460 coil resistance numbers
#1
460 coil resistance numbers
Our '76 F250 with the 460 engine quits after a few minutes, often starts right up, then quits again. A "friend" says its the coil. The primary circuit shows 0.15 ohms resistance and the secondary shows 9000 ohms. The dealer can't tell me the correct values. Can anyone tell me what the coil readings should be? Thanks!
#2
Well your situation might be a fun one! the 9,000 sounds pretty normal, the .15 seems a little low, but probabaly acceptable
Most of these systems have a resistor wire going to the coil Bat+ term. If you run straight 12V power to the coil it will heat up, and shut off, I've had this happen to somehting I built.
I've never tried messing w/ the stock Ford Ballast ressistor, or ressistor wire...whatever it is
I've set em up before by using a chyrsler resistor I think it was rated for 1.5 ohms or soemthing. Just bolts to the firewall, has 2 terminals, in and out! Can buy one at any Napa don't even have to tell em' what it's for, they'll know. they'll just ask 2 or 3 prong!
You must also have the starter solenoid that has 2 little posts. That second small terminal puts out 12V only when cranking, think of it as a little wire hooked on w/ the wire that goes down to the starter. This wire is to give your coil full 12V at cranking only, bypassing the resistor so it starts easier....I guess
Apparently if you had a mopar you had to always keep one of these in the glove box.....so on second thought maybe it's not a good idea????
Sounds like a resistor wire problem to me, and the only way I've fixed it is w/ this mopar ressistor....so don't take what i said as the only way, but something to think about....
Most of these systems have a resistor wire going to the coil Bat+ term. If you run straight 12V power to the coil it will heat up, and shut off, I've had this happen to somehting I built.
I've never tried messing w/ the stock Ford Ballast ressistor, or ressistor wire...whatever it is
I've set em up before by using a chyrsler resistor I think it was rated for 1.5 ohms or soemthing. Just bolts to the firewall, has 2 terminals, in and out! Can buy one at any Napa don't even have to tell em' what it's for, they'll know. they'll just ask 2 or 3 prong!
You must also have the starter solenoid that has 2 little posts. That second small terminal puts out 12V only when cranking, think of it as a little wire hooked on w/ the wire that goes down to the starter. This wire is to give your coil full 12V at cranking only, bypassing the resistor so it starts easier....I guess
Apparently if you had a mopar you had to always keep one of these in the glove box.....so on second thought maybe it's not a good idea????
Sounds like a resistor wire problem to me, and the only way I've fixed it is w/ this mopar ressistor....so don't take what i said as the only way, but something to think about....
#3
Thanks LedheadELH: Haven't had a chance to play with the old truck yet. Last week I took the old coil down to the local NAPA store and compared the resistance values to a new unit. They were the same! Then I noticed something...
It pains me to admit my stupid mistakes but I failed to notice the scale on the multimeter said 10X - so, the 0.15 ohms is actually 1.5 ohms. If anything, a bit too high! But it seems that my coil is OK (unless it is shutting off as you explained due to overheating/getting 12 volts all the time)
Your info about the 'resistor' wire is interesting, I know nothing about that. I'll check that out once I've done to obvious stuff like cleaning and checking connections.
Appreciate your help,
Cheers
It pains me to admit my stupid mistakes but I failed to notice the scale on the multimeter said 10X - so, the 0.15 ohms is actually 1.5 ohms. If anything, a bit too high! But it seems that my coil is OK (unless it is shutting off as you explained due to overheating/getting 12 volts all the time)
Your info about the 'resistor' wire is interesting, I know nothing about that. I'll check that out once I've done to obvious stuff like cleaning and checking connections.
Appreciate your help,
Cheers
#4
#5
Bear 45/70 Yes, I know you are right but I'm supposed to be old and wise... which means not throwing parts at a problem until you blunder on the actual remedy! Besides, NAPA wants $33 for a $10 coil... (I only paid $100 for the truck)
There is also the chance it is the ignition switch - someone opened it long ago, so the contacts inside are probably buggered.
I'll check out the price of a new distributor sensor... and then there's a problem with the 4bbl carb emptying its float bowl overnight... heavens above!
