Hello everyone,

got the engine rebuilt and put back in my dad’s 79 F250 trailer special. I am having electrical issues. I have checked and replaced the in-line fuses, battery cables are new, solenoid has power, brown wire at solenoid has power when key is switched on, new ignition switch, new key cylinder, new power distribution block along fenderwall has power when switched on. But I cannot get it to start when ignition key is turned, no crank, dash has no power, and gauges do not move.

only thing I see from one of black wires coming into cab from power distribution box leads to a yellow collector switch but I do not see where that would plug into anywhere within reach.

what could it possibly be or where should I start to search next ?

 

Since it does not sound like a stock setup anymore, it's going to be harder for us to diagnose. Would most likely have been simple if you had no power anywhere, but you obviously have power to the ignition switch, so it rules out a fusible link.

What kind of power distribution box do you have? Pics would help of your under-hood area.
And what is a yellow collector switch? Sorry if it's a common part, but I've never heard reference to it.

You might have multiple issues going on as well. What else was done to the truck? The gauges not working could be a problem with the instrument voltage regulator (IVR), or the cluster's printed circuit board (both common issues), and the no-start situation could be the ignition switch, or the neutral safety switch (if you have an auto trans) or bypass jumper if you have a manual.

Ignoring the dash for the moment, pull the Red w/blue wire off of the "S" post of the starter relay/solenoid and have someone turn the key to START while you check for 12v at the wire's connector. That's at least a place to start the hunt for the missing power.

Good luck.

Paul

 

Here are pictures of yellow connector that I traced some wires back to thru firewall and near fuse panel. Picture of power terminal that was replaced and of whole engine.

gauges were working, dome light and small bulb near pedals were working when door was opened.

power to brown wire from solenoid when truck keyed to on position
no power to red with green on solenoid when turned to start position

 

If this exact diagnosis was on a vintage Dodge Truck.....that would be an easy fix and just install a new amp gauge !!!

On these old Fords, not so much.....more likely one would go thru process of elimination and start enabling continuity and voltage checks if the obvious easy stuff is confirmed and functional....

After confirming main ground cable is sound and no restriction or loose connection of power cable is confirmed, I would start checking ignition switch, then fusible link before exploring to other circuits and wiring.

 

Are you sure that your power lead to the cab is connected to the battery side of the solenoid/relay? There is also a fusible link in that wire.

Does your horn work? On my truck, that is the only accessory which doesn't get powered through the fusible link.

 

Thanks for the pictures. Nice color truck by the way! (in case I hadn't already mentioned it, same as mine...

I do not recognize that factory looking yellow connector, but if that is a Red w/blue stripe wire in that first position, it's a good be that you should be at least looking into it further. That's the correct color for the START wire rather than the Red w/green you mentioned. Was that a typo?
Next time you have someone turn the switch to START, check for power on that Red w/blue wire at the yellow connector. If you have it there, then something has been disconnected. I've never heard of another connector in that line, but I've been fooled before by Ford wiring.
But see below for a likely possibility.

But back to the other possibilities, and even more likely ones at that, since you have some power at least to the ignition switch, but are not getting it to the starter relay, check your Neutral Safety Switch.
On earlier models it was on the steering column under the dash (another member fixed his just last week) but on your '79 it should be on the side of the transmission if you have a C6/Automatic. If you have a manual (NP435 for that truck?) then there should be a simple jumper wire, probably at that yellow connector? Not sure, but someone will know.

Anyway, as said trace that Red w/blue wire back from the starter relay/solenoid and find out where the power stops. Suspect #1 is the NSS and suspect #2 is your "new" ignition switch.
And no, that's not a typo or me going off the rails. The expectation of working parts these days is quite low and it's not unheard of for someone to get two, three and even four bad parts in a row if they're using the same supplier. Ignition switches are not high on that list, but they're still on it.

Paul

 

Yes the correct color is red w/blue stripe
yes lead is connected to battery side of solenoid
no horn
no power anywhere inside.
Verified continuity and power to both ground and positive battery cables (new & clean)

 

So no power at all? Sorry I thought you said you had power to the ignition switch. May have been thinking of another discussion.
Then back to what was said about the fusible link. You have your large Black wire (10ga) between the battery side of the starter relay that runs across the firewall to that junction block above the brake booster. Check the connections and the wire itself. You should be seeing battery voltage at that stud on the junction block.
Use an ohm-meter, or if you prefer using the voltage settings, connect it straight to the battery and measure the voltage at the other end.

Since there is so much rust present at all the electrical items, you may simply need to clean them all and check connections. If you're lucky that junction block just needs some cleaning and re-tightening of the nut to hold all the wire ring terminals together on that one post. If not you may end up having to replace some things.

The fusible link is the molded rubber blob at the battery side with the ring-terminal molded into it. If it's soft and spongy, it's been over-taxed and has melted (doing it's job) and needs to be replaced. Just like a fuse.
Since the battery cables are new, and the wires in question are in physical contact with each other, you just have to be sure they're clean and tight.

