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240z, no spark from coil

3171 Views 11 Replies 5 Participants Last post by  speednick, 
C
Hey all, need a little help. Just got my first 240z, been sitting for 20 years. Got it started, then replaced condensor, points, cap and rotor. And now i have no spark from the coil. Has 12v out the coil from secondary, but drops to about 9v when turning over. The points open/gapped correctly, its timed correctly. Could it be resistor? Condensor wiring issue? What would cause no request for spark?
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N
Re: 240z, Make a spark...

It's sort of rare BUT sometimes a new condensor (capacitor) can be bad out of the box. Also anything that's grounding in the primary circuit will stop the secondary circuit (the coil output) from operating at all. With points OUT or not contacting to ground, try a small jumper from coil negitive to ground with the key on. It should throw a spark like this. Then you can figure out what "went wrong." ! HA. Norm K.
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palladin
Did it work before? Did you change the coil? Is the rotor on correctly (should be only one way), is the cap on correctly (again should only be one way but it is possible), are there 2 wires clipped onto the points(one from the condenser and a black one from the distributor)?

I want you to do this. Run a jumper wire from 12v+ at the battery to the pos+ side of the coil. Does it work? If yes, then points condenser, cap, rotor not your problem. If not, then either the condenser is bad (put in the old one), points are NOT set correctly, or it is possible thatI have a point system on my boat. It reached the point that I had to run a jumper wire to start it, but once running I could remove the jumper wire. Makes no real sense. But once we ascertain these things we can go from there.
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C
Norm K: It did throw a spark, which indicate no fault from the coil yes? What does that rule out though?

Palladin: I have a new coil in, even though the new one hadn't gone bad, and I've put the old coil in as well, just to rule out a faulty new one. I've run a jumper wire from battery to coil, but it didn't change a thing.

I think what's going on is a faulty wire either from points to condensor or from condensor to coil. I've rewired both, however, and they both failed to make a difference.
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T
actually, the most likely cause is that you installed the wire going to the points on the wrong side of the little insulator block....so they are in effect closed all the time...I've seen it done several times, and maybe even might have done it myself.....
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S
The Ghost has a point, but old condensors short, thus preventing secondary spark discharge. Till you get a new one (WITH a condensor and point set) To keep the car running, just cut the condensor wire in the dizzy And check point gap while you're in there.
Nick
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palladin
Coil wire itself? Is it all the way in. I've had them go bad.
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S
The condensor is a capacitor wired in parallel with the points. It shorts AC spikes to ground and is tuned to the ring frequency of the coil For fastest time charging and it keeps the nasty arc created when the points open And the coil discharges, going through the condensor to ground instead of blowing the points apart. If that condensor gets worn out and shorts, the coil never SEES the points opening, and thus never fires. You can just cut the wire to the condensor and be on your way until the points burn up!
Nick
PS- I can be accused on Friday nights of PWI. :)
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palladin
So Nick, does this mean we can test a condenser with an ohm meter? We should get a reading on the needle?
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S
YES! Sort of... Best to use a pointer style meter over a digital as the visual is better. Start by shorting the condensor wire to its own case so it is completely discharged. Measure the "resistance" from the terminal at the wire's end to the case while observing the meter. It should show a short (near 0 ohms) and immediately swing toward infinity ohms. The meter is producing a voltage which charges the condensor at which time it appears to be "open". Try this on several different ohm scales (short the wire to the case before each test) and you may see the swing times of the pointer vary. This is a "Go/No Go" type of test as you may get the results I just listed, but it gives you no quantitative info as to the condensor being at the correct capacitance value.
If the meter stays at or near 0 ohms, the thing is considered shorted and the car won't run. The coil WILL throw a spark as the ignition is turned off, which is confusing to some. If the meter shows no indication at all, the condensor is considered open, the car will run but will have heavy arcing at the points and they won't live long. Condensors are matched to the coils for best spark and ideally you would want to know the correct capacitance for the application and test with a meter that measures capacitance. New Old Stock ain't so great as they tend to dry out and radically shift in value with age. The newer, the better. Prices are coming down on meters that test capacitance and they are becoming more common.
Nick
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C
soo turned out to be the wire connecting points to condensor was faulty, and that base point where the two connect was gunked up. should be good to go now, thanks for all the help! Im sure you all will be hearing from me again real soon
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S
Congratulations!
Nick
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