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Questions Regarding My '68 390 F100

Before I get to the questions, let's start with a little info.

Based on what I was told by the guy from which I purchased the truck, it is a numbers matching original with me being the forth owner. He told me that the engine was pulled to put in new pistons along with an "RV" cam. It also has a Weiland single plane aluminum intake with a rebuilt and upgraded Holley 4160 4bbl carb, long tube headers (Hedman I believe), and an upgrade to a digital ignition very similar to the ignition system that was OE on the '85 5.0 Mustang I used to own.

I got to drive the truck for all of a week when I pulled into a station to get gas and the truck suddenly died while idling and wouldn't restart. After it did finally start about an hour later, it died again when I was about a third of the way home. After checking to make sure the carb was getting gas and that all electrical connections were good, it ultimately ended up catching a ride on the back of a wrecker.

Since then, I've replaced the fuel pump through Summit Racing after matching what was on the truck already, and I've also replaced the spark plugs, wires (Accel), magnetic pick up inside the distributor, and the coil (Accel Super Sport). I started pulling the carb apart a couple of weeks back and stopped at the metering blocks after realizing that what was put into the carb was already better that what was in the kit sourced from the local parts store.

I also have a FoMoCo ignition box to put in the place of the no-name box already in the truck, I haven't put the new box in yet because the wires are spliced in and I would rather utilize the stock style connections already on the new box. This combo of parts seemed to work great together so this gremlin is really throwing me for a loop.

I also must mention that the C6 3sp auto was also pulled for a refresh and shift kit when the engine was pulled. It does shift a little early for my taste, but I think it was done with fuel economy in mind.

So there it is in a nutshell. The truck has been down since March and I really don't have any intentions on selling it before I get a chance to really enjoy it the way that I like it.

Any and all questions and suggestions are greatly appreciated and I hope to get her back up again soon!
 
I checked and cleaned all ground connections that I could find and even improved some of the connections that were sketchy.

For some odd reason there was a cable going from the positive battery terminal to a bolt on the core support. While trying to start the truck, I spotted smoke coming from the positive terminal and the cable appeared to be melted so I removed it.
 

Fellro

Moderator
Staff member
Are you certain that the cable was intended for positive? You can get replacement cables that are red and put on as a negative, so don't always trust that the color is indicative of polarity. I have had a few vehicles that if you did that, you would hook it up backwards.

As to the dying, sounds fairly common for the ignition module. With all the different changes though, it will take a bit to narrow down again. Also is possible that you are getting a case where the carb boils the fuel, and then floods. After sitting, it clears and all is happy until it starts to boil out again. It can be tricky catching it in the act on such.
 
Are you certain that the cable was intended for positive? You can get replacement cables that are red and put on as a negative, so don't always trust that the color is indicative of polarity. I have had a few vehicles that if you did that, you would hook it up backwards.

As to the dying, sounds fairly common for the ignition module. With all the different changes though, it will take a bit to narrow down again. Also is possible that you are getting a case where the carb boils the fuel, and then floods. After sitting, it clears and all is happy until it starts to boil out again. It can be tricky catching it in the act on such.

maybe a plastic carb spacer is in order? cheap test/fix
 
Are you certain that the cable was intended for positive? You can get replacement cables that are red and put on as a negative, so don't always trust that the color is indicative of polarity. I have had a few vehicles that if you did that, you would hook it up backwards.

As to the dying, sounds fairly common for the ignition module. With all the different changes though, it will take a bit to narrow down again. Also is possible that you are getting a case where the carb boils the fuel, and then floods. After sitting, it clears and all is happy until it starts to boil out again. It can be tricky catching it in the act on such.
It was definitely on the positive side, the negative goes to a bolt on the block.
maybe a plastic carb spacer is in order? cheap test/fix
It already has a 1" aluminum carb spacer.
 
One thing to note is that when I first got it, the clear filter just before the carb would stay full of gas at all times, even when it was shut down. Now it will only fill up about halfway then drain out completely when the truck dies.
 
