Does the key turn loosely, like its not connected to anything? If so then the ignition switch actuator in the column or the ignition switch itself is bad (its usually the switch if anything). If that checks out do you hear anything when turning the key, like clicking? If you got nothing, or even if it does click i would check the ignition switch anyway as they can act funny when they go bad. There are numbers and letters on the backside of it.
From the FSM:
Disconnect the ignition switch from the harness. Connect a self powered test light or an ohmmeter to the terminals listed below. Continuity should be present for the following combinations only:
ACC = 37 (BATT) and 297 (A1)
LOCK = No continuity
OFF = No continuity
RUN = 37 (BATT) - 16 (I1) - 687 (A2) - 297 (A1)
START = 41 (P2) - 977 (P1) Chassis ground: 37 (BATT) - 32 (ST) - 262 (12)
* Circuit pairs (37, 687, and 297) are connected together internally.
* There should be no continuity between any terminal and chassis ground except for circuits 41 and 977 in the START position only.
From the EVTM:
1. Internal connections check
Connect a self-powered test light or ohmmeter between 37 (BATT) and 37 (BATT). Turn the key to all 5 positions. The circuit should be closed in all 5 positions.
2. START circuit check
Connect a self-powered test light or ohmmeter between 37 (BATT) and 32 (ST). Turn the key to all 5 positions. The circuit should be closed in START only.
3. RUN circuit check
Connect a self-powered test light or ohmmeter between 37 (BATT) and 687 (A2). Turn the key to all 5 positions. The circuit should be closed in RUN only.
4. Ignition circuit check (2 part test)
Connect a self-powered test light or ohmmeter between 37 (BATT) and 16 (I1). Turn the key to all 5 positions. The circuit should be closed in RUN only.
Connect a self-powered test light or ohmmeter between 37 (BATT) and 262 (I2). Turn the key to all 5 positions. The circuit should be closed in START only.
5. ACC circuit check
Connect a self-powered test light or ohmmeter between 37 (BATT) and 297 (A1). Turn the key to all 5 positions. The circuit should be closed in RUN and ACC only.
6. Bulb test circuit
Connect a self-powered test light or ohmmeter between 41 (P2), 977 (P1), and the ignition switch. Turn the key to all 5 positions. The circuit should be closed in STARTonly.
If that checks out the neutral safety switch is a possibilty (at the trans). Try starting the engine with the key as you wiggle the shifter. If it starts then, the switch is bad. Sometimes that works. Wouldnt hurt to check the wiring as well. Check the clutch safety switch (at the pedal) for any pinched or broken wires. Melted, even. If its an auto, try starting it in neutral. Same problem (neutral safety switch). If its none of the above id say its bad wiring, or the starer solenoid you just replaced is bad. They can be bad right out of the box. And just to be sure, you are using the 3 post solenoid, yes? two large posts and one smaller post. There is a 4 post solenoid for older Mustangs and wont work. I have made that mistake myself atleast once with my 93.
---------- Post added at 04:57 PM ---------- Previous post was at 04:12 PM ----------
i have 88gt wont start using key have to jump it across solenoid so i replaced solenoid still same problem so replaced ignition switch still same so replaced ignition key switch still same what else can it be
I missed that part, im having one of those days it seems. Oh well, if you ever need to test the ignition switch electrically or simply want to just because, there it is. To elaborate on the wiring there is a fusible link between the ignition switch and coil, just behind the driver side strut tower. Should be a red/green wire. If that link is blown the engine will not start with the key (no power). It should be fairly obvious if its blown as it will look melted. If its bad, be sure to replace it with the same dark blue 20 gauge as factory and heatshrink the splice. Never bypass a fusible link.