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4 bucket 67's 1967 GTO

2019 March
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Wrongway

Working out the bugs

Question

Ok so I'm working out the bugs in the 428 I just built. Iv ran into a couple issues and would like to know your thoughts and advice. So I'm driving to a buddy's shop yesterday to use his lift to check out my pans and frame before I start tearing down for body work and paint. He about 10mi from me. I get about half way there, pull up to a red light, light turns green and I step on the gas. Car dies. Doesn't shake, doesn't spit or cough, just dies like somebody unplugged it. I try to restart and the motor turns really slow. This has happened before on around the block trips but I thought I had solved the problem. So I push it off the road and it still wouldn't start. I figured typical Pontiac, big engine with headers and heat soaked starter. So im sitting there letting it cool after only driving 4-5mi. My buddy's on the way and she starts. So I pull into Kroger's parking lot to wait for him to follow me and shut the car off so the starter to cool a bit more. He shows up maybe 5min later and again, no start. But it jumped right off! So we get to the shop where we were going and I pull right in and onto the rack. I shut the car off and tried to start it back up. Engine turns slow. We noticed the positive battery cable was hot and jumped when you turned the key. I replaced it with a 2ga and restarted it. It DID start up, but the starter was cold at the time. I let the car run for a few min while sayin thank you and good bye. I started backing up and my buddy who's shop said something and figuring the problem was fixed I shut the car off. (Cant hear over open headers). Anyways the car would not start. Thinking the starter was hot again, getting frustrated and looking up mini starters my buddy puts a jump box on my battery and turns the key. Fires right up. WTF, I get in and shut it of. Starts right up. I shut it off 4 or 5 times and she jumps to life each time. No slow starts jump boom right there. So, with all this said, before this happened yesterday and while trying to solve this problem I had replaced the alternator, voltage regulator, new battery twice. My autometer volt gage shows almost 12 volts when the engine is running. My thoughts are that there may be a broken wire in the charging circuits somewhere. Iv looked but didn't see any. What's your thoughts? Also if I remember correctly I should be able to connect a jumper wire from the Bat+ terminal on the back off the alternator to the positive post on the battery and by pass everything to make it charge, correct? Btw when I got home and shut the car off, it wouldn't start.

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Inspect your battery cables.

Look to see if the cables have come in contract with the either the engine or exhaust manifolds/headers on the way to the starter. Looks to see if the insulation is melted off and exposing bare metal wire. If so, then you are mostly likely grounding the battery to the engine without knowing it.

I had this happen to me on a cross country drive from Michigan to Biloxi Mississippi back in 2002. I thought it was the starter but once I got home I found the melted wire. When the engine is hot, the wire comes in contact with the engine and grounds out. When it cools off, it moves away from the engine just enough to allow the car to start. The correct fix was to use the proper length wire, and the proper factory insulation set-up ( I run factory reproduction HO exhaust manifolds, not headers). I've not had a problem in 16 years since.

Edited by Frosty

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Thanks frosty, I did replace the positive while at his shop and when I was taking it off I found a spot where the installation was melted and about a half inch of bare wire was showing. Thought that was the issue but when I got home it wouldn't restart. I believe you're correct and that was why it died to begin with though and it did make it home without dying again.  Not sure as to why it wouldn't restart after I got home though. Any thoughts on that?

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Sounds like the battery may have a dead cell in it..When you put a multi meter on it...With nothing turned on does the battery show a 12 volt surface charge..?? Then with the multi meter still on it have someone turn the key to start the engine if the voltage drops way off...like maybe to 10.8 volts or less..That would indicate a dead cell or two in the battery..

I noticed that you said that according to the volt guage that it it showing almost 12 volts..If that is the case the alternator won't keep the battery charged enough to keep up with the electrical load and will slowly kill the battery...If the alternator is not putting out between 13.8 to 14.5 volts it will not keep the battery sufficiently charged...The easiest way to check is to get the engine running then take the multi meter and check the voltage right at the back of the alternator...Place the red lead on the big stud where the main battery wire hooks to the alternator then take the ground or black lead and ground it right to the case if it checks OK there..13.8 to 14.5 volts...any less it won't keep up...(Anymore than that indicates a voltage regulator problem)...If it checks within those parameters the the alternator is probably OK...One other check to do with the key off...Is to take a regular 12 volt test light...Pull the ground cable off the battery..Then put the test light between the ground cable and the negative post on the battery if the test light lights up... That shows that there is an unwanted power draw in the electrical system somewhere... Could also indicate a bad diode in the alternator...

Next thing to do with the engine still running check the voltage right at the battery..If the voltage there is less than the alternator is putting out....look at your cables really close to be sure that they are not dirty at the connections or broken and is properly grounded (the heavier guage wire you use for the battery the better) ......

Edited by TWO LANE BLACK TOP
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Thanks Black top, ill do all of those test tomorrow and let y'all know the result's. Its to late right now to start it up, its a bit loud lol. Be glad to get the exhaust ran.

