Bobby
Well-known member
Very true. If the starter cable is original to the car then it would be a good idea to replace it. The starter may also have an internal short requiring the extra battery amperage to turn over.
Testing my patience
- Thread starter Jayro
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Jayro
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- Joined
- Mar 30, 2022
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- 146
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- 57
- My Car
- 73 mustang baby blue with clevo 351
Ok so loads been done since I posted this one. So I managed to get the car into a genuine tune shop. The 1st shop had nfi. Turns out they couldn’t sort my car running Rich so ended up down sizing the new holley 750 jets 5 sizes to lean it out. Killing me some people.
Anyway, long story short, new starter solenoid, new alternator, a cable of cable upgrades, retuned correctly and jets back to right size. New exhausted header gaskets as they were not sealed. Car starts great, drives great. So happy to get there in the end.
Anyway, long story short, new starter solenoid, new alternator, a cable of cable upgrades, retuned correctly and jets back to right size. New exhausted header gaskets as they were not sealed. Car starts great, drives great. So happy to get there in the end.
- Joined
- Apr 24, 2020
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- 1,288
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- My all time favorite vehicle is our 1969 Shelby GT500
I am coming in quite late in this thread. I see a lot of really good suggestions. I am not sure4 if I can do much to enhance the opportunity to come up with a solution, but if noting else I can offer perhaps a different perspective. I will begin with the accelerator cable issue, back when I was 17 I was fortunate enough to have a 1969 Mustang coupe, Candyapple Red, to help me carry my books to school and back home. The good news is I had a really nice looking car in high school to drive (1970 - 1972). The downside is it had a 25- six cylinder and a 2.79:1 rear axle ratio. So, as good as it looked it was not a fast car, which in hindsight likely helped me survive my teen driving years. Anyway, in 11th grade I took a deep interest in automobile design and repair. I was fairly mechanically inclined, and ended up actually doing really well in the auto repair industry (two years of auto repair classes at a local college helped). In my fledgling beginning I had taken note of how the accelerator cable worked, and had my brother floor the accelerator pedal (engine off). I was so excited with what I saw. Not, not how the cable opened the throttle. Rather, I saw that when the throttle was opening, it was not opening fully when the pedal was mashed to the floor. Wow! I discovered why the 6 cylinder was so slow!! I surmised that by simply bending the cable mount bracket back a little bit the throttle would be able to open fully via the pedal being push fully to the floor. I was right, and yet I did not have to bend the bracket so far as to open the throttle past its idle position when the pedal was released.
Okay, the excitement I felt in discovering the once limited throttle opening, and the subsequent correction was muffled a bit when I found the further opening of the throttle did not turn my 6 cylinder powered Mustang into the kind of asphalt shredding machine I was really after. But, it was still a victory as I was able to make a small change and fix what those dumb *** engineers did wring! heh heh,,, Believe me, in time I began to develop a respect and appreciation for automotive engineers - limited of course, but still better than having a noxious attitude about them.
Anyway, adjusting the geometry of the throttle lever location for the pin the throttle cable connects to is an option. But, first, try to see by how far you are not able to open the throttle with the pedal pressed fully to the floor. If it is a small amount of travel perhaps you need only carefully bend the mounting bracket back a little like I did so many years ago. A good place to start for me turned out to be disconnecting the cable from the carb linkage and seeing how far forward from the idle position the cable went forward. It turns out that many times while working on a customer's car I would find the forward travel range of the accelerator cable was far more than was needed, and that by altering the mounting bracket I was able to help reorient the cable to allow for both an undisrupted idle speed, and provide a full throttle opening from the pedal. I would say I found that situation to be a problem in maybe 1/5th of all the cars I ever worked on, new and older, when I was wrenching at a Ford dealership in SoCal in the 70s and 80s. In short, it was always worth checking it out. Always. Just like it was always worth checking the vacuum advance diaphragm to make certain it was not ruptured or leaking. Or checking the alignment of the sealed beam headlights. I never charged for adjusting the cable linkage mounting, I just did it, And I rarely mentioned it to a customer unless he.she had mentioned a performance concern, or I felt he.she would be interested to know (they were always thankful).
