1975 304 coil
- Thread starter MattC71
- Start date
It's a '75 according to the title.
Too bad the title does not show anywhere on the page when you read the message (I've compained about this before).
No pics.
You have a lot of choices.
Assuming you still have the Prestolite ignition, it would not be a sin to replace a failed coil with a new OEM-type coil.
I would try to borrow a coil from another car to test before I bought a new replacement.
The Prestolite stuff is known for being unreliable, and there's no easy way to test it.
Check the TSM for diagnostic procedures - the later the manual the better.
The full '77 TSM is on the Tom Collins site.
Not a fan of the HEI distributors, but people like them it seems.
I would go with a '78 or newer Duraspark distributor and the HEI module, like I have in my CJ-6.
Another alternative is the '73 or older Delco points distributor.
You can use this to trigger a MSD module, and the points will last a looong time.
If the module fails, just bypass it and run points ignition for the time being - built in backup.
Too bad the title does not show anywhere on the page when you read the message (I've compained about this before).
No pics.
You have a lot of choices.
Assuming you still have the Prestolite ignition, it would not be a sin to replace a failed coil with a new OEM-type coil.
I would try to borrow a coil from another car to test before I bought a new replacement.
The Prestolite stuff is known for being unreliable, and there's no easy way to test it.
Check the TSM for diagnostic procedures - the later the manual the better.
The full '77 TSM is on the Tom Collins site.
Not a fan of the HEI distributors, but people like them it seems.
I would go with a '78 or newer Duraspark distributor and the HEI module, like I have in my CJ-6.
Another alternative is the '73 or older Delco points distributor.
You can use this to trigger a MSD module, and the points will last a looong time.
If the module fails, just bypass it and run points ignition for the time being - built in backup.
The title is there under the "Home > Forums > Jeep Discussions > ...." Links. It's just black on a dark blue background so it's hard to see. You can highlight it with your mouse to make it visible. Ideally, the theme will get fixed, but it sounds like Vanguard has had a lot on his plate.
In the meanwhile, you can select the "Alternate" theme to see the titles.
Ahhh.... it takes you to the dark side....
I don't see pics either; why not describe what the P.O. replaced the stock dist with (brand, etc.)
FWIW, I have a SBC in my Wagon. I was having all sorts of odd problems that looked like fuel and or ignition. It came to me with an original (not Holley) MSD dist and 6an box. The vac advance module took a dump, and while replacing it I noticed the advance mech inside the dist was all made of plastic. The arm connected to the vac module had some cracks... I ended up replacing the dist, 6a box and MSD coil with a Pertronix Dist and coil, no box. I was impressed with the Pertronix, mostly metal and made in USA. Uses standard GM cap and rotor. And now I have more room without that 6an box. It fires on the first crank... and the free coil that came with the new dist is chrome, that adds 10hp!
I guess what I'm saying here is take a look at standard non-hei disty's. The Pertronix I got was less than the HEI versions, well made in the US. And I would guess it might be an upgrade over the stock AMC dist. (?)
I don't see pics either; why not describe what the P.O. replaced the stock dist with (brand, etc.)
FWIW, I have a SBC in my Wagon. I was having all sorts of odd problems that looked like fuel and or ignition. It came to me with an original (not Holley) MSD dist and 6an box. The vac advance module took a dump, and while replacing it I noticed the advance mech inside the dist was all made of plastic. The arm connected to the vac module had some cracks... I ended up replacing the dist, 6a box and MSD coil with a Pertronix Dist and coil, no box. I was impressed with the Pertronix, mostly metal and made in USA. Uses standard GM cap and rotor. And now I have more room without that 6an box. It fires on the first crank... and the free coil that came with the new dist is chrome, that adds 10hp!
I guess what I'm saying here is take a look at standard non-hei disty's. The Pertronix I got was less than the HEI versions, well made in the US. And I would guess it might be an upgrade over the stock AMC dist. (?)
Just to be clear - a '75 Jeep came from the factory with the Prestolite igniton including the electronic distributor and module.
Even when new they were trouble, and are often replaced.
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Even when new they were trouble, and are often replaced.
Desktop computer or phone?
Desktop:
Get your picture in the form of a jpeg or tiff or png.
Make sure the file is less than 1M in size (larger will be rejected).
Drag and drop into your message.
Or, you can put a link to your images in your message.
You will need somewhere to host the files that's accessible online via a http address.
jeepdaddy2000
Well-Known Member
Points distributor:
Easy to troubleshoot.
First:
Remove the points and clean the contacts. You can do this with a small file.
Reinstall
Set the gap. You can do this with a feeler gauge.
Crank the engine to see if you have spark.
Or:
Turn the rotor between two towers. You can bump the motor or loosen the dist to do this.
Turn the key on.
Pull the coil wire and hold it about 1/4" from the block.
With your fingernail, hook the point arm and open the points. You should get a fat spark out of the coil wire.
If you get spark:
reassemble everything, double check your gap (you can use a dwell meter now) and set your timing.
If not:
Disconnect the pigtail at the - side of the coil.
Check for power at the + side of the coil. If you don't have power, then the issue is between the coil and the ignition. Trace your way back till you find it. Don't forget to check any ballast resistors.
If you have power at the +side:
Check at the - side of the coil. If no power, then the coil is bad.
If you have power:
With the points open (you can use a piece of paper or cardboard), use your ohm meter and see if there is resistance between the - pigtail and the engine. There should be infinite resistance. If you get a 0. then you have a grounded wire/points set.
If you get an infinite reading:
Pull the cardboard out of the points and check again (insure the points are closed. The rotor should be between two towers on the cap). You should get a 0.
If not, then you have a broken pigtail wire or the points aren't making contact/bad.
