Hey everyone, I recently bought an '86 F150 with the 300 six to help with work around the house, hauling firewood, camping and whatnot. It has been so unreliable though I'm afraid to drive it more than around the block! It's my first full size pickup, I used to have a 94 Ranger that was a great little truck. This one I need some help troubleshooting with though, as I am pretty good with mechanical stuff but seriously lacking when it comes to diagnosing and repairing electrical problems.

It starts right up but will stall out if you turn on the heater fan or turn signals within the first few minutes of it running. Sometimes if you press on the brake pedal before it has ran for a few minutes that will stall it out as well. When it stalls it usually won't restart - with the key on nothing happens, no crank, no click, anything - but then if you wait 5 minutes to an hour it will restart normally. It has a hacked up wiring harness, a/c components missing & vacuum lines missing, there was a remote start halfway wired in when I got it and I'm still trying to track down where 2 of the OEM wires were originally connected. So I'm hoping with posting pictures and using this site for research I can get get this old girl back on the road with some reliability. In the meantime here are some pictures of the outside.

 

Welcome to FTE
Other than that 1 rust spot over the wheel on the bed what I see is not too bad to start with.
We need a few pictures of the engine bay area, mainly the carb with the filter removed and the dist.
Get one of the wiring at the starter relay / solenoid so we can see what is going on there also.

Why the pictures you ask?
After 83 to 87 when they went to EFI the 300 six went to a feed back carb & IGN system controlled by a computer.
If any of the sensors componets are missing or not working the computer gets confused and makes the motor run like crap but I think you have more going on.
Some feed back systems have been converted to the DSII system that uses a normal carb & dist. and we need to see if any of the feed back has been switched.

Because you have more going on as a start I would clean the battery connections. If they use then crappy bolt on clamps just replace the cables.
Heck because there is only 3 (from the factory) I would replace them just because, you cant see if they are bad or not with out testing.
I say 3 cables:
1-POS battery to relay
1-relay to starter
1-NEG battery to top starter bolt that also has a tab half way down the cable bolted to the frame.
This "ground" cable grounds the motor / trans and the tab grounds the frame. You will not be able to find a cable with a tab, you have to make it using the old tab.
OR
Use 2 cables for the ground. battery to frame & frame to starter bolt.
There should also be a heavy gauge wire from the right side of the motor(head?) to the firewall, this is the body ground.

Also make sure the starter relay is grounded to the fender. Remove it clean the relay mounting and fender and bolt it back down good.
When you put the wires back on the relay when replacing the cables clean them with sand paper before placing them back on the relay.

On the battery cables if you go for new ones find the biggest gauge you can the better.
With that part out of the way you should not have any issues with the truck starting even if it stalls as it should crank / turn over / have lights etc.
We need to fix this part first before we can jump into other problems you may have with the truck.

Any issues just yell we are here to help.
Dave ----

 

Sounds like it has a lot of problems you need to work through. But the first thing I would do is replace the negative battery cable. I believe on the sixes it goes from the battery directly to a bolt on the starter? And then look for a ground strap from one of the bellhousing bolts to the firewall sheetmetal. If you can't find it, make one out of a piece of 10 gauge wire and bolt it to the engine block/bellhousing, and the firewall to ground the cab properly.

When things start cutting off just because you turned something else on, that is usually a ground problem somewhere.

 

Dave, I fixed it for you
But we both are sure it is a battery cable ground issue.
I do have pictures of this cable with tab and where it is on the frame rail if you need me to post them.
Dave ----

 

I know these trucks usually grounded the frame with that band around the negative cable. But as far as the factory electrical system and how it was wired, I have never seen a electrical purpose for grounding the frame for the factory electrical. I agree it's needed if you are going to install a lift gate or some other sort of add-on electrical, say you want to use the frame as a ground for a trailer plug. Or add a winch and use the frame as a return path for the ground cable. But I don't think it's needed for the minimum factory electrical needs.

 

There had to be a reason why the factory had it and I put it back.
I also forgot there is a braided wire from firewall to the hood also.
I cant remember if I put mine back on or not
Dave ----

 

The only reason I can guess to ground the frame is for aftermarket stuff like I mentioned. Grounding the hood helps keep ignition noise out of the radio. My 89 also had small grounding straps from the bottom of the cab to the frame, I guess that would be another reason to ground the frame. But they are so rusted down there they can't be doing any good. The main one up behind the engine out of the weather is going to be the one to count on for the cab grounding. Plus that is right on the other side of the main harness ground that is behind the radio.