Okay, enough nostalgia. If the cable linkage is not causing a problem, but the throttle is not opening fully with the pedal to the metal, it could be the geometry needs to be changed. I would keep the efforts focused on the carb linkage, unless you see a problem with the cable linkage or its associated mountings. If you can move the linkage pin the cable connect to toward the throttle shaft on the linkage, it will take less cable travel to open the throttle. It will not take a lot to change it, so no radical moves. Drilling and tapping a small mounting hold on the throttle linkage is where I was begin. Also, i would be very careful to make certain nothing is binding or sticking after you make your changes. And, if there is any disruption to the smooth closing of the throttle when the pedal is released, a stronger throttle return spring may seem a good idea. But, those older throttle cable assemblies are designed to have the throttle return spring built into their very design. If you are getting resistance to the cable moving in and out of its sheath, a heavier return spring is not the solution (it may work but...). In one sticky cable I found the end of the sheath had a piece of plastic the cable traveled back and forth through. I determined the problem was that the plastic's hole the cable was going through had become somehow constricted. I tried to clean and lube that interference point, but it only helped a little. I ended up using a pair of pliers to break off the very end that had become something constricted around the cable. It was just a time piece or the very end tip that I broke off, carefully so the rest of the cable assembly was not damaged., Voila! That is all it needed, saving the customer the expense of a new cable assembly and the labor to install it. actually, it was a new car, so it would have been paid by warranty. But, as I recall the time allowed for replacing the cable was far less than the time it would have actually taken. So, by doing what I did I resolved a problem, and avoided a low paying, thankless task, while srtill solving the problem with a sticking accelerator. I recorded the repair as being cleaning and lubricating the accelerator cable assembly, which was true even if an incomplete description.
Okay, that dead horse is well beaten. Now onto the cranking.starting problem. I agree with the folks that say you need to start with a fully charged battery. However, before charging down that path it is good to know if you have a no crank, slow crank, or cranks fine but won't start issue. In the case of an engine cranking fine but not starting we are dealing with an issue other than the charging or starter system. But, if it is a no crank or slow crank issue we can do some other stuff that will be helpful. For either a no or slow crank situation you really need to start with a fully charged battery. If you are lucky that will be all you need, although it does beg the question about why the battery had become discharged to begin with. That is a subject unto itself. So, if a charged battery does fix the problem, it is time to do a charging system test, and/or check for a current draw from the battery when the ignition switch in in the Off position.
I will address the starting issue in a different post as there is a 10,000 character limit in these postings...
Okay, the excitement I felt in discovering the once limited throttle opening, and the subsequent correction was muffled a bit when I found the further opening of the throttle did not turn my 6 cylinder powered Mustang into the kind of asphalt shredding machine I was really after. But, it was still a victory as I was able to make a small change and fix what those dumb *** engineers did wring! heh heh,,, Believe me, in time I began to develop a respect and appreciation for automotive engineers - limited of course, but still better than having a noxious attitude about them.
Anyway, adjusting the geometry of the throttle lever location for the pin the throttle cable connects to is an option. But, first, try to see by how far you are not able to open the throttle with the pedal pressed fully to the floor. If it is a small amount of travel perhaps you need only carefully bend the mounting bracket back a little like I did so many years ago. A good place to start for me turned out to be disconnecting the cable from the carb linkage and seeing how far forward from the idle position the cable went forward. It turns out that many times while working on a customer's car I would find the forward travel range of the accelerator cable was far more than was needed, and that by altering the mounting bracket I was able to help reorient the cable to allow for both an undisrupted idle speed, and provide a full throttle opening from the pedal. I would say I found that situation to be a problem in maybe 1/5th of all the cars I ever worked on, new and older, when I was wrenching at a Ford dealership in SoCal in the 70s and 80s. In short, it was always worth checking it out. Always. Just like it was always worth checking the vacuum advance diaphragm to make certain it was not ruptured or leaking. Or checking the alignment of the sealed beam headlights. I never charged for adjusting the cable linkage mounting, I just did it, And I rarely mentioned it to a customer unless he.she had mentioned a performance concern, or I felt he.she would be interested to know (they were always thankful).
