Need help please!!

86' GT 5.0 HO said:

Hello anyone who can help me,
So I've got a 86' 5.0 GT with a high output engine and the people I got it from were smart enough to switch the positive and negative wire colors on the battery so now black is positive and red is negative. I go to give it a jumpstart one day and put the positive cable on the negative and the negative on the positive and a white little plastic box located in the middle of the right side under the hood IDK what it was but it started to smoke so i took the jump cables off as fast as I could. What kind of damage could that have possibly done and how much would it be to fix it? If anyone can give me some advise I would greatly appreciate it!!!!
Thank you,
86' GT 5.0 HO

Click to expand...

What are the wire colors that are attached to the smoked part? That will tell what smoked and give some clues to the possible extent of the damage.

No Crank checklist for 5.0 Mustangs

Revised 09-July-2009 to reorder stuck solenoid help.

No 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. Anyplace 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 Automotive Test Tools 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 Netural Sense Switch (auto trans) or ignition switch.

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


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.

is that box that got smoked right on the firewell by the intake? Start by replacing the solenoid. Easy fix plus they are only like $12. If nothing then yank the starter and take it to get tested. Replace all the smoked wiring. Pics would also help

The two wires to the right are fuse links.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host) for help on 86-95 5.0 Mustang wiring Mustang FAQ - Engine Information Everyone should bookmark this site.

In it are 3 diagrams of the 86 Mustang electrical system.

See http://www.stangnet.com/mustang-forums/789403-86-fuse-eletrical-problem.html and look for a post by V8only. He has posted a link to download a complete electrical manual for an 86 Mustang.

The following link should do it.
http://slantnosefox.com/picturehosting/jeremy/86%20electrical%20%20&%20vacuum%20troubleshooting%20manual.zip

You'll need WinZip or similar archive tool to unpack it. See www.majorgeeks.com for WinZip.

86' GT 5.0 HO said:

One more thing what are the wire names of the ones that are connected the the solenoid switch? And is there a certain a special way that I have to replace them?
Thanks

Click to expand...

Look at the diagram I posted for Starter solenoid wiring for 86-91 Mustang. Everything you need is there.