Starting issue

[jpaz]

Ok guys, gotta strange electrical issue going on with my 72 Mach 1. This is the car that I got in the accident with. Anyway, I will try my best to explain this. 

After having everything rebuilt and put back together, the engine will not fire after sitting overnight. When the solenoid is jumped, then it does start and runs great. It will even fire right back up without jumping the solenoid. So the shop replaced the solenoid I had on with a new one. Same thing, solenoid has to be jumped to start for the first time of the day, but once it’s been started it will start over and over again. The coil is brand new also cause the one I had didn’t work after the accident. The shop owner who has been working on Mustangs for 30 plus years is stumped, he has never seen anything like this before.

Any idea of what to look for? The NNS is only a couple of years old, adjusted properly and in great shape. Maybe the ignition switch? 

The only wiring that was damaged from the accident was the drivers side sport lamp, turn signal ,headlight and a headlight wiring relay harness. Thanks, any ideas will be appreciated

 

[tony-muscle]

Maybe they should systematically backtrack all the way to the ignition switch jumping one item at the time. Jump the NSS, jump the switch, etc, until they find the culprit. At least that would be my approach.

Sent from my SAMSUNG-SM-G930A using Tapatalk

 

[Don C]

When you say won't fire, does the starter turn the engine over? Or does the starter not function, nor the solenoid even click? I'm guessing the starter and solenoid don't work. Easy enough to verify where the issue is. With the ignition key held in the start position check for voltage on the "S" terminal on the starter solenoid.

My guess is that the ignition switch is the culprit. After sitting for some time, while the car was repaired, the decades old ignition switch terminals are likely corroded and the lubricant in them has turned semi-solid, preventing the contacts in the switch from making connection. After the car has started the vibrations and/or heat generated by bad contacts in the switch allows the starter contacts to make connection.

Added: It could be the same issue with the NSS, just less likely because it is newer and was functioning before the crash.

 

[jpaz]

When you say won't fire, does the starter turn the engine over? Or does the starter not function, nor the solenoid even click? I'm guessing the starter and solenoid don't work. Easy enough to verify where the issue is. With the ignition key held in the start position check for voltage on the "S" terminal on the starter solenoid.

My guess is that the ignition switch is the culprit. After sitting for some time, while the car was repaired, the decades old ignition switch terminals are likely corroded and the lubricant in them has turned semi-solid, preventing the contacts in the switch from making connection. After the car has started the vibrations and/or heat generated by bad contacts in the switch allows the starter contacts to make connection.

The starter does spin, but no spark, no power to coil.

I’m leaning towards the ignition switch too. Most everything else on my car has been replaced and or rebuilt except that. I had to replace the brake light switch about a year or so ago and it was the original one. I noticed that the ignition switch also looked like it was the original one too. I just didn’t know if it would show these symptoms. 

Thanks Don, I will let them know to try that first and I’ll post results.

 

[jpaz]

Maybe they should systematically backtrack all the way to the ignition switch jumping one item at the time. Jump the NSS, jump the switch, etc, until they find the culprit. At least that would be my approach.

Sent from my SAMSUNG-SM-G930A using Tapatalk

Ya that’s what needs to be done, and I think I will have them start with the ignition switch.

Thanks tony.

 

[midlife]

If it is the ignition switch, then jumpering the starter solenoid won't cause it not to give voltage to the coil. From your description, the starter solenoid gets the signal to crank the starter, but won't give voltage to the coil line. When the starter is engaged, so is the line from the starter solenoid (sorta) directly to the coil, bypassing the ignition switch circuitry. The car should catch, but if the ignition switch is dead or inoperable, the engine would die. That's not what you're describing.

Using your ignition switch, remove the I lead from the starter switch and see if you have 12V there when cranking. If so, re-attach and remove the lead to the coil, and test there for 12V. If no 12V, you have bad circuitry in your headlight harness (which those wires do route to the left side of the engine compartment). My guess is you have a bad splice somewhere that is flakey.

When you first stated it wouldn't start sitting overnight, my first thought was a bad battery. It still could be that, but you say the starter does crank. Check to see what the voltage is at the battery while cranking. If it drops much below 10.5V, you won't be able to start the car.

 

[Hemikiller]

Since they had the whole car apart and engine out, verify you have a proper battery (-) -> fender apron -> block ground cable. If this is not done properly, or is missing the fender apron ground, you'll have all sorts of odd electrical issues.