You still running the behind the seat fuel tank?

I would check the lines an make sure theres nothing getting sucked
into them.
You can try a gas can by itself under the hood from the fuel pump!..:)
 

Fellro

Moderator
Staff member
Concerning the cable, did it perhaps go to a terminal that was on a round plastic part on the fender? If so, that is the starter solenoid/relay. Could have simply been a bad connection. All of your power distribution is from that terminal.
 
You still running the behind the seat fuel tank?

I would check the lines an make sure theres nothing getting sucked
into them.
You can try a gas can by itself under the hood from the fuel pump!..:)
Yes, still using the tank behind the seat. The lines are flowing freely as far as I can tell, but the gas can is a good idea to verify for sure.
Concerning the cable, did it perhaps go to a terminal that was on a round plastic part on the fender? If so, that is the starter solenoid/relay. Could have simply been a bad connection. All of your power distribution is from that terminal.
No, that cable is still there and those connections are some that had to be improved. The cable I was referring to was a second cable running off of the terminal. Removing it didn't seem to help or hurt though.
 
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It was definitely on the positive side, the negative goes to a bolt on the block.

It already has a 1" aluminum carb spacer.

the aluminum one dont isolate the carb base from manifold heat, but to the thermal property of aluminum. phenolic, other plastic and even wood spacers keep the carb cooler if you are having a boil/ vaper issue.

on the tank comment. i have had a few trucks and a backhoe have rocks and other stupid crap like a piece of plastic get sucked on to the bottom of the pict up tubes starving the engine. shut it off let it sit (rock/ plastic move away) engine starts and fine, till the next time that happends
 
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I'm going to install the ignition module and bypass the tank this weekend after work. I'll post my findings when they are found.

Thank you all for the help and suggestions!
 
Quick update:

I got the ignition control wired in, not the way I would've liked, but it'll work until I get a more permanent connection.

I didn't get a chance to try it yet because the battery I had charged at Walmart didn't have enough juice to even try to turn it over and I don't have a jump vehicle handy. I also need a longer fuel hose to reach down into a gas can to bypass the tank.

Baby steps, but we're getting there!
 
Update:

Charged the battery overnight and put it back in the truck only to have it really try to start for about half a second then go completely useless, won't even take a jump. I took the battery back to Wallyworld a couple of weeks ago for an exchange just to have them charge it and give it back. I bought the battery back around late Feb of this year so I hope they swap it this time.

I knew I should've went with a better battery, but Wallyworld was convenient at the time.
 
stupid wallyworld batterys errr!!!!!!!!
 
Update:

Swapped the battery for a new one, checked and rechecked all connections, turned the key . . . nothing, not a @!&#! thing.

I'm at my wits end here, the only thing left in the starting loop is the solenoid.

However, there is also an "anti-theft" device connected to the steering column between the switch and module that locks out the ignition unless the truck is in drive. I've wondered if this could be the problem and I've contemplated ridding myself of it as I really only see it as another failure point in the loop, I'd honestly rather have a hidden toggle switch to lock out the ignition instead.

My absolute last resort is putting this thing in a shop because I don't really have one I trust and I don't have screw-me-over money to blow before finding a reputable one.
 

SuperCab

Moderator
Staff member
10,067
543
Montana
Id take any extras out of the equation... Anti theft crap like that is often the source of headaches.

The solenoid could also be bad though... thats not uncommon. Are you getting power to it when you turn the key to 'start' ?
 
Id take any extras out of the equation... Anti theft crap like that is often the source of headaches.

The solenoid could also be bad though... thats not uncommon. Are you getting power to it when you turn the key to 'start' ?
Agreed, I'll check for power next round.
+1...YelloThumbUp

The old trucks almost run with out nothing hooked up!...That why
I like them!....:)
That's part of my frustration, I was assured of a tip top reliable ride. I got about a week of enjoyment followed by 6 months of nothing but trouble.
 
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