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No Start, Need Help!
#1
runninpony 
I thought today would be the big day, the day I got my Mustang running.

I installed a new solenoid, and fuel filter, as well as a battery yesterday.

Today, with help I got the carburetor rebuilt.

I turned the key and nothing. The battery somehow overnight drained out.

There's as short somewhere in the electrical. When I put the key in, I get the buzz sound, and the brake light comes on. And the brake light stays on after the key was removed. I'm not sure where or how to determine an electrical short. My friend who helped with the carb, thinks its in the ignition sitch or possible in the gear shifter- that there's an indicator somewhere that tells the engine its in park, so it can start. Is this accurate?

It would not do a thing with a jump either, only give me my headlights, no crank, nothing else.

What do I need to check? Do I test the new solenoid?

A reminder, it's a 71 Ford Mustang.

Yes, I did disconnect the battery in the mean time.



Please help, I don't want to shoot this horse
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#2
Do you have a multimeter? The first thing I would check is to see if when you turn the key to run, whether there is 12V at the solenoid ignition terminal. And of course 12 V on the battery side, but that's hard not to have since it's connected directly to the batterySmile

Not sure if there is a neutral safety switch on a 71? If there is and it's not being engaged properly then that could also prevent cranking. Not sure how its triggered in a 71 if there is one.

Greg
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#3
If you have a short. Remove the negative from your battery while you troubleshoot this problem. Then take a 12V light plug with a bulb in it and wire long enough to go from the negative of the battery to ground. If it lights, You have something wrong and need to go back to any wiring you have been involved in and re-inspect it until the bulb no longer lights with the key off.

[Image: 2rr7aiv.png]

Just cruising along minding our own business when BAM!!! The LAWS show up.
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#4
Here's my generic test for current drain and shorts:

When ready to check out the harness, close all doors, turn off all lights, ignition key in the OFF position, accessories off, etc. Make sure both battery connectors are disconnected. Connect the positive battery cable to the starter solenoid. Leave the negative terminal disconnected from the battery. Then use a digital volt meter to measure the current draw across the battery. Place one probe of the DVM on the negative battery cable terminal, and the other probe on the negative battery post. Be sure that the DVM is set to amps, DC. If there are no shorts in the wiring connections, the reading should be on the order of 30 milliamps or less. Anything above 1 amp indicates some accessory is on; readings above 10 amps (may blow the fuse on the DVM) indicates a dead short.

If you have a short, disconnect all other wiring from the starter solenoid post where the battery connects and re-measure the current. If current drops, the source is the underdash wiring harness or the harness from the starter solenoid to the firewall. Reconnect the wiring to the starter post and then disconnect the underhood harness from the firewall and test again to isolate the source of the short.

If the short is not in the underhood or underdash harness, the problem lies in the alternator or voltage regulator. Disconnect each of these in turn to isolate the source.

If the short or high current comes from the underdash region, keep the battery negative side disconnected and remove one fuse at a time. Measure the current as above. If you now see low current, there is either a short or an item on that particular fuse circuit is on. Turn off that item and continue checking.

Eventually, you’ll have low current readings with all fuses installed and all wiring connected. This series of tests checks all of the battery directly powered systems. To check the Accessory systems, now repeat all of the tests above with the ignition key in the ACC position. The current with the key in the ACC position may be up to 1 amp or so. When all of the tests are done and no anomalous current it noted, at that time, and only at that time, is it safe to connect the negative battery cable to the battery.
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#5
gpierce;86528 Wrote:Do you have a multimeter? The first thing I would check is to see if when you turn the key to run, whether there is 12V at the solenoid ignition terminal. And of course 12 V on the battery side, but that's hard not to have since it's connected directly to the batterySmile

Not sure if there is a neutral safety switch on a 71? If there is and it's not being engaged properly then that could also prevent cranking. Not sure how its triggered in a 71 if there is one.

