# 1978 F100 Pickup won't start



## Fla Gal (Jul 14, 2003)

I hope someone here can help me. 302 engine with electronic ignition. I had already changed the brain on it because sometimes it just wouldn't start until it had set for a while, sometimes five minutes, sometimes up to just over half an hour, but, it would start. That had gone on for almost two years. I don't know if I still have that problem because I can't get it started.

The truck started missing real bad, backfiring and cutting out when I gave it gas. It sounded like it was running on four or five cylinders. I thought it was bad gas so I put a container of Heet and a container of Sea Foam in the gas tank along with about two and a half gallons of fresh gas from a known good source. Before adding the gas it had just less than half a tankful.

After I also changed the distributor cap, rotor, plugs and wires the truck started up and ran fine. I was able to move it to the driveway. I thought I was good for go but the next morning it started missing again the same way it had. After a while I tried to start it again and it wouldn't start unless I turned the ignition to "start" and held the key there. I revved it up a little and it was running. When I let off the key the engine stops.

I changed the ignition switch (not the ignition) and it still will not start unless I keep the key in the start position. What can I check, repair, replace or do to get it to start?


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## Bearfootfarm (Jul 13, 2006)

> had already changed the brain on it


Does that mean you changed the "ignition module"?

Thats probably what the problem is if its only doing it when hot

Also, I had a 78 300 6 cylinder, and the carb would work loose over time and cause it to run rough. I think there were 4 screws that held it on, and it took an offset screwdriver to tighten them


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## Jim S. (Apr 22, 2004)

I went nuts with a 79 302 Ford van with this problem. I'm gonna tell you what I found. It may not work for you, but it is a very cheap part, so why not try it?

Go in the distributor and replace the pickup. It's under $20 at Auto Zone or whatever, and easy to swap out. The pickup has wire windings in it and it also moves on the little plate it is on when the ignition advances, so those connections over years can get iffy. What was happening on my van was that when it warmed up some, the connection wanted to break.

Your no start and stumble symptoms sound very familiar to my experiences.

Those Duraspark ignition boxes (which you replaced as the "brain") are very very tough and only rarely fail. When they do, it is usually all done...will not start, period.

As far as running on start but quitting in the run key position, be sure you have hooked all the wires back up and all correctly. Do not continue to run it on start only, as the starter motor is still engaged then and could be damaged.


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## fordy (Sep 13, 2003)

............it's also possible that you put the distributor cap on 180 degrees out of sync . I'd pull the #1 plug and get that piston on top dead center then check the firing order from the distributor to each individual cylinder via the plug wires . An icepick stuck in plug hole will tell you when the pistion is TDC . , fordy


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## Fla Gal (Jul 14, 2003)

Bearfootfarm said:


> Does that mean you changed the "ignition module"?
> 
> Thats probably what the problem is if its only doing it when hot
> 
> Also, I had a 78 300 6 cylinder, and the carb would work loose over time and cause it to run rough. I think there were 4 screws that held it on, and it took an offset screwdriver to tighten them


Bearfootfarm, yes, I changed the ignition module (I also changed the ignition switch). I've always heard the module referred to as a "brain". It's similar to the one in the picture at this link.
http://www.trustmymechanic.com/parts_gallery/module.htm
The parts guy here in town suggested the same thing the site suggests with pouring a glass of cold water on it. That didn't work with the old module that was still good.

The guy at the parts store told me the same thing as you did so I changed it, even though the cold water didn't do a thing to help. The intermittent starting still persisted after changing it. By the way, the old one was starting to get sticky on the backside.

I don't know if the truck is still missing. It doesn't seem to be when I hold the key in the start position. I can't get it started to find out. I'll still take your advice and tighten the screws on the carburetor down. Thanks for the reply.


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## Fla Gal (Jul 14, 2003)

fordy said:


> ............it's also possible that you put the distributor cap on 180 degrees out of sync . I'd pull the #1 plug and get that piston on top dead center then check the firing order from the distributor to each individual cylinder via the plug wires . An icepick stuck in plug hole will tell you when the pistion is TDC . , fordy


Fordy,

The old distributer cap and the new one looked almost identical, including "#1" embossed at the number one position. I turned the new cap to the proper position and changed out each wire, one by one, from the # 1 position, while I left the old cap on the distributer. The truck has started since then and was running fine except for a tell tale puut, puut on two cylinders that had fouled plugs. After that, it stopped starting.

