I've worked with lots of German engineers. They have a reason for everything they do. I've found that it's better to approach them by asking them why it's done that way vs that is a stupid way of doing it. Americans seem to have an approach that things are build stupid and their way is much better. They seem to butcher everyone's way of doing things.
So I get power to the coil but no spark. Measured across the coil its 4.5v which seems low to me but after it tries to turn over a few times there is no power to the coil. I guess I'll replace the fuel pump relay and if that doesn't fix it then the ignition switch. Fix 1 thing and another breaks.
The easiest way I have found to test the ignition switch is to put a test light on the coil. One end on 15 and the other end on 1 [the two posts of the coil]. Crank over the engine. If the light flickers, you have power and the switching ground for the coil to fire.
If you do not, then take your test light and put one end on ground and the other end on 15 [the power side of the coil]. Crank over the engine. It should like up whenever the key is in position #2 and cranking. If not, find out why you do not have power.
If you put the test light on 1 and the other end on the positive side of the battery, with the engine cranking, the light should flicker. If not, you are not getting the ground signal from your points/ign control module.
If you have all that, the coil is probably bad. If you have that and spark, you may have a weak spark. A spark you can see, but wont jump the spark plug gap under pressure.
With one test light, you can determine in 1 min if you have an ignition problem or not.
So going off my Bently manual i tested power to the ICM, getting 12v. So the fuse box is sending the power out. Then I tested power at the coil and im getting 2v then it fades to 0 which is normal but the wierd thing is im getting -2v. So im guessing I have a ground thats become loose or disconnected. I've been looking for but nothing is out of place. The lights work and all the accessories work I just don't have any power from the coil.
A steel car body, in this case a 30 year old one is not a good match against copper as a conductor. I used to make the jokes about the old British electrics. Now I put ground busses in to bypass the body as a ground path.
There is no such thing as -2v. Your leads may be backwards or your volt meter is FUBAR. I do recall a technician that worked on a Mercedes and the owner charged the battery backwards. It had power on the negative and ground on the positive. Not certain what happened about that, but the car did get a new battery before it left.
What i mean is its reading the volts backwards. Reading from across the coil it reads -2 like the posts are backwards. If I keep the positive terminal from the meter on the positive terminal on the coil and remove the negative terminal from the meter and touch it to the engine like im grounding it on the engine block it reads 2v the way its supposed to be, but leaving the meter plugged into the positive and negative on the coil it reads reversed.
It reads like its connected backwards but its not. 2 black wires to negative and the red and green to positive.
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