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#16
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I re-read you post (and mine), and I believe your points are not connected to ground -- they should conduct from the green wire (terminal #7) to ground when closed. Check the stupid simple stuff first -- have you set the gap with the distributor cam set so that the "point" of the eight sided cam is directly under the rubbing block of the points? If you set it to 0.030" at just about any other point on the cam, the points will never actually close, so the switchbox will never "fire" the coil.
Next, make sure you have the green wire connected to the moving contact on the points (the wire from the points connects to the green wire at the spade connector inside the distributor). Also, check for miscellenous junk on the points themselves. A tiny bit of oil or grease can prevent them from conducting -- they are a trigger only and do not carry the main current like standard points do. Doesn't take much to keep them from working! I know, I've had fits with mine recently. I'd get a small piece of clean paper or very thin cardboard (a matchbook cover is perfect). Open the points with a fingernail, put the paper or card inbetween, and pull it a short distance. Open the points and remove the paper or card. Don't just pull it out, bits of fiber will get stuck. Keep the points open and spray with carb or brake cleaner and check for continuity between the outer point and ground. Until they conduct and are connected to the switchbox, you won't get spark. Verfiy if you want by cranking the engine while watching the voltage on the green wire -- it must ocsillate between 12V and less than 0.1V. If not, the points aren't working. Peter
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1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs! |
#17
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Had a little luck today diagnosing the problem with the information Peter provided. I unhooked the switch gear and wired in series a 1 ohm resistor from the connection block (#7) to coil lead #1. The coil gave out a spark to ground. Sure glad to see that. However the car did not start.
Before doing any of that, I verified that the points were hooked up and installed correctly. I set the gap at 0.030" at one of the high points on the distributor cam. I checked the voltage with the points closed from the connection block (#7) to ground. There was no voltage. When I check from the switch gear (#7) to ground the voltage was equal to the battery voltage. Also the voltage from the coil leads (#1 and #15) also measured as the battery voltage with the points closed. Based on the results, I am assuming that the switch gear is defective. Can anyone verify? Thanks so far Dana |
#18
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If you have voltage at the coil when the points are closed and none when the points are open, the switchbox is working. If you have voltage all the time, the switching transistor in the switchbox is probably shot. YOu can get a replacement at Radio Shack and solder it in, but you need to check the voltages first -- I don't believe you should have 12V at the coil with all the resistors in place.
If you get a spark by applying and removing voltage from the coil, it at least is good. If the points go to ground and drop the voltage at the green wire on the junction to near zero, the points are good, too. If nothing happens (no spark) there is very little doubt the swithbox is bad. As I said, the usual cause is a bad high voltage switching transistor, and it can be replaced for very little cost if you don't mind opening up the box. Otherwise, I'd go for a Crane or Pertronix system. The switchbox is VERY expensive, if you can in fact find one in working condition! If you get a spark with the points hooked up directly, but no start, you may have a timing problem too -- make sure the timing is set correctly (a helper to crank the engine while you check is necessary). Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs! |
#19
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Very busy lately, but here is what a have so far:
By passed the switchgear and got the coil wire to spark when grounded. With the switch gear bypassed: 1. I removed spark plug number 8 and connected the spark plug wire directly to the coil. I grounded the spark plug and got a spark. I repeated the process for spark plug number 7 and got a spark. 2. I reconnected all the wires back through the distributor cap. I grounded spark plug 8, got a spark. Then grounded spark plug 7, no spark. Plug wires for 7 and 8 are almost 180 degrees across from each other on the distributor cap. I repeated this several times to make sure that the ground connect was good. 3. I pulled off the distributor and noticed the wear pattern on the top of the rotor (contact with the distributor coil wire) had only a half circle pattern. Possibly indicating that there was not a full 360 degrees of contact during rotation, therefore not allowing all spark plugs to fire when necessary. Any insights? When I did get a spark with the switch gear bypassed, the spark plug wire connected to the coil and spark plug grounded, I reconnected the switch gear, disconnected the by pass wire and resistor and checked again. The coil did not fire (no spark). In summary here are my assumptions: a. The points are good because I did get a spark to the number 7 spark plug through the distributor cap and rotor. b. The switchgear is defective because the coil did fire when the switchgear was bypassed and not when the switchgear was reconnected. c. I have a half circle wear pattern in the rotor contact (new rotor) from the distributor cap. I put the old rotor back in and got the same result. Not sure what this really means, other than possibly the distributor is also bad. I am in the process of getting pricing on an upgraded ignition system from Pertronix...Any advice? I am assuming that this is my logical next step. I still don’t know if the timing is off, because the car still won’t start. Thanks...any advice welcomed Dana |
#20
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Dana:
I'm fairly sure you have a dead swithbox, and the Pertronix will take care of that. It will also help eliminate loose distributor shaft problems since the points won't be pushing on it. Get a new cap, too -- bad contact with the rotor will prevent running. Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs! |
#21
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After checking the Pertronix catalog, I assuming that I need the following for my 1972 280SE 4.5L :
Pertronix Ignitor model number 1885 Second Strike - part number 500. Can anyone help to confirm? What have others used? Where is a good place to buy these components? Is installation difficult? What should I watch out for? Thanks, Dana |
#22
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Yup, I think that's the correct part number (kit, contains the magnetic disk and the pickup). Order directly from Pertronix works fine.
It's about as diffucult as replacing a set of points, I think. Mine is running OK at the moment, although a Pertronix is in the future -- I'm having trouble with the trigger points for the EFI, probably from a worn distributor. Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs! |
#23
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Are those two parts the parts that must be purchased to install the pertronix? my firend is doing the same upgrade soon and he only saw noe for a 450SL. If he called pertronix with those two numbers that would be all he would need?
Thanks in advance David
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_____________________________________________ 2000 Honda Accord V6 137k miles 1972 300SEL 4.5 98k miles _____________________________________________ |
#24
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I am going to be contacting Pertronix so that I can get pricing. I will let you know what they say.
Thanks Dana |
#25
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Those parts should fit any 4.5L M117 with breaker points/switchbox ignition. Later models with breakerless ignitions won't need them!
Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs! |
#26
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Thanks everyone (especially psfred) for the valuable info in this thread. I've been hunting to solve poor starting issues for ages now and this helped me to nail the problem to crud on the contacts. Starting is much improved and perfect if I crank every other day.
Problem is I normally leave the car for months and then crank her over - what I find is that she wants to start when you hold the key to engage the starter (i.e. 12V to coil) but then will often cut out or the first 3 or 4 times when you let the key go to ignition position (i.e. 9V to coil). I am thinking of installing a simple push button or 10 sec timer to keep that 12V boost on the coil during ignition position. Does anyone have any views on this and if it will be OK for the transistorized unit? |
#27
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Just a long shot, but #1 cylinder is on the passenger side.
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Closing the store Benzbonz.biz on your smart phone or tablet. |
#28
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Quote:
Usually 0.016" or 32° dwell.
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1993 400E Mercedes Benz technician since 1982 ASE Master technician to 12/2015 |
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