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Discussion Starter #1
hello all! i'm back w/ my same problem - '66 chevelle bigblock that cuts out and cuts back in.

happened three times today driving to work.
i can safely say i was wrong and ONLY the motor goes out, radio still plays. i can glide along, and i guess the TH400 "roll starts" it again. sometimes it is to the side of theroad. doesn't seem to be connected to weather, temp., etc...
does this tell me its in the primary ignition circuit? i still think "bad ground" can someone tell me if a car will run w/o the ground strap? i cant' seem to locate it. i found frame to fender but no motor to frame.
all other wiring looks good but i guess looks arent everything.
please help, i'm at wits end and my upstairs bathroom just flooded my downstairs - i don't need this.

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'66 chevelle 402 TH400
 

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yes the engine will run without a ground from the block to the frame. does it cut off and then immediatly restart? Or do you have to sit a while in order for it to fire? Next time it fires I would immediately check for spark, to see if that is the problem. Next see if you have voltage to the coil if no spark. Lots of things could do this..worn ignition switch, loose wires, etc. At least if everything else works and the engine turns over all you need to look for is gas and spark, then go from there.

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Dave (NY)
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thanks for input -
i would say that it always starts about 5 seconds after it dies. like; bad connection and then back on. i don't have time to look for spark when its dead as it runs like a champ for 99% of the time. seems to me a replacemnt ignition switch would be the next best place to turn?

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'66 chevelle 402 TH400
 

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I suggest hooking a voltmeter directly to your coil wire and leaving it hooked up while you're driving. Or, if you have a voltmeter in your dash, hook up the hot side to your coil instead of wherever it is hooked up now.

When it happens, take a look at the voltmeter and see if it drops. This will keep you from doing the old "parts changing" style of troubleshooting.

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Discussion Starter #5
thanks for reply -
if voltage drops does this tell me bad coil?


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'66 chevelle 402 TH400
 

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Does it give any warning before it cuts off or does it just die like someone turned off a switch. If it gives a warning like coughing, I'd suspect a fuel filter pluging up.

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Tino #28 Gold
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Discussion Starter #8
no warning - just off like a light switch.
i have a mallory (sp?) HEI type distributor. battery is in trunk w/ a screw type shut-off on the ground terminal.

these are things i'm considering:
condensation in the dist.?
bad ground - motor to frame
bad key switch
bad coil wire or coil
bad wire or connection in ignitionn circuit
searching the archives on dash harness installation.
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For what its worth: I inherited a '72 Plymouth Valiant with a 318 V-8 and torqueflight. It would ocassionally just cut-out. Sometimes it would restart before I could pull over. Sometimes I would pull over and peer under the hood and scratch my haed and after a few minutes it would start again, One day it did it at a particularly inauspicious location. I figured it was the ignition. It was. A shop replaced the ignition pickup coil or something like that and the "module". The coil was intermittently bad, and the module, I suppose, was replaced as a preacaution. I had threatened to replace the distributor with a points type. I will next time it happens. This was the second time the ignition had failed like that. Like I have noted before when we talk about ignitions, I've never had a point ignition let me down. Electronic ignition has left me stranded several times, not just on this Plymouth.
Hope this helps

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Discussion Starter #10
jj'65:
sounds like exactly what is happening...
did they "test" or was it just a crap shoot?
i'd like to get this behind me.



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'66 chevelle 402 TH400
 

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I don't know. It wasn't a Chrysler garage; just a good independent shop. I'd guess that it was their educated/experienced guess to replace the parts. Maybe one of the "real" mechanics on this forum can tell you if there is a special tester for these. Other than checking for poor connections, bad grounds, etc. there's not much a guy can do about most electronic stuff except put in a new one. Like a spark plug--who bothers to clean/test plugs these days? They practically give them away. Good luck.
 

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Engine grounding strap(s) are either located off the front of your passenger side head, alternator backets, or the rear of your block.

Also, since your battery is trunk mounted, do you have the ground from the battery go directly thru the trunk to the frame?? Verify & check that your connection is clean and tight and that the pass thru is grommeted thru the trunk floor and not cutting into the ground cable.

Time to check ALL connections first before spending countly $$'s on trial & error parts replacement. "Damn electrical gremlins !!"

Pass ya later,
Greg

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I would highly suspect the ignition system circuits.

First off, a battery in the trunk means YOU NEED TO RUN A SMALLER WIRE (ABOUT 12 GA.) FROM THE NEGATIVE TERMINAL OF THE BATTERY TO THE ACTUAL CAR BODY, FIND A GOOD METAL PLACE IN THE TRUNK AND BOLT THAT SUCKER TO IT! You need to "reproduce" what GM did up front, they had a negative wire going right to the passenger side fender. This gives the BODY a good ground--this is needed as all of your lights and accessories feed thru the body, not the frame.

It's okay and recommended to keep the "massive" ground wire to the frame. Make sure it is good clean and tight at both locations--where it comes from the battery and were it comes up to the engine.

You say the radio works? Stock radio?? Or wired to stock radio wires? If the radio still plays, yet it gets it's power Directly from the battery (if you wired it like that), it doesn't mean jack, as of course it will still play.

The question to ask is DOES THE WHOLE CAR LOOSE POWER. When it dies, hurry and put on your turnsignals, if they don't work, the vehicle's ignition-on power is completely lost.

However, I suspect it is in the igntion itself, bad module, bad coil, bad connections, etc.

Joe



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Discussion Starter #14
thanks for input -
here's what i have found... others may have this info already but i am reading tech info about my ignition from www.centuryperformance.com/mallory/mallorytech.htm

seems HEI distributors hate bad grounds and spikes. i'm learning.

my battery has good ground to frame, but block has ground strap to BODY. then body to frame strap is in engine compartment. doesn't sound like good ground to me. i would like to put ground to frame and body both from batt like coppertop said, then run ground strap from block to FRAME. and clean body to frame ground - then get to ignition pickup which is probably going out... also need a different coil. i'll figure it out.
coppertop: you talk about the "massive" ground cable from batt to frame, but "up to motor"? isn't this the ground straps job? (block to frame?) thanks!(rolling up sleeves and heading for the garage)

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'66 chevelle 402 TH400
 

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Whooa,

That's the problem if you are depending on those tiny pathetic ground straps!

You need to have another "massive" ground (about 4 guage) from the frame to the actual engine block. If you don't have this, all of that major starter current is trying to flow thru the little ground straps that link the body to the engine and the engine to the frame! They are NOT meant for that kind of current demand!


So, like I said before you need to reproduce what the "General" originally did on these cars. A little ground wire (about 12 guage) from the negative battery terminal to the ACTUAL body. Then the main ground--the massive ground wire off the battery (-) needs to get bolted to the frame--and bolted well!

Now, you need another "massive" ground wire coming off of the frame under the hood and connected to the engine block. So when you start your vehicle, the high current needed to turn the starter gets drawn thru the large ground wires and the frame itself.

To be really safe, you could even use 2 guage wires for the grounds at each frame connection.

The ground straps in vehicles are only to make ground "unity", not designed to carry heavy current.

Joe



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