You brought up an excellent point. I didn't know a distributor cap could be 180 degrees off. Never thought about it. You taught me something new! Thank you for your reply.


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## farminghandyman (Mar 4, 2005)

there talking about the part that is inside the disturbor, 

that replaced the points, 








and if the picture does not come through thy the link below,
http://www.wrljet.com/fordv8/images/duraspark-stator.jpg

link on the ignition system
http://www.wrljet.com/fordv8/duraspark.html
some more (actually how to switch from points to "Duraspark II Electronic Ignition" system but may help you out,
http://home.earthlink.net/~rcfaulconer/duraspark/eec.htm another picture of it, the part in the picture that is on the left, "called stator and lower plate" in the caption, 
one more from autozone
http://www.autozone.com/az/cds/en_us/0900823d/80/15/0c/b2/0900823d80150cb2/repairInfoPages.htm


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## Fla Gal (Jul 14, 2003)

Jim S. said:


> I went nuts with a 79 302 Ford van with this problem. I'm gonna tell you what I found. It may not work for you, but it is a very cheap part, so why not try it?
> 
> Go in the distributor and replace the pickup. It's under $20 at Auto Zone or whatever, and easy to swap out. The pickup has wire windings in it and it also moves on the little plate it is on when the ignition advances, so those connections over years can get iffy. What was happening on my van was that when it warmed up some, the connection wanted to break.
> 
> ...


Jim,

I had to laugh. I was reading your one sentence as "Go into the distributer (Ford) and buy a new pickup (truck)"!!!  

Seriously now, I just went out and looked into the distributer and I see the plate and two wires. It's too late tonight to call the parts store but I will be calling them tomorrow.

My employer tried to help me with the truck. He said it sounded like it jumped timing. He took the distributer cap off, poked around in there for a few seconds, put the cap back on and the truck fired right up. The next time I tried to start it, it wouldn't go. That's when I got the new cap, rotor, plugs and wires. The contact points on the rotor and distributer were very worn.

I know electrical connections will break when they get hot or even warm. I didn't think about the wires inside the distributer.

And about running it with the key in the start position, only for a very short time, that was a last ditch effort to find out what I could learn about the problem. I've done it only twice and each time I learned something (as I was listening to the starter grind against the flywheel). It's a relatively new starter and I don't want to tear it up.

Oh how I hope this is the problem. I don't want to pay a $60 towing bill and the price of getting it fixed at a shop.

I'm going to call the parts store tomorrow. This is a very small town so they probably don't have the part in stock. I won't be able to get it until Monday or Tuesday.

In the back of my mind I believe it has to be something simple like this. Thanks Jim for the reply and I hope this is the answer to my problem. After I change it I'll let y'all know what happened.


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## Fla Gal (Jul 14, 2003)

farminghandyman,

Thank you so much for those links! That's the system on my truck. 

I have to go take care of the critters now but I'll be checking the links out throughly when I get back in. Thanks again!!!


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## agmantoo (May 23, 2003)

My experience on vehicles that run on start position but die when the key is back on run, all go along with the electronics that create the spark. Many vehicles start on 12 volts and drop back to 6 to run. The 12 volts voltage to feed the plugs is connected in the start position but fails in the run position when the 6 volts should be present due to component failure. I know a person that drove a Honda 9 miles at about 45 MPH with the starter engaged and the key held in the start position. Obviously it damaged the starter


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## tamsam (May 12, 2006)

OK I am racking my brain to remember how the wiring on that model went. First, does it have a coil which I am sure it does. The older Fords if I remember correctly uses the solonoid for spark when stsrting. If you have 2 bat cables and 2 small plug on wires when the switch is in the start pos the ign system gets its 12 volts from the sol. Next check for 12 volts at the coil when ign switch is in the on pos. Some one correct me if I am wrong here. If you don't have 12 volts start checkinh the wire back toward the ign switch for a break. I think there used to be a fuseable link {which is is a wire that acts as a fuse} between the switch and coil. If you find a wire that looks different than the others and is about 8in to a foot long, feel it and if there is a soft or brittle feeling spot in it try pulling on it to see if it stretches. If so it is bad. Even if it feels ok check for voltage there with ign switch on. Hope this isn't to confusing but the Ford ign takes 12 volts to operate right and if that fuse was going bad it could be your problem. Good luck with it. Sam


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## Beeman (Dec 29, 2002)

Sounds like the pickup inside the distributor.


