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Went to start my truck (75 F250 360) after a day of driving it, when i turned the key the engine fired but then it died, after several tries I thought it might be carb so I rebuilt it with same results.  When starter is engaged with key the engine will continue to fire when the key is let off it dies.  thinking now it is electrical, could this be the coil, of the ignition module or maybe the switch on the dash? need to figure out how to bird dog it.  thanks.  

stick a test light in the positive side of the coil connector. ground the clip on the test light..

turn the key to the ON position.. does the test light come on.?? it should...

turn the key to crank the engine.. the light should stay on..    

as you release the key to the run position .. the light should stay on..


75 ford pickup .. probably has electronic ignition...

there will be a bunch of wires plugged into 2 connectors at the fender mounted module box...

there will be a red and white wire...  sometimes a third.. in one connector..
red is power in the RUN position . also connects to the coil positive..

white is power while cranking.. comes from the I terminal on the solenoid near the battery.. this white wire when powered with the probable blue grommet ignition module you have retards the timing 10 degrees while cranking.. easier starting..

in the other.. you will find a green wire that connects to the negative side of the coil...

a black wire that connects to the harness to the distributer.. thats the ground connection for the module.. its connected to the hold down screw for the pick up coil grommet

there will be a purple and an orange wire also running to the pick up coil wiring..
this is the AC voltage signal the pick up coil generates to turn the power transistor on and off to fire the coil..

you could have a bad ignition switch...  this happens a lot.. as the contacts move across .. the edges burn so when you release.. it does not make proper contact..

you could have a bad ignition switch connector body ... where the terminals have overheated and melted.

you could have a bad starter solenoid on the inner fender.. once in a great while.. the I terminal inside will short to ground or to the starter motor side of the wiring and drag the ignition power down to where the engine won't run..

you could have a bad ignition module..   if you buy a replacement.. you can get some with a life time warrantee from some chain stores..  



circuit tester into the positive side of the coil is the best and quickest test...

if you get a constant light.. ..

pull the connector off the coil...  use something to hook the test light from one wire to the other.. on the harness that connects to the coil.   have somebody crank the engine..    if the whole system is good.. the test light will flash while cranking


more to come... stay tuned...  

this is what your dash board mounted ignition switch.. ignition lock cylinder and switch pigtail connector looks like




your ignition module probably has a green plastic strain relief where the wires come out from under the back..  

I bought a new module and installed it, the motor wouldnt even fire, put the old one back on and at least it fired when the starter was engaged, was this a bad module? is there something else?  

run circuit tester TEST..

do you HAVE power at the POSITIVE SIDE OF THE COIL?? when you turn the key on.. and when you turn the key to the CRANK position... and back to the RUN position Without blinking OUT

LIGHT ON   good,   continue to other tests below..

light OFF bad..

do you have power at the RED wire coming into the MODULE when the key is turned on.. while cranking and still when you let the key back to the run position...

it should go off when you turn the key off..

you could have a bad ignition switch.. or a bad ignition switch connector..  

do you have a digital volt meter?????

there are 3 wires coming out of the distributer..

ORANGE and a PURPLE wire...  these will be the parallel terminals in the distributer pigtail connector..  |     |

set meter to 2K ohms.. 2,000 OHMs scale..   measure the resistance of the orange to purple wire..   usually around 980 ohms..  but somewhere between 500 and 1500 is usually acceptable..

before disconnecting.. flip the digital volt meter over to 2 volts AC... have somebody crank the engine over.. you need to see just over 1.0 volts AC to pass this test..


if you pass the resistance test.. but don't pass the 1.0 volt AC test... you have a bad reluctor.. that fingered thing on the shaft..   they do go bad.. cost about 7 bucks...

the pick up coils also go bad..


please copy my text.. go over it ONE line at a time...  

bought a module for my f250 but would not even fire, then matched the part# on the old module on line to a 1976 f250, have ordered the module for the 1976 now, all the numbers are matched up now per cross reference so hopefully this will be it.  had the same problem with a 2003 elentra, the 02 sensor required is for a 04, that was fun figuring out also.  

ford duraspark modules are assorted by the strain relief grommet..

early  were red or green...   then blue...  yellow... white as i recall..  black...  brown versions were for EEC3 with a crank sensor...  yellow with 2 strain reliefs were for feed back Variable venturi carbs.. usually..