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No spark when cranking but tries to fire as soon as I let off the key.

ignition module most likely , i had that problem years ago but when my car either started or studddered after letting go of the key it would then start normally .
Good modules are hard to find .
Msd is nice or points or pertronix .
 
I've had that from the module as well.
 
I've had this very thing happen numerous times and never found a smoking gun.
I did pull the bulkhead plugs, clean the terminals and pack them with dielectric grease....and not had an episode in 2 months.
That may mean nothing...I sometimes went several months between incidents. Time will tell.
What i did is good practice regardless.
Yup...
Kleening the bulkhead connectors and coating with dia-electric grease is a great idea...
But another recommendation is to slightly bend down the sides of the female bulkhead connectoras over time the connector tend to expand making lower, quality connection...

Just my $0.02... :thumbsup:
 
Good tutorial for diagnosing no start issues:

 
He says it doesn't fire WHEN cranking. It starts when he lets go of the key. Ballast is fine...
I'm gonna stroke that comment after fighting with my 64 last month. It had the exact symptoms after installing a new ECU. Ballast was good but had 0.7 or so ohms. Would only fire when I let go of the key. Replaced it with a 0.5 ohm ballast and starts like a dream now.
 
There is 2 circuits one for starting and one for running. If you put a jumper wire across the ballast and it solves your problem then the run wire is dead.
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Last year I had a starting problem, it turned out that the rod that pushes the fuel pump was too short (worn down) so I would get a little bit of fuel to start then it would die. Changed the rod and it starts like a champ. if you have a Holly you can check the fuel at the bowl levels.
 
Every time you replace a Ballast Resistor , you are removing wiring connectors , reconnecting , moving cleaning connections

I have seen more bad connectors , resistance in the wiring , then actually bad Resistors or ECUs

Start at the bulkhead connector with your meter , then move to the Ballast Resistor at the actual wiring connectors themselves then onto the Ballast Resistor male spades

Then to the positive side of the Ignition Coil , same thing
 
had this drive me crazy for years... whenever you tried to troubleshoot it it would start fine again....assumed dead spot in switch that would only make contact when you released it...nope, turned out to be a bad pickup in the distributor
 
I would really like to thank y'all for the help. I have since got my car running. It turned out it was a combination of a poor connection at the bulkhead and the pick-up coil. Thank you guys for the great suggestions and help. It is greatly appreciated.
 
I had this same problem, it would fire when I released the starter and if I was lucky it would start. Checked everything and finally replaced the ignition switch and all was good, fired everytime.
 
Post #25 is incorrect. Voltage to the coil IS critical. All coils are designed to work with a certain supply voltage. Supplying the coil with less than that voltage might result in no spark produced.
 
Post #25 is incorrect. Voltage to the coil IS critical. All coils are designed to work with a certain supply voltage. Supplying the coil with less than that voltage might result in no spark produced.
And too much will cook it in the OEM setup. Built to crank and run on 9v which is why the ballast resistor is there
 
Post #25 is incorrect. Voltage to the coil IS critical. All coils are designed to work with a certain supply voltage. Supplying the coil with less than that voltage might result in no spark produced.
The coil is simply a stepup transformer so its output voltage is a function of input voltage, as long as there is an input voltage the coil will supply an output voltage. But to better understand about the function of the coil it has to be considered as part of the entire ignition system. As the other components of the system including the distributor, ballast resistor(if used) and ignition module(if electronic) has to be matched to work together. The majority of reported problems with ignition systems is the result of a mismatch between its components.

Just my $0.02... :thumbsup:
 
Yeah, blah, blah, blah. The statement in post #25 'coil voltage is not crucial' is still wrong.
 
If the ignition switch power checks out good try powering the ignition circuit only with a separate battery. This means leave the ignition switch off, and add power to the ballast resistor with a jumper to the other battery, and negative connection to block. Use the original battery to crank the starter by jump power to the start terminal of the neutral safety switch.
This will separate the cranking and ignition power circuits for troubleshooting.
1. If the engine fires up, the ignition circuit is fine.
2. If no start, make sure there is a ground from the block to the control module, and try again.
3. Is no start, disconnect field wiring to alternator just in case the brush is shorting.
If the engine won't start, the issue is somewhere in the ignition circuit.

If the car starts at #1 above, your battery cables/connections have high resistance. Replace battery ground cable.
If car starts at #2 above, you likely needed the engine to body (ECU) ground.
If #3. have the alternator checked, and inspect the brush holders.

The why do this? The ECU needs to detect the signal from the distributor pickup. In detecting the signal, the ECU needs a ground reference for the signal.
If the battery ground wire has too much resistance, the starter current (Amps * resistance = voltage) will raise the "ground" voltage at the engine block, but the ECU is grounded to the firewall which might not be the same "ground" reference as the block. When releasing the key, the high starter current stops, and the ground references are much closer because there is much lower battery ground voltage drop (lower current = less voltage drop.)
This is for when you have already checked all the obvious things, and get really stumped.
 
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Sinitro,
I know how ign systems work & probably knew decades before you did. I was switching ign coils on/off with SCRs in the 1960s....
See if you can spot the errors in the link you provided....
 
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