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## HermitJohn (May 10, 2002)

Didnt those old Ford ignitions have either a ballast resistor or resistor wire to protect the coil? It started at full voltage with key in start position and then with key in run it fell back to the resistor circuit. If ballast resistor (or resistor wire) has went kaput then its only going to run in start position. I also remember original Duraspark ignition had problems with corrosion, especially where wires connect to coil.

In my old F250 I used a GM 4 terminal ignition module with the Ford Duraspark distributor. This let me use a high voltage coil and no need for resistor or resistor wire. Coil I used on that truck is off an old HEI Vega. The one I used on my Ranger is original TIF Ford coil used with the original factory computerized system. Its pretty much same coil as used on 4 and straight 6 cyl GM engines with HEI in the pre computer era.


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## pitbulls20 (Nov 15, 2007)

Just thought I would post this link. It is on Autozone.com site and it has some good repair guides and diagrams that may be useful to you.

http://www.autozone.com/addVehicleId,1307103/initialAction,repairGuide/shopping/repairGuide.htm?pageId=0900c1528004b668


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## pitbulls20 (Nov 15, 2007)

Just thought I would post this link. It is on Autozone.com site and it has some good repair guides and diagrams that may be useful to you.

http://www.autozone.com/addVehicleId,1307103/initialAction,repairGuide/shopping/repairGuide.htm?pageId=0900c1528004b668


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## wy_white_wolf (Oct 14, 2004)

302 - If it's not the brain or the ignition pickup sounds like the timing chain is real loose to me. See how much you can turn the crank back and forth before the distributor moves. May have to pull all the plugs to turn by hand.


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## Fla Gal (Jul 14, 2003)

The saga continues. I got the pickup assembly today and was going to put it in the distributor. On the shaft is an eight toothed, for lack of a better word, cog. It has, if I recall the name correctly, a roller pin holding it in place. What do I have to do to remove this pin? Will I be able to reuse the pin or will I need a new one?

Do I need to even remove the pin or just use a baby wheel puller to take the cog off or what? There's also the reinstallation of the pin. What's the best way of doing that without beating up the distributer?

Hermit John, I don't know about the resistor wire except to say that Sam said one of the wires going from the coil to the ignition may have a fuseable link in it (Thanks Sam!). I haven't gotten that far yet. I wanted to find out if the problem was the pickup assembly before replacing that wire.

It's been at least 12 to 14 years since this truck had a tuneup. I'm willing to replace all the components I have to because it's a strong running work truck. This old truck has been in the family for 22 or 23 years. This is the second time I've owned it. I've put so few miles on it that the tires lasted for almost 10 years. I'm not going to give up on it until the body rusts off the chassis or the engine blows up. 

Wy_white_wolf, I tried to turn the crank and it wouldn't turn for me. I didn't think it would without the plugs out. I guess that means the engine has good compression! After I replace the pickup assembly, and if necessary the fuseable link, and the truck will still not start that will be my next step.

My employer is letting me use his small farm truck to do my job so I'll be able to track down this problem without losing time on the job. Thanks to all of you for your replies and help. It's greatly appreciated.


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## fixer1958 (Dec 12, 2005)

The reluctor wheel will be sort of stuck on there till you get it moving off the shaft.
The rollpin is something like a keyway. You should be able to reuse it.
I have used something similar to a top post battery terminal puller on those. They are small and not expensive. Just something to grip each side of the wheel evenly.
I don't recall if you have to set the airgap between the reluctor wheel and the pickup or not. Most likely you will. Just check what it is before you take it off if you don't have specs.


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## Rocky Fields (Jan 24, 2007)

Hey.

If you hold the ignition switch in the start position the starter should grind. If not, the starter may be stuck in the engaged position(bad bendix) or something is wrong with the ignition switch.

