Sudden Engine Die, Rough Idle Carb'ed 351

[TX-ZACH]

I'll work on that once I find my voltage tester. The lighting does surge in and out but that has been going on since I got it. Not brighter just low to dim. Regrounding the strap with fresh metal on metal had no affect. After going through all the connections and visual inspection is clear now. A few loose connections but did not change a thing. Im positve its a fire or spark issue. On a cold start engine runs as normal. Once a couple min's of running just goes dead no matter idle or under load. Once cool you can start it back up only to die within a min.

Could it be a pick up coil? My next steps are to just replace the dizzy and or voltage reg both.

 

[DirtDonk]

It can be a pick up coil, but there’s an easy test for that.
Stop throwing new parts at something that are just going to potentially cause more problems because new parts are piles of crap these days.
You might take a perfectly good part and add a bad one to your list of culprits.

I’ve already forgotten what distributor you have, but it sounds like Dura spark?
If so, Disconnect the distributor and use an ohm-meter. you’re looking for between 400 and 700 ohms between the purple and orange wires.

 

[TX-ZACH]

Thanks Paul. Its a Proform Street Strip HEI with now Pertronix Ignition Module and Coil. Wire wise I got a red, white, off coil. Black ground off coil and green for the tach.

 

[DirtDonk]

OK got it.
I do remember reading some ways to test those years ago, but no idea how that works.
But if it’s a GM Hei style, then it’s got a GM HEI module inside. But this one’s been running fine for a long time?
I wonder if they didn’t put enough thermal paste between the module and the heat sink? Might be a reason for a failing module. If that’s what’s happening.
Could be worth pulling it apart to take a look.

 

[DirtDonk]

But I should also go back and read the whole thread to make sure I’m not just whistling Dixie.

 

[TX-ZACH]

Both the standard ignition mod and the new one I put in had/has thermal paste applied. I did not use dielectic grease and cleaned it spotless. This is all in an fresh built motor, dizzy etc. About 6k miles. Cap, rotor, look good apart, contacts clean. This thing has more maint and repair hours per drive time than freaking aircraft. So frustrating.

You can almost time it on a cold start before it dies. It will start again after about 20 min but run time about 50% less. Like it warms up to a certain temp and dies. Recently moved and not find my volt meter. Once stores open after the holiday Ill get a new one.

 

[bax]

are you running a ballast resistor? Are you using the stock ignition resistor wire for power to the Dist? The proform Dist requires a full 12 V to work properly. If you are running a resistor wire the coil will break down as it gets warm under low voltage.

 

[TX-ZACH]

It appears I have this style harness to the ignition mod.

 

[bax]

It appears I have this style harness to the ignition mod.

All I was asking is if you are using the stock wire from the key on power to the coil. If so replace that wire. It may be a resistor wire.

 

[Broncobowsher]

Stock Bronco wiring will have a resistor wire in the harness under the dash. This limits power to the ignition to keep the points from burning up.
HEI does not use a resistor. It is designed to use the full 12V and does not want the power feeding it to be limited.

 

[TX-ZACH]

I made a jumper from 12v on Battery to positive side of coil and fired right up.

 

[bax]

Funny how that works. Now see how long it will stay running.

 

[TX-ZACH]

Running good so far. Staying up and running past temp.

 

[56f100bbw]

It can be a pick up coil, but there’s an easy test for that.
Stop throwing new parts at something that are just going to potentially cause more problems because new parts are piles of crap these days.
You might take a perfectly good part and add a bad one to your list of culprits.

I’ve already forgotten what distributor you have, but it sounds like Dura spark?
If so, Disconnect the distributor and use an ohm-meter. you’re looking for between 400 and 700 ohms between the purple and orange wires.

Good point some new parts are junk , be better off going to a junkyard get an OEM part maybe

 

[bax]

Running good so far. Staying up and running past temp.

Very good. Perhaps it's fixed.

 

[TX-ZACH]

No sir. Only runs with jumper in place.

 

[bax]

No sir. Only runs with jumper in place.

The jumper is providing the 12 volts. It needs the 12 volts. I am still saying you have a resistor wire in your Bronco harness. You need key on 12 volts. replace your wire and run a new wire to feed the coil

 

[TX-ZACH]

Well that sucked.. 30hrs and about $300. I guess it could have been worse.

Regrounding engine to frame helped seemed to improve things bonus cleaned up my Tachometer response.
Starter cables from Solenoid both were loose both sides, possible conflicts with I terminal creating a constant draw. I went through 2 replacements
HEI Cap was compromised at wiring harness to coil. New CAP, Coil, Ignition Module, Voltage Regulator
Remove Ignition switch ran new wire direct to coil. Ignition Switch was a chore. Red Green wire even down stream at front end was no good by passing the resistor. Never found that after pulling all wiring from dash.
Tested and cleaned up a ton of abandoned wire.

She seems to be running pretty good. I knock the dust off with a 30-45 min cruise. Thanks to all the help.

 

[DirtDonk]

Sucks indeed. But the good news/rose colored glasses/glass half full aspect is that it works better now!
So thanks for good results at least.

 

[TX-ZACH]

The saga continues. I have managed to cause other issues or had/have multi issues to begin with. Ampmeter on dash is showing 0 no movement at all. My battery died shortly after the abuse I put on it with having the ignition problems. I am not sure my alternator is working, could have a draw. Also can someone tell me what the black/brown wire is on the Stater solenoid? Hooking it on the S terminal is where it seems to be happy, I terminal it engages the starter while running. Ignition wise all is still running well.

Its possible I jacked up wiring under the dash when I pulled everything out doing the new coil wire. Which wire do I chase for the amp meter in gauge cluster?