Starter Engaged After Car Running

Discussion in 'Fox 5.0 Mustang Tech' started by mikestang63, Jul 17, 2013.

  1. Last week went to start the car and the starter kept engaging. Turned off the car, starter kept running. Neg battery cable started to smoke badly and it used the 2nd ground wire as the ground and burned all off the insulation off . Had to disconnect the neg cable to get it to stop. Crawled underneath and saw the neg battery cable was not connected. WTF. The bolt on the timing cover was snapped and the cable was just hanging.

    Replaced the neg and positive battery cables. Connected the neg battery cable to the lower A/C bolt. Bought a new motorcraft solenoid. Battery seems fine and fully charged.

    Car starts and runs fine for a week.

    This morning go to start it up and starter hangs up again. Turn the key off it keeps running, Disconnect the purple wire at the solenoid and it keeps running. Did not replace the ignition switch. The car actually restarted but in the midst of it all cannot remember if it did so before or after I pulled the purple wire. The car eventually stopped but did not have to disconnect the neg cable.

    My thoughts are the starter is the problem and the bendix drive is shot? I can replace the ignition switch but again when I pulled the wire off the solenoid it did not stop the starter from engaging,

    Just went out and the the car started up fine so apparently this is intermittent.
  2. Just went through some of this. Besides the cables and grounds, it could be the solenoid or ignition switch. Next time it sticks, pull the little wire from the side of the solenoid. If it still runs, it is not likely the switch. You can confirm the signal wire has power only when it is supposed to without it connected. With it stuck, Tap the top of the solenoid, and if it stops, the contacts are sticking.

    Jrichker gave me a good set of instructions that are more complete. But it seems if there is no power to the starter and the Bendix is engaged, it will sound different than if it has a stuck power circuit. Just stuck, not stuck while turned on, will not involve enough electricity to get cables hot either.
  3. Mine did that a long time ago at a gas station. I too had to disconnect the neg cable. Gas station was just around the corner from my house and my tag also had just expired. Then I look up and a cop is in the gas station, so trying to stop my car from bucking at the pump was an intense I went and got my solenoid, tag pronto. Then later it comes out that the gas I just got was bad and it destroyed my entire fuel system. Had to replace tank, pump, clean injectors etc, the whole 9 yards. Next time it bucks at a gas station, .....Do not get the
  4. Sounds like a bad starter. I wouldn't drive it till its sorted. I've seen broken fly wheel teeth from a bad starter engaging while driving.
  5. it could be the ignition switch too.
  6. No Crank checklist for 5.0 Mustangs

    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 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 .5 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 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 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.
  7. put a new starter-NEW not reman- in today. After install, the first time to start up the starter kept engaging, then the motor slowly stops cranking as if the battery is dying. Pulled the wire off the S post and still cranked. Removed the neg cable to get it to stop it with a spark when removed- probably because the solenoid still closed sending power. With the neg cable still off. I took a test light and hooked one end to the neg battery post and the other end to the battery side of the solenoid- light goes on. Move the light to the starter side of the solenoid- light goes on. tapped the solenoid a few times and then did the test again, no power to the starter side of the solenoid. hook up the neg cable again to the battery and then turned the key- car starts up fine. Did it about 10 more times and the car starts fine. Car started up much quicker and stronger with the new starter at least. The one I took off was the original FOMOCO from 1990 and was covered with grunge.

    All posts are clean. All new cables. Grounds for battery to block, upper intake to firewall, 2ndary ground from battery to firewall, and an additional 4g ground from lower A/C bolt to 2ndary stud on firewall all clean and tight. New Starter today, New Motorcraft solenoid a week ago. Only thing left is the ignition switch but showing no signs of it being bad. When you pull the wire off the S terminal that does not kill the starter when it acts up. This was a brand new Motorcraft solenoid I put in a week ago. Drove the car to a Mustang shop I trust and we are thinking that maybe the new solenoid is faulty and sticking. Tried starting the car 10 more times and could not duplicate it at the shop.
  8. New sol is sticking. You said you had power on both sides until you tapped it . You disengaged it being stuck. I would change it again.
  9. It may have been a good idea to replace the starter, but the solenoid problem could have been tested for much less. Sorry, but we tried to tell you so. It is hard to believe a new part could be a bad one so quickly, but a faulty new solenoid is the part of my story I left out. If a low battery will weld the contacts, it at least explains all the Ford solenoids I sold over the years.

