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If I remember correctly when my 77 F350...had this issue....the coil went bad. The truck quit running. When you went to start it.....it would try to fire while cranking but as soon as you would release the key...it died.
Did the voltage test etc...turned out it was the coil. I think I replaced the ignition module also. I replaced the coil with another original 77 Ford coil off of my 400 and checked voltage etc...never had a problem since. I have another spare original coil (looks rough but it’s good) and two spare older Napa ignition modules still in the boxes. I keep one in the trucks glove box for when I’m on road trips. It’s been like 5 years now and as I said...no issues since.
Quote:
If you are going to ask for help then ignore the advice and steps to identify the issue then rectify the problem why bother posting the question at all.....
Sorry if i upset you that i did not OHM out the coil instantly after your post.
family got in the way of me trying to research how to OHM out the coil.
i will get to it soon. it has been raining all day here today and i do not own a garage.
i will try to get to the testing steps faster as to not disappoint you in the future.
Oh and i will no longer ask questions here as to not upset you any further.
matthewq4b Quote:
If you are going to ask for help then ignore the advice and steps to identify the issue then rectify the problem why bother posting the question at all.....
Sorry if i upset you that i did not OHM out the coil instantly after your post.
family got in the way of me trying to research how to OHM out the coil.
i will get to it soon. it has been raining all day here today and i do not own a garage.
i will try to get to the testing steps faster as to not disappoint you in the future.
Oh and i will no longer ask questions here as to not upset you any further.
When I was where you are now in life there was no internet. I had bought my first truck a 1973 F250 2wd std. cab. The PO had brush painted it in black primer but it was my baby. How we got information back then was from the old timers at the local junk yards who were often crusty old fxxkers with kerosene breath and dispositions to match but if you wanted to get to the wisdom they had from working on these old trucks you had to keep coming back and approach them with the respect you show a junkyard dog. Over time the sacred knowledge would come spilling out and you and your truck would be the better for it. I became a great grand father this last year and lost a daughter all that against a life time of working on ford trucks and listening to crusty old fxxkers to learn one more thing I didn't know about these trucks. I hope you keep coming back.
P.S. bringing an occasional cup of coffee or a donut to the table back then seemed to get the desired result and a better price on parts
i found a good youtube video on how to test the coil.
as soon as the rain stops i will be out there testing.
i still cant find the specks for our coil.
is ours a 3 ohm or 1.5 ohm coil ?
1.5 ohm positive to negative?
and between 7500 to 8800 OHM center post to positive or negative post ?
Here's one for you between a coup[le of FTE crusties BTW I turned into a crusty old fxxcker without ever knowing it happened until the grand kids called me on it Oh well!
Elec troubleshooting. Talk between 3 FTE members.
(MIKE) Some of those earlier models had a starter solenoid with 2 small terminals one should say I for "ignition" and the other be stamped with an S. That way the coil will get power while cranking and power will stay when the key is released. Use your DVOM and check for power to the coil with just the key on. They used resistors of some sort to cut the voltage down at the coil after cranking, and during cranking you should get a full 12.6 or somewhere about. Once the engine starts, the resistor cuts down the voltage to 10-12 so you don't burn out the coil. You need to trace the wire that powers up the coil with the key on.
(MIKE) With the key "on" check for voltage at the coil + terminal. If you show voltage, next, disconnect the battery cable that goes from the solenoid to the starter. This is just so the starter doesn't turn over. Now, turn the ignition to the "start" position and check for voltage at the + coil terminal. If you show voltage there, I would suspect four possibilities. First, the inner fenderwell starter solenoid. Second, a wiring problem. Ford uses a resistor wire and these do sometimes go bad. It's rare but it does happen. These can be "wired around" by using a regular ceramic resistor wired parallel to the original circuit. Next, a bad ignition switch and last a bad ignition module. The thing about intermittent problems is, unless it's acting up at the moment, they're difficult to troubleshoot and once you fix it, you're not really sure it's fixed.
(Original member test results) With battery at 12.3v, coil at "run" has 6.47v, at "start" has 11.9v next step, please?
(MIKE) If you have a test light, touch it to the negative terminal of the coil and crank the engine. It should blink as the engine turns over. While you're there, check the resistance between the - and + coil terminals, it should be less than 1 ohm.
