Hi gents,

This is my first time posting here and I am not a pro-mechanic. I was put to task to restore a 78 F150 Ranger that came with a 351M. It is in somewhat decent shape however the wiring is a complete mess. Since I have limited knowledge on these trucks, I am assuming PO did many mods on the wiring. Hoping to receive suggestions from more experienced forum members.

At this point I am inclined to think that the wiring is the issue. The battery was reading 13.30 volts when I tried to start it but nothing happened and I lost electricity to all accessories such as, wipers, flashers, taillights etc. I left the lights on by accident last night because there was no electricity to them anyways. To my surprise, after 24 hours, I got electricity back but this time battery read 12.80 volts which is expected. I gave another try to start it. Same thing happened. No crank-no start-no electricity accept the battery and the starter solenoid. Any ideas?


There seem to be two solenoids. Is this normal?

https://www.flickr.com/photos/69131112@N07/19710807413/


Also, will someone post a link about how an electrical system of an old truck works?

 

Welcome to the FTE forum

Has the truck ran recently or have you heard it run? Would first start with new cables to starter, frame, cab, and negative to engine block. Trust me.

Next, has the battery been charged? 13.x indicates the truck was running very recently?

It is possible for a defective battery to read OK but choke under load. Poor or missing grounds, old cables will soak up lots of current and prevent things from working right. If you left the lights on overnight, the battery would be toast by morning so it's like as not cleaning connections will get you started at least.

 

This may sound stupid but make sure all your connections are tight on the battery and grounds. Also check the cables to make sure they are not broken or frayed. Since is randomly loses power it sounds like something is loose.

 

Thank you for your quick response.

Yes, we drove the truck 3 days ago or so. My father-in-law got it from the mechanic shop where they changed the fuel tank and he drove it to his house. He was going to bring it to my house the following day but it did not start. I went there, we tried to jump it but nothing happened. There was no electricity. I ran back home got my multimeter and the battery was reading 13.30 volts already but no electricity in the cabin. So, we got it towed to my house. Since then, I have been working on it. I removed the e-brake for the trailer, the radio and the instrument cluster because all of them need to be replaced. The wiring is so messed up. An 8-gauge red wire carrying 12V running from the engine bay through the firewall to the ignition switch is crimped up and taped to probably the original ignition wires.

I am planning to replace all the wires with AAW classic update series and get rid of that other solenoid. Have you ever seen multiple solenoids like that? I need to know whether it is factory setting or not.

 

My 75 only has one solenoid mounted on the inner fender but the power for the cab should not run through the solenoids. It is just to send power to the starter when the key is turned on. If you loose cab power and it doesn't turn over it sounds like a problem between the battery and where the cable splits off because it should go two different ways.

 

Thanks. I guess there is no point in trying to figure out what's wrong with the old wire setup. I will purchase the new wiring harness and go from there. Is there a wiring harness kit you can recommend? I decided on AAW 510342

Complete Wiring Kit - 1973-79 Ford Truck We Make Wiring THAT Easy!

 

That looks pretty complete from what i can see, you could always contact the company and see if there is anything else that would be necessary that they dont include so you would know for ease of installation.

 

Please forgive me but I have a similar problem with my 1986 F250 diesel, top loading 4 speed and have posted here in the past but to save my soul I can NOT see how to make a post! Can someone, anyone direct me? Thank you, Mike Abbey

 

Mike to make a new post just go to the forum of your choice depending on your year and such and on the upper left hand corner just click "new thread" its a blue button. Any more questions feel free to ask.

 

Here's your pic...



I don't know what to think of all that, two starter relay's? I've seen some crazy backwoods wiring jobs before but nothing like that. I don't know what's up with the fuse/whatever zipped tied to the top of the starter relay.

In the normal configuration there should just be the one that's mounted vertically on the inner fender.

Have you chased out the orange wires coming from the second relay to see what they're doing?

As mentioned earlier, triple check all of your grounds. Inspect, clean and/or replace any "iffy" looking cables or straps.

 

I am not sure whether you looked at other photos that I put on flicker but if you haven't that you have not seen all. It is a complete whack job. I thought there should be only one solenoid but I just wanted make sure. Here's what I deciphered so far. One of the orange on the "auxiliary" solenoid is ground. Second one goes to the ignition coil after mating up with different other wires. One of the red wires on the original solenoid runs to the back of the truck for a trailer electricity plug -or that's what I think what it is-.

 

Here's a link to some electrical diagrams for the 73-79's

Link


Yes, I looked at your other pics..Here's a direct link to your flickr page so others can see the pics...


flickr link


it's messy no doubt, but you should be able to get the basics established without resorting to a $700 harness.
If the truck was recently running, and given the battery issues, I'd start looking for weak links in the electrical system.
Simple things first, grounds, starter relay, etc.

Is the battery a known good battery, how old is it?


I went back and re-read your posts. First you'd mentioned that you have no power past the starter relay.
Did you try to test for power on the starter post of the relay with the ignition switch turned on?

Secondly, you'd mentioned that you have no power in the cab, is everything dead?
Does the dome light work, cig lighter, etc? Why did you remove the gauge cluster? Have you proved out the fuseable links/fuses?

Is there any way to contact the previous owner to ask what's going on with all the additional wiring?


Here's a pic that explains what's going on with the starter relay. Power in, ignition switch, coil, power out to starter.

 

Thanks for taking the time to help me out. I really appreciate it.

Battery is brand new although the battery cables are in horrible condition. I will change those asap probably tomorrow.

Here's what going on in the cab. Cab will have power if you wait 24 hours after you attempt to crank the engine. Once you try to crank it, you will hear just a click and all the electricity in the cab will be gone. It won't even bother to attempt to turn the starter. Wait 24 hours or so. The electricity in the cab will be back. I could not think of a reasonable explanation for that.

The reasons I wanted to invest in the new wiring are; 1) it takes a lot of time to figure out what is going on when I do not know which wire is supposed to be there and which one is not, 2) I will have to do it anyways because I was asked to.

The gauges were working when the truck was running but removing the gauge cluster was for cosmetic and visibility reasons. I removed the cluster because the plastic cover behind the gauges were crumbling like dry bread and I wanted to have a better vision of the cables behind the gauges since they were really messed up, tangled etc.

Previous owner is of no help, unfortunately. He does not seem to be very knowledgeable which made me think that the crazy cabling was done prior to his ownership.

Do I need crank it in order to test the voltage on "s" terminal or would simply turn the key to the on position be suffice?

 

It sounds to me the intermittent power is battery cable related. Go back to basics and get the simple circuits corrected. I'd trace and possibly disconnect the extra solenoid. I think it is not only confusing the system but is also having a negative psychological effect on trouble shooting. Extra, incorrectly connected circuits can backfeed some systems and exhibit strange symptoms.

Second, verify that the cab, inner fenders, bed, engine, and frame are properly grounded. I run extra grounds as a matter of redundancy to hedge off gremlins.

Clean and well connected terminals and plugs are paramount

 

Per the pic of the four post relay, just turn the ignition switch "ON" and check for voltage coming out of the relay.

Here's a pic of the "basic" ignition layout.If you need more details on circuits,etc. let me know.