Okay, enough nostalgia. If the cable linkage is not causing a problem, but the throttle is not opening fully with the pedal to the metal, it could be the geometry needs to be changed. I would keep the efforts focused on the carb linkage, unless you see a problem with the cable linkage or its associated mountings. If you can move the linkage pin the cable connect to toward the throttle shaft on the linkage, it will take less cable travel to open the throttle. It will not take a lot to change it, so no radical moves. Drilling and tapping a small mounting hold on the throttle linkage is where I was begin. Also, i would be very careful to make certain nothing is binding or sticking after you make your changes. And, if there is any disruption to the smooth closing of the throttle when the pedal is released, a stronger throttle return spring may seem a good idea. But, those older throttle cable assemblies are designed to have the throttle return spring built into their very design. If you are getting resistance to the cable moving in and out of its sheath, a heavier return spring is not the solution (it may work but...). In one sticky cable I found the end of the sheath had a piece of plastic the cable traveled back and forth through. I determined the problem was that the plastic's hole the cable was going through had become somehow constricted. I tried to clean and lube that interference point, but it only helped a little. I ended up using a pair of pliers to break off the very end that had become something constricted around the cable. It was just a time piece or the very end tip that I broke off, carefully so the rest of the cable assembly was not damaged., Voila! That is all it needed, saving the customer the expense of a new cable assembly and the labor to install it. actually, it was a new car, so it would have been paid by warranty. But, as I recall the time allowed for replacing the cable was far less than the time it would have actually taken. So, by doing what I did I resolved a problem, and avoided a low paying, thankless task, while srtill solving the problem with a sticking accelerator. I recorded the repair as being cleaning and lubricating the accelerator cable assembly, which was true even if an incomplete description.
Okay, that dead horse is well beaten. Now onto the cranking.starting problem. I agree with the folks that say you need to start with a fully charged battery. However, before charging down that path it is good to know if you have a no crank, slow crank, or cranks fine but won't start issue. In the case of an engine cranking fine but not starting we are dealing with an issue other than the charging or starter system. But, if it is a no crank or slow crank issue we can do some other stuff that will be helpful. For either a no or slow crank situation you really need to start with a fully charged battery. If you are lucky that will be all you need, although it does beg the question about why the battery had become discharged to begin with. That is a subject unto itself. So, if a charged battery does fix the problem, it is time to do a charging system test, and/or check for a current draw from the battery when the ignition switch in in the Off position.
I will address the starting issue in a different post as there is a 10,000 character limit in these postings...
- Joined
- Apr 24, 2020
- Messages
- 1,227
- Reaction score
- 1,288
- Location
- Pittsford, NY
- My Car
- My all time favorite vehicle is our 1969 Shelby GT500
Following are some thoughts on the starting problem. This is not a completed or exhaustive comment. B9t, it will hopefully give you a good start, assuming you have not yet corrected the problem.
Now onto the cranking.starting problem. I agree with the folks that say you need to start with a fully charged battery. However, before charging down that path it is good to know if you have a no crank, slow crank, or cranks fine but won't start issue. In the case of an engine cranking fine but not starting we are dealing with an issue other than the charging or starter system. But, if it is a no crank or slow crank issue we can do some other stuff that will be helpful. For either a no or slow crank situation you really need to start with a fully charged battery. If you are lucky that will be all you need, although it does beg the question about why the battery had become discharged to begin with. That is a subject unto itself. So, if a charged battery does fix the problem, it is time to do a charging system test, and/or check for a current draw from the battery when the ignition switch in in the Off position.