 

[delawarebill]

i 100% agree with midlife. those few points will give u a ton of info. this will take just a few minutes so in doing this report back the info found..

 

[boilermaster]

jpaz, 

sounds to me like your ignition is capable of firing in the run mode but not in the crank mode.

They are 2 different circuits.

your results are all based on how the car was tested, when you are jumping the solenoid with the key in the run position you are not testing the crank circuit.

You need to test the crank circuit.

check for spark while someone is actually cranking the engine using the ignition switch (key) and Not jumping the starter solenoid.

You will find you have spark in run and no spark in crank.

Spark in the CRANK circuit is provided by the I terminal of the starter relay, first thing, you need to have voltage on that terminal while cranking, then you need to have voltage to the coil positive while cranking, will check the 1972 wiring guide and give you circuit number, color and splice location.

Boilermaster

 

[jpaz]

If it is the ignition switch, then jumpering the starter solenoid won't cause it not to give voltage to the coil.  From your description, the starter solenoid gets the signal to crank the starter, but won't give voltage to the coil line.  When the starter is engaged, so is the line from the starter solenoid (sorta) directly to the coil, bypassing the ignition switch circuitry.  The car should catch, but if the ignition switch is dead or inoperable, the engine would die.  That's not what you're describing.

Using your ignition switch, remove the I lead from the starter switch and see if you have 12V there when cranking.  If so, re-attach and remove the lead to the coil, and test there for 12V.  If no 12V, you have bad circuitry in your headlight harness (which those wires do route to the left side of the engine compartment).  My guess is you have a bad splice somewhere that is flakey.

When you first stated it wouldn't start sitting overnight, my first thought was a bad battery.  It still could be that, but you say the starter does crank.  Check to see what the voltage is at the battery while cranking.  If it drops much below 10.5V, you won't be able to start the car.

Thanks midlife, I will have them check all this out.

 

[jpaz]

jpaz, 

sounds to me like your ignition is capable of firing in the run mode but not in the crank mode.

They are 2 different circuits.

your results are all based on how the car was tested, when you are jumping the solenoid with the key in the run position you are not testing the crank circuit.

You need to test the crank circuit.

check for spark while someone is actually cranking the engine using the ignition switch (key) and Not jumping the starter solenoid.

You will find you have spark in run and no spark in crank.

Spark in the CRANK circuit is provided by the I terminal of the starter relay, first thing, you need to have voltage on that terminal while cranking, then you need to have voltage to the coil positive while cranking, will check the 1972 wiring guide and give you circuit number, color and splice location.

Boilermaster

I think they did check it like the way you said. So yes, no spark in the crank position, but spark in the run position. I just am not sure if this is always the case. I don’t have my car here, it’s still at the shop. Sorry, but I’m probably missing some information to give you. Electrical is definitely not my forte. Thanks,

                           John

 

[boilermaster]

jpaz,

Circuit 16A is ignition feed for crank mode  c 9 at starter relay, Red/ light green

Circuit 16 is ignition feed for run mode also Red/ light green

they are connected at C-14 (believe it is under the dash near steering column ignition switch.

16 a supplys battery voltage to the positive side of the ignition coil while the engine is being cranked

circuit 16 provnides about 9 volts to the positive side of the ignition coil while the ignition switch is in the RUN mode.

So you need to see 12 volts at C14 while cranking and about 9 volts at C14 while the key is in the run position.

Because the engine runs when you jump the starter relay, that tells me that circuit 16 is ok.

When you crank the engine there needs to be 12 volts at the positive side of the ignition coil BECAUSE the ignition switch does NOT provide any voltage to circuit 16 while the engine is cranking.

really sounds to me that you have no voltage being supplied to 16A out of the starter relay or 16A is open from the starter relay to C14.

you could have got the wrong or defective relay or the 2 push on terminals at the relay could be crossed up too.

Boilermaster

 

[jpaz]

Since they had the whole car apart and engine out, verify you have a proper battery (-)  -> fender apron ->  block ground cable. If this is not done properly, or is missing the fender apron ground, you'll have all sorts of odd electrical issues.

I’m pretty sure they checked that out first, but will make sure. I even added two other grounds, one from back of block to firewall and one from front of block to frame. I was having some weird electrical issues so I did this a couple years ago. Definitely made a difference.