(FMC) The fact that the coil voltage drops in RUN means that both the coil and module are getting powered properly, the drop in RUN tells you that the module is grounding the coil at a stand-still, as it should. In addition to what Mike has described (which will help isolate the problem to either the primary or secondary sides), check the resistance between the ORANGE and PURPLE wires coming from the distributor. It should be between 400 and 700 ohms. Neither wire should have continuity against the BLACK wire (total of three measurements). Often times, if the pickup fails (which is what you're checking), it will not switch the module while the engine is cranking, but letting off the key collapses the coil, which gives that final spark. If the BLINK test BLINKs, then my test is a moot point. I'm just listing it out now in case.
(Original member) The results of the testing:
1. Light BLINKED as starter turned engine over
2. 1.5ohm across coil terminals
3. 647ohm across ORANGE and PURPLE wires from dist
4. DMM read "OPEN" ORANGE to BLACK and PURPLE to BLACK
On #2, at first I could not get a reading that was stable for 10 or 15 seconds until it finally settled to 2.8 ohm. I cleaned the terminals with scotchbrite and that dropped the time to immediate and measurement to the reported number. Dist was replaced 2 yrs ago because vac adv mech was corroded and locked up, along with plugs and wires, when I got the truck running. Coil and ign module remain as purchased from PO
(FMC) All of your observations (1 through 4) are perfect. They tell you that the entire primary side of the ignition system is in perfect working order. If there is no spark in the presence of these conditions, then the problem is isolated to the secondary side - distributor cap, rotor, wires, or plugs. Note, however, that these items have no "sense" of the position of the key, so a problem there would not correlate to your original observations (only get spark when you let off the key). In other words, your two sets of observations can't co-exist, so something changed, or is missing from the story.
Quote:
If you are going to ask for help then ignore the advice and steps to identify the issue then rectify the problem why bother posting the question at all.....
Sorry if i upset you that i did not OHM out the coil instantly after your post.
family got in the way of me trying to research how to OHM out the coil.
i will get to it soon. it has been raining all day here today and i do not own a garage.
i will try to get to the testing steps faster as to not disappoint you in the future.
Oh and i will no longer ask questions here as to not upset you any further.
\
Then instead ask HOW to ohm out the coil and it can be explained to you. We are trying to do diagnostic remotely so that means YOU need to communicate if you are not sure or do not know how to do or approach something. We give you these diag steps so YOU are not chasing your tail or buying parts that you do not need.
And if you are going to ignore it and then get butthurt cause you get called on it, you will find that not many people will offer up to help.
There are people on this board who have decades of experience some with more years of experience than you have been alive, some who were former Ford techs and some who were Ford systems engineers who worked on or designed these systems and items.
So keep in mind these diagnostics are being done remotely by people who are giving YOU their knowledge and experience and time free of charge (how often does that happen in today's world) so if you do not know how to do something or are unsure how to do it speak up, instead of ignoring people who are giving you their time experience and knowledge. So maybe when you are given steps to do then fail to do them or explain that you do not know how to do them, then get called on it suck it up like a mature responsible man instead of going all butthurt. The only stupid question is the one not asked.
If you want the procedure to ohm out the coil just ask...
Then instead ask HOW to ohm out the coil and it can be explained to you. We are trying to do diagnostic remotely so that means YOU need to communicate if you are not sure or do not know how to do or approach something. We give you these diag steps so YOU are not chasing your tail or buying parts that you do not need.
And if you are going to ignore it and then get butthurt cause you get called on it, you will find that not many people will offer up to help.
There are people on this board who have decades of experience some with more years of experience than you have been alive, some who were former Ford techs and some who were Ford systems engineers who worked on or designed these systems and items.
So keep in mind these diagnostics are being done remotely by people who are giving YOU their knowledge and experience and time free of charge (how often does that happen in today's world) so if you do not know how to do something or are unsure how to do it speak up, instead of ignoring people who are giving you their time experience and knowledge. So maybe when you are given steps to do then fail to do them or explain that you do not know how to do them, then get called on it suck it up like a mature responsible man instead of going all butthurt. The only stupid question is the one not asked.
If you want the procedure to ohm out the coil just ask...
IGNITION COIL TEST
1) With ignition off, check secondary resistance between coil "DEC" (negative) terminal and coil tower. See Figs. 1 and 2. Resistance should be between 7000-13,000 ohms.
2) Check primary resistance between "BAT" (positive) and "DEC" (negative) coil terminals. Resistance should be 1.13-1.23 ohms (.71-.77 ohms Dura-Spark I ignition system). It resistance is not within specifications, replace ignition coil.