RF


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## Fla Gal (Jul 14, 2003)

fixer1958 said:


> The reluctor wheel will be sort of stuck on there till you get it moving off the shaft.
> The rollpin is something like a keyway. You should be able to reuse it.
> I have used something similar to a top post battery terminal puller on those. They are small and not expensive. Just something to grip each side of the wheel evenly.
> I don't recall if you have to set the airgap between the reluctor wheel and the pickup or not. Most likely you will. Just check what it is before you take it off if you don't have specs.


fixer, I now know, in this case, it's a key way. I know a little about woodruff keys and key stock. The only experience I've had with a roller pin was replacing one of them in a small Hoover washing machine I had. I had to replace the roller pin for the machine to not leak water. That one cost me a paint job for the people downstairs. 

So... now, a few questions. This cog looking thing is called a reluctor wheel? Would you tell me how I can measure the airgap if I have to?


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## Fla Gal (Jul 14, 2003)

Rocky Fields, I replaced the starter less than two weeks before this problem began because the bendix on the old starter was sticking. I could drive the truck at low speed (idling) with no noise. I accelerated and the "very loud" grinding began. I went about five city blocks before I could find a place to turn around and bring the truck back home at an idle. It's a new ignition switch too.

Thanks for your reply. I appreciate your help.


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## HermitJohn (May 10, 2002)

This is diagram I found for using Ford Duraspark module on garden tractor used for tractor pulling purposes. However it shows simplified way module is connected in an ignition circuit. 










I just cant remember if Ford Duraspark coil has resistance built in or uses ballast resistor, or a resistance wire since I am using a GM module on my F250. A fusable link would have nothing to do with this resistance or so I would think. In this diagram it shows red wire coming from module to coil + terminal with ballast in the loop. 

I am not suggesting you do this though I dont "think" it would harm anything, but if it were me I would run jumper wire from positive battery terminal directly to + coil terminal. Then try to start truck and see what happens. My guess is truck would stay running with key in run position. You cant drive truck like that but it would tell you that the wire (or ballast resistor if it has one) going to coil is bad. 

I just dont think your problem is in distributor since truck starts with key in start position. Also not the ignition module since again it starts. Its only dieing in run position. So either bad wiring or bad ballast resistor if it has one. Ford wiring was well known for corrosion problems, thats why they were one of first to using dielectric grease in many of electric connections. Hey be happy that Ford put distributor on their V8s in front. GM and Chrysler put them back near firewall and you have to crawl into engine compartment to work on them.


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## fixer1958 (Dec 12, 2005)

Fla Gal said:


> fixer, I now know, in this case, it's a key way. I know a little about woodruff keys and key stock. The only experience I've had with a roller pin was replacing one of them in a small Hoover washing machine I had. I had to replace the roller pin for the machine to not leak water. That one cost me a paint job for the people downstairs.
> 
> So... now, a few questions. This cog looking thing is called a reluctor wheel? Would you tell me how I can measure the airgap if I have to?


Use a feeler guage. The only spec I could find is .025 to .035
Make sure you have it lined up properly. It's like setting points on a pre 1975
engine. Looks like you will have to set it.


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## Rocky Fields (Jan 24, 2007)

Hey.

Did you address the possibility of a bad starter solenoid? This is usually located on the firewall...has starter and ignition connection.

RF


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## Fla Gal (Jul 14, 2003)

RF, the starter solenoid was changed about three years ago. It hasn't been clicking or making any noise at all I have a brand new one I bought a while back in case the current one failed.

Hermit John, thank you very much for the picture. I haven't gotten that far with the truck yet.

Fixer, thanks for the picture of the reluctor wheel. That explains how to set the air gap.

I just got back from town. I bought a small wheel puller. I have to finish taking care of four houses of chickens before I can work on the truck. It isn't supposed to rain today so I should be able to get something done on the truck.

Thanks again for all the links, pictures, replies and help. I'll let you all know what I find out.


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## Fla Gal (Jul 14, 2003)

I forgot to ask one question. At the parts store the guy told me I could spray wd-40 on the reluctor wheel to help get it off the shaft. Can I spray that, or Sea Foam into the distributor and not cause problems?

Thanks again.


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## Fla Gal (Jul 14, 2003)

Thanks guys for bearing with me. You're good teachers and some of the best neighbors I've never met! 

I'll get it whooped! I don't care how long it takes. I'll learn, and with you guys help, that truck will run.



fixer1958 said:


> Use a feeler guage. The only spec I could find is .025 to .035
> Make sure you have it lined up properly. It's like setting points on a pre 1975
> engine. Looks like you will have to set it.