Greg

Yes, we did try one and it was no where near 12, thanks

thanks Mark and midlife, good ideas, and a good cheat sheet to hold on to! so, you'd rule out the ignition switch? the brake light came on almost instantly when the key touched the switch. thanks again!
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#6
All good advice listed here, but remember, you want to test your circuits with the battery fully charged, so you'll need to charge it back up first. There is a neutral safety switch if you have an automatic. If the brake light is staying on after the key is removed, it could be, among other things, the switch isn't adjusted correctly. It's on the lower column and has slots to move it up and down on the column.

Steve
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#7
Disconnect the brake light switch wire under the steering column, charge the battery and note if it drains down again.
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#8
thanks RVRtrash-- would the switch needing adjustment be enough to drain the battery? I did recharge the battery. i researched the neutral safety switch and will slide under the car to see if it became disconnected.
thanks 72HCODE will do. I need to remove my drivers seat so i can get under there, not much wiggle room in there.
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#9
There isn't much on these that will drain a battery when it isn't running. Lights and if the ignition is on (but the car is not running) are the two most likely culprits. This assumes you would notice if the stereo is still playing... It's also possible your AC clutch is the problem. That's easy to check. Disconnect the wire and see if the clutch CLICKS off. It will be obvious.

So... park it in the garage. Turn off the lights and look for light bleeding from somewhere. In total darkness you will spot it really quick.

Now, regarding the starting problem (turn on key and nothing happens). Jump the solinoid. Take a wire from the positive battery and touch it to the small post next to the large post the battery is connected to. (you can also just lay a screw driver from the big post to the small post). Did the engine crank? If so, you know the solinoid is good and you have enough power to turn the motor over. Now it's a matter of tracing down why turning the key doesn't energize the solenoid.

Are you certain you put the two small wires back on the solinoid correctly? They are easy to mix up. One comes from the ignition and provides 12 volts to the small post i described above. The other runs from the other small post to the coil to give it a full 12v while craning. if you mix these two wires up, the car will not turn over.

'Mike'
73 Convertible - 351C/4V CC heads/4bolt/forged flat tops/comp 270/rhodes/mallory unilite/tri-power/hookers/glasspacks/c6/3.50 limited slip/Gear Vendors/Global West sub frames, strut rods and shelby style traction bars/ Rear sway bar/tilt steering (not original)

Pics of modifications included in:
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#10
the brake lights stuck on will drain a battery in an hour if you don't notice it. the radio and lights will work but you just will not have the power to crank the motor over.

you could just have a bad switch, i had to replace mine as well. i don't remember the switch being adjustable i just remember poping the cotter pin and then wiggling the switch out with the bushings and then figuring out how the new switch wiggled back in. then hooked it up.
the switch has an internal spring that can get stuck or break and not allow the tail lights to turn off.


if your battery is dead the car won't crank, the solenoid may just click on and off.

you can bypass the neutral safety with a paperclip in the connector which is on the firewall drivers side behind the motor just above the trans tunnel.

the switch could be out of adjustment if the trans linkage is loose.

now even if the neutral safety is defective the starter will still turn over but there is no spark.

you could also, setup a remote starter and sort of weed out if there is a wiring issue.

first charge the battery fully and then give it a go.

when you turn the key to ON listen for the solenoid click, then turn to start, and see if the starter is kicking the motor over.
if it still won't kick over then you check for spark, you can use a remote starter and either a spark tool or you pop off the coil wire and get it near a ground as you crank and see if there is a spark or your hair is standing straight up, and you start talking in latin ;-)

if the starter isn't turning at all, it could be wiring, or the solenoid or, even the ignition switch, or even a bad starter.

there was a complaint about the reproduction ignition switches that the start position wouldn't work.

but start simple, i would disconnect the suspected short, and fully charge the battery and try again.



now worst case you can hotwire the car bypass the ignition switch and try to crank the car over,that way.

now in that case. you are bypassing all safety measures.

Seems Stupid but just Check the car is in Neutral or park, happened to me once. i was working on the dashboard and i moved the shifter into 1 position and had the parking brake on with the engine off.
i finished working, wanted to go for a drive and the car refused to start. 2 hours of wracking my brain and it never dawned on me to check the shifter position.
felt really stupid that night.
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