After charging a battery (slowly) overnight I would take it to a parts store that can do a load test to see if the battery has the capacity to both hold, and deliver a charge sufficient to crank over a start motor under load. Or, if you like to tinker and work on your own car you can get your own carbon pile batter load tester for a fairly reasonable amount. An aside, I see the newer "smart testers" are allegedly capable of load testing a battery without using a high resistance, high current carbon pile. Okay, maybe. But, at some point my Old School-itis kicks in and says nothing beats a carbon pile tester like another carbon pile tester when it comes to really testing a battery. My preference is to use an old Sun VAT-40, or even VAT-28, but those are really old and may not be easy to find - much less in working order. I have a VAT-40, which came to me with a damaged inductive lead cable. I was able to fix the cable with some baring of a wire ands resoldering it to its socket. But, I wanted a load tester that easier to carry around, just because I need an excuse for a heavier duty unit - seriously. I ended up with a Solar brand battery carbon pile based load tester from Amazon that really works nicely. The VAT-40 is still an impressive machine, and can do some things the Solar tester can't. But, for an easy to carry around test unit the Solar machine does a great job. No regrets. Here is a link for one of those units:
https://www.amazon.com/Clore-Automo...mzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bc
The way to use the load tester is to connect the large gauge cables to the battery. Then turn the carbon pile dial until you are showing 1/2 of the battery's Cold Cranking Amperage (CCA) rating (or use 250 - 300 amps if you are not sure). You continue to let the battery be loaded for no more than 15 seconds. If the battery is unable to sustain 9.6 volts, or higher, at the end of 15 seconds of the load testing, the battery needs to be replaced (assuming you were testing a fully charged battery). It is that simple. If you need a new battery do not go cheap. Get the highest CCA rated battery you can for the size you can fit into the battery holding area in your car. For First Generation Mustangs I use group 27F, not 24F, as the 27F can hold more lead, which means they have a higher charge capacity than the 24F batteries. Personal choice,, plus experience over the pat 50 years.
If the battery passed, or is new, and still fully charged, and you still have a cranking issue it is time to begin to diagnose the real issue. But first, is it not cranking? Or a slow crank?
If the charging system checks out, as well as the Neutral Safety Switch for a no crank issue, the next thing to check is the battery terminals themselves to ensure the connection between the battery posts and lug terminals are clean and have nothing preventing a good flow of current. I do not like screw/bolt on terminal ends on battery cables. Too often I find the connection is poor, usually due to corrosion under the clamping plate. I far prefer the lug terminal ends to be pressed and/or soldered. Check the ground cable to make certain it is affixed to the body/frame of the vehicle, as well as the engine. It is critical the engine and body/frame are connected one way or another with a high current capacity cable. In the First Generation Mustangs there are two general kinds of negative cables that one can use to help ensure there is a good ground to both the engine and the frame (yes, I know the Mustangs are unibody, I use the term "frame" loosely). To clean the lug end terminals I like to use a found wire brush designed to clean both the batter posts and the inner circumference of the lug terminal ends.
Now onto the cranking.starting problem. I agree with the folks that say you need to start with a fully charged battery. However, before charging down that path it is good to know if you have a no crank, slow crank, or cranks fine but won't start issue. In the case of an engine cranking fine but not starting we are dealing with an issue other than the charging or starter system. But, if it is a no crank or slow crank issue we can do some other stuff that will be helpful. For either a no or slow crank situation you really need to start with a fully charged battery. If you are lucky that will be all you need, although it does beg the question about why the battery had become discharged to begin with. That is a subject unto itself. So, if a charged battery does fix the problem, it is time to do a charging system test, and/or check for a current draw from the battery when the ignition switch in in the Off position.