 

Thanks for the detailed reply! I will get on it this weekend checking over the things you suggested. This is exactly the kind of info I was hoping for when I made the post, so thank you! I'll also get detailed shots of the engine bay.

 

Alright here are some over the whole engine bay




Here is a close up of the battery and starter solenoid, the negative to starter looks good and has the tab that is grounded to the frame, but I don't see a wire going from the starter directly to the frame. Is the small ground wire with the eyelet supposed to go to the empty bolt hole on the starter solenoid? Also of note is what looks like a vacuum line is unbolted from the frame, the previous owner said he replaced the transmission so maybe he didn't bolt this back up.





And here are some close ups of the vacuum blocks to give an idea of what is capped off, a mystery hose coming out of the firewall and the passenger side of the carb.

 

Do not hook that short wire coming off the battery negative terminal to that empty stud on the starter solenoid. You do that and you will let the smoke out. If you want to put it somewhere, put it under one of the bolts that mounts the solenoid to the fender.

Have you found another loose wire back there behind the engine? You need a ground wire from the engine to the firewall. If you can't find one, just make a new one like the one on the battery negative, but it will have two eyelets, one on each end of the wire. Bolt one end to a good shiny spot on the engine, and bolt the other end to the firewall/cab. You have a nice big fat ground wire going from the battery to the starter/engine block. You may not have anything going from the engine block to the cab, so the cab may not have a good ground. If you bolt that short ground wire under the solenoid mounting bolt, that will ground the fender, and since the fender is bolted to the cab that may help you out, but I would not count on that alone.

 

Man you got a lot going on in there but we can get it all fixed 1 issue at a time

Ok the picture below is the ground cable on the left with the tab to the frame were dose the other end of the cable go? It should go to 1 of the 2 starter bolts to ground the motor / trans.
The other cable to the right is the starter power cable and that is just a insulated cable holder. The cable looks to go to the lug on the starter and is right.

The eye let can bolt to the empty hole for the solenoid and would help ground the solenoid & body.

It looks like someone has done the feed back delete and installed the DSII system, this is a good thing but think they may have left the feed back wiring from the look of all the wires in the engine bay.
If you look inside the cab where this egg shape plug with the wires is I bet you will see the feed back computer. Also see where that vacuum line goes as I have never seen that on our trucks.

Now don't go ripping the computer & wiring out just yet. You need to trace out the wires to make sure they don't go to anything that is needed. I have not messed with a feed back system but from what has been posted you trace out the wires and if any go to something list the wire color(s) and what it is to and we can tell you what to do from there.

It looks like you have a auto transmission. I think that line is the modulator vacuum line, goes from intake manifold to the modulator on the transmission. Yes that line / bracket should use 1 of the trans bolts to hole it kind of out of the way. Think easy fix.

Let see if fixing the ground cable, I don't think the other end goes to anything, and why it may crank slowly. Or that new starter is bad.
Then we can get on to the other things like vacuum lines & hoses, carb choke not hooked up or working right. 1 thing at a time
Dave ----

 

The truck also looked to have factory AC so it will have some other wiring and vacuum lines for that just so you know.
So on the wiring just be careful you don't remove that wiring. IIRC it should come in on the right side from the heater box area and have 2 wire plugs (green / yellow stripe?) not going to anything.
1 would go to the carb idle kick up solenoid and the other to the AC compressor that would be over by the P/S pump.
Dave ----

 

Alright everybody it's been a busy couple weeks with Christmas and all, but I checked over all the grounds I could find and added a 4g ground from the engine to the firewall. After that the truck cranks over fast and starts right up, but continued to have a problem where if you turned the turn signals/heater fan on or hit the brakes it would immediately stall, and then it acted like the key had no power or something (no crank, no click, nothing.) I saw some crappy looking connections and figured out they were near fusible links that go up to the starter solenoid, so I soldered some new ones in and that seems to have fixed the stalling when using anything electrical problem. So that feels like a victory.

I would have driven it around but it is pouring rain and the wipers aren't working. Took the governor box out and checked the solder joints and nothing seems amiss, will check it for power at the switch tomorrow when it is light out. For what it's worth the washer pump sprays fluid, but the wipers don't move at all.

Thank you to everyone who has helped out so far, I was really about to take this thing to a shop but I now have new hope. And Happy New Year!

 

Check for power at the wiper motor itself also. Whenever the key is on, there should be power on the red wire at the wiper motor, even though the wiper switch is off. This is how it parks when you turn the switch off.