was driving my 78 f150 351m today and it just died no power, found the wire coming off the starter solenoid with fuseable link broke, repaired and now cranks but wont start, checked and no spark, replaced coil and still no spark, where should i look next? what test's should i perform?

 

Do you have 12 volts to the plus side of coil? Start there.
If thats good, have someone crank it while you have a test light on the neg side of coil to ground. The light should pulse on and off while cranking. If not, chances are you have bad pick up coil assembly in the distributor. Dont forget to make sure the distributor is turning, and the tang on top of the rotor is in good shape. Check to see if you have spark coming off the coil wire by holding it about a quarter inch from the block. Nice blue spark.

 

You should only have 6 to 7 volts to the coil with the key in RUN on Duraspark II ignition. The only time you will see full voltage to the coil is with the key in START, but because the starter is cranking, the actual voltage at the coil is still below 12 volts.

The test you mentioned is a good start. A bad ignition module (or no power to a good module) can also cause the same behavior.

 

Yes that is true..i should have said cranking voltage. I never under stood why ford dropped the voltage during engine run. Its not like there are points to burn out

 

I will check voltage to the coil after work, if it's good were should I go then? And if it's bad what should I do?

 

The three step scenario of a failing DuraSpark ignition module.

1) Module overheats, engine dies. Module cools down, engine restarts almost at once.

2) Module overheats, engine dies. Module cools down, engine restarts in an hour...or so.

3) Sooner or later, usually sooner, the module overheats, BURNS OUT. Now the engine will not restart.

Engine heat is the mortal enemy of these modules, which are mounted on the left fender inner apron.

If replacing the little charmer, use some washers to space it further away form the apron. The more airflow the better.

Since the module fails when it overheats: Taking it to an autoparts store to be tested: It will test OK unless it has burned out.

There are three possible modules used on 1976/79 FoMoCo vehicles. Modules have a colored plastic square above where the wires feed out. The most common module has a blue plastic square.

1U2Z-12A199-AA (replaced D6AZ-12A199-A & D9VZ-12A199-A) .. Ignition Module-blue plastic square (Motorcraft DY-893).

D4PZ-12A112-A .. Stator aka magnetic pickup coil, mounts inside dizzy (Motorcraft DU-1A). Similar symptoms apply to this little charmer.

Applications: All 1974/79 FoMoCo V8's except 1979 LTD/Mercury Grand Marquis 351W with EEC.

 

This is to keep the voltage at the coil somewhat close between START and RUN so that the ignition system components can be designed and optimized for a single primary voltage. It helps compensate for the fact that battery voltage drops when the starter is connected. As such, the resistor upstream of the coil in RUN is called a "ballast" resistor.

Note that cranking voltage is not 12 volts either, for the reasons I stated above.

If it's good, then move on to the test that nine inch described. This can help pinpoint why you're not getting spark. Based on those results there are some more tests to try too.

 

Voltage to the coil tested good, didn't have a test light for the negative side so used a dvom set to continuity while someone cranked and it stayed open the whole time so I replaced the module same thing, tried to replace pickup coil but couldn't get the star gear "armature" off the distributor I will get a puller to do that tomorrow, if it still doesn't start the only thing left would be the ground wire right? Could I splice in a new wire temporarily to get the truck home?

 

A multimeter does not always work for this test because the needle may not swing fast enough; if it's a digital multimeter that auto-ranges then it definitely will not work. A test light is the proper tool to use.

You don't have enough information to go farther yet. Perform these tests:

1) Disconnect the distributor. Measure the resistance between the ORANGE and PURPLE wires coming from the distributor. The resistance should be between 400 and 700 ohms.
2) There should be no continuity between either ORANGE or PURPLE and BLACK.
3) Measure the continuity between the BLACK wire coming from the distributor and ground on the engine (with the distributor installed). It should be a short.
4) Disconnect the 2-wire connector at the ignition module. Measure the voltage on the TRUCK side of the connector. The RED with BLUE stripe wire should have 12 volts in START. The WHITE wire should have 12 volts in RUN.

Note: before people try to correct me on #4, the colors are swapped between what actually comes from the truck and what goes to the module. Coming from the truck, RED with BLUE stripe is hot-in-START and WHITE is hot-in-RUN. However on most replacement modules (even Motorcraft brand), RED is hot-in-RUN and WHITE is hot-in-START on the module.

 

OK all here's an update i replaced the Pickup coil and have spark now, then I have no fuel, find the previous owner did away with mechanical pump and put an electric online pump in, replaced it and have fuel now if I push the pedal to the floor and crank it will start for a second and shut right off even if I play with the throttle, also I replaced all the plugs so the entire ignition except for base down distributor Is new, any ideas?

 

You can probably eliminate the ignition system at this point. Is the choke set up properly?

 

I haVent a clue to tell yah the truth, I just know it ran 100% fine before it shut down now it won't even start, how can I check the choke set up?

 

I just figured out if I keep the key turned to start it will run and I can rev it up but as soon as I let go and it goes to run it dies, could that be the switch?

 

Changed the switch and same problem, I'm running out of ideas

 

Broken wire or burnt ballast on ignition run circuit..