But, after charging a battery (slowly) overnight I would take it to a parts store that can do a load test to see if the battery has the capacity to both hold, and deliver a charge sufficient to crank over a start motor under load. Or, if you like to tinker and work on your own car you can get your own carbon pile batter load tester for a fairly reasonable amount. An aside, I see the newer "smart testers" are allegedly capable of load testing a battery without using a high resistance, high current carbon pile. Okay, maybe. But, at some point my Old School-itis kicks in and says nothing beats a carbon pile tester like another carbon pile tester when it comes to really testing a battery. My preference is to use an old Sun VAT-40, or even VAT-28, but those are really old and may not be easy to find - much les sin working order. I have a VAT-40, which came to me with a damaged inductive lead cable. I was able to fix the cable with some baring of a wire ands resoldering it to its socket. But, I wanted a load tester that easier to carry around, just because I need an excuse for a heavier duty unit - seriously. I ended up with a Solar brand battery carbon pile based load tester from Amazon that really works nicely. The VAT-40 is still an impressive machine, and can do some things the Solar tester can't. But, for an easy to carry around test unit the Solar machine does a great job. No regrets. Here is a link for one of those units:
https://www.amazon.com/Clore-Automo...mzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bc
The way to use the load tester is to connect the large gauge cables to the battery. Then turn the carbon pile dial until you are showing 1/2 of the battery's Cold Cranking Amperage (CCA) rating (or use 250 - 300 amps if you are not sure). You continue to let the battery be loaded for no more than 15 seconds. If the battery is unable to sustain 9.6 volts, or higher, at the end of 15 seconds of the load testing, the battery needs to be replaced (assuming you were testing a fully charged battery). It is that simple. If you need a new battery do not go cheap. Get the highest CCA rated battery you can for the size you can fit into the battery holding area in your car. For First Generation Mustangs I use group 27F, not 24F, as the 27F can hold more lead, which means they have a higher charge capacity than the 24F batteries. Personal choice,, plus experience over the pat 50 years.
If the battery passed, or is new, and still fully charged, and you still have a cranking issue it is time to begin to diagnose the real issue. But first, is it not cranking? Or a slow crank?
More to come in in another post, hit the 10,000 character limit.
Now onto the cranking.starting problem. I agree with the folks that say you need to start with a fully charged battery. However, before charging down that path it is good to know if you have a no crank, slow crank, or cranks fine but won't start issue. In the case of an engine cranking fine but not starting we are dealing with an issue other than the charging or starter system. But, if it is a no crank or slow crank issue we can do some other stuff that will be helpful. For either a no or slow crank situation you really need to start with a fully charged battery. If you are lucky that will be all you need, although it does beg the question about why the battery had become discharged to begin with. That is a subject unto itself. So, if a charged battery does fix the problem, it is time to do a charging system test, and/or check for a current draw from the battery when the ignition switch in in the Off position.
After charging a battery (slowly) overnight I would take it to a parts store that can do a load test to see if the battery has the capacity to both hold, and deliver a charge sufficient to crank over a start motor under load. Or, if you like to tinker and work on your own car you can get your own carbon pile batter load tester for a fairly reasonable amount. An aside, I see the newer "smart testers" are allegedly capable of load testing a battery without using a high resistance, high current carbon pile. Okay, maybe. But, at some point my Old School-itis kicks in and says nothing beats a carbon pile tester like another carbon pile tester when it comes to really testing a battery. My preference is to use an old Sun VAT-40, or even VAT-28, but those are really old and may not be easy to find - much less in working order. I have a VAT-40, which came to me with a damaged inductive lead cable. I was able to fix the cable with some baring of a wire ands resoldering it to its socket. But, I wanted a load tester that easier to carry around, just because I need an excuse for a heavier duty unit - seriously. I ended up with a Solar brand battery carbon pile based load tester from Amazon that really works nicely. The VAT-40 is still an impressive machine, and can do some things the Solar tester can't. But, for an easy to carry around test unit the Solar machine does a great job. No regrets. Here is a link for one of those units:
https://www.amazon.com/Clore-Automo...mzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bc
The way to use the load tester is to connect the large gauge cables to the battery. Then turn the carbon pile dial until you are showing 1/2 of the battery's Cold Cranking Amperage (CCA) rating (or use 250 - 300 amps if you are not sure). You continue to let the battery be loaded for no more than 15 seconds. If the battery is unable to sustain 9.6 volts, or higher, at the end of 15 seconds of the load testing, the battery needs to be replaced (assuming you were testing a fully charged battery). It is that simple. If you need a new battery do not go cheap. Get the highest CCA rated battery you can for the size you can fit into the battery holding area in your car. For First Generation Mustangs I use group 27F, not 24F, as the 27F can hold more lead, which means they have a higher charge capacity than the 24F batteries. Personal choice,, plus experience over the pat 50 years.