And speaking of the junction block, why does it look like there are two different ones being used? In the close-up it's just like the others I remember (including the one on my truck) but in the first overall engine compartment picture it looks like a completely different type, with maybe two studs and a plastic cover?
Could be my eyes playing tricks, but that's what it looks like.

Paul

 

I replaced the power terminal and took an overall pic of engine bay. Sorry for confusion.

there is constant voltage there at the new power terminal. There is voltage on a red w/green stripe wire also that runs along firewall only when key switched to right one click (on) position

 

I found this grey connector to be loose and now truck starts with key (no more alligator clips)

following works: fasten seat belt, red brake light, d/C battery gauge, blinkers, headlights, parking lights, brake lights

no dome or under dash light bulbs working, heater not working, radio not working,

Is it possible to disconnect fuse box to clean out ?
maybe a bad/loose ground ?
another loose connector that powers all of these ?
should fuel sending unit (new w/new tank) be sending signal up to gauge ?

 

Ahh, that makes sense now. Good to have that new one there all clean and nice. Where did you get it?

Good news. Means that the fusible link and the Black wire are in good shape still.
That's where power goes to basically the entire truck. So far, so good.

On earlier Fords there was only one Green w/red wire, but on a '79 there might be several. However it sounds like yours is consistent with the normal function, having 12v only when the key is in the ON position and not when it's in ACC.
This circuit usually powers things that you don't want to have turned on when in ACC, so you can listen to the radio and do other testing of the electrical system without either draining the battery too quickly, or overheating the ignition system (Red w/green wire). The one on yours "might" be the voltage regulator's "S" wire. Not sure what the other functions are of that color wire unless I have a diagram in front of me.

Hooray! Depending on what color wires are in it (can't see in the pic) it might in fact be the connector for the neutral safety switch. Are there four wires, colored as two Red w/blue and two Black w/red by any chance?
If so it's the NSS connector. Good catch on it being loose.

An ammeter that works! Congratulations on being one of probably the 10% of our vintage truck that has a working ammeter!
Lots of vehicles used ammeters back in the day, usually one of three designs (two of which gave ammeters a bad name) but for some reason the Ford version in our '70's trucks was not very reliable.

They do have their own fuses and circuits, so you might be on to something with the fuses. But there can be other reasons some of these items don't work, so more digging is called for.

Yes, definitely. Disconnect the battery first of course, since some of the fuses are powered up all the time even with the key OFF. You might find that one buss-bar is powered by a Black w/yellow wire (main power from the battery) and another by a Black w/green wire (ACC position of the key) and one separate one (dash lights) that gets it's power from the headlight switch.
I can't remember our '76-'79 fuse panel exactly, but there are usually two screws that hold it to the firewall. Remove those and it pops right down where you can work on it, depending on just how much extra wire Ford had built into the harness. It's likely to be tight, but you should at least be able to pull it away from the floor far enough to see if rust, loose or broken wires, or just a wasp nest is giving some trouble.

Does not sound like one, but basically you should always suspect a bad ground no matter what!
In this case it can be either a dash ground, or just the individual ground connections at each load that is not working. With the dome and courtesy lights though, it can be a buggered door switch, bad ground, bad power source, blown fuse, etc.

Again, not likely. But not out of the question either. Perhaps the PO was working on the electrical stuff and just never got around to tightening and reconnecting things before selling it.
should fuel sending unit (new w/new tank) be sending signal up to gauge?

I don't think those items have a common connection, but I could be wrong.

Paul

 

The power terminal is from Amazon. Came with ring terminals to fit, heat shrink & colored boot covers, and a cap that screws over it all to help keep it somewhat protected.

the neutral safety switch, I suspect to be fine since it would start previously before it went dark in cab and still does now that the grey connection is making full and better contact. That connector has 4 wires (white w/red, red w/white, two redw/green) going into dash and 3 going across firewall. (Brown w/green, red w/white and red colors may be off)

the fuse box wasn’t bolted down but has limited slack to really work on it under there. I guess I was hoping it would have a harness so I could unplug, then clean and put back. Most fuse holders are rusted.

PO is us. my dad bought truck around ‘87 and it sat from ‘96 to now.

I guess I’m going to get all fuses and my dremel to try and clean out each of the fuse clips and replace the fuses. See if that helps. Unless I am able
to buy a whole new fuse panel.

i have new tanks and sending units and I am not sure if the power issue effects the fuel gauge or not getting fuel. I still need to try and help
prime the lines to see if fuel pump can pull the rest of fuel up.

 

Good news for sure.

Guess I'll have to go look at the diagrams again then. Not sure what all those colors are for, but it's still great that pushing it together tightly got things working.

Well that's an interesting development. Somebody was messing around with it at some point (either you guys, or even before you) and had it unbolted. Not that this is automatically going to hurt things, but it "could" put stress on some of the wire connections given enough time.