Thanks for the input
There is also the chance it is the ignition switch - someone opened it long ago, so the contacts inside are probably buggered.
I'll check out the price of a new distributor sensor... and then there's a problem with the 4bbl carb emptying its float bowl overnight... heavens above!
Thanks for the input
#6
Bear 45/70 Yes, I know you are right but I'm supposed to be old and wise... which means not throwing parts at a problem until you blunder on the actual remedy! Besides, NAPA wants $33 for a $10 coil... (I only paid $100 for the truck)
There is also the chance it is the ignition switch - someone opened it long ago, so the contacts inside are probably buggered.
I'll check out the price of a new distributor sensor... and then there's a problem with the 4bbl carb emptying its float bowl overnight... heavens above!
Thanks for the input
There is also the chance it is the ignition switch - someone opened it long ago, so the contacts inside are probably buggered.
I'll check out the price of a new distributor sensor... and then there's a problem with the 4bbl carb emptying its float bowl overnight... heavens above!
Thanks for the input
#7
mrfixit. i hope this helps. i got this from the second chance garage website. you can either read what i added or go to the website. after reading the article it is obvious that gm and ford put the resistor wire in and chyrsler went with the resistor on the firewall.
Automotive Electrical Systems-Part 5-Ignition Systems
The next component is the ignition resistor. It is necessary because ignition coils are designed to step up battery voltage high enough - and fast enough - to keep the engine running at high rpm. That means that, as designed, the coil would produce too much high voltage at low rpm and heat up. Automakers long ago realized that there were two solutions to the problem: using two coils (one for low rpm and one for high) or an ignition resistor. Obviously, the resistor approach is the least expensive and most reliable, so that's what they did. The resistor used varies is resistance as a function of temperature, and limits the voltage to the coil accordingly. As the engine revs up the resistance lowers, allowing more voltage to the coil for fast running, and the reverse happens when the engine slows down. At idle, for instance, only about 7 volts is going through the coil primary windings.
The only time the resistor is out of the circuit is during startup, when the engine needs all the spark it can get. It's bypassed in the ignition switch's start position so that, during starting, the coil gets full battery voltage. Ignition resistors can take many forms, depending upon the manufacturer of the vehicle. Some builders mounted a big resistor on the firewall and some others utilized a special type of wire (resistance wire) running from the ignition switch to the coil. Still others used coils that were built with an internal resistor. None of these is any better an approach than the others, but it's important to know which type you have, and that you have one!
Automotive Electrical Systems-Part 5-Ignition Systems
The next component is the ignition resistor. It is necessary because ignition coils are designed to step up battery voltage high enough - and fast enough - to keep the engine running at high rpm. That means that, as designed, the coil would produce too much high voltage at low rpm and heat up. Automakers long ago realized that there were two solutions to the problem: using two coils (one for low rpm and one for high) or an ignition resistor. Obviously, the resistor approach is the least expensive and most reliable, so that's what they did. The resistor used varies is resistance as a function of temperature, and limits the voltage to the coil accordingly. As the engine revs up the resistance lowers, allowing more voltage to the coil for fast running, and the reverse happens when the engine slows down. At idle, for instance, only about 7 volts is going through the coil primary windings.
The only time the resistor is out of the circuit is during startup, when the engine needs all the spark it can get. It's bypassed in the ignition switch's start position so that, during starting, the coil gets full battery voltage. Ignition resistors can take many forms, depending upon the manufacturer of the vehicle. Some builders mounted a big resistor on the firewall and some others utilized a special type of wire (resistance wire) running from the ignition switch to the coil. Still others used coils that were built with an internal resistor. None of these is any better an approach than the others, but it's important to know which type you have, and that you have one!
Trending Topics
#8
mrfixit. i hope this helps. i got this from the second chance garage website. you can either read what i added or go to the website. after reading the article it is obvious that gm and ford put the resistor wire in and chyrsler went with the resistor on the firewall.
