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Total Electeical Power Loss When Starting

6K views 8 replies 6 participants last post by  Huskinhano 
#1 ·
#1
mikerunt's Avatarmikerunt , Today 06:55 PM
hey everyone, new to the forum, new to vintage mustangs.

I have a 1966 Mustang w/ a 351W and a C4

Have recently run into an issue that I can't seem to troubleshoot. suddenly and for no apparent reason I loose all electrical power when I try to start my Mustang. What happens is I put the key in the ignition, turn to on (all fans and pumps turn on) and when I go to crank / start everything shuts completely off like I've blown a fuse and the car does not start. Starter doesn't even try and turn over. If I try to immediately turn to key to off then back to on or start I get nothing at all. Completely dead no fans or pumps. No juice at the ignition key. After about 10 or 15mins it seems like something somewhere resets.


I can wait about 5/10/15mins or so and then for some reason everything seems to reset and I'll get all the power at the On position (pumps/fans) again. Once I go to start and try to crank it over, everything shuts down again and no power at the ignition key at all.

I assume it it has to be a pump or relay or something that can reset it self? Not sure.

No blown fuses at stock fuse box under dash at driver side.

No MSD 6AL or aftermarket.

Could it it be a bad starter solenoid?

broken ground wire? I checked the battery negative and that seems to be good.

Any my help would be epic
 
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#2 ·
It sounds like you have battery primary connection issues. I would take off and inspect both battery terminals clean as well as the ground connection on the engine. Check the starter relay main terminal to be clean and tight etc.
If you are proficient with a test light or a voltmeter pop the hood when it happens next. Leave the head lights and the ignition on (sometimes leaving power consumers on will prolong the problem). Use your test light/ meter by putting the negative test lead on the neg battery terminal. Not the battery terminal clamp. Put your positive lead or probe on the negative cable clamp. No light should be lit nor voltage on your volt reading on your meter. If yes then pull clean and retest. Do the same test on the positive terminal.
 
#3 ·
How come your (radiator?) "fans" and your (fuel?) pumps turn on at KO? Sounds like too many amps get pulled, tripping a relay.
 
#4 ·
Welcome to the forum!
Gremlins in electrical systems can drive you nuts. I have found that the fastest way to get rid of them is to track them down and eliminate them systematically. Follow the electrons. If I were you, I would start by checking your battery like Gordon suggests. Then work your way through the circuit. First check your ignition switch, then the solenoid, then the starter, etc. If all the components check out, you have an intermittent grounding problem. In a 51 year old Mustang loose, partially painted, and or rusty ground connections cause more come-and-go electrical problems than broken wires. Good hunting!
 
#5 ·
I agree absolutely what's been said. Since the car is 51 years old and has a non stock 351, who knows what else has been done? Mach671 said a very important thing, check systematically. Look for non factory wiring.

By any chance is the battery in the trunk? The reason I ask is that a lot of people do not feel comfortable with a hotter, unfused battery cables running from the back to the front and put a fused or circuit breaker in. The problem is you really can't fuse the starter. The old series wound motors have a very high inrush of current as any motor does. It's basically like a short circuit. Maybe someone put a circuit breaker in line someplace? The symptom sounds like it. Not saying that is it but certainly sound like that could be it.

More info on the car and photos would be very helpful. A lot of times when someone has a problem they omit something because they think it isn't relevant to the problem but many times it is.
 
#6 ·
Putting a heavy load on the electrical system (the starter) will expose lots of problems like corrosion on the battery posts or cable clamps. If you try to start the engine and everything goes dead twist the battery cable clamps and see if everything comes back alive. I've seen it hundreds of times.
 
#8 ·
Hey everyone, quick update. After taking all of your advice i think i've found the issue; a poor battery negative to engine block ground. This AM when going through all of the wires as suggested, that one felt a little flimsy at the neg battery post. when to the auto store, got a new cable and post cleaner, reinstalled, and then jumped the starter solenoid to test (battery positive to "S")and the car fired right up, faster than it ever has! reinstalled the started wire from ignition on the starter solenoid and it started right up again, faster than ever before! insane that something so easily overlooked seems to of made such a huge difference. thank you all again!
 
#9 ·
I use to do field service work on high speed packaging machinery. You're really got the gun to your head to get them up and running so you learn pretty quick to give a pretty quick look to everything first and that's when you'll usually find the problem. Simple stuff is just as devastating as complicated stuff. Don't forget to check if you have a ground cable from the engine to the body. That's important.
 
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