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Old 11-14-13, 10:52AM   #1
spareparts
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Angry Ignition problem?

Call me Stupid. Now that's out of the way, I'm getting my ass kicked by a points ignition system.
1968 Grand Prix 428, 4 speed, 8 lug wheels, a/c, power everything- nice car. It wants to break up and stumble until it dies. it won't hold any rpm steady. Timing mark bounces around, spark drops out. If I hold a timing light on it & watch it, it stops flashing intermitantly until it finally cuts out. Dwell holds steady at 30* while the spark breaks up, shows 30 * until the engine winds down completely after it stalls. It's a standard ignition, everything has been gone through.
Rebuilt distributor (GM), new points, condenser, cap, rotor, wires, plugs. Repaired a bad connection at the coil, Spark still breaks up until the engine quits. What did I miss???
Rich
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Old 11-14-13, 11:42AM   #2
Mark G
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Test the coil. Make sure the battery is good and is fully charged. Also make sure you have a good grounds.
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Old 11-14-13, 12:55PM   #3
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I second the coil. If that's not it, I would put another condenser in it.
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Old 11-14-13, 01:36PM   #4
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Quote:
Originally Posted by spareparts View Post
Rebuilt distributor (GM), new points, condenser, cap, rotor, wires, plugs. Repaired a bad connection at the coil, Spark still breaks up until the engine quits. What did I miss???
Rich

check the primary wire from the coil to points, it comes through the bottom of dist. through a rubber grommet, they get worn/frayed from flexing with vac advance movement, I've had one short out on me while on vacation during the early 1980's on an 1972 Olds Cutlass with Rocket 350-4bbl. I've also looked at quite a few that were worn and needed to be replaced.

also, change the CONDENSER. Put the old points and condenser back in that ran the car ok. I changed points/condenser in my 1970 GTO back in 1982, and the damned thing would not start for 2 days. I thought maybe I f-cked something up while tuning it, or broke a wire, etc, but it turned out out the new condenser was DEFECTIVE.

I put the old one back in and it fired right up.

Check main coil wire to cap, the big one in the middle of cap. Check cap for cracks. Make sure rotor is on right, sometimes they get tilted in there and are not fully screwed down into position.

yes, check coil, with a known good one substitute- but I want to tell you something, in 35 years of wrenching on Pontiacs and various other GM's, I have not found a single bad coil in my life. It always was something else. The "coil" is basically a STEP UP TRANSFORMER that induces a high voltage into the secondary using a magnetic field- unless they are dropped, smashed, or heated cherry red with a torch, there's not much that can go wrong with them, they are simply copper wire wound inside.

make sure the post connections at top of coil, are not pulled out loose on the coil, or the primary wire shorting to the metal case or other nearby metal on the intake.

are you ready for some tough love ?
TRACE THE RESISTANCE WIRE from the primary side of coil back to the ignition switch, make sure it's not broken or shorted somewhere, this wire cuts the 12 volts down to 9 volts to save on points life.

NOW THE BIGGIE- when cranking an old Pontiac, it feeds 12 VOLTS directly to the coil during cranking only, this wire goes from the coil down to the STARTER SOLENOID, it's one of the little wires on the solenoid. If this wire is frayed and touching the header, block, heads, other brackets down there, it will short out the coil and kill the engine- and sometimes do it intermittently like you are experiencing.

the plug that goes into the column mounted starter switch, may have come loose from the prongs, or wires coming out of the plug- I've had to re-harness and re-wire a few Pontiacs that had worn out harnesses from previous stripped-bolt mechanics working on them

and one more- the ignition switch on the column, can come loose, those little 5/16" screws on there loosen up, then the starter switch slides to "off" position due to spring tension in the switch, and will shut the car down- I had a 1970 GTO shut off on me the day I bought it, while driving it home, it was that. I had to drop the switch, start it with a screwdriver in the switch, on the side of the road, and drive it home with switch hanging under dash.

yes, I've seen and had all these problems over the past 35 years, but never a bad coil.

don't discount a possible fuel starvation problem, gas line cracked/hole, carb needle/seat sticking

Last edited by Zedo : 11-14-13 at 01:49PM.
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Old 11-14-13, 07:32PM   #5
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Hey Zedo, gotta admit I didn't consider the bypass wire shorting to ground. Thanks for that tip - thanks for all of them, and thanks to GTOfreek & PolarPontiac also.
This morning after my desperate plea for help & my frustration subsided a bit, I looked up the original GM coil specs. p/n 1115238 has an INTERNAL resistor. The replacement coil from Standard is wrong - it is your common external resistor. I pulled the points out of the distributor and found a melted set of contacts, complete with carbon trail almost to ground- just enough of a gap to give the arc another path. I kept going back to the 11.3 v I had on the coil wire, key on. Never checked the voltage running, it was probably ramped up by the alternator, little shtt like that you take for granted burns your ass as much as the torch you sat on. Converting to electronic, let you guys know what happens. Tried to upload a pic of the misery, hope it's visible.
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Old 11-14-13, 07:37PM   #6
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trying the pics again, then I give up
Rich

