Engine No start on foxbody project - ideas?


Active Member
Aug 7, 2017
Hello all,

I recently completed a motor and transmission swap on my 90 GT and I went to start it for the first time this weekend but it was no dice, unfortunately, so I am looking for ideas.

The problem I am experiencing is this:

When I turn the key on, I have power. The fuel pump runs, the lights on the dash come on, the door chimes, however when I turn the key, I have nothing.

I can hear the starter solenoid clicking when I turn the key. I have tested the starter (which is an aftermarket one which required the change in wiring. I made a post about it when installing it) and the starter does work, just not when I turn the key. (It is wired with the trigger wire on one post, and everything else on the other post)

While poking around under the car I noticed is that the transmission does not seem to have a neutral safety switch and I am wondering if that could be my problem?

I swapped the car from an AOD to a built C4 and I realized that not only did I not connect the switch but that the C4 doesn’t have a provision for one. (At least not the same style as the AOD.)

So, based on what I have described here, does it sound like that could be the issue?

Can I bypass the neutral safety switch?

What are some other things I could / Should check?

Does what I am describing sound like a different problem all together?

I’d be happy to follow up with pictures or video if it helps clarify what I am asking.

thanks again for all your help.

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5 Year Member
Apr 16, 2015
I would start by jumpering the neutral safety switch and see what happens.


I'd be looking at jacking under the house
Jun 28, 2020
Memphis TN
Yes you can bypass the neutral safety switch, only thing it does is prevent car from cranking in gear.
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5 Year Member
Apr 16, 2015
To test if this is why it will not start, yes. Take a short piece of wire and use as a jumper. If car starts then you can come up with something more long term (cut connector off and connect wires together, wire in a toggle switch that can serve as a low tech anti-theft, get a pigtail that will connect and make a jumper in it).


StangNet's favorite TOOL
SN Certified Technician
Mar 10, 2000
Dublin GA
No Crank checklist for 5.0 Mustangs

Revised 24-Oct-2013 to update voltage drop figures.

No crank, slow crank and stuck starter solenoid problems have the same root causes – low battery voltage and poor connections. For that reason, they are grouped together.

Use the same initial group of tests to find the root cause of slow crank, no crank and stuck solenoid problems.

Since some of the tests will bypass the safety interlocks, make sure that the car is in neutral and the parking brake is set. Becoming a pancake isn’t part of the repair process…

1.) Will the car start if it is jumped? Then clean battery terminals and check battery for low charge and dead cells. A good battery will measure 12-13 volts at full charge with the ignition switch in the Run position but without the engine running.

A voltmeter placed across the battery terminals should show a minimum of 9.5-10 volts when the ignition switch is turned to the Start position and the starter engages or tries to engage. Less than this will result in a clicking solenoid, or slow cranking (if it cranks at all) or a starter solenoid that sticks and welds the contacts together.

Most auto parts stores will check your battery for free. It does not have to be installed in the car to have it checked; you can carry it with you to the auto parts store.

The battery posts and inside of the battery post terminals should be scraped clean with a knife or battery post cleaner tool. This little trick will fix a surprising number of no start problems.

The clamp on with 2 bolts battery terminal ends are a known problem causer. Any place you see green on a copper wire is corrosion. Corrosion gets in the clamped joint and works its way up the wire under the insulation. Corroded connections do not conduct electricity well. Avoid them like the plague...

If the starter solenoid welds the contacts, then the starter will attempt to run anytime there is power in the battery. The cables and solenoid will get very hot, and may even start smoking. The temporary fix for a welded starter solenoid is to disconnect the battery and smack the back of the solenoid housing a sharp blow with a hammer. This may cause the contacts to unstick and work normally for a while.

A voltmeter is handy if you are familiar with how to use it to find bad connections. Measure the voltage drop across a connection while trying to start the car: more than .25 volts across a connection indicates a problem. The voltage drop tests need to be done while cranking the engine. It's the current flowing through a connection or wire that causes the voltage drop.

