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I have a 69 455. I had some misfires before so I replaced all ignition stuff:Coil, points, plugs, condeser, wires, etc ec tuned to stock specs..
Checked for continuity, shorts, grounds, etc ete per 69 Olds chassis manual
RAN GREAT!
20mi later, coming home from a car show it started running so rough I had to have a tow.
I checked the points gap, connections, etc. still the same..
Pulled the cap, pulled coil spark wire so I could hold it to see spark, turned ignition on, used a paint stick to open and close points.
added a 12v DC light bulb on coil plus side,
Sparked for a while and seemed OK, bulb always lit.
checked points again, put cap back on, only a few hits, would not start.
OK then removed negative side wire from distributor and added a separate wire, to use as a ground.
With ignition on, I held the coil spark wire 1/4" from ground and grounded out the negative side of coil simulating points opening and closing.
NO spark
is this a good way to test coil? Did I kill it??
not convinced coil was the original problem of it dying, I've done a ton of points cars over the years, always be able to solve issues.. Driving me crazy?
Yeah i read erics post on points troubleshooting
Advice
Update
measured coil + to - terminals got 1.01 Ohms, Measured + to center(spark) terminal measured 10K Ohms
took off stock wires to coil + and - terminals
added a wire to - side and also ran jumper cable from + side to + battery terminal, grounded - side intermittently like points(sparks noticed when grounding) held center spark(2ndary) wire 1/4" near a ground. only very occasional weak spark noticed, even with Ohm measurement is coil shot?????, am I doing test correctly???
Even if the coil passes Ohm test, can it still be bad??? No sparK?
Last edited by FStanley; July 18th, 2016 at 08:39 PM.
Reason: Update 1:44PM PST
In order to get this figured out, you have to isolate each component of the system and check each one systematically.
I would start at one end, whichever you prefer, and confirm each necessary characteristic:
+12.5-13.5V at coil (+) with points open,
+9v, more or less, at coil (+) with points closed,
Less than 1 ohm resistance between points plate and battery (-),
Move points plate through its arc (suck on and release vacuum advance) and confirm no resistance with meter, then re-confirm no flickering with a test light from +12V to the points plate,
Zero resistance through points,
Infinite resistance through condenser,
Check that coil is well grounded, connect spark plug wire to coil and secure other end about 3/4" from ground, connect jumper from (+) to battery (+) intermittently and look for spark each time you pull (+) wire away from battery.
Connect coil to car normally, continue previous spark plug wire connection, turn on ignition, open and close points with a screwdriver and look for consistent spark,
Continue with same arrangement, but now crank engine over and look for consistent spark at end of wire 4 times per revolution,
At this point, connect dwell meter and confirm 30 degree dwell angle,
If everything is perfect at this point, try connecting all spark plugs to their wires, placing each one in a visible location in contact with ground, installing distributor cap, and cranking engine to confirm spark at all plugs (this step is massive overkill, and not a great test of your plugs and wires, but it may tell you something if you're desperate).
As a last chance, if all else fails, find someone with an oscilloscope and see what the waveform says.
In order to get this figured out, you have to isolate each component of the system and check each one systematically.
I would start at one end, whichever you prefer, and confirm each necessary characteristic:
+12.5-13.5V at coil (+) with points open,
+9v, more or less, at coil (+) with points closed,
Less than 1 ohm resistance between points plate and battery (-),
Move points plate through its arc (suck on and release vacuum advance) and confirm no resistance with meter, then re-confirm no flickering with a test light from +12V to the points plate,
Zero resistance through points,
Infinite resistance through condenser,
Check that coil is well grounded, connect spark plug wire to coil and secure other end about 3/4" from ground, connect jumper from (+) to battery (+) intermittently and look for spark each time you pull (+) wire away from battery.
Connect coil to car normally, continue previous spark plug wire connection, turn on ignition, open and close points with a screwdriver and look for consistent spark,
Continue with same arrangement, but now crank engine over and look for consistent spark at end of wire 4 times per revolution,
At this point, connect dwell meter and confirm 30 degree dwell angle,
If everything is perfect at this point, try connecting all spark plugs to their wires, placing each one in a visible location in contact with ground, installing distributor cap, and cranking engine to confirm spark at all plugs (this step is massive overkill, and not a great test of your plugs and wires, but it may tell you something if you're desperate).
