I have a 1985 MB 280TE, Euro edition, with repetitve coil failure. I purchased the car (M110 engine, 123 body) in Atlanta a couple of weeks ago and drove it 500 miles home. In the second leg of my trip, it stalled a couple of times at traffic lights, but started again. After I got home it wouldn't start the next day until I put another coil on it. I drove it a short while (15 minutes), then it died waiting in a fast food drive thru and wouldn't start again until I put another coil on it.

I put all new plugs, wires, distributor cap, rotor, coil and battery cables on the car and it started and ran fine. Then I had my mechanic friend take a look just to be sure (before I cooked another $60 coil!). He says it will run as long as you don't shut it off. Once it's turned off, it won't start again.

Does anyone have any ideas what's going on here? Also, what should the resistance readings be for this car?
Thanks.

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Tony G.
Dayton, Ohio

1985 300TE (Euro)
1996 E320

This is one of those problems that should have a perfectly logical and simple answer. I can think of perhaps only two situations that could lead to coil failure.
1. Excess HT caused by excessive resistance or gaps in the secondary (HT) side.
2. Over-temperature caused by excess primary current or dwell.
For causes of the former I would look for resistance or suppressor spark plugs or wires where there shouldn't be. Has your mechanic looked at it on a scope to see if voltages are excessive? For the latter I would be looking for incorrect value or missing (ie. bypassed or shorted) ballast resistor or possibly a faulty ignition module causing excess dwell (should also be visible on a scope). These latter situations would cause high coil temperature. Is the coil running unusually hot?

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107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.

Yes, the coil is so hot it's exploding the oil out of it. According to my mechanic:

*This is the last year calling for built-in resistance values. The manual calls for values on the distributor rotor and everything. There's no true ballast resistor in the system; appears built in. He's measured all secondary ignition values and they are below specs "by a lot."
What's the best way to check the distributor and switching box (swithgear) on these cars? (remember, Euro engine)

Thanks!

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Tony G.
Dayton, Ohio

1985 300TE (Euro)
1996 E320

I had the same problem when I bought my 1985 280TE, drove it away and thought I'd bought a lemon when it shut off. I replaced the fuel filter and it ran and continues to run like a dream. Inexpensive option, so worth the try.

The problem was the switchbox (switchgear/ignition module?). The car had the wrong one, so I found the right one ($360) and installed it. Now my problem is fuel related. Car runs poorly, but starts immediately. It has a new fuel filter, so I'm thinking fuel distributor, another expensive part.

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Tony G.
Dayton, Ohio

1985 300TE (Euro)
1996 E320

I was about to suggest there was another problem and I was goinf to second Greg's point number two, but the real reason I am replying is that I disagree with Gregs point number one.

The amount of energy expended in every firing event has nothing to do with where it goes. It is only dependant on dwell time (up to saturation) and the other design criteria of the coil.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Steve,

Agreed. My thoughs behind my first point were of the possibility of a high tension breakdown (ie. insulation failure) within the coil due to excessive HT (resulting from high resistance plugs, wires, etc). I should have taken his thread subject literally when he said "cooking" coils. After realising that they were failing through over-temperature, I agree that my first point cannot be the cause. Obviously excessive dwell or primary current resulting from the incorrect ignition module was the cause. Pleased to hear he found the problem.

Greg

__________________
107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.