Those orange spark plug connectors - pull off?

[MCR01]

Happy New Year to all.
I've read many pages of interesting posts on the ignition system, wiring etc.
I'm about to do an ignition system rebuild including new wires. I'm assuming that a thorough clean of the caps, rotors etc won't work BUT I can't get any of the orange sparks plug connectors off.
So first dumb question of 2026: do they just pull off? These orange caps have never been off in the last 6 years.
Thanks

 

[emerydc8]

Happy New Year. If the boots aren’t coming off the plugs the top of the boot can be turned clockwise and counter-clockwise a bit to help loosen it up, then it should pull straight up and off. Try not to put much of a side load on the boot or it could break. You might want to have this tool ready to use if the boot breaks off in there.

https://www.amazon.com/dp/B08PRZFG99?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_2

Now, if you’re talking about getting the wire off the boot, the wire is crimped into a brass nipple that is threaded at the end and screws into the boot. If you twist the wire too hard you could break loose the crimp and all that will be connected to the boot is the bare core wire, leaving you no way to unscrew it from the boot. You might try some Liquid Wrench or PB Blaster and see if that will help. If the wire breaks off in the boot it is a pain trying to get the brass nipple out (ask how I know). There is a special Mercedes crimper tool for the wires that is NLA but you might be able to get by with a substitute. I don’t know if the wires are still available by the meter if you decide to go this way and cut your own. It’s probably cheaper to buy the whole assembly as a set of eight.

 

[MCR01]

Thanks; as you said rotating the orange caps back and forth a few times allowed the spark plug connectors to be pulled off.
All the HT leads look very old and tired so will check this out. Some where on this forum a post mentions running the engine in the dark and looking for sparks.
Presumably with all HT leads exposed and the air cleaner housing not connected? Is this how it's done?

 

[gsxr]

Thanks; as you said rotating the orange caps back and forth a few times allowed the spark plug connectors to be pulled off.
All the HT leads look very old and tired so will check this out.

Measure the resistance in ohms. Normal will be 1600-2400 ohms. Bad ones will be 5k, 10k, or higher. If any are bad, I'd replace the entire wire set with Beru (details in this thread).

Some where on this forum a post mentions running the engine in the dark and looking for sparks.
Presumably with all HT leads exposed and the air cleaner housing not connected? Is this how it's done?

Correct.

 

[MCR01]

Viewed in the dark no visible sparks anywhere.
All caps, rotors, insulators look pristine (I know, I know).
Starts reluctantly then runs perfectly at 2000 - 4000rpm in Park or Neutral BUT the moment Drive is selected engine revs drop to <1000rpm and it stops.
Am I missing something obvious, a vacuum line disconnected/broken?
Any help appreciated; just like to get it running to load onto a transporter.
Thanks.

 

[rayhennig]

I'd replace the entire wire set with Beru

I did that but the new Beru suppressors refused to seat nicely on to the plugs. Nothing like the ancient Beru ones. The SEEMED to be seated but no satisfying click.

The solution? A complete new MB orignal lead set made up by MB in Bochum. Satisfying clicks. All well 3+ years later.

No idea if MB still offers this service. I was keen to make them up myself but the crimp tool was so costly that it wasn't worth it.

RayH

 

[gsxr]

I did that but the new Beru suppressors refused to seat nicely on to the plugs. Nothing like the ancient Beru ones. The SEEMED to be seated but no satisfying click.

The solution? A complete new MB orignal lead set made up by MB in Bochum. Satisfying clicks. All well 3+ years later.

Ray, was that on M104 or M119? Never had an issue with Beru M119 plug boots.

Not sure if Mercedes dealers will still make custom wires, but if they use the lengths specified in the EPC, it will be an ill-fitting set. BT, DT. I posted details like 10 years ago on the forum, and made my own custom-length sets that fit better. The Beru aftermarket set for M119 is almost perfect, and clicks onto the plugs as expected (link in post #4 above).

The Beru boots are NLA from the dealer and aftermarket, IIRC... only the Bosch orange plastic boots are still available.

 

[rayhennig]

only the Bosch orange plastic boots are still available.

Yes, that's what I got. And yes, for my 104.

R

 

[rayhennig]

Ray, was that on M104 or M119?

By the way, would not the suppressors be the same for both engines? This for interest only.

R

 

[gsxr]

I think the orange plastic suppressors may be the same for both engines? Not sure about the metal 90°-angle type.