    I think folks assuming it is the starter comes from GM starters that have the solenoid built in and overheat it along with cooking the oil any grease in.
    toolow91 likes this.
  10. The old starter was shorted to ground causing your solenoid contacts to weld themselves. That's a lot of full load amps across the solenoid. One reason ford went to mini starter in 92.
  11. Here's the solenoid I bought. Motorcraft SW1951C. Paid about $30.Reason I did not think it was the new solenoid is that it worked for a week and then out of the blue stuck today. I too thought the old starter was toast from the first solenoid going bad and had either a short or a bad bendix. When I tapped on it this morning when it stuck it didn't effect it. Seems letting it sit for a few minutes the car started fine. Went out now and battery is at 12.78 volts cold. same reading at the solenoid battery and at the alternator post. Same reading using using neg battery, solenoid starter post, and battery ground cable as ground points. Now the test light does not come on at the solenoid starter side. I'll see how it goes tomorrow, if it sticks again and if I smack the solenoid and it stops I will swap it out for another one and see if that does the trick. Only thing left after that is to check the wiring and then also the ignition switch.

    Thought about just swapping to a mini starter but as this is my DD didn't have the luxury of time to mess with that and the wiring today. If this becomes a reoccurring problem, I might just bite the bullet on that as I have read that tends to solve the issue as they draw much less amps.
  12. Do you have long tube headers on your car? If so, that could cause some problems too. A mini starter is a great investment either way.
  13. Evidently you didn't read my previous post.I must have scared you off with too much techincal detail. If all you want to do, or can do, is throw parts and money at this problem, you may never get it fixed. Think, Test, and Diagnose is the correct way to fix things. I gave you the roadmap, so print it off and follow it.

    The solenoid sticks and welds the contact because there is low voltage when the starter is cranking. This causes an increase in current draw, which causes more voltage drop and more heat. The excess current and resultant heat are what welds the contacts in the starter solenoid. ALL the voltage checks including the voltage drop MUST be performed while the starter is cranking. You will find a bad connection or wire somewhere in the main starter circuit: use the voltage drop test to locate it.
  14. Had this happen circa late 90's on an 86 GT. It was the starter if I recall but I replaced the solenoid too.
  15. ALL the right information at once can be overwhelming. Especially for what could be a simple problem and a newbie to the system. I hear some frustration in your answer; this is only the X number of person to have the same problem lately. That is why I gave a short answer that would take care of most problems first. But as soon as you leave a piece out, someone needs it. So we are both lucky and stuck having it to digest instead of just a quick answer. Those quick answers can cost more.
    Grabbin' Asphalt likes this.
  16. My bet is on a bad Ignition Switch @ the steering column Mike. Someone else here recently had a similar problem, where we talked about it catching fire when grounded-out; but I thought you had already changed yours........

    After that thread, I pulled mine to check it on the 86GT and it was solid, clean as a whistle inside and holding prongs locked.

    For precaution, I mixed a little JB Weld and applied a thinnn layer around the seams of the switch where they are prone to come apart.
  17. I agree with the low-battery-solenoid-weld theory being a possible cause for premature solenoid failure and thus replacement, but replacement frequency could also be due to the part being inexpensive and folks just throwing darts at a starting problem....

    When trouble shooting systems that involve high-tech automotive skills, I too often eliminate any possible cheaper parts by buying new and replacing them.

    This is a good one that you all surely will say DuH!!!
    Wife's car wouldn't start, just clicked when the key was turned. I had just months earlier replace the battery with a new high-crank piece, so it couldn't be that. So I figure after 156,000 miles it's surely got to be the Pontiac GM starter gone bad, right?

    Actual problem - after starter replacement: Discovered still won't start and that Wife had left dome lights on!

    You never know all the simple possibilities....
    7991LXnSHO likes this.