 

[jpaz]

jpaz,

Circuit 16A is ignition feed for crank mode  c 9 at starter relay, Red/ light green

Circuit 16 is ignition feed for run mode also Red/ light green

they are connected at C-14 (believe it is under the dash near steering column ignition switch.

16 a supplys battery voltage to the positive side of the ignition coil while the engine is being cranked

circuit 16 provnides about 9 volts to the positive side of the ignition coil while the ignition switch is in the RUN mode.

So you need to see 12 volts at C14 while cranking and about 9 volts at C14 while the key is in the run position.

Because the engine runs when you jump the starter relay, that tells me that circuit 16 is ok.

When you crank the engine there needs to be 12 volts at the positive side of the ignition coil BECAUSE the ignition switch does NOT provide any voltage to circuit 16 while the engine is cranking.

really sounds to me that you have no voltage being supplied to 16A out of the starter relay or 16A is open from the starter relay to C14.

you could have got the wrong or defective relay or the 2 push on terminals at the relay could be crossed up too.

Boilermaster

Thanks boilermaster, I’ll have to see exactly how much of the circuit they tested. 

The one thing that I’m wondering about is that the coil that was in the car at the time of the accident went bad. It didn’t get hit or physically damaged, but it wouldn’t work when they were starting engine on their engine run stand.

 

[jpaz]

Ok, I just checked with the shop and they have checked everything you guys recommended and they think there’s a bad spot in a wire somewhere that fails intermittently. I guess I’ll just have to track it down when I get the car back.

Thanks for all the replies, I really appreciate all the help and info you guys provide.

 

[Pegleg]

Ok, I just checked with the shop and they have checked everything you guys recommended and they think there’s a bad spot in a wire somewhere that fails intermittently. I guess I’ll just have to track it down when I get the car back.

Thanks for all the replies, I really appreciate all the help and info you guys provide.

Send your harness to Midlife and get it refurbed.

 

[boilermaster]

jpaz,

Here is a simple test you can try to determine if the ignition crank circuit is good or not.

disconnect the ignition coil wire POSITIVE, with the key in the run position.  in the RUN position measure the voltage at the coil positive that you just disconnected and record the voltage (should be around 9 volts dc.

With that lead still disconnected now remove the I lead at the starter relay, it too should read about 9 volts dc (if the splice/connector is good).

The starter relay is designed to do 2 things, supply the starter with voltage when the key in the crank position AND supply the ignition with voltage while in the crank position.

the starter is supplied with voltage thru the S terminal when in the key is in the crank position and the ignition is supplied voltage thru the I terminal of the starter relay when the key is in the crank position.

No voltage out of the I terminal of the starter relay = no voltage to the ignition while in the crank position.

The ignition switch does NOT supply the ignition coil with voltage while it is in the crank position, that is the starter relay's I terminals job.

Whenever the starter relay is energized, sending voltage to the starter (S TERMINAL ) it should be also sending voltage to the ignition coil positive wire

thru the starter relay I terminal.

Boilermaster

 

[jpaz]

jpaz,

Here is a simple test you can try to determine if the ignition crank circuit is good or not.

disconnect the ignition coil wire POSITIVE, with the key in the run position.  in the RUN position measure the voltage at the coil positive that you just disconnected and record the voltage (should be around 9 volts dc.

With that lead still disconnected now remove the I lead at the starter relay, it too should read about 9 volts dc (if the splice/connector is good).

The starter relay is designed to do 2 things, supply the starter with voltage when the key in the crank position AND supply the ignition with voltage while in the crank position.

the starter is supplied with voltage thru the S terminal when in the key is in the crank position and the ignition is supplied voltage thru the I terminal of the starter relay when the key is in the crank position.

No voltage out of the I terminal of the starter relay = no voltage to the ignition while in the crank position.

The ignition switch does NOT supply the ignition coil with voltage while it is in the crank position, that is the starter relay's I terminals job.

Whenever the starter relay is energized, sending voltage to the starter (S TERMINAL ) it should be also sending voltage to the ignition coil positive wire

thru the starter relay I terminal.

Boilermaster

The problem is with the crank position. Sometimes there’s power to the coil, and sometimes not. They are sure that the problem is with that circuit. It’s just that it’s very intermittent. I will see if they tried this too. Will probably have to wait till next week to find out more.

Thanks again boilermaster.

 

[Pegleg]

My 48 year old wiring was falling to pieces inside the engine bay when i removed the engine and disturbed the wiring