I have a 1984 F 350 Crew Cