'77 F150 w/ a 460.

I'm at a loss...here is the back story. Last Wednesday I initially noticed that the truck sounded a bit sluggish when I started it up, but it did start. I drove for about 30 mins and parked it - maybe 60 seconds later I tried to start it and it was 100% dead.

Bought a new battery. 700cca. Wasn't it.
Tested the starter - tested fine.
Replaced solenoid - started up.
Removed positive terminal to test alternator - truck ran fine.

Parked it a few days and dead again.
Replaced the positive/negative battery cables, charged battery. Truck started. I did notice a small arc when I connected the + terminal.

Parked it over night - truck dead.
I thought the radio created that small arc, so I disconnected it - charged the battery. The I did not see an arc when I installed the charged battery, the truck started and ran for an hour.
Last night after work - truck was dead again.

Any suggestions on where to go next? I mean the truck has ran fine for 1.5 years then all the sudden this is happening. I've checked everything I can think of and followed up on observations (the arc).

One guy I know suggested that the armature on the starter may be drawing current and draining the battery...but wouldn't the solenoid have to be open for that to happen?

Time to start eliminating things and working my way back the wiring harness from the battery?

 

A "divide and conquer" troubleshooting technique will help narrow down the culprit. Be sure to leave the radio and/or clock disconnected while troubleshooting. If you have an ammeter, check how much current is being drawn from the battery with the engine and accessories off.

Good luck. Please let us know what you find.

 

Even a simple test light will get you started. Place between battery post and battery cable. Dim light= small draw. bright light=large draw. Remove fuses one at a time till light goes out and that will narrow down where to look. Common problems include interior lights on, brake light sticking. Simple things, but easily overlooked.

 

Here's how to hook up the testlight.



It could also be your alternator. Yes it's charging, but one of the diodes in it could be shorted, causing a drain when you turn the key off. When you set up the testlight and it glows bright, take the large battery wire off the alternator and see if the light goes out.

By the way, please do not pull the battery cable off with the engine running. If there was something wrong with the charging system, you could burn up a lot things doing that.

 

Thanks for the replies.

The last few days I've been disconnecting the positive terminal when I park and every time it's started fine after I reconnect the lead. Today I finally had time to tinker.

I bought a voltage regulator and a circuit tester. The light is on when I put it between the negative cable and terminal on the battery - there is definitely a draw some where. It's not the volt. regulator (I wanted to replace it anyway).

I did find one wire that when disconnected caused the tester light to go out. The wire circled in red.



I think this leads to the ignition system so I tested all the fuses and the fuse panel, and then tested all the switches I could find. Head lights, high beams, blinkers, windshield wipers, neutral sending unit, ignition module, ignition switch, and completely removed the radio. I also disconnected every connector that I could reach in the engine compartment (horn, window washer reservoir, etc). Nada - the circuit test light remained on other than when I disconnect that one wire from the solenoid.

I did not test the alternator as Franklin suggested. Yet.

Could the solenoid be bad? A neighbor thought that maybe the two smaller wires on the front of the solenoid could be backwards...

 

Tested the alternator this morning. Does not seem to be the problem. The circuit light was still on after I completely removed the alt. Though I did manage to break the alternator - something inside of it I think. Truck will not remain running when I disconnect the positive cable on the battery.

The only thing that has put the circuit tester light out is disconnecting the contact I circled in red in the picture above. I think that leads to my ignition. I tested the ignition itself (dash board) by disconnecting the plug behind the key entry and disconnected the ignition module. Are there any other components that I'm missing?

 

Did you not read this? Heed Franklin's advise. You may be creating more problems than you are fixing.

 

Just to make sure, the wire you circled is on the smaller terminal labeled "s" correct? Most of the time on the older trucks, this wire did go to the coil + terminal. It sends a full 12v to the coil + during cranking only, and after you let go of the starter, the coil + is fed through a resistance wire coming from the keyswitch. If the truck is warmed up, you should be able to take that wire off and the truck should run normally. It helps it start quicker in colder weather. You could take it off just to see if it still runs and the drain goes away for a experiment.

 

Whoops, totally mis-read your advice NOT to pull the + terminal Franklin. I replaced the alternator today and everything seems to be fine with that system.

The draw is present and the post I circled on the solenoid is labeled 'I' - which I would assume means ignition.

Thanks again for the advice. I'm probably just getting frustrated and overlooking something simple. Time to think about this a bit more.

 

Whoops, I made a mistake also. The terminal labeled "s" comes from the neutral safety and is what activates the solenoid to send power to the starter. The "i" terminal is the one that goes to the coil +, you would also be correct calling this "ignition" like you mentioned.

I am not sure if the "i" part of the solenoid could stick or not. But for an experiment I would take it off and leave it off and see what happened and if it would bring to light what could be wrong with it.

 

The Alternator repaired UR problems ?

 

I took it to the shop today. I've spent too much time & money trying to figure it out. It's something with the ignition or starter. The truck tries to start when the key is not in the ignition.

I would like to rip out the half assed wiring job the previous owner mucked his way through - but I don't have the time as this is my primary vehicle for the time being.

 

I wanted to follow up on this...

When I went to pick up the truck from the shop they went over the repairs.

1. The PO had spliced a line from the ignition to the starter with a bolt, nut, and two washers.
2. The gauge of wire they had used was unable to handle the current.
3. The charging gauge had a amp-meter, but should have had a volt-meter. (I don't understand this one)
4. The negative and field leads were backwards leading into the voltage regulator.

Backyard mechanics at it's finest. Thanks for the advice, maybe eventually I could have figured this stuff out...but probably not.

 

When things break by themselves, they usually do it in certain well documented ways. But when someone gets in there and hooks things up wrong or does other things to make it not work, it's almost impossible to figure out what they did.

 

I'm seeing it staying energized.