Cranking Over Problem

[coffmaad]

Ok. My car will not crank over. I started by checking the the little red/blue wire to see if it was getting power. It was not getting power when the ignition is in the start position. So I started tracing it from the beginning and I have power coming out of the white/pink wire on the ignition switch when I turn the key to the start position. I then checked to see if the clutch safety switch was getting power and it is not getting power on any of the terminals while in the start position. Why is the neutral safety switch not getting any power when the ignition switch is when it is in the start position?

1991 LX 5.0

 

[ID89GT]

Might have an open in between the ignition switch and the neutral switch.

 

[jrichker]

You are chasing two different birds in two different directions.

The neutral safety switch has nothing to do with the starter circuit. It is to enable the computer diagnostic tests with the engine running. The computer wants to make sure the A/C is off due to the added load on the engine for the engine running tests. It also checks to see that the transmission is in Neutral or the clutch depressed (T5, T56, Tremec 3550 & TKO)). This prevents the diagnostics from being run when the car is driven. Key On Engine Running test mode takes the throttle control away from the driver for several tests. This could prove hazardous if the computer was jumpered into test mode and then driven.


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

See http://www.autozone.com/images/cds/gif/large/0900823d80195963.gif for 88-90 year cars
See http://www.autozone.com/images/cds/gif/large/0900823d80195964.gif for 91-93 year cars.
See AutoZone.com | Vehicle Selection - Year for 94-98 model Mustangs



Diagram courtesy of Tmoss & Stang&2birds

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring Mustang FAQ - Engine Information Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for94-95 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/94-95_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

 

[coffmaad]

According to the diagram, the power runs through the ignition switch into the clutch safety switch. The power then goes to the starter solenoid to energize it for cranking the engine over. When I used my test light on the ignition switch, it had power coming out of it but from there it goes to the clutch safety switch to complete the citcuit to the solenoid. Why wouldn't I have power at the clutch safety switch but I do have power coming out of the ignition switch. It has me stumped here for a second.

Thanks

Aaron C.

 

[ID89GT]

I think you will probably have to trace the wire coming out of the ignition switch to the clutch switch and see if there is anything you can see wrong with it. Try some drop voltage testing to see where you are losing your power at.

 

[coffmaad]

Where does the white/pink wire coming out of the ignition switch transfer over to the red/light blue that goes to the clutch safety switch?

 

[coffmaad]

Just thought I would let everyone know that my problem was in the transmission harness. I had the plugs unhooked and jumped the plug with 4 terminals and now car cranks over great.