Red this thread yesterday, it made me think back on a few guys I had the good fortune to work for, and am glad to see the outcome.
Back in 1981 I was a young Seabee Third Class Equipment Operator Petty Officer and worked for an older (early Vietnam generation) Second Class Equipment Operator. I guess the Chief in charge of us both realized I could work for the old Second Class, he was seasoned and had a short fuse, but he was a top notch Drag Line operator, smooth and fluid, not jerky and I knew I could learn from him, if I showed him I was worthy. Knowing the importance of eating humble pie, allowed me to demonstrate through action, hard work and a sincere desire to learn from him, his name was Dewy. He told me before you can operate, you must know how to maintain a machine, or as Dewy referred to the Drag Line, must know how to maintain a piece of "heavy iron". I remember he painted red finger polish on the eight hour grease fittings, to check if I was greasing them. I told Dewey there was red paint on the eight hour fittings, but I removed it before I greased them. He told me he painted them red with finger polish to check if I was greasing them. At that point I knew I Dewy realized I was worthy.
Fast forward. Dewy was divorced from 1969 until 2013. In 2000 Dewy visited my family and I and asked me to take him onto the Port Hueneme Navy Seabee base to see the cranes. I did and it broke his heart to see the lack of maintenance not being performed and not being taught in the school house. He was taking powerful medication for back pain prescribed by the VA and his pain medication apparently wore off while we were in the field looking at the cranes. He almost lost consciences and I carried him back to the truck, took him back to his hotel where he had his medication. That scene of me carrying him, when 19 years earlier while I worked for him he was so strong brought tears to my eyes. Dewy and I stayed in touch through letters, Christmas cards and occasional phone cards. He married in 2013 and pasted away in 2018. Unbeknownst to me until a layer contacted me because he made me his beneficiary. All his assets I gave to his spouse and would not take anything. I already received a life time of good teaching from him while I worked for him. Moreover, back in 1974 my late Grandfather medically retired, an ambulance took him from work to the hospital. He was discharged from the hospital and my late Father asked me if I wanted to spend time W/my Grandfather, of course I did. Spent six weeks W/him. Within the six weeks, he asked me to take back to work so he could clean out his locker. I helped him, he wasn't strong. He handed me his old aluminum lunch bucket and said to me, "maybe you can use this". To this day I still use that old lunch bucket. Over the years a few guys have commented about it in a semi-sarcastic manner, and I've told them the story behind it. None of them have made a sly remark about it since. Fall 2019 my youngest son started working as an HVAC apprentice, about six months ago he was telling me the Journeyman he been assigned to isn't teaching him much. I told my son that it's important to show the Journeyman your worthy to receive his teaching, by exhibiting a sincere desire to learn, hard work, good work ethic and be willing to eat humble pie. And to remember, the Journeyman had to do the same when he was coming up through the trade.
Humble Pie it is.
i keep trying no matter what happens. cant give up on the truck.
it was not properly maintained in the first place. i am trying to
keep it mechanically sound. it is much better now than when i got
it. i replaced the important stuff first. i understand i asked for help
and got it. i am going to get this thing fixed with the help of all
the great minds on this site. i cant thank you all enough for your time.
i agree with all that you said. When i get home i will finish testing
the above information that was posted once i get home from work.
i also ordered the new coil. My current coil looks to be the original.
It is rusty looking. i cleaned all contacts for the terminal ends and
the coil + and - contact points before i took the readings. i am
waiting for the coil to arrive. should be here tomorrow.
Humble Pie it is.
i keep trying no matter what happens. cant give up on the truck.
it was not properly maintained in the first place. i am trying to
keep it mechanically sound. it is much better now than when i got
it. i replaced the important stuff first. i understand i asked for help
and got it. i am going to get this thing fixed with the help of all
the great minds on this site. i cant thank you all enough for your time.
i agree with all that you said. When i get home i will finish testing
the above information that was posted once i get home from work.
i also ordered the new coil. My current coil looks to be the original.
It is rusty looking. i cleaned all contacts for the terminal ends and
the coil + and - contact points before i took the readings. i am
waiting for the coil to arrive. should be here tomorrow.
I always say You got to like a guy who doesn't mind working on an old ford truck.
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BTW I turned into a crusty old fxxcker without ever knowing it happened until the grand kids called me on it 
Your welcome and see you down the road.. Thanks for posting your results 