New problem, engine randomly dies, no spark

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RIBS

Well-known member
Joined
Jun 9, 2021
Messages
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Location
Metro Atlanta
My Car
1971 Sprint Tribute 302 C4 Convertible
So the car generally has been reliable, but only drove it maybe 200-300 miles in first year while I rehab it. I recently rewired car with AAW kit, and have about 100 miles on it since completion, with no problems until now.

here’s what’s happening…start car normal, nothing amiss…drive a short distance, a half mile or less, and the engine just stops, cuts out completely and instantly, no cough, no chug, just dead. Fits got gas, determined everything else works, all electric, just no spark. Starter works, lights work, horn, turn signals, ac fan, all good. AAW kit has ballast resistor wired for my stock points distributor. All points, plugs wires caps coil are less than a year old.

I finally wiggled my coil to distributor spark wire, and it seemed, loose, it had always been a little flakey. After I did that, the car ran. A day later, same thing, but car would not run, I tested the coil wire for continuity and it seems dead, so I bought a new coil wire, and a full new spark plug wire set so I would have a backup…. I put on the new coil wire and car fired, so I pulled it out of my driveway into the street and it died 20 feet from my driveway…I tried the coil wire from the new wire set, car is still dead….it was dark after messing with it, so i towe’d it up my driveway and stashed in garage for the night.

a friend of mine said possibly ignition switch, he suggested replacing both the key cylinder part and the electrical part mounted on steering column…I am going to double check some wiring tomorrow in the daylight, the plug had to be reworked for the ignition wire bundle for the AAW kit, maybe something didn’t seat.

what other causes should I look at
 
Ok, you need more information before you start spending money on parts that may be good. You’ve got to trace the loss of power when this happens. Start at the coil and work backwards until you find power. Of course, a loose ground could be the culprit, or one that’s come undone; hanging my a thread thing. If it turns out wiggling the ignition key gives you on/off power, then you can determine if it’s a loose wire or bad switch. We’ve all done the swap parts till we find it and swore we wouldn’t do it again. Good luck, Steve.
 
The first thing to do is to make sure that you have power to the coil. With the ignition on check the coil +. If you have power to the coil and the engine will not start and there is no spark, then the key cylinder and everything under the column should be fine. Have someone crank the engine while you check the voltage to the coil +. during cranking you should have 12 volts, which will drop after the engine starts and you are no longer cranking it. If you do not have power to the coil + you can temporarily run a wire from battery + to the coil + and see if it starts. Remember that the wire from the battery will not have a resistor so you should not operate the car like this, as it will burn the pints and condenser. If the car starts with power directly from the battery to the coil, your issue is with the wiring to the coil. Your no start could be as simple as bad points, condenser, coil, or your starter relay.
While cranking, the starter relay provides 12V to the coil through the i terminal, when cranking the i terminal should have 12V and your coil should have 12V, check that to make sure your starter relay is working correctly. When running normally the voltage to the coil goes through the resistance wiring and voltage will be much less.
Also check the obvious, remove your distributor cap and crank the engine, make sure that your rotor is rotating as you crank it, and that your points are opening and closing. Check your rotor to make sure that it is seated correctly and that it is not loose. Check your points wire to the coil negative and make sure that the wire is in good condition and does not have a break in it.
 

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Sounds similar to my problems.

1) I found the connection above the brake pedal, ignition switch to main harness was loose.
2) I was told to get a blue wire condensor. Standard motor products FD77. I also replaced my coil.

Have not started it since putting the condenser and coil on it, so I am unsure if that fixed it or not.

Kcmash
 
I have it resolved for now, new coil. Also, my ballast resistor is shooting 12.3 volts to coil, my understanding is it should be more like 6-9 volts, so I am ordering new ballast resistor.
 
I have it resolved for now, new coil. Also, my ballast resistor is shooting 12.3 volts to coil, my understanding is it should be more like 6-9 volts, so I am ordering new ballast resistor.
Glad to hear that you found the gremlin. I went through a similar situation a few years ago and mine was the connection on the I post of the starter relay as they are M/F socket connectors and for some reason were worn out and loose enough for intermittent contact.
 
