78 302 starts right up then shuts right off. Help please!

[slepper63]

'78 302 the car starts right up for about a second then shuts right off. Drove the car today, drove fine car sat for couple hours, went to park in garage and it would start up then shut off. Took the fuel line off and cranked it a couple times, its getting fuel, change fuel filter, checked spark plugs and the gaps, it has new wires, new coil, new roter and new module. Took the module off and put old one back on, still doing same thing and its getting spark. What can it be? thanks

[34_40]

'78 302 the car starts right up for about a second then shuts right off. Drove the car today, drove fine car sat for couple hours, went to park in garage and it would start up then shut off. Took the fuel line off and cranked it a couple times, its getting fuel, change fuel filter, checked spark plugs and the gaps, it has new wires, new coil, new roter and new module. Took the module off and put old one back on, still doing same thing and its getting spark. What can it be? thanks

Turn the ignition key to on. Is there power going into the module / ignition?

[slepper63]

i think there power going to it module becase if there wasnt it would just turn over but it starts for a second .how do i check to see if there is power

[Itoldyouso]

Here is the deal. Your ignition switch supplies power to the coil in two positions.

* When you turn the key to "on" or "run" (first positon) it is supplying less than 12 volts to the coil, usually something like 4.5 to 7 volts. This reduced voltage is used keep the motor running but not so high as to burn out the coil or module.

* When you turn and hold the key in the "start" positon, a full 12 volts is being supplied to the coil via a wire that is connected to one of the little posts on the fenderwell mounted starter solenoid. That 12 volts is supplied to the coil as long as you hold the key in the "start" position, but quits once you release the key into the "on/run" position. (The Ford solenoid has 4 posts on it.....1 fat cable, power in..... 1 fat cable, power out to the starter.........1 skinny wire, power in from the ignition switch when turned to the "start" position.........and 1 skinny wire, 12 volts out to the coil when cranking.)

What is happening, probably, is that your coil is getting that 12 volt shot of juice, enough to start it, but as soon as you release the key it is NOT getting the lower voltage to keep the motor running.

Easy to track down. Just turn on the key to the "on/run" position and put a test light or volt/ohm meter on the + post on the coil and the other lead to ground. I bet you see no voltage there, but you should be reading that 4.5 to 7 volts. Ford uses a special wire that reduces the voltage from 12 at the ignition switch down to that lower voltage..............it is called a resistance wire. You either have a bad wire or bad ignition switch. If you have no voltage at the coil when you do this test, then go to the ignition switch and see if you have 12 volts coming out of it when you do the same test with your tester. If you get 12 volts coming out of the switch but none at the coil, you are losing it somewhere in the wire, possibly a break or it is burned out.

Another test you can do is run a piece of electrical wire from the positive battery post temporarily to the + side of the coil and start the car again. It will probably keep running as long as you have that wire in place, but don't do it too long as 12 volts is too high for it to get for a long period and it might damage the module or coil. What you have done by running this temporary wire is you have bypassed the entire ignition switch and resistance wire.

Don

[slepper63]

Don,

I put a volt meter on like you said and the coil read 12.7-12.8 volts. I don't know if that was good or bad. I did a wire from the positive battery to the positive coil and the car would not start it just turned over. Is there anything I can do? Thanks

[stovens]

How old is the coil? Everything else sounds good, Maybe replace the resistance wire Don was mentioning. I had similar issues on my 460, and that was the culprit.

[Trjohn57]

Hi Sleeper. I had an issue with a coil once. It just wasn't grounded good enough. I screwed around and when I got a good ground on it, I had no issue again. If you get a good ground on it and no spark out of a plug wire then it probably should be replaced. Good luck on this.

[Itoldyouso]

Hmmm, that's strange that you have that kind of voltage when the key is turned to the "on" position. Next step I would try is to have someone try to start the car while you shoot some starting fluid into the intake (carefully). Once it kicks keep shooting a little more in there to see if you can keep it running for a little while longer. If it keeps going longer than the second or so it has been running that will tell you your problem is fuel related.

I would also have someone crank the engine while you hold that voltmeter onto the positive post of the coil to see if juice is constantly there while cranking and once you release the key into the "on" position.

Don