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Two Lane's advice is spot on. Broken or ground battery cables will drive you crazy trying to start. However if the battery is no good or the alternator is not charging the battery sufficiently, then you clearly have other gremlins to chase. 

One other thing to check. If you have the original wiring harness, then there may be a small glass fuse near the alternator. Inspect the fuse and the case for dirt or moisture contamination. Clean or replace as necessary. I had to replace this fuse once on my Lemans because I noticed it was slightly cracked and it had water in it! Not a good thing!

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Thanks guys, I really do appreciate all the help. OK so here we go, 

Battery cables are good and new, replaced them yesterday but I did double check them.

With the car off the battery shows 12.2V

Negative cable disconnected, one end of 12v tester clipped to negative terminal and the other end touching the negative post. Tester did not light up.

Battery while cranking 11.5V

Alternator while running 12.1V

Battery while running was 12.1V

The fuse behind the alternator is a 2.0 and showed to be good. BUT oddly enough it was covered in what looked like used motor oil. Not like just a smear but when I touched it I had drops on my finger. Would love an explanation on how that could've happened? So I went and exchanged the alternator tonight since it was less then 3 weeks old. I will install it tomorrow weather permitting. 

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Ok, so new alternator is on and with car started its still showing 12V at the back of the alternator. That's 2 new alternators that were showing about the same. Could it really be 2 defective alternators or could it be something else like the 55 year old wiring? 

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Does your car have a standard voltage regulator or is it a transistor voltage regulator....

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I Have an actual GM factory pontiac manual from 1963....(not a reprint) has at least 15 pages worth of info on how to trouble shoot ,test and repair the whole complete charging system...Adjust the voltage regulators Both types  standard and transistorized voltage regulators...Complete wiring schematics.....Tried to take photos but they ain't coming out clear and legable with my phone..I have a way that I can scan the pages and send them directly to your Email..If that is something you would be interested in...

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 Its an external voltage regulator bro. I called the alternator manufactures tech line and ran a bunch of tests. I think you're on the right track with the regulator bro. I don't think that the alternator is getting excited. The plug on my regulator is marked  F 2 3 4  indicating each terminal. Terminal 4 has power but terminal F does not. The tech said that both should be hot. It looks like the blue wire at terminal F on the regulator goes to the R terminal on the back of the alternator and nothing is plugged into the F terminal on the alternator. I asked the tech if that was connected correctly and he didn't know. Seems to me that the F terminal on the regulator should plug into the F terminal on the alternator, but I don't know that may be too logical lol. The voltage regulator is still under warranty so I had the parts house order me another one and it'll be here tomorrow, figured it couldn't hurt. Any idea what plugs into the R and F terminal on the back of the alternator? 

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It appears to me looking at the schematic that the F terminal on the regulator does connect to the F terminal on the alternator....The #3 terminal on the regulator runs through the ignition switch...and would be hot with the key turned on...The #4 terminal is used on cars with a radio.... A condenser is connected to #4 and is not used if there is no condenser.....this is the diagram hope you can see it clearly

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Great pic bro, so I'll hook the F to F tomorrow after I get the new regulator. My car does have a factory radio so I'll keep terminal 4 hooked up, but I don't remember anything hooked up to terminals 2 or 3 so I'll double check that also and then retest and let you know. 

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Ok so I replaced the regulator and still only had 12V at the alternator. I DID NOT have a wire in terminal 3. I couldn't find one loose or laying around either so I connected a jumper wire from the #4 terminal which is 12V keyed and connected it to the #3 terminal. The blue wire F terminal is now hot when the key is switched on as it should be. But I still only had 12V at the alternator. Once I moved the blue wire (F on regulator) at the R terminal to the F terminal on the back of the alternator she got excited. I checked it again and 14.5V at back of the alternator! I'll post pics to help explain everything.

So now my only question is, why when the key is off and I check the voltage at the back of the alternator is it hot? I would assume that with the key off and putting the red probe on the positive on the back of the alternator and grounding the black probe to the alternator case or the battery that my multimeter should read 00.0 instead of the same voltage as my battery which at the time of the test was 12.9. (My volt gauge in the car does show 0)

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Glad to here everything is working as it should.....

The main battery terminal on the back of the alternator is supposed to be hot all the time and should show the same voltage as the battery even when everything is turned off...As that wire goes directly via a junction block with no interruption to the battery.....The diodes in the alternator act like a one way gate and they keep the battery power contained...from feeding back through the whole electrical system and killing the battery when everything is turned off....

The test you performed when you put the test light between the ground cable and the negative post on the battery is one way to confirm if the diodes in the alternator are working correctly and not backfeeding thru the system and killing the battery...had the light came on when you did that it would have indicated an unwanted power draw in the system ( like maybe the glove compartment light staying on all the time or something) and or a bad diode in the alternator.....

On newer cars though...They are designed to have a very slight power draw....When everything is turned off....For the radio memory...Clock...PCM etc...

 

 

Edited by TWO LANE BLACK TOP

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Great, man that makes me happy lol. I was hoping that you'd say it was supposed to be hot. My only concern WAS it draining the battery. Thanks for everything, I really appreciate all the help bro.

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