If the battery passed, or is new, and still fully charged, and you still have a cranking issue it is time to begin to diagnose the real issue. But first, is it not cranking? Or a slow crank?
If the charging system checks out, as well as the Neutral Safety Switch for a no crank issue, the next thing to check is the battery terminals themselves to ensure the connection between the battery posts and lug terminals are clean and have nothing preventing a good flow of current. I do not like screw/bolt on terminal ends on battery cables. Too often I find the connection is poor, usually due to corrosion under the clamping plate. I far prefer the lug terminal ends to be pressed and/or soldered. Check the ground cable to make certain it is affixed to the body/frame of the vehicle, as well as the engine. It is critical the engine and body/frame are connected one way or another with a high current capacity cable. In the First Generation Mustangs there are two general kinds of negative cables that one can use to help ensure there is a good ground to both the engine and the frame (yes, I know the Mustangs are unibody, I use the term "frame" loosely). To clean the lug end terminals I like to use a found wire brush designed to clean both the batter posts and the inner circumference of the lug terminal ends.
Now onto the cranking.starting problem. I agree with the folks that say you need to start with a fully charged battery. However, before charging down that path it is good to know if you have a no crank, slow crank, or cranks fine but won't start issue. In the case of an engine cranking fine but not starting we are dealing with an issue other than the charging or starter system. But, if it is a no crank or slow crank issue we can do some other stuff that will be helpful. For either a no or slow crank situation you really need to start with a fully charged battery. If you are lucky that will be all you need, although it does beg the question about why the battery had become discharged to begin with. That is a subject unto itself. So, if a charged battery does fix the problem, it is time to do a charging system test, and/or check for a current draw from the battery when the ignition switch in in the Off position.
But, after charging a battery (slowly) overnight I would take it to a parts store that can do a load test to see if the battery has the capacity to both hold, and deliver a charge sufficient to crank over a start motor under load. Or, if you like to tinker and work on your own car you can get your own carbon pile batter load tester for a fairly reasonable amount. An aside, I see the newer "smart testers" are allegedly capable of load testing a battery without using a high resistance, high current carbon pile. Okay, maybe. But, at some point my Old School-itis kicks in and says nothing beats a carbon pile tester like another carbon pile tester when it comes to really testing a battery. My preference is to use an old Sun VAT-40, or even VAT-28, but those are really old and may not be easy to find - much les sin working order. I have a VAT-40, which came to me with a damaged inductive lead cable. I was able to fix the cable with some baring of a wire ands resoldering it to its socket. But, I wanted a load tester that easier to carry around, just because I need an excuse for a heavier duty unit - seriously. I ended up with a Solar brand battery carbon pile based load tester from Amazon that really works nicely. The VAT-40 is still an impressive machine, and can do some things the Solar tester can't. But, for an easy to carry around test unit the Solar machine does a great job. No regrets. Here is a link for one of those units:
https://www.amazon.com/Clore-Automo...mzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bc
The way to use the load tester is to connect the large gauge cables to the battery. Then turn the carbon pile dial until you are showing 1/2 of the battery's Cold Cranking Amperage (CCA) rating (or use 250 - 300 amps if you are not sure). You continue to let the battery be loaded for no more than 15 seconds. If the battery is unable to sustain 9.6 volts, or higher, at the end of 15 seconds of the load testing, the battery needs to be replaced (assuming you were testing a fully charged battery). It is that simple. If you need a new battery do not go cheap. Get the highest CCA rated battery you can for the size you can fit into the battery holding area in your car. For First Generation Mustangs I use group 27F, not 24F, as the 27F can hold more lead, which means they have a higher charge capacity than the 24F batteries. Personal choice,, plus experience over the pat 50 years.