I have it resolved for now, new coil. Also, my ballast resistor is shooting 12.3 volts to coil, my understanding is it should be more like 6-9 volts, so I am ordering new ballast resistor.
Be careful how you measure this. Best to read the voltage at the coil while running. With a resistor wire and the coil in place, you should see voltage somewhere about 10.5-11.5 V. With engine not running, you'll see full battery voltage. The 6-9 volt is the minimum the engine will run on, but poorer the lower the voltage is.
 
Be careful how you measure this. Best to read the voltage at the coil while running. With a resistor wire and the coil in place, you should see voltage somewhere about 10.5-11.5 V. With engine not running, you'll see full battery voltage. The 6-9 volt is the minimum the engine will run on, but poorer the lower the voltage is.
Thanks, it was 12.3 at coil while running…the other side of the ballast resistor was 14.2-14.6 depending on alternator output..so it was scrubbing off some…but is over 12 too much for coil and points?
 
Are you running a resistor wire and a coil in your new wiring setup? You are still using points? You can continue to use points, but they probably won't last as long as they could, so be prepared for that. Switching to a Petronix I would be a good change if you are still using points, and it likes the 12V.
 
So the backfiring is gone with a new coil and the new condenser. Idle is good, acceleration good.

Now I am still experiencing fluctuation power when cruising. At 2200 to 2500 rpm in 4th gear I am at 55 to 65 MPH. The Tach holds steady, but the car has random surging in the power. If I accelerate it does does not bog.

Is there a chance my power valve is the wrong size in the Holley?

Is this something that can happen with a cheap set of points?

Should I do all new plugs and wires, cap and rotor?

I know, everyone will say "go Pertronix or Duraspark". I am shy on the Duraspark because of the Ram air cleaner and the original look under the hood. Pertronix, had a bad experience, and I have a factory tach. I try to read how simple the conversion is, and I get lost in adding resistors, and re-wiring the tach so it will work. And of course, with all this crap, a Pertronix is just another black box of gremlins that can keep you off the road. (I lost a year with my last Pertronix)

Any good suggestions or guidance out there?
 
Sounds like a lean surge to me, double check the primary float level. You shouldn't be cruising on the power valve, it should only open at it's rated vacuum level. What jets are in the primaries? What's the idle vacuum reading?
 
Hemikiller,

Thanks for the reply. I need to check jet sizes. I have been thinking it is fuel related. Even the last engine had fluctuation at highway speed(same carb here). With this engine I am at a totally different cam, and it is acting the same.

What size do you suggest for primary jets? I left the standard ones in there. The primary float is at mid window. Even when I have the power fluctuation it accelerates smooth without a bog or hesitation.
 
Check the list number on your Holley and check and see what primary jets it has, while you are there check the power valve as well. As hemikiller said, it sounds like it is probably a bit lean. Check to the plugs to see how they look too.
 
I am really thinking I am undersized on the Jets. This carb is the 86670 Part # 0-86670BL. This has 63 Jets in the primary and 73 in the secondary.

I am thinking I should go with 66 in the primary. Your Thoughts?

kcmash
 
Wow, they don't give those carbs away....

63 seems awfully lean, thats something I'd expect to see in a 600VS carb. 66 would be a good start to diagnose the issue. Make sure you're midway on the sight glasses before swapping jets, a low float bowl level will act the same. You could even raise the level a bit to see if it helps.
 
Surging in 4th at 2200-2500... do you have the same condition in 2nd or 3rd gear at that rpm range? I don't know your set-up, but may be simply lack of ignition advance which will mimic a "lean" surge condition. As previously stated, check your plugs as a ballpark indicator immediately after driving AND check timing in that rpm range.
 
BTW... a standard cap and rotor will fit a Duraspark distributor. The large cap is to eliminate the possibility of cross fire not that the small cap is guaranteed to crossfire. I've gone back and forth without issue.
 
BTW... a standard cap and rotor will fit a Duraspark distributor. The large cap is to eliminate the possibility of cross fire not that the small cap is guaranteed to crossfire. I've gone back and forth without issue.
Do you have a picture of your Duraspark installed? If it fits with my Ram Air, I will put it on my wish list. I would plan to put the module in the right side headlight box.
 

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