1978 F150 Electrical Issues

rcalexander105

rcalexander105

JV Wheeler
Joined
Nov 3, 2017
Location
High Point
Got a 1978 F-150 w/ the 4.9L 300ci straight six.

Tree dang near fell on it a few months back which forced me to move it from around back and into my driveway. This ultimately lit a fire under me to get it back on the road (or at least to start tinkering). I've been chasing an electrical issue ever since and I'm at a loss at this point.

Symptoms: If you put the key in the ignition and try to crank I get nothing. Even when you turn it clockwise one turn to ACC I literally get nothing...no power to anything. Gauges will normally register with key in this position and the fuel gauge will show fuel level and other electrical components would work (e.g., headlights, etc.) but I get NOTHING. @77GreenMachine came by a few months ago and we were able to get it running by jumping the starter relay from the positive battery terminal and finally got it to turn over and run. It didn't run great (sounded like it's had a miss) but it ran decent. Ever since then, it seems to have gotten progressively worse at idle and now I can't get it to crank (it'll turn over but won't fire off).

New parts thrown at it:
- Battery
- Alternator
- Starter relay
- Ignition switch
- Voltage regulator
- Cap and rotor (thinking it was running rough bc it needed a little tune up)
- Ignition coil
- Ignition control module (yea, that box on the driver side inner fender that's notorious for failing in these trucks)

Still getting nothing on the gauges or anything electrical (headlights won't even come on) unless truck is running.

I'm at a loss at this point. No idea where to look at this point. Any suggestions?

I LOATHE electrical issues!!!
 
Check the alternator connections and stuff and follow the main grounds coming off of the battery. Any corrosion or anything like that?
Does the windshield leak?
 
Drunktaco said:
Check the alternator connections and stuff and follow the main grounds coming off of the battery. Any corrosion or anything like that?
Does the windshield leak?
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I did scratch up the main ground w/ a wire brush. That was one of the first things that came to mind (bad ground).

Windshield does leak...yes
 
rcalexander105 said:
I did scratch up the main ground w/ a wire brush. That was one of the first things that came to mind (bad ground).

Windshield does leak...yes
Click to expand...
Yeah check behind the dash and see what’s going on there. I’ll drink more beer and ponder and see if anything else may come to mind. It’s hard to diagnose stuff like this without being there, but I’ll try. @Croatan_Kid he’s a walking service manual too, maybe he can chime in.
 
Drunktaco said:
Ok that was a broad answer but we’ll roll with it. Fix the loose connections and/or corroded lines, and pull the dash and see how bad the windshield leak has corroded stuff behind it. R/R and update.
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Lol, sorry...after I posted I was like well, let's give a little more to go off of. Deleted and then reposted to quote
 
rcalexander105 said:
Lol, sorry...after I posted I was like well, let's give a little more to go off of. Deleted and then reposted to quote
Click to expand...
It’s all good man. I’d check around the dash. A windshield leak can raise hell on stuff and cause crazy issues. I’d say that’s where your gauges and stuff are playing out at and maybe the starting/running issues too. Is the ignition switch on the column or dash? Kinda blurry thinking back on that year(s).
 
Drunktaco said:
It’s all good man. I’d check around the dash. A windshield leak can raise hell on stuff and cause crazy issues. I’d say that’s where your gauges and stuff are playing out at and maybe the starting/running issues too. Is the ignition switch on the column or dash? Kinda blurry thinking back on that year(s).
Click to expand...
It's on the dash like the one below.

1618862468470.png
 
"Nothing" is usually ground/column/NSS related. Since it was running...I have a tough time thinking it's a ground. If the main ground is clean, there should be another thin ground to the firewall (drivers side), that I've seen get brittle and potentially cause no ground symptoms. I've seen poorly secured signal switches cause this issue. Can't remember if you have a 4spd or not, but a neutral safety switch will do the same thing.
 
