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78' F-150 electrical issue!! HELP

2K views 14 replies 5 participants last post by  ruger1022 
#1 ·
Well this isnt my truck, but it belongs to a wheeling buddy of mine. Here is the issue. His 390 powered truck was running fine. HE has mentioned before that if he pulls one of the leads on his battery his amps jump really high. Well today he had a brain fart and did it again. Now his truck wont start, and when he turns the key forward the coil gets hot?? I have not had a chance to look at it yet, but im heading over there friday so hopefully we can wheel saturday. What could be the issue? Bad voltage regulator? Alternator? Coil?

Please help us get on the trail this weekend!
 
#2 ·
Well couple things come to mind. Voltage regulator going bad could do just what he described. If you take the voltage from the battery away and the running truck with a bad regulator let the voltage sag it will cause a high current spike. My guess is he lost a fusible link.

Does the engine turn over at all? If it does and the coil is getting power is the spark making it through the wires? Basically need more info to work with man?
 
#3 ·
Truck was running and he reved it up when suddenly it shut off and now it wont start. IT will crank, but not start. Also the coil gets really hot just by turning the key forward. I will call him up again tonight and see if he figured anything else out. I will have him check the wires and replace the voltage regulator to see if that fixes anything. I think he was jacking with it right before work and didnt have time to do all of the trouble shooting. And thanks for the help 79' hopefully i can get this stuff figured out for the mud races this weekend!
 
#4 ·
78' F-150 electrical issue!! HELP
Analog meter to the rescue! :)

Do yourselves a favor and get an analog meter and/or
a buddy that has one to figure this thing out. Really. :)

---------------------------

Cool, a 390FE, but what year truck?
Points or Dura-Spark system?

Alvin in AZ
 
#7 ·
Noticed the wire in question comes off the starter relay goes to the "I" terminal on the voltage regulator and then taps off and goes to the ignition module. Which explains why the coil is hot and no starting. I would test for voltage down stream of that fusible link. Use a meter of a test light either way.;)
 
#8 ·
79' Thanks alot, that wiring diagram helped out alot!! With this i can follow all the wires and better trouble shoot it! Everyone one else thanks, but i suck at using a meter, i have never been able to use one successfully! I use a dummy light and thats the best that i can do. I recently lost my job and have decided to take a yr or two off, so i might take a few classes to learn how to use voltmeters at a local community college!
 
#11 ·
Very nice 79! Is there a way to get a pdf file of these to be able to print
them out so they are are really clear? If not, i think i can figure this out
and make what you have provided work. Thanks again buddy!
x2 they are just what you need but hard to read is all. :)

Autozone has them sign in with the year and make of the
vehicle and type- wiring diagram -in the search window.

Not Sure if Broncolinks has 'em or not...
http://www.broncolinks.com/index.php?index=1

Alvin in AZ
 
#12 ·
They are an image file so if you right click on the pic and click "save as" when the pop up come up pick where you want it saved. Then just click the picture and when it comes up click print preview and it will blow the image up to it original size and much easier to read.

While you looking at it in this thread just hold down the "ctrl" button and hit the "+" button and it will enlarge the screen to read it better. To shrink it back down hold the "ctrl" button and hit the "-" button.

This diagram isn't bad to read not much on it. I am chasing down a wiring issue on my 1986 Gran National and damn there is a lot of wires on that thing.:doh0715:

OH and glad to help man. That is why we are here!:thumbup
 
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