Automotive Electrical Systems-Part 5-Ignition Systems
The next component is the ignition resistor. It is necessary because ignition coils are designed to step up battery voltage high enough - and fast enough - to keep the engine running at high rpm. That means that, as designed, the coil would produce too much high voltage at low rpm and heat up. Automakers long ago realized that there were two solutions to the problem: using two coils (one for low rpm and one for high) or an ignition resistor. Obviously, the resistor approach is the least expensive and most reliable, so that's what they did. The resistor used varies is resistance as a function of temperature, and limits the voltage to the coil accordingly. As the engine revs up the resistance lowers, allowing more voltage to the coil for fast running, and the reverse happens when the engine slows down. At idle, for instance, only about 7 volts is going through the coil primary windings.
The only time the resistor is out of the circuit is during startup, when the engine needs all the spark it can get. It's bypassed in the ignition switch's start position so that, during starting, the coil gets full battery voltage. Ignition resistors can take many forms, depending upon the manufacturer of the vehicle. Some builders mounted a big resistor on the firewall and some others utilized a special type of wire (resistance wire) running from the ignition switch to the coil. Still others used coils that were built with an internal resistor. None of these is any better an approach than the others, but it's important to know which type you have, and that you have one!
Automotive Electrical Systems-Part 5-Ignition Systems
The next component is the ignition resistor. It is necessary because ignition coils are designed to step up battery voltage high enough - and fast enough - to keep the engine running at high rpm. That means that, as designed, the coil would produce too much high voltage at low rpm and heat up. Automakers long ago realized that there were two solutions to the problem: using two coils (one for low rpm and one for high) or an ignition resistor. Obviously, the resistor approach is the least expensive and most reliable, so that's what they did. The resistor used varies is resistance as a function of temperature, and limits the voltage to the coil accordingly. As the engine revs up the resistance lowers, allowing more voltage to the coil for fast running, and the reverse happens when the engine slows down. At idle, for instance, only about 7 volts is going through the coil primary windings.
The only time the resistor is out of the circuit is during startup, when the engine needs all the spark it can get. It's bypassed in the ignition switch's start position so that, during starting, the coil gets full battery voltage. Ignition resistors can take many forms, depending upon the manufacturer of the vehicle. Some builders mounted a big resistor on the firewall and some others utilized a special type of wire (resistance wire) running from the ignition switch to the coil. Still others used coils that were built with an internal resistor. None of these is any better an approach than the others, but it's important to know which type you have, and that you have one!
#9
Bear, your right about the start up voltage being less because of the starter drawing the battery to whatever.
However the resistor has nothing to do w/ points. Newer elec. ignition (duraspark) Have these resistor wires. I think(but not sure) even EEC IV systems have the resistor too. my guess is anything with a single coil has a resistor. Anything with coil packs does not
By the way, what's with the car in your thumbnail?!......reverse rotation marine engine or something??or just an optical illusion? Cool pic either way!
However the resistor has nothing to do w/ points. Newer elec. ignition (duraspark) Have these resistor wires. I think(but not sure) even EEC IV systems have the resistor too. my guess is anything with a single coil has a resistor. Anything with coil packs does not
By the way, what's with the car in your thumbnail?!......reverse rotation marine engine or something??or just an optical illusion? Cool pic either way!
#10
Bear, your right about the start up voltage being less because of the starter drawing the battery to whatever.
However the resistor has nothing to do w/ points. Newer elec. ignition (duraspark) Have these resistor wires. I think(but not sure) even EEC IV systems have the resistor too. my guess is anything with a single coil has a resistor. Anything with coil packs does not
By the way, what's with the car in your thumbnail?!......reverse rotation marine engine or something??or just an optical illusion? Cool pic either way!
However the resistor has nothing to do w/ points. Newer elec. ignition (duraspark) Have these resistor wires. I think(but not sure) even EEC IV systems have the resistor too. my guess is anything with a single coil has a resistor. Anything with coil packs does not
By the way, what's with the car in your thumbnail?!......reverse rotation marine engine or something??or just an optical illusion? Cool pic either way!
That was my 1969 Ford Cobra with 428CJ Ram Air.
Thread
Thread Starter
Forum
Replies
Last Post
02 Super Duty Guy
1999 to 2016 Super Duty
5
03-12-2014 09:25 AM
lhutter1
1968-Present E-Series Van/Cutaway/Chassis
3
01-15-2013 06:06 PM