Also check the firewall bulkhead.
If the dash is leaking I've seen corrosion build in there.
78..I think thats driver side besdie and slightly below the brake booster (assuming equipped)

This is one of those times where the more stuff youve thrown at it - the harder the diagnosis because you dont know if you solved one problem and introduced a new one with a shitty new bad out of the box product
 
Ron said:
Also check the firewall bulkhead.
If the dash is leaking I've seen corrosion build in there.
78..I think thats driver side besdie and slightly below the brake booster (assuming equipped)

This is one of those times where the more stuff youve thrown at it - the harder the diagnosis because you dont know if you solved one problem and introduced a new one with a shitty new bad out of the box product
Click to expand...
Exactly
 
UTfball68 said:
"Nothing" is usually ground/column/NSS related. Since it was running...I have a tough time thinking it's a ground. If the main ground is clean, there should be another thin ground to the firewall (drivers side), that I've seen get brittle and potentially cause no ground symptoms. I've seen poorly secured signal switches cause this issue. Can't remember if you have a 4spd or not, but a neutral safety switch will do the same thing.
Click to expand...
Eh I’ve saw a sketch ground run for a bit then get progressively worse as it vibrates and such. Neutral safety switch, will that cause a rough run too? I’ve usually saw that as a will/won’t run deal or just suddenly die.
 
Ron said:
a shitty new bad out of the box product
Click to expand...

Kinda what I was thinking...I've seen these items be bad right out of the box on consecutive attempts when not buying OEM replacements for these trucks:

rcalexander105 said:
- Starter relay
- Ignition switch
- Voltage regulator
- Ignition coil
- Ignition control module (yea, that box on the driver side inner fender that's notorious for failing in these trucks)
Click to expand...
 
Drunktaco said:
Eh I’ve saw a sketch ground run for a bit then get progressively worse as it vibrates and such. Neutral safety switch, will that cause a rough run too? I’ve usually saw that as a will/won’t run deal or just suddenly die.
Click to expand...

Honestly...I think the run rough and the no start are two different problems. There's not a helluvalot there in these trucks that should prevent him from having power...and the items I listed are the culprit 90% of the time. Running rough...there's a whole slew of issues it 'could' be.
 
UTfball68 said:
Can't remember if you have a 4spd or not, but a neutral safety switch will do the same thing.
Click to expand...
Yep, NP435. With a bad NSS, though, I'd still get some power though, right? I'da thought headlights would still come on w/ a bad NSS or do I not know what I don't know?

Ron said:
This is one of those times where the more stuff youve thrown at it - the harder the diagnosis because you dont know if you solved one problem and introduced a new one with a shitty new bad out of the box product
Click to expand...
Thought for sure it was the ignition switch so I threw one at it, didn't fix so returned and then bought the way mo'spensive Motorcraft at it still to no avail.
 
UTfball68 said:
Honestly...I think the run rough and the no start are two different problems. There's not a helluvalot there in these trucks that should prevent him from having power...and the items I listed are the culprit 90% of the time. Running rough...there's a whole slew of issues it 'could' be.
Click to expand...
Yeah I think the no start is ignition switch/dash related. The rough idle/run is something else. Like you said, there not a lot of computer to it.
 
rcalexander105 said:
Yep, NP435


Thought for sure it was the ignition switch so I threw one at it, didn't fix so returned and then bought the way mo'spensive Motorcraft at it still to no avail.
Click to expand...
You know harbor freight sells a cheap (<$10) multimeter that could test the ignition switch in seconds and save you the trip...
 
When I messed with it, I got it running by wiggling plugs on the fore wall and then crossing the solenoid on the fender. It fired right up, and ran excellent. We let it run and checked fluids. Then after running about 10 minutes it began to miss and run like crap. We went for a test drive to “clear it out” and it never got better.

Corrosion in the plugs around the dash does make sense. Originally, it would just spin over and not crank. Once I messed with those plugs and tried again it fired off right away and ran great. Then progressively got worse.
 
orange150 said:
I feel like a picture of the actual truck would help us diagnose the problem
Click to expand...
Someone would just make a circle the problem post
 
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