1978 F100 Pickup won't start

Fla Gal · #1 05/09/08, 03:23 PM

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?

Bearfootfarm · #2 05/09/08, 04:27 PM

Quote:

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

Jim S. · #3 05/09/08, 04:38 PM

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.

fordy · #4 05/09/08, 05:02 PM

............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

Fla Gal · #5 05/09/08, 05:19 PM

Quote:

Originally Posted by Bearfootfarm

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.

Fla Gal · #6 05/09/08, 05:40 PM

Quote:

Originally Posted by fordy

............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.

farminghandyman · #7 05/09/08, 05:54 PM

there talking about the part that is inside the disturbor,

that replaced the points,
1978 F100 Pickup won't start - Shop Talk

and if the picture does not come through thy the link below,
http://www.wrljet.com/fordv8/images/...ark-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/~rcfaulcon...aspark/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...rInfoPages.htm

Fla Gal · #8 05/09/08, 06:32 PM

Quote:

Originally Posted by Jim S.

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.

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.

Fla Gal · #9 05/09/08, 06:47 PM

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!!!

agmantoo · #10 05/09/08, 08:18 PM

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

tamsam · #11 05/10/08, 12:40 AM

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

Beeman · #12 05/10/08, 09:09 AM

Sounds like the pickup inside the distributor.

HermitJohn · #13 05/11/08, 04:11 PM

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.

pitbulls20 · #14 05/13/08, 10:58 AM

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...00c1528004b668

pitbulls20 · #15 05/13/08, 11:06 AM

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...00c1528004b668

wy_white_wolf · #16 05/13/08, 11:45 AM

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.

Fla Gal · #17 05/13/08, 04:28 PM

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.

fixer1958 · #18 05/13/08, 04:45 PM

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.

Rocky Fields · #19 05/13/08, 05:49 PM

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

Fla Gal · #20 05/13/08, 08:16 PM

Quote:

Originally Posted by fixer1958

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?