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My 1968 Bmw wont start "Hot"


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Ok, im new to the forum but im getting desperate so i thought this would be worth a shot

i know its not a 2002 but its similar..

i recently acquired a 1968 BMW 1600-2 that im going to completely restore

ive been trying to get one for a few years

i thought it had a fuel problem at first, and this may be related or seperate electrical problem

the gas was dirty and clogged the inline fuel filter so i took out the gas tank and cleaned it and the fuel lines, replaced the inline fuel filter, replaced the mechanical fuel pump, rebuilt the carburator... relaced the distributor cap, replaced a corroded connection one of the spark plug cables, took off the plastic cap off of the voltage regulator so i could be sure to get a firm connection, (tho now i come to think of it, i havent tested the voltage regulator with a voltometer after it wont turn on hot...)

replaced the ignition coil, spark plugs and properly gapped them, and the coil was getting no spark.

i read somewhere here by zenon (ignition coil myths busted) that a ballast resistor was needed and gets the power to around 9 ohms so it wont overdrive the ignition coil.

i got a ballast today that was suposedly set around .56/5 ohms, as what i read online somewhere for the proper ohms on a proper ballast resistor and it was still pumping out 10 or 11

which may be too much (so off to try to find another one that will get me lower ohms tomorrow)

a friend also suggested that i try running a lead from the positive battery terminal, to an on off switch i put under the dash, back to the positive terminal on the ignition coil (that wasnt putting out spark) and even tho it got power it still didnt work.

so aside from trying to find a lower ohm ballast to not overdrive the ignition coil... any suggestions?

hope somebody can give me a new lead

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did you verify that you bought the correct coil?

how is your starter? may want to replace the starter as well if it is the original

1970 Agave work in progress

Born on May 14 1970 and delivered May 19th 1970 to NYC to Hoffman Motor Corp. Agave code 071

new guy

help appreciated!

other cars: 1991 318is / 1999 540iT

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You didn't mention the points. Have you checked them?

I don't know if your coil needs a resistor, but if it does, the voltage at the resistor (+ terminal at the coil) has to be measured when the points are closed. If the points are not closed you will measure whatever the battery supplies. Forget the voltage regulator, it has nothing to do with your problem.

And by the way, if you want lower voltage, you need higher resistance (more Ohms), not lower. What happened to the old resistor? Did you measure it?

No amount of skill or education will ever replace dumb luck
1971 2002 (much modified rocket),  1987 635CSI (beauty),  

2000 323i,  1996 Silverado Pickup (very useful)

Too many cars.

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hey, sorry everyone, i didnt realize people would write back so quick

i did get the correct coil

and nothing has changed between the two, and i did get a (1.8 ohm resistance) ballast in there and its still doing the same thing so i would have to agree that i think its a dead end here

my mechanic friend checked my points the last time he was by and he said they were fine

same problem as ever tho,

the car runs, and as far as i can tell at least at the ignition coil im getting power til i turn off my car and try to restart it

then its dead at the positive terminal on the ignition coil.

and about the resistor, i dont think it ever had one, and i think the guy who put this car back together used another car, so i didnt know if it was missing one or not so i threw one on just to be safe (with the stock resistance of 1.8) and it made no difference

power hot, shut it off and try to turn it back on with the same problem.

ill try to keep a better eye on this and reply quicker btw

any other ideas?

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