Intro/Ignition problem '74 280C - Mercedes-Benz Forum

 
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post #1 of 10 (permalink) Old 03-23-2012, 02:05 PM Thread Starter
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Intro/Ignition problem '74 280C

First I would like to introduce myself. I am from north AL and this is my first vintage Benz I've owned. Its a 1974 280c with the 2.8L I6. I saw it sitting in front of a body shop when I was on my way back from looking at another project. I had an empty trailer and some cash and got a deal on it. Its supposedly a 2 owner car and is stock as far as I can tell except for the MOMO steering wheel.

I am very excited about getting it on the road but I have a few questions. Ive been fighting with the ignition system on the car for some time now.

I replaced the coil but the car isnt getting any spark. It gets 12v at the +side but its not being grounded to produce spark. At this point I could replace the points and try to get it to run in stock form OR run the HOT SPARK setup. Im leaning towards the hot spark setup for simplicity and maintenance sake.

1. Will I still use the 0.6ohm and 0.4ohm ballast resistors and transistor box with the Hot Spark setup?

2. Im having trouble finding a circuit diagram for the transistor box to test it. Anyone have the input/output values for it?

3. Whats the best setup to delete the box and resistors all together? Anyone using an MSD box?

Thanks in advance.
Chandler




Getting a trailer tire blowout repaired


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post #2 of 10 (permalink) Old 03-24-2012, 12:13 AM
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Check to make sure the points are set correctly, and are clean. You'll need a dwell meter to get it right on, but try starting out with a gap of about the thickness of a business card.

While you have the business card out, use it to clean the points contacts, just stick it between the closed contacts and pul it back and forth a few times. There may be a bit of oil vapor deposits (non-conductive) on the contact surfacees.

If you want to replace the points, Pertronix usually has a kit that isn't too ecpensive for most applications.

Just a couple possibilities from my experiences.
Scott

Remember: It's not just a car. It's an Adventure.
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post #3 of 10 (permalink) Old 03-24-2012, 07:27 AM
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Hot Spark/Pertronix (H.S. is the same as Pertronix. H.S. is making the older versions of the Pertronix under license) eliminates the control box. 2 wires run to the switching unit. One lead to the positive terminal of the coil and the other to the coil negative terminal. That's it. I left the coil ballast resistor in line but if you go to an after market coil you don't need the resistor.
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post #4 of 10 (permalink) Old 03-24-2012, 02:26 PM
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Yeah, go Pertronix. GOOD idea and one that'll show immediate improvements, especially if the car's not starting
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post #5 of 10 (permalink) Old 03-25-2012, 10:20 AM
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Quote:
Originally Posted by wat turbo? View Post
First I would like to introduce myself. I am from north AL and this is my first vintage Benz I've owned. Its a 1974 280c with the 2.8L I6. I saw it sitting in front of a body shop when I was on my way back from looking at another project. I had an empty trailer and some cash and got a deal on it. Its supposedly a 2 owner car and is stock as far as I can tell except for the MOMO steering wheel.

I am very excited about getting it on the road but I have a few questions. Ive been fighting with the ignition system on the car for some time now.

I replaced the coil but the car isnt getting any spark. It gets 12v at the +side but its not being grounded to produce spark. At this point I could replace the points and try to get it to run in stock form OR run the HOT SPARK setup. Im leaning towards the hot spark setup for simplicity and maintenance sake.

1. Will I still use the 0.6ohm and 0.4ohm ballast resistors and transistor box with the Hot Spark setup?

2. Im having trouble finding a circuit diagram for the transistor box to test it. Anyone have the input/output values for it?

3. Whats the best setup to delete the box and resistors all together? Anyone using an MSD box?

Thanks in advance.
Chandler




Getting a trailer tire blowout repaired


Ummmm, those wheels are also not stock. Read your post with interest as I am fighting the same scenario on my '70 280S. Hope you get it worked out. Oh, and I agree with the group, go Pertronix. KMJ Performance seems to have the best deals. KMJ PERFORMANCE - Chevy, Ford, MOPAR, Buick, Oldsmobile, Pontiac, Lincoln, Mercury, Dodge, Chrysler, Plymouth
dws


1973 Mercedes 450SLC (PineGreen/MahoganyLeather)
1981 Mercedes 380SL FORSALE (LtIvory/PalominoMBTex)
1984 Mercedes 500SEC Euro (040Black/BlackLeather)
1992 Mercedes 300SL-24 Signal Red/Black Leather

Last edited by NorCalSL; 03-25-2012 at 10:21 AM. Reason: spelling
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post #6 of 10 (permalink) Old 03-26-2012, 09:17 AM Thread Starter
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Quote:
Originally Posted by NorCalSL View Post
Ummmm, those wheels are also not stock. Read your post with interest as I am fighting the same scenario on my '70 280S. Hope you get it worked out. Oh, and I agree with the group, go Pertronix. KMJ Performance seems to have the best deals. KMJ PERFORMANCE - Chevy, Ford, MOPAR, Buick, Oldsmobile, Pontiac, Lincoln, Mercury, Dodge, Chrysler, Plymouth
dws
I figured the wheels being bbs RS 1-pieces was obvious enough that they are not factory. I would like to have the factory wheels though!

I replaced the points and it fired right up with a little starting fluid and gasoline. I let it idle and get up to temp and all is well so far. It also came with a '78 quadrajet carb on it. I have the original Solex as well but the quad looked to be in slightly better shape. Im not really interested in using the Quadrajet or the Solex so I am looking into some adapter kits. I have the most experience with Holley carbs but im not opposed to a Webber setup either.
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post #7 of 10 (permalink) Old 03-29-2012, 12:24 AM Thread Starter
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Also where is the best place to connect the dwell meter lead to?
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post #8 of 10 (permalink) Old 03-29-2012, 09:42 PM
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Negative terminal of the coil.
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post #9 of 10 (permalink) Old 03-30-2012, 09:16 AM Thread Starter
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Quote:
Originally Posted by Mike D View Post
Negative terminal of the coil.
Ok good. Thats where I had it but I was getting a reading of 5deg so I thought maybe it was a bad connection. Looks like the dwell was just really far off
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post #10 of 10 (permalink) Old 03-31-2012, 06:55 AM
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Double check your "cylinders" setting on the dwell meter.
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