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Loss of Spark

F

Fordman302

New Member
Hello,

I have a 67 mustang with a 302. It recently has developed an issue were after running (idling or driving) for 10-15 minutes it will lose spark and die. After sitting for 1-2 hrs it will start back up and do the same thing. It has a Mallory Unilight distributor and all wiring was replaced about 5 years ago and has never had a problem like this before. I checked the ignition coil thinking it might be bad and found some corrosion on the top and replaced it, but still have the same issue. Any help would be appreciated.
 
IMHO you have somewhere a bad connection and therefore a voltage drop at the distributor.
I would start by checking all ground connections. First connections would be Battery to Body and Battery to Engine. It can't hurt to mount a bigger ground strap from Body to Engine/Trans.
A bad connection can be felt where it gets hot or warmer. Depends on how much current it draws.
For the distributor its not so much so you have to take a multimeter .
Maybe it also can be the electronics inside the distributor.
My 2 eurocents.


Verstuurd vanaf mijn SM-A605FN met Tapatalk
 
A little more information would be helpful for everyone. The Mallory Unilight distributor was bought out by MSD in around 2019, so we can assume you have a new version and it has a MSD electronic ignition module and some style of electronic pickup in the distributor?
 
How are you sure it has spark loss? Not really questioning as much as looking for confirmation it is truly an ignition issue.

Just from a general experience perspective, if a situation arises as you describe and a sufficient "cool down" period seems to resolve it that aligns very well with an "over-heating" electronic diagnosis. I don't disagree with Bruno's suspicion about a connection except that I find it very difficult to account for what you write is a pretty consistent resolution to the issue being nothing more than letting it sit for a while. I can't come up with an acceptable explanation that would line up what certainly sounds like elevated temperatures playing a role paired up with a poor electrical connection. My money is on electronics in the dizzy.
 
Horseplay said:
How are you sure it has spark loss? Not really questioning as much as looking for confirmation it is truly an ignition issue.

Just from a general experience perspective, if a situation arises as you describe and a sufficient "cool down" period seems to resolve it that aligns very well with an "over-heating" electronic diagnosis. I don't disagree with Bruno's suspicion about a connection except that I find it very difficult to account for what you write is a pretty consistent resolution to the issue being nothing more than letting it sit for a while. I can't come up with an acceptable explanation that would line up what certainly sounds like elevated temperatures playing a role paired up with a poor electrical connection. My money is on electronics in the dizzy.
Click to expand...
If it is a spark issue, I agree with Terry the most likely candidate is an overheated electronic component in the distributor. I assume you have confirmed that there is still fuel in the carb when this is happening, maybe vapor lock is no longer an issue in today's world?
 
If its the electronics inside the distributor , a "freeze" spray could be used to diagnose this problem or any electronic problem.

Verstuurd vanaf mijn SM-A605FN met Tapatalk
 
B67FSTB said:
IMHO you have somewhere a bad connection and therefore a voltage drop at the distributor.
I would start by checking all ground connections. First connections would be Battery to Body and Battery to Engine. It can't hurt to mount a bigger ground strap from Body to Engine/Trans.
A bad connection can be felt where it gets hot or warmer. Depends on how much current it draws.
For the distributor its not so much so you have to take a multimeter .
Maybe it also can be the electronics inside the distributor.
My 2 eurocents.


Verstuurd vanaf mijn SM-A605FN met Tapatalk
Click to expand...
I checked all the grounds and they seem to be good. Tight clean connections and wires look good. I had a voltmeter on the + side of the ignition coil when it died to make sure it wasn't loosing power there and it still had full voltage when it died. I also double checked all the wires at the starter solenoid and they seem to be good as well.
 
Mach1 Driver said:
A little more information would be helpful for everyone. The Mallory Unilight distributor was bought out by MSD in around 2019, so we can assume you have a new version and it has a MSD electronic ignition module and some style of electronic pickup in the distributor?
Click to expand...
The unilite distributor has a Electronic ignition with a one-piece self-contained optical pickup and module
 
kb3 said:
If it is a spark issue, I agree with Terry the most likely candidate is an overheated electronic component in the distributor. I assume you have confirmed that there is still fuel in the carb when this is happening, maybe vapor lock is no longer an issue in today's world?
Click to expand...
Yes there is still fuel in the carb when it dies. I put a spark tester on one of the spark plug wires and has no spark while cranking after it dies. But let it sit and it fires back up and runs fine until dies 10 minutes later.
 
Sounds to me ignition module in the diz. Don't they use some heat conducting paste underneath that module ???
Maybe the lack of it distroyed it ???? My 2 eurocent .
 
It doesn't appear that any of us are familiar with the Unilight distributor, except that we are in agreement that the electronics are probably at fault. It sounds like the only alternative is to replace parts until it works. Its not a solution that instills confidence that the car is road worthy, and it is expensive. That's one of the problems with one of a kind aftermarket parts- being stranded someplace and not being able to fix it. If you don't intend to take the car far from home that may not be an issue for you.
I'm going to say something that won't be popular. I would switch to a stock points and condenser distributor- send it to Mustang Barn to get the advance curve set-up, and not worry about the electronics dying at some time in the future, because there won't be any electronics. Electronics will not last 50 years- you are lucky to get 20 years out of them. They raced these cars back in the day with the stock distributors, and the electronic versions offer no real improvement in performance. They made millions of these things with the stock parts and those parts are still readily available at your local parts store anywhere in the country- so you can repair it while on the road.
That's my 2 cents for what its worth. In case you guys haven't figured it out, all of today's cars are disposable- they CAN'T last. My 2001 Corvette is a great car, but only about 3 of it's 20 electronic modules are available now- and when they die, the car is dead. They aren't making replacements because it isn't economically viable.
Now I'll go get a bowl of popcorn and be entertained by everyone's comments ;)
 
Let me start the show!

IMPORTANT point number 1. Do you know how hard it is to find a decent set of newly manufactured points these days? Good luck.

Anecdotal sure but backed up by tens of thousands of other users, I have run a Pertronix set-up in my car for five years now. Fears like yours prompted me to buy replacement components to have on hand just in case. I've had a spare dizzy module collecting dust in the glovebox since day one. Bought a spare electric fuel pump too. It's just as old, just as unused as the Pertronix bit.

If I end up having to eventually replace that module sometime in the next 15 years I am not going to complain about the durability of it. How often does one have to replace a set of points again? ;)
 
I wrote DECENT set of points. Hell, you can find parts all over. Find ones that work or last for more than month. Blue Streak used to be a good go to many years ago but not so sure anymore. Most stuff is very cheap import anymore and you could waste a full weekend reading about and watching Youtube videos about how crap stuff is these days.
I'm older and hate new shit as much as anyone else with a few miles under their belt but to try and argue that old points ignitions are anywhere near as good or more reliable than a modern electronic ignition is just silly. I fought EFI for decades until I finally broke down and tried a system. An early one at that. How can you argue with turn key operation regardless of circumstance? Self-learning so no real tuning needed for a cruiser. No power loss but likely better performance across the entire RPM range. Love me old shit but putting modern twist to stuff to make it more enjoyable/useable is where it is at. Having written that, I'll be firing up a triple Stromberg set-up shortly so wait for all the cursing when I try to get that thing sync'd and tuned. BTW, the old blown flatty sports a full MSD electronic ignition system complete with boost referenced timing control. It has cloth wrapped sparkplug wires though!
 
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