Click image for larger version

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Old 11-15-13, 09:43AM   #7
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Quote:
Originally Posted by spareparts View Post
trying the pics again, then I give up
Rich

Attachment 26619

Attachment 26620


Bingo....
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Old 11-15-13, 09:50AM   #8
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Quote:
Originally Posted by spareparts View Post
Hey Zedo, gotta admit I didn't consider the bypass wire shorting to ground. Thanks for that tip - thanks for all of them, and thanks to GTOfreek & PolarPontiac also.
This morning after my desperate plea for help & my frustration subsided a bit, I looked up the original GM coil specs. p/n 1115238 has an INTERNAL resistor. The replacement coil from Standard is wrong - it is your common external resistor. I pulled the points out of the distributor and found a melted set of contacts, complete with carbon trail almost to ground- just enough of a gap to give the arc another path. I kept going back to the 11.3 v I had on the coil wire, key on. Never checked the voltage running, it was probably ramped up by the alternator, little shtt like that you take for granted burns your ass as much as the torch you sat on. Converting to electronic, let you guys know what happens. Tried to upload a pic of the misery, hope it's visible.
Yeppir- you nailed it- can't run points on 11.3 volts, it will melt them, they have to run on 9 volts and even then they wear out. Whenever dealing with electrical use the right tools and check with a multimeter, resistance and voltage. That's why we used to file points and change them so often, they wear out in spite of running on 9 volts and using a condenser. Check the voltage at your ignition switch primary wire, because if it's already down to 9 volts due to harness resistance wire, and you add more resistance to it, it cuts it down even lower and the spark will be greatly diminished.

Points are made to crank/start on 12 volts, run on 9 volts.

Yes convert it to electronic, get a Mallory Unilite conversion, they are easy to install and last a long time, IIRC they may run on 12 volts ?? but I'd have to check to be sure. The kit goes right in the stock distributor. I run one on my 455 RA V with an Accel Super Coil. The car can sit for a year outside, I connect the battery, pump the gas pedal on the Holley 750 twice, and it fires INSTANTLY- I can get out of the car and walk away in about 1 minute and it stays idling, with a tunnel ram and no choke.

With points it would take 10 minutes to warm up, stabilize, and stay running. Point ignition just doesn't have the juice and accuracy that electronic does.

These Mallory and Accel parts are not high dollar, I got the coil for free, and the Unilite conversion was like $65 or something back then. There are more high tech better racing and high perf ignitions for sure, like an MSD, but you can't beat the simplicity and low cost of an MSD for a street car. (all the aluminum housings for MSD boxes are made by a local firm 10 miles from my house, called Sapa Aluminum, I have family working there for 25 years- but I wouldn't run one on the street- it's overkill).

HEI is more reliable than points but I don't like that big cap, it gets in the way sometimes, and I can't run an HEI with the tunnel ram, it hits the intake. Also the HEI has a very crappy advance curve in stock form, it's easier for me to dial in a small point distributor that's been converted to electronic.

Last edited by Zedo : 11-15-13 at 10:17AM.
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Old 11-16-13, 03:40AM   #9
sprint250
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Default Unilite conversion

some info
Attached Files
File Type: pdf UniliteTest.pdf (407.1 KB, 96 views)
File Type: pdf 29371.pdf (22.2 KB, 65 views)
File Type: pdf 29351.pdf (42.2 KB, 65 views)
File Type: pdf Mallory Unilite Conv558_559_560.pdf (91.2 KB, 78 views)
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Old 11-16-13, 04:50PM   #10
spareparts
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Default hood tach hookup?

I wanna say thanks again for all the info, guys. A friend's car by the way, He had a Pertronix electronic pick up, so I threw it in, readjusted timing. car runs! Now my problem is how to get the hood tach to work. The (factory)Dixco tach had a lead with an inline fuse to the negative side of the coil. Now with the electronic conversion, the tach doesn't recognize the ground signal. I know some other cars that ran a Dixco had the lead on the hot side (AMC, Ford). Has anyone ran an MSD or similar tach adapter to fix this? What do I need to get?
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Old 11-16-13, 08:30PM   #11
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Took it for a ride, all is well. Tach does work on the negative side, realized the tach was unplugged.
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