Fixer, I've never gapped points, only plugs. When you say .025 to .035 does that mean any point between those two set points would work?

I just gaged the gap. The .025 feeler gage slides through with a little resistance. The .035 gage has more resistance. I didn't force the .035 gage too much but it will fit, just a lot tighter with more resistance.


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## fixer1958 (Dec 12, 2005)

Fla Gal said:


> Fixer, I've never gapped points, only plugs. When you say .025 to .035 does that mean any point between those two set points would work?
> 
> I just gaged the gap. The .025 feeler gage slides through with a little resistance. The .035 gage has more resistance. I didn't force the .035 gage too much but it will fit, just a lot tighter with more resistance.



Set it at .025 and it does mean anywhere between .025 and .035.
Setting points is about the same procedure.
Now you can do it all.:rock:

I hope it fixes the problem. Having it run with the key in the start position has me bugged though. That tells me it may be the ign. module (brain).
I know it's new, but new isn't always good.
I've been wrong before.
See what happens with the new pickup coil. WD-40 won't hurt anything.


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## agmantoo (May 23, 2003)

Sometimes desperate situations call for desperate measures. Are you will to do a little Rube Goldberg rigging to get this vehicle running? If so, here is what I suggest. Go to the link above http://www.wrljet.com/fordv8/duraspark.html
open this and then go near the bottom of the page and look at the schematic.
At the top of the schematic where the ignition switch is shown you will see on the right the Ballast resistor. On the side of the ballast resistor away from the coil temporarily connect a small jumper wire. Run that jumper wire to the positive terminal on the battery. Now get in the vehicle and start it and turn the ignition switch loose and see if the engine continues to run. It should. You will have to take the jumper off the battery to get the engine to stop. If all this happens the problem is either in the ignition or the Duraspark module. PS....IMO,since the vehicle runs in the start position there is nothing wrong with the distributor other than the possible pickup electronics. If your are not careful you will have the truck to where it will not run even in the start position.


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## HermitJohn (May 10, 2002)

agmantoo said:


> If all this happens the problem is either in the ignition or the Duraspark module. PS....IMO,since the vehicle runs in the start position there is nothing wrong with the distributor other than the possible pickup electronics.


Like in my answer, you are just bypassing the ballast resistor. If that lets it run, pretty good indication that *the ballast resistor* is the problem, not the ignition module, not the distributor. Course it could be wiring to/from the ballast resistor. I just wasnt sure that the original Duraspark coil had external or internal resistance. Your diagram indicates it has external ballast resistor. That and the corrosion problem in that era Fords is why I used a GM module in my F250. It eliminates need for resistance circuit altogether. Its also bit simpler to wire up and I like the HEI/TFI coil design better than a souped up points coil like Duraspark is. The GM module is just a better mousetrap than Ford or Chrysler or Bosch or various Japanese modules of that era. You really want a shock go price a Bosch module off a Volvo 245. Does exactly the same thing as the GM, Ford, or Chrysler module but costs like $250, thats how I found out these modules are all interchangable if you are willing to do bit of wiring. $250 and special order at that. Bosch is German for very expensive. The $15 GM is just the best design though you have to provide your own heatsink for it if not using it in GM or Fiat application.


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## Beeman (Dec 29, 2002)

If I remember correctly you don't pull the reluctor wheel. Instead I think you have to drive out the roll pin and pull off the dist gear and then remove the shaft with the reluctor wheel. Check before you break anything or you'll be buying a reman dist.


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## pitbulls20 (Nov 15, 2007)

I know this is a little old now but did you ever fix it? I own a 78 F250 and I ended up having to replace alot of stuff on it to get it to run good.


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## michiganfarmer (Oct 15, 2005)

Bearfootfarm said:


> D
> 
> Also, I had a 78 300 6 cylinder, and the carb would work loose over time and cause it to run rough.


mine did that, LOL


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## michiganfarmer (Oct 15, 2005)

HermitJohn said:


> Didnt those old Ford ignitions have either a ballast resistor or resistor wire to protect the coil? .


I think that was dodge


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## carboy (May 24, 2008)

I have worked on a few of these old ford trucks and the first thing to check is a dirty ground connection from the battery to the engine. Remove the ground strap and clean the mounting surface. Good luck


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