Easy to troubleshoot.
First:
Remove the points and clean the contacts. You can do this with a small file.
Reinstall
Set the gap. You can do this with a feeler gauge.
Crank the engine to see if you have spark.
Or:
Turn the rotor between two towers. You can bump the motor or loosen the dist to do this.
Turn the key on.
Pull the coil wire and hold it about 1/4" from the block.
With your fingernail, hook the point arm and open the points. You should get a fat spark out of the coil wire.
If you get spark:
reassemble everything, double check your gap (you can use a dwell meter now) and set your timing.
If not:
Disconnect the pigtail at the - side of the coil.
Check for power at the + side of the coil. If you don't have power, then the issue is between the coil and the ignition. Trace your way back till you find it. Don't forget to check any ballast resistors.
If you have power at the +side:
Check at the - side of the coil. If no power, then the coil is bad.
If you have power:
With the points open (you can use a piece of paper or cardboard), use your ohm meter and see if there is resistance between the - pigtail and the engine. There should be infinite resistance. If you get a 0. then you have a grounded wire/points set.
If you get an infinite reading:
Pull the cardboard out of the points and check again (insure the points are closed. The rotor should be between two towers on the cap). You should get a 0.
If not, then you have a broken pigtail wire or the points aren't making contact/bad.
Last edited:
jeepdaddy2000
Well-Known Member
Addendum:
Don't forget to inspect the cap and rotor for any issues.
Don't forget to inspect the cap and rotor for any issues.
TheBeav1955
Member
Don't forget to check the resistor on the firewall had my share of those opening up causing issues
The Delco distributor is an excellent part.
If it were for me, I would add the MSD 6A capacitive discharge module, operating from the points signal.
Then the module handles the coil switching, and the points provide a logic-level signal for the module.
The points will last as long as the fiber block on the cam lasts, say 100K miles.
If all you want is to replace the points, there should be a Pertronix kit that fits the Delco distributor.
Replaces the points with an electronic switch.
Realize that the only part that's "high energy" about the HEI distributor is the hotter coil.
You can get the same spark performance from your Delco points distributor by substituting an aftermarket "performance" coil.
The MSD module boosts the spark intensity by resonating between a capacitor and the existing coil.
It charges the capacitor to higher voltages than the system voltage, and uses the capacitor discharge to fire the coil.
The distributor provides a signal to the module for firing the coil.
If you want the big cap and rotor like the HEI has, the MSD "Cap-Adapt" parts for their distributor should fit.
This will give you the big cap and rotor, and accept the HEI style spark plug wires.
As you may know, Jeep dropped the Prestolite system for 1978 and went to the Ford Duraspark ignition for the AMC engines.
It's a fine distributor, though some service parts (vacuum diaphragm) are NLA.
Both the HEI and the Duraspark (and many others) use the variable reluctance principle of an iron reluctor moving in a fixed magneti field next to a coil.
You can run a HEI module with a Duraspark distributor, or a Duraspark module with a HEI distributor... completely compatible.
The difference is in the packaging.
HEI puts everything under the distributor cap, while Duraspark is separate components.
If it were for me, I would add the MSD 6A capacitive discharge module, operating from the points signal.
Then the module handles the coil switching, and the points provide a logic-level signal for the module.
The points will last as long as the fiber block on the cam lasts, say 100K miles.
If all you want is to replace the points, there should be a Pertronix kit that fits the Delco distributor.
Replaces the points with an electronic switch.
Realize that the only part that's "high energy" about the HEI distributor is the hotter coil.
You can get the same spark performance from your Delco points distributor by substituting an aftermarket "performance" coil.
The MSD module boosts the spark intensity by resonating between a capacitor and the existing coil.
It charges the capacitor to higher voltages than the system voltage, and uses the capacitor discharge to fire the coil.
The distributor provides a signal to the module for firing the coil.
If you want the big cap and rotor like the HEI has, the MSD "Cap-Adapt" parts for their distributor should fit.
This will give you the big cap and rotor, and accept the HEI style spark plug wires.
As you may know, Jeep dropped the Prestolite system for 1978 and went to the Ford Duraspark ignition for the AMC engines.
It's a fine distributor, though some service parts (vacuum diaphragm) are NLA.
Both the HEI and the Duraspark (and many others) use the variable reluctance principle of an iron reluctor moving in a fixed magneti field next to a coil.
You can run a HEI module with a Duraspark distributor, or a Duraspark module with a HEI distributor... completely compatible.
The difference is in the packaging.
HEI puts everything under the distributor cap, while Duraspark is separate components.
jeepdaddy2000
Well-Known Member
An electronic system will eliminate having to reset the timing every time you do a tune up. That being said, don't toss your points dist. The points system is dirt simple and very reliable and may be worth holding on to.
Personally, I'm a fan of the HEI system. The only issue you may run into is manufacturer quality. They are a simple one wire installation and can really clean up the engine compartment. If you go this rout, I recommend using a relay to run it, as they really like a lot of juice.
Personally, I'm a fan of the HEI system. The only issue you may run into is manufacturer quality. They are a simple one wire installation and can really clean up the engine compartment. If you go this rout, I recommend using a relay to run it, as they really like a lot of juice.
Yes, a Delco distributor, probably the best and most reliable for the AMC V8’s. Follow Jeepdaddys suggestions, but add swapping out a known good condenser. In the past decade, “new” condensers have become very unrelable.
Timgr’s suggestion for adopting an MSD CD box makes for a hot, reliable spark, and the points that trigger it often go 50,000 miles or more without touching them.
Timgr’s suggestion for adopting an MSD CD box makes for a hot, reliable spark, and the points that trigger it often go 50,000 miles or more without touching them.