See http://assets.fluke.com/appnotes/automotive/beatbook.pdf for help for help troubleshooting voltage drops across connections and components. .


Voltage drops should not exceed the following:

200 mV Wire or cable
300 mV Switch or solenoid
100 mV Ground
0.0V Connections

A voltage drop lower that spec is always acceptable.

2.) Check the battery to engine block ground down near the oil filter, and the ground behind the engine to the firewall. All grounds should be clean and shiny. Use some sandpaper to clean them up.

3.) Jump the big terminals on the starter solenoid next to the battery with a screwdriver - watch out for the sparks! If the engine cranks, the starter and power wiring is good. The starter relay is also known as a starter solenoid.

The rest of the tech note only concerns no crank problems. If your problem was a stuck solenoid, go back to step 1.

4.) Then pull the small push on connector (small red/blue wire) off the starter solenoid (Looks like it is stuck on a screw). Then jump between the screw and the terminal that is connected to the battery. If it cranks, the relay is good and your problem is in the rest of the circuit.

5.) Remember to check the ignition switch, neutral safety switch on auto trans and the clutch safety switch on manual trans cars. If they are good, then you have wiring problems.

Typical start circuit...

Diagram courtesy of Tmoss & Stang&2birds


6.) Pull the starter and take it to AutoZone or Pep Boys and have them test it. Starter fails test, then replace it. If you got this far, the starter is probably bad.

Starter solenoid wiring for 86-91 Mustang


Starter solenoid wiring 92-93 Mustang or earlier Mustang with upgraded high torque mini starter.


Electrical checks for the switches and starter solenoid

Remove the small red/blue wire from the starter solenoid. Use a screwdriver to bridge the connection from the battery positive connection on the starter solenoid to the small screw where the red/blue wire was connected. The starter should crank the engine. If it does not, the starter solenoid is defective or the battery lacks sufficient charge to crank the engine.

If the starter does crank the engine, the problem is in the clutch safety circuit (5 speed) or Neutral Sense Switch (auto trans) or ignition switch.

See the Typical start circuit diagram above for wiring information for troubleshooting.

You will need a voltmeter or test lamp for the rest of the checks. Connect one lead of the voltmeter or test lamp to ground. The other lead will connect to the item under test.

Look for 12 volts on the white/pink wire when the ignition switch is turned to the Start position. Check the ignition switch first.

No 12 volts, replace the ignition switch.

The next step will require you to push the clutch pedal to the floor (5 speed) or put the transmission in neutral (auto trans) while the ignition switch is turned to the Start position.

Good 12 volts, check the clutch safety switch (5 speed) or Neutral Sense Switch (auto trans) for good 12 volts on both sides of the switches. No 12 volts on both sides of the switch and the switches are defective or out of adjustment. Check the wiring for bad connections while you are at it.
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Active Member
Aug 7, 2017
To test if this is why it will not start, yes. Take a short piece of wire and use as a jumper. If car starts then you can come up with something more long term (cut connector off and connect wires together, wire in a toggle switch that can serve as a low tech anti-theft, get a pigtail that will connect and make a jumper in it).
Hey all!

Using the broken pigtail from the AOD’s neutral safety switch I was able to jump the wiring and get the car to crank.

However, their is a new issue and, perhaps one that I should start a new thread with the electrical thread, but the cranks automatically while the ignition is in the “on setting” and that’s something I have never experienced before. I’m wondering if I have a bad ground someplace?



Active Member
Aug 7, 2017
Hold on, don't start stabbing in the dark. Check the wires at the starter and the solenoid are in the correct places,
So, I have a newer style starter in the car. (Like the kit sold on LMR) and I used that video and a post I made here to install it.

On the solenoid on the inside fender I have all the wires on one terminal, and just the trigger wire for the starter on the other.

I have a new power wire running to the starter and the trigger wire running to the top post. I don’t think they are incorrect because when I switch the wires at the starter, and attach the battery, the starter gets power form the battery.

Pictures attached


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