Yeah, they used to do that sometimes in the very old days (and even in the sometimes-not-so-old days. But they also learned long ago that the fewer connectors, the better. Connectors are just one more thing to go wrong as far as the OE's are concerned, so they eliminate them wherever possible.
Even into the seventies at least (not sure about after that) some factories still used "firewall connectors" or main connectors where you could literally disconnect entire harness sections and work on them or replace them as needed. But after this many years, those same convenient connectors are also the primary subjects in lots of owner/mechanic complaints as electrical gremlins dig themselves into the wiring of a vehicle.
Same thing for Early Broncos actually. From '66 to '70 Ford had two rectangular connectors on the firewall right behind the fuse panel that you could disconnect for service, and almost remove the fuse panel by. But those were such a problem after just a few years that for the '71 model year they moved the fuse panel to the glovebox for more protection and got rid of the connectors completely just to run wires straight through the firewall with grommets. Fewer problems after that.

I can see from your pic! Funny how one of them looks almost clean, while the rest look like they're 50 years old. Wait, they almost are! Lots of debris built up in there too it looks like. Time for a real thorough cleaning after all. Before you spend too much more time trying to track other gremlins down, clean that thing up the best you can.
It'll be better when you clean them up, whether it fixes the current problems or not. It's just a good practice to keep those clean and tight.
They even sell new replacement clips you can solder on the ends and stick in the fuse panel slots to get rid of the old rusty ones that just won't clean up. A new fuse panel is not out of line either. A lot of owners are replacing theirs with more modern blade type fuse panels which have a generally tighter grip and are less prone to corrosion except under pretty bad conditions.

Very cool on the '87 bit, but not so neat on the "sitting since '96" part. Just gives you more to do most likely.

Well it could effect the gauge reading, but would have nothing to do with getting fuel with a factory mechanical pump. If you have an electric fuel pump though, that's a different story.
New sending units are not always reliable like the originals unfortunately. You literally have to test them before you install them just to save you the trouble of removing and re-adjusting them if they turn out to be bad or poorly calibrated. Cheap junk in some cases...
But since they use power from the ignition switch, from the ACC side over to what's called the "IVR" (instrument voltage regulator or CVS "constant voltage supply" in some older Ford books) on the back of the instrument cluster and then to the gauge, and then out to the switch on the dash (If you have dual tanks) and then out to the sending units, you might not have a working gauge until you can verify each of those components is passing the power on to the next.

How much fuel in the tanks? If it's just minimal I would put more in so that gravity can help with the siphoning effect helping the pump pull gas out of the tank.
Either way, there are some other things you can do to help a mechanical pump prime itself the first time.
1. You can fill the fuel lines from the back near the tank manually and hope that gets enough to the pump to prime. More work, but might be effective.
2. You can disconnect the line near the pump and put your finger over the hole and feel for suction. First to make sure the pump is not defective, and second to help it prime. Is this an old pump, or a new one? Either way you can be screwed. See more below.
3. You can verify that all else is ready to go, then pour some gas into the carburetor's float bowl vent to fill up the bowls so that gas can flow normally, plus a little bit into the throat of the carb. This will get the engine to fire immediately and help the pump build more suction. A pump working at starter cranking speed is not near as effective as one working at 1,000 rpm.

Regarding the pumps. If your pump has been on the truck since '96 then there is a good chance it's junk now. Not that it wasn't in excellent condition when you parked it, and a brand new dry pump can sit on a shelf for years and still be good, but once it's had gas in it and worked for awhile, letting it sit for more than a couple of years is almost a guarantee of failure of the diaphragm.
On the flip side of that, new pumps are like any other cheap imported part. They may be perfectly fine, or they may fail right out of the box. It's a crap shoot and nobody's got an angle on which ones are always good and which ones are always bad yet that I know of.
So good luck on that!

And on all the rest of course.

Paul

 

Thanks Paul.

I will look into new fuse panel and decide. I really like the old one and don’t want to retro-the truck too much if not necessary. But not opposed if saves headaches and one less thing to worry about.

new edelbrock pump currently I have it rigged to a small fuel tank and have no issue fighting gravity and pulling fuel upwards. I ran this way to break in engine and work out other things that come up when engine running.

I ran compressed air through lines prior to finishing the new tank installs. So will run fuel through lines and add more fuel to each tank. So far each tank has about 3 to 4 gallons. I should get a Holley fuel pressure regulator today and will plumb in after lines are primed.

The truck was a daily worker but overheated/blew a head gasket back in 96’ and my dad picked up a truck at dealer since still needed to haul horse ASAP. (Still hauling 96 ext.cab f250 4x4 w/460) We kept this one covered and/or under car port since. Rolled it out and Washed it about once or twice 2 a year.

i Got to removing old engine, cleaning out and painting engine bay last fall. I finally found a 400 crankshaft and finished rebuilding another engine with selective components that got me this far. I’m
trying to wrap up this one to start on next one (my first truck-79 f150 XLT 4x4).