Ignition Help PLEASE!!

[mustang501993]

Guys, I am having a problem with the ignition on my mustang. It is a 93 lx 50. When I turn the key to the "Start" position it cranks and fires but the second you let it go it dies. It is NOT the igniton switch, I have replaced it and I have also verified that the little rod that actuates it is working properly. What could this be? The car ran great one day and not at all the next!

 

[mustang501993]

Oh, and the fuel system is ok

 

[Camman]

when it dies does your radio still work?

 

[rd]

You need to check the wiring that powers the coil and ignition with the key in the run position. Pull the starter relay actuation wire so you can leave the key on in run, w/o the car starting.

Not sure about a 93 with TFI, but, for example, through the Duraspark era, there was a separate wire to the coil, and module for start and run. It sounds like one of those has failed. They used to have a resistor in them, called a ballast resistor, and sometimes that would fail. Ford used a piece of resistor wire in the run wire, Mopar used those ceramic ones, that everyone had to keep spares for in the glovebox.

Recheck the power circuits from the ignition also. Remember that the ignition switch must be adjusted so the contacts align in the different positions. The switch should have slotted mounting holes to allow adjustment. Mine once got where the keychain swinging would bump the switch off going down the road.

If that does not get it, start checking ECM power.

 

[HISSIN50]

if you goose the throttle, will it stay running?

 

[mustang501993]

The car will not run when i goose the throttle, floor it, nothing. I do not have a radio. I like the idea of the ballast resistor. I just recently installed an electric fan and took the power off of the starter solenoid (battery side). That is where the resistor is. The car ran after that but it sits most of the time and maybe the connection got corroded. It has been about a month since I did the fan. Any other suggestions will be welcome. The next time I try I will have my multimeter on hand.

 

[mustang501993]

Just for a point of reference, what does the ballast resistor do? It looks as if it is in the middle of the negative side of the ignition circuit going to the computer. I took a gander at the autozone manual, which is a lot better than the Haynes, and noticed that there is another wire going to the distributor/TFI that says "to starting and charging system". The question is, will this wire provide the juice to the distributor on startup and then switch over to the circuit using the ballast resistor? Also, is the ballast resistor the one on/near the starter relay?

 

[04sleeper]

Just for a point of reference, what does the ballast resistor do? It looks as if it is in the middle of the negative side of the ignition circuit going to the computer. I took a gander at the autozone manual, which is a lot better than the Haynes, and noticed that there is another wire going to the distributor/TFI that says "to starting and charging system". The question is, will this wire provide the juice to the distributor on startup and then switch over to the circuit using the ballast resistor? Also, is the ballast resistor the one on/near the starter relay?

BALLAST RESISTOR


Definition: A resistor in the primary ignition circuit that lowers voltage after the engine is started to reduce wear on ignition components.

Maybe jrichker will jump in and help you out in a few with the other questions.
Or PM him. He is very well versed with the wiring.

 

[jrichker]

From the Cranks Ok but no start checklist:

Turn Ignition switch to on, Place car in Neutral or Park for a safety measure. Do not crank the engine, since you seem to be able to get spark if you turn the key to the crank position.

E.) ECC relay next to computer - look for 12 volts at the fuel injector red wires
F.) Fuse links in wiring harness - look for 12 volts at the fuel injector red wires. All the fuse links live in a bundle up near the starter solenoid.
G.) Ignition switch - look for 12 volts at the ignition coil red/lt green wire.
H.) Computer

See http://www.autozone.com/images/cds/gif/large/0900823d80195960.gif for 91-93 wiring diagrams.

See http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for all 89-93 wiring diagrams.

The resistor shown in the wiring diagrams in not a ballast resistor, but a isolation resistor with a 22,000 ohm resistance. It drops down the voltage & limits the current that flows to the computer's pin 4, IDM sense input. I don't have specific information on the IDM sense does at this time. It is a rabbit that may not yield anything useful to you if it was chased.

 

[04sleeper]

Thanks jrichker!

I knew you would come through as usual.

ttt for you mustang501993.

 

[88hatchblack]

have you checked your connections to the starter dsolenoid? i accidentally hooked everything up backwards on it and that's EXACTLY what it did.

 

[jrichker]

Additon to the "Cranks Ok but no start checklist"

C.) TFI module - Note: the car may fire off, and immediately die once the key is returned to the Run position if the TFI is bad. The starter wiring has a separate wire that goes to the TFI. I don't know if it provides extra power or just tells the TFI that the engine is cranking and to pass more power to the coil.