If the battery passed, or is new, and still fully charged, and you still have a cranking issue it is time to begin to diagnose the real issue. But first, is it not cranking? Or a slow crank?
More to come in in another post, hit the 10,000 character limit.
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- Joined
- Apr 24, 2020
- Messages
- 1,227
- Reaction score
- 1,288
- Location
- Pittsford, NY
- My Car
- My all time favorite vehicle is our 1969 Shelby GT500
If the charging system checks out, as well as the Neutral Safety Switch for a no crank issue, the next thing to check is the battery terminals themselves to ensure the connection between the battery posts and lug terminals are clean and have nothing preventing a good flow of current. I do not like screw/bolt on terminal ends on battery cables. Too often I find the connection is poor, usually due to corrosion under the clamping plate. I far prefer the lug terminal ends to be pressed and/or soldered. Check the ground cable to make certain it is affixed to the body/frame of the vehicle, as well as the engine. It is critical the engine and body/frame are connected one way or another with a high current capacity cable. In the First Generation Mustangs there are two general kinds of negative cables that one can use to help ensure there is a good ground to both the engine and the frame (yes, I know the Mustangs are unibody, I use the term "frame" loosely). To clean toe lug end terminals I like to use a found wire brush designed to clean both the batter posts and the inner circumference of the lug terminal ends.
Here are some links for video and jpg files showing the positive cable routing, and negative cable routing along with two general ground cables needed for a First Generation Mustang:
https://drive.google.com/file/d/1Kf3oI5lIPCr3YsbcXWiyZT3F-Ov3mnOA/view?usp=share_link
Below is a photo of the kind of terminal cleaner I like to use. Any parts store will have them, or get one from Amazon or online from a parts store web site:
Another area that can cause grief with slow or no start condition is the Starter Relay (aka "solenoid," even this it is really a relay). Testing those Starter Relay units is not hard. When cranking the engine from the ignition key, one of the two smaller terminals on the Starter Relay (the one marked "S" for "Start") should light up with a test light, or show voltage with a voltmeter. Do not test the "I" (Ignition) terminal by accident, as doing that will send you down a rabbit hole if it is working properly). You should be getting voltage to the "S" terminal ONLY when trying to crank the engine. If you are not getting voltage to the "S" terminal during cranking you need to test the starting system circuit (ignition switch, Neutral Safety Switch, wires, etc).
If you are getting not voltage to the Starter Relay when cranking, you can still test the rest of the starting circuit by using a jumper wire to momentarily get battery positive voltage to connect to the "S" terminal of the Starter Relay. When voltage is applied to the "S terminal of the Starter Relay the engine should crank over. If it cranks over when jumpering, but has no voltage at The "S" terminal via the ignition switch in the Start position, you need to trace down the wiring as mentioned above.
If there was no loud, solid "Click" from the Starter Relay when the relay was jumped, and the relay is properly mounted to the inner fender with a charged battery, the Starter Relay actuating coil circuit has failed. Replace the Starter Relay.
