Just took MBZ to a local MBZ shop, something he said concerned me

[BoneStock]

As of late I haven't had time to persue the running rough [280sel 4.5] so I droped it off at a local mercedes only shop. I explained that I wanted the oil changed and afew other things including cleaning the distributer EFI points. The owner who I spoke to said they will try but some times those points can break while being cleaned because of age. I had never heard of that on this message board and wondered if this is a ploy to get more money out of me [I'm sure they are expensive] or if its true. Everything else sounded good, mabey I'm just paranoid.

Ben

[psfred]

Very good chance of breaking the plastic sheilds over the contact points if you try to get them off. I just used carb cleaner (or brake cleaner, don't remember) because I had good contact. Mine don't work very well cold, but I believe I can cure that with a Pertronx ignition or by rebushing the distributor -- the shaft wobbles too much to open the trigger points on the pressure side cold.

New ones are expensive -- dealer cost is $280, I think.....

Peter

[erubin]

Peter,
I replaced my '72 4.5L ignition points with a Pertronix ignition (it also replaces the pesky transistorized switch module). It does not eliminate the need for the trigger points which trigger the fuel injectors. Do you mean Pertronix also sells a seperate solid state system to replace the trigger pooints?

Ben,
To clean the trigger points I used a soldering pencil to create a small opening in the plastic cap(s) that are not removable. This allowed me to slide in a really small flat file to clean up the contacts. These points only carry low voltage (12V). They don't have any real arcing deposits so they clean up real easy.

[Tomguy]

Erubin: Solid-state? I HIGHLY doubt it - the D-Jet needs to read engine RPMs from those points to determine fuel delivery as well as when to open the injectors.
He's saying that the side of his dizzy that has to open the points, when it has stress on it (from opening said points), causes the shaft to wobble a bit and be out of place, thereby having the trigger points miss completely.
Also, the points are platinum-plated, according to Peter, so filing them is an expensive mistake.

Peter: How do ya rebush it, is it just a standard ball bearing that's easy to find/replace, once you get that PITA pin out?
Also, to counter wear, I've been thinking of finding a way to uniformly bend the metal on which the trigger points ride about 0.020" to the center on each side (perhaps cutting a tiny groove, bending them, and then resoldering the goove)... good, bad, or indifferent idea?

[erubin]

Tomguy,
Thanks for the info on the trigger point plating. Better to clean them without a file! Still need to create a hole in the plastic caps to clean them though.

Did I misunderstand Peter? I thought he suggested replacing the trigger points with a Pertronix.

[Tomguy]

He said Petronix ignition though Of course I can only guess that's what he meant - breaker points have a spring to keep them closed, this spring moves the shaft away from the trigger points if it wobbles enough!

[psfred]

The Pertronix (or Crane optical) system will replace the ignition points. Since the bushing is pretty far down in the dizzy, the points pushing on one side only will wear it so that the shaft sits slightly sideways. This is enough with old worn trigger points that the pair on the driver's side don't open properly on a cold engine. This is a result of worn rubbing blocks on the points themselves and the crooked shaft, not wear on the contact. The trigger points are separate.

You can clean the points themselves with carb or brake parts cleaner -- brake parts cleaner is safer, if you get some carb cleaner with methylene chloride in it the plastic parts will melt and you will be out a new set -- something like $300.

The bushing is, I think, simply a straight oil-lite, but I'm not sure. It may have an o-ring in it, I'll find out someday when I re-do mine. I've not checked yet because I couldn't get the pin out to take the drive gear off.

Peter

[WANT '71 280SEL]

Is this something Tim and I could do to help get it running right? I am speaking of cleaning the trigger points. Could someone post a picture of the trigger points?
Thanks
David

[BoneStock]

I second that!

To bring this back to what I started the post off with....

In the end the shop refused to the the point cleaning job because the adjusting screw was broken on the fuel pressure regulator [thing mounted on the firewall with wires going to it]. Personally I don't see how not being able to adjust the FPR keeps you from cleaning the contact points but I didn't take it any furthur. On the bright side, I only had to pay for the oil change, points replaced/timing checked and trany linkage adjusted. It seems to run better, but from what everyone says these points absolutly have to be cleaned.

Could someone post some pics indicating whats ahead once the dizzy is off?

[Tomguy]

Once the dizzy is out it's as plain as day what you have to do.

There are 2 slotted screws that hold them in. Take said screws out and the points pull straight out. That's it!

[psfred]

There is a big, wide connector to the bottom of the dizzy -- this is the trigger points connector. Pull it off (usually stuck pretty good), before removing the dizzy.

Once you get them out, they are four contact point sets, much like distributor points, on a u-shaped carrier. Lighter springs and smaller points than ignition points.

There is a plastic cover over each set. LEAVE THEM ON -- they will shatter if you try to take them off, and the points will foul all the time from airborne oil and dust.

You can clean them by spraying brake parts cleaner into the points, opening and closing them at the same time with a fingertip. Usually full of oil, which causes misfire from no fuel injection cold. Gets better hot. Test them with a voltmeter -- should have 0 ohms closed and return to 0 immediately when closing and opening repeatedly.

If the dizzy bushing is worn, they will oil foul periodically and have to be cleaned,

If the rubbing block (where the plastic point part touches the cam on the dizzy shaft) is worn down as show by a burr of plastic, they will evenually fail to open cold, then refuse to open at all. Only cure is replacement, and they ain't cheap.

Peter