As a last chance, if all else fails, find someone with an oscilloscope and see what the waveform says.
I pulled an Olds HEI distributor/plug wires from a working '79 Olds 350. Ran a positive bat + to Bat side of HEI. Checked TDC, fired right up matter of fact running REALLY good... no heed to curve,e tc et c it just frickin' works at least I can now move it in an out of garage as my real project is rebuilding 79 Cutlass suspension, so I need this side track like a hole in the head.
I had one guy tell me it skipped a tooth.. don't think so.
so the problem is with the old coil type ignition. Will go through your list again you sent.
But now I have a way to at least move it..
never had a points system be so much of a PITA before I've done quite a few in my old fart years....
OK think I finally got it one of the welds holding the breaker plate was broken... very illusive would run great for a while.. then not, reset points then OK again for a while.. replaced plate, so far so good. thanks everyones help...
If possible, I think many of us would like to see a picture of this, so that we know what to look for should we ever encounter it.
And I, personally, think it's great that you took the time and energy to finally run down this problem once you had the time, and truly figure it out, rather than just saying "Bad distributor," tossing it over your shoulder, and never really knowing what happened/
Thanks for sticking with this, since your troubleshooting information may be helpful to people in the future.
Be sure you use a ballast resistor, or resistor wire in the vehicle harness, if you're vehicle has one. The idea is: full voltage switched and supplied from the starter solenoid when cranking to start, then ±8v running once engine has started, or ±8v 'key on' voltage measured at coil, so you have actually two wires connected to coil primary connection. If you run un-ballasted supply voltage to coil while running for any length of time, the coil fails in a short time, although I had one last a season finally stranding me at the store on a hot day. The bottom of most quality OEM type coils have a popper like a soup can, and when it is popped out in the center indicating it has been overheated, discard it.
The HEI you installed must have full voltage, meaning no voltage drop when running, although it bears mentioning many end user installed GM HEI systems have been running for decades through a factory resistance wire in older cars.
If you have a liquid filled coil (which you can hear when you shake it), be careful about mounting the coil 'tower up'. The three connections must remain immersed in the oil, or will overheat and cause intermittent hard to trace trouble. Many aftermarket round coils fail installed in factory mounting brackets for this reason.
So many times intermittent trouble is traced to the coil being connected backwards: it should be '+' is where supply voltage is connected, '-' is where distributor wire is connected. Radio noise condensers or 'suppressors' might be connected to either side of the coil depending on what noise situation generally on a AM broadcast receiver is dealt with.
Hold your plug gap to .035 maximum. Wide gaps stress every component in any ignition system, and most of us are not racing, chasing every single last HP.
Inspect the points set after a failure like this, and look for migration of the contact material from one contact to the other, like a pit in one and a identical bump in the other. This can happen pretty quickly if the condenser value in mf is a mile off, or also rarely perhaps some coil problem. In the old days ignition men would check the points and perhaps choose a condenser from a chart of a different value, if the points wear is not even. This is why if your point set wears well it is unwise to change the condenser unless it fails. Keep a spare points set, condenser and screwdriver in the vehicle.
If you know what specs the coil you have should produce, you can use a coil tester, if you can find one. I have a old Herbrand, it has a buzzer inside to act as a points set, and a gap mounted on a wheel which you turn causing the gap to become larger. It should produce a quality spark color up to a certain specified gap. This test can be very hard on a coil especially a older coil which may have some part number cash value, so be careful. Here is a Snap-On:
Last edited by coldwar; January 23rd, 2017 at 10:35 AM.
If possible, I think many of us would like to see a picture of this, so that we know what to look for should we ever encounter it.
And I, personally, think it's great that you took the time and energy to finally run down this problem once you had the time, and truly figure it out, rather than just saying "Bad distributor," tossing it over your shoulder, and never really knowing what happened/
Thanks for sticking with this, since your troubleshooting information may be helpful to people in the future.
July 18th, 2016, 10:45 AM
Coil test