If the Starter Relay did make a solid, loud "Click" sound when jumpering it you MAY or may not have a bad Starter Relay, maybe. The inside heavy current posts and/or internal copper disc inside the relay may be damaged from arcing to the point where it is preventing a good flow of current to the battery. You have some more work to do still. You may (still) have a bad connection at any of the battery cable ends, inside the Starter Relay, or the cable leading from the Starter Relay to the Starter Motor (the large cable on the Start Relay that leads down to the Starter Motor, or a bad starter (internal winding failed, brushes are worn out, internal binding, etc). To try to go into all of the remaining tests (voltage draw, amperage draw) tests and what trhe results mean, is way outside the scope fpr what could and should have been an otherwise simple post. I haver seen entire articles, even books, written about the diagnosing of a failed starting system.
I have already gone deeper than I likely should have for this thread. I just find it hard to find a good stopping point, but I have now reached what I feel is a good end for now. If you have taken the prior steps, and are still having a cranking problem, please say so in a response and I will try to get into what else to check next. Hint, the next thing I would be checking is for voltage drops, followed by a current flow test (requires a heavy load ammeter, inductive is fine).
Here are some links for video and jpg files showing the positive cable routing, and negative cable routing along with two general ground cables needed for a First Generation Mustang:
https://drive.google.com/file/d/1Kf3oI5lIPCr3YsbcXWiyZT3F-Ov3mnOA/view?usp=share_link
Below is a photo of the kind of terminal cleaner I like to use. Any parts store will have them, or get one from Amazon or online from a parts store web site:
Another area that can cause grief with slow or no start condition is the Starter Relay (aka "solenoid," even this it is really a relay). Testing those Starter Relay units is not hard. When cranking the engine from the ignition key, one of the two smaller terminals on the Starter Relay (the one marked "S" for "Start") should light up with a test light, or show voltage with a voltmeter. Do not test the "I" (Ignition) terminal by accident, as doing that will send you down a rabbit hole if it is working properly). You should be getting voltage to the "S" terminal ONLY when trying to crank the engine. If you are not getting voltage to the "S" terminal during cranking you need to test the starting system circuit (ignition switch, Neutral Safety Switch, wires, etc).
If you are getting not voltage to the Starter Relay when cranking, you can still test the rest of the starting circuit by using a jumper wire to momentarily get battery positive voltage to connect to the "S" terminal of the Starter Relay. When voltage is applied to the "S terminal of the Starter Relay the engine should crank over. If it cranks over when jumpering, but has no voltage at The "S" terminal via the ignition switch in the Start position, you need to trace down the wiring as mentioned above.
If there was no loud, solid "Click" from the Starter Relay when the relay was jumped, and the relay is properly mounted to the inner fender with a charged battery, the Starter Relay actuating coil circuit has failed. Replace the Starter Relay.
If the Starter Relay did make a solid, loud "Click" sound when jumpering it you MAY or may not have a bad Starter Relay, maybe. The inside heavy current posts and/or internal copper disc inside the relay may be damaged from arcing to the point where it is preventing a good flow of current to the battery. You have some more work to do still. You may (still) have a bad connection at any of the battery cable ends, inside the Starter Relay, or the cable leading from the Starter Relay to the Starter Motor (the large cable on the Start Relay that leads down to the Starter Motor, or a bad starter (internal winding failed, brushes are worn out, internal binding, etc). To try to go into all of the remaining tests (voltage draw, amperage draw) tests and what trhe results mean, is way outside the scope fpr what could and should have been an otherwise simple post. I haver seen entire articles, even books, written about the diagnosing of a failed starting system.
I have already gone deeper than I likely should have for this thread. I just find it hard to find a good stopping point, but I have now reached what I feel is a good end for now. If you have taken the prior steps, and are still having a cranking problem, please say so in a response and I will try to get into what else to check next. Hint, the next thing I would be checking is for voltage drops, followed by a current flow test (requires a heavy load ammeter, inductive is fine).
