enters the head and there is no insulation left at all!

Obvioulsy when I removed the coilpacks I also disturbed the last remaining areas of insulation between the coilpack wires causing a short somewhere.


So - its all my own fault for wanting things clean



Anyone got a coilpack loom (or complete engine harness) for an M104 engine ?



Mark

 

[television]

Is it not feasable to make a new one from the old and do it wire by wire

 

[Dieselman]

Better to find it now while the car is still under 'shake down' rather than in regular use.

Why not fit a fuse in the line from the ECU to the coils.

I take it the +ve side has shorted out as if it was the -ve returns not all would go down together as they are on different lines and output chips at the ECU.

Makes mental note: Don't let Mark near your engine....

Thinking about it, if it is the +ve supply then there's nothing to stop you bypassing the ECU and using another ignition switched supply.

 

[television]

Makes mental note: Don't let Mark near your engine....

.

But think of the joys of working on the car with white shirt and gold cuff links in

 

[Mark300SL]

Makes mental note: Don't let Mark near your engine....

thanks for the vote of confidence

Is it not feasable to make a new one from the old and do it wire by wire

I have removed the coilpack section of loom and then 2 of the coil connectors from that section. Colour identification to the individual connectors was very difficult as the insulation just fell apart as I took the covering off


I'm still trying to figure out how the coil connectors come apart!

The parts are available seperately, and if they can be put together then they can also be taken apart The existing wires have no insulation left so I need to take the connectors apart to replace the exisiting wiring.

 

[television]

Ian walkers guy made one up for one a few weeks back I believe.

Its hard to do a good job with old connectors due to the chemical reaction of the insulation onto the connectors, but not impossible.

 

[Ian B Walker]

Ian walkers guy made one up for one a few weeks back I believe.

Its hard to do a good job with old connectors due to the chemical reaction of the insulation onto the connectors, but not impossible.

Brian (Lastminute) is the guru on these as he did a wiring loom for a 300-24 for me a while ago. The guy is a genius when it comes to sparking bits.

 

[LastMinute]

Brian (Lastminute) is the guru on these as he did a wiring loom for a 300-24

... which still doesn't work

I only did a bit of soldering...

 

[Mark300SL]

I will have a word with Brian then! (though as a C&G qualified auto electrician I should be able to manage!)

I met Brian recently at the Brooklands GTG and were in fact discussing that very loom

Though its probably going to be easier to just order the new parts and start from scratch with a few lengths of wire, some heat shrink and a soldering iron.


Thanks to everyone for the ideas and support

 

[grober]

I will have a word with Brian then! (though as a C&G qualified auto electrician I should be able to manage!)

I met Brian recently at the Brooklands GTG and were in fact discussing that very loom

Though its probably going to be easier to just order the new parts and start from scratch with a few lengths of wire, some heat shrink and a soldering iron.


Thanks to everyone for the ideas and support

Depends on how valuable your time is? Bearing in mind the remaining parts of the engine loom may also be on their way out maybe a new engine wiring loom is the best long term solution and will reassure any future buyer? http://www.mercedesshop.com/Wikka/M104WireHarness

 

[television]

Depends on how valuable your time is? Bearing in mind the remaining parts of the engine loom may also be on their way out maybe a new engine wiring loom is the best long term solution and will reassure any future buyer? http://www.mercedesshop.com/Wikka/M104WireHarness

But he will only need the car for a few weeks until someone bashes into it

 

[Dave Lewis]

Mark, I have my doubts about replacing just the coil pack section of the loom, if it's degraded there, it will be elsewhere. I would bite the bullet and get a new loom, as just one short somewhere could cause all sorts of misinformation getting to the ECU from the various sensors. The unburnt fuel is a worry - the ECU is supposed to shut off the injector if there is no spark on a particular cylinder. It's quite possible that the short circuiting has fried one or more of the coil packs and the ignition module in the ECU - this is what happened to mine. I'd be interested to see what diagnostic codes you come up with.

 

[Mark300SL]

Thanks Dave I appreciate your concern and the loom will be changed in the near future when it all comes apart. I just want to splice a loom section in for the coilpacks to see if there is any further existing damage.

I have located a complete loom but I did spend over an hour yesterday looking over large areas of the loom and couldnt find any problems outside of the coilpack loom. Just a couple of inches from the head the coilpack loom is also fine - its flexible and doesnt crack. Inside the head area the insulation almost turns to dust.

Injector wiring is fine and isnt causing an issue and that is right next to the head ?????
It appears to be a heat issue, but the heat issue is constained inside the cover for the leads/coilpacks. This could also be because the engine is genuinely very low mileage it may be not as far deteriorated as some others.


I WILL be swapping out the whole loom in the near future - but for now I need a functional section for diagnosis which I am quite happy to make if I can find the right repair section on WIS.


Mark

 

[moakesr]

What you need is A2025406081

 

[Mark300SL]

Now that does look useful and it's really appreciated !

Do they come with the connectors inside already fitted ? - if so that is nigh on perfect.

I have a part no for the complete rubber section that holds the cables, complete with coil plugs and 5' of cable.
However the part number apparently appears in WIS but not on EPC ???

From another site for an E class
MA124 546 09 80 GO40102 CABLE LOOM PRICE 29.60 + VAT 34.78

This apparently just leaves me 4 wires to splice and the job is done - as long as the E class coil pack connectors fit my coilpacks.





Mark

 

[moakesr]

Now that does look useful and it's really appreciated !

Do they come with the connectors inside already fitted ? - if so that is nigh on perfect.

Mark

Not sure, but I will be picking them up this week, and can let you know if they have everything inside as we hope.

I have got them for my fathers 1994 W124 E320 (M104), I plan to change them before any trouble sets in.

 

[Mark300SL]

I have got them for my fathers 1994 W124 E320 (M104), I plan to change them before any trouble sets in.

They come with the connectors
I have a set of 3 ordered and will pick them up on Sat morning from Lakeside and get a few other bits whilst I'm there.

If anyone else also has an M104 EFi engine I would suggest you wait until I have tested these this weekend and then order some for immediate fitment!
My harness appears to be perfect - with the notable exception of the coil wiring. Remember my engine has done under 50k miles so it hasn't had the heat treatment that many much higher mileage engines have suffered.


Now I just hope the ECU and coilpacks are still in the land of the living !



Mark

 

[moakesr]

Once you have this done, could I suggest a list of part numbers and a procedure on how to change them is made a DIY sticky forum post?

I think this will help lots of people with crumbling wiring looms.

 

[television]

I did not know I had this link, just put it up for those reading your thread
http://www.mercedesshop.com/Wikka/M104WireHarness