107 Ignition points burning out quickly??

[Mikesmerc]

Anyone know whats causing the above, replaced points and condenser last summer, took it for a spin yesterday and ran like a pig. Checked out the points and one side had burned a hole in the other(deep recess). V8 3.5L.
Can these be converted to electronic ignition?
Thanks
Mike

 

[mlc]

I cant believe that it is not possible to fit an aftermarket electronic ignition - however does anyone actually make them anymore, its nearly 30 years since I last bought one!

I have a 350SL and it still has the same points I fitted when I bought it 3 years ago (4000 miles). I think burning points are normally caused by a failed condenser, so the cheapest route would be to just swap the two items and see what happens.

Mark.

 

[Mikesmerc]

Just bought new points and condenser, so I will give it a go again. 0.3mm gap?
Cheers Mark
Mike

 

[Spike]

Sounds like it maybe had a faulty condenser...

Time will tell. BTW I just love cars with simple mechanics like points ignition etc. No fancy ecu's to go wrong etc - just pure simple mechanics.

 

[Mikesmerc]

Tell me about it Spike, my 560SEC is a bit of a pain to get your head around how it all works.
Mike

 

[mlc]

Spike - I would agree - but it does have a fancy ECU, and they do go wrong! The car has standard points in the distributor, plus a clever (and expensive) set of trigger points below them to trigger the fuel injection, then the whole lot is controlled by an ECU that sits above the front passengers feet and is the size of a laptop and is covered with heat sinks because it is all transistors (dont think chip were invented in 1972). Mine failed about 3 years ago and I was quoted £1500 for a new one and £500 to fix the old one, managed to get a second hand one for £100 in the end.

Mark.

 

[mercman_1]

Had the same problem a few years ago turned out to be a faulty coil that was burning out the points.worth a try ?

 

[Mikesmerc]

Will change coil, just in case. The 9v resistor seems to be bypassed on my one, could this be causing the points to fail quickly?Dont even mention ECUs, that would be the last straw. So thats what the plug under the dizzy cap is for. Anyone replace the injectors on one of these? expensive?
Cheers
Mike

 

[TheJim]

Regarding changing from a dizzy to electronic ignition- I put a system in a friend of mine's Marcos the other day. A Mallory Unalite I think it was called.
The basic idea is that you keep the distributor body but remove the points and replace them with an LED and a sensor. The rotor arm is swapped for a sort of fan thing and the breaking of the beam of light determines the ignition advance or retarding. No points to wear out or need adjusting. Genius. The old Essex V6 runs more smoothly at high revs too.
Only took an hour to fit. Shame I can't afford one at the mo.

 

[Mikesmerc]

Thanks for that Jim, will look in to it. Replaced the points,condenser and coil and still runs rough with poor acceleration. Cap, leads and rotor next I suppose. Are fuel pressures critical for the injection system on this car?, seems alot simpler than my 560s. Please let it not be the ECU
Thanks
Mike

 

[turnipsock]

A faulty condenser will cause a lot of arcing at the points so they will burn out quicky. The condenser has to be matched to the coil, otherwise the points will burn out quicker than they should.

I'm not sure if MB use a quick start setup, this would mean that the coil is set to run of a lesser voltage for normal running, but for starting, there would be a full 12V over the coil. It may be getting the full 12V all the time, this is usually quite dramatic though and any plastic bits would melt within a few minutes.

 

[Mikesmerc]

Thanks turnipsock, the resistor is bypassed but will do a volt check an the coil.
Mike

 

[mlc]

Mike,

The next check I would make is the plugs. When I first had my 107 and had points problem it would flood the plugs for fun, I got to be an expert at getting 8 plugs in and out at break neck speed. rough running and poor performance suggest you could be easily running on only 5 or 6 cylinders.

Mark.

 

[Mikesmerc]

Thanks Mark, replaced them last year when I replaced the points. Will put a new set in again if just to eliminate them. Going to order a cap rotor and leads next, hopefully that will sort it.
Mike

 

[dawood]

my 450SL had all the same symptoms and it turned out to be the ECU. Online they are $800. Any idea where I can get a used one from in Ireland?

 

[gfern]

Don,t know about second hand but I had similar problem with 300SE some years ago and after finding out that Main dealers couldn't help tried my old friend Barry Manders at Mc Namaras Carb Centre Nottingham Street Dublin. They were able to hook up and diagnose problem and supply an ECU at a reasonable price can't remember how much but was good price at the time compared to dealer prices

 

[turnipsock]

http://forums.mercedesclub.org.uk/showthread.php?t=10829

There is a post here by Myros that talks of a company that deals in second hand parts.

Why is this thread not in the ignitition section?

 

[pascal]

Noted. And moved. Thanks Turnip.