Electrical Non Starting Issue


...I can take it. I think.
20+ Year Stangneter :roc</strong><span class=
Mar 2, 2003
Sea of Tranquility
03 4.6 SOHC. For a few weeks I've had an issue where I would try to start my car but I would only hear the click of the solenoid. It would start after the 2nd or 3rd try. After a while I would load the tune again and then it would start. Now it will not start at all. Still hear the solenoid click and fuel pump whir but the engine will not turn over. I had the starter and battery tested and both were good. I replace the starter relay as well. I datalogged and I have good running voltage...stays around 13.9-14. I can push start it as long as I have room. I'm stumped.
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I would start looking at the wiring off the starter to make sure it is properly installed and not corroded. Trace it back as far as you can. Also check the engine grounds. That would be my next moves. Good luck and keep us posted.
I have two hazard guesses:

1. Dead spot on the starter but I think you'd have diagnosed this by now

2. Burned contacts in the starter solenoid. It's making contacts but not GOOD contact and it's not turning the starter with any authority.

@[USERGROUP=77]SN Certified Technician[/USERGROUP]

Maybe these guys will have other ideas.
Note: the wiring diagrams are specific to 5.0 PUSHROD engines, but the troubleshooting plan is common to all Mustangs.

b] No Crank checklist for 5.0 Mustangs[/b]

Revised 05-Oct-2010 to update Fluke references.

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 both 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 know 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 unstuck 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 .5 volts across a connection indicates a problem.

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


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.

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.

Typical start circuit...
Diagram courtesy of Tmoss & Stang&2birds

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.
I don't recall seeing a push on wire on the solenoid. Is that just for 5.0? I know I have this on the old 66 with the old style solenoid mounted on the fenderwell.

Car will not start when jumped. It does start occasionally...Yesterday after I turned the theft system on then off with the key fob it started. Shut it off and nothing again. It was random non-start most of the time...now it is non start most of the time. I'm thinking a loose connection. The starter was tested but if it is random solenoid issue maybe it is the starter assembly after all?
I don't recall seeing a push on wire on the solenoid. Is that just for 5.0?
The solenoid is built into the starter. The starter should have two positive connections. The BIG one to the battery. The smaller one to the solenoid circuit.
Yesterday after I turned the theft system on then off with the key fob it started. Shut it off and nothing again.
The factory alarm system does NOT disable the starter for the 99+ model years. So unless there's an aftermarket alarm, doing something with the FOB wouldn't have any effect.

Just to be clear. The primary symptom is "no crank" right? Very different from a "crank with no start".

One of the tests I would do is to jump the solenoid connector directly from the battery positive. If the starter works, then the problem is in the solenoid circuit.

If the starter does not engage, the problem is in the starter.

This assumes that the battery, terminals, posts, clamps, and grounds are in tip top shape. Check the motor grounding strap from the left hand motor mount to the frame rail.
The solenoid is built into the starter. The starter should have two positive connections. The BIG one to the battery. The smaller one to the solenoid circuit.
Yessir...I was aware of that

Yes, no crank. Everything on the starter/solenoid connection is clean as well as battery. I made sure when I reinstalled it yesterday. Didn't pay attention to engine or chassis grounds. No theft light flash with key on. I went out just now and tried and the solenoid would click. Washed the car then tried again (no washing didn't help :D) and no click at all. So it could be intermittent or weak solenoid?

I'm going to get it up on stands again and check grounds. I can push start it and once running it is fine.
The test done rules out the car's starter solenoid circuit.

However, this could still be cause by low batter voltage. So you are down to:
  • Bad starter
  • Weak/loose battery connection.
  • bad battery
  • Excessive motor cranking torque required.
Can the motor be turned over by hand? If so, this tends to rule out a base motor problem.

Consider measuring the voltage at the starter while attempting to engage the solenoid.

If little or no voltage drop, the problem is in the starter.

If the voltage drops below 9 volts, this indicates either excessive current draw or a weak electrical connection. One way to confirm is to compare the voltage at the starter to the voltage at the battery during cranking. A weak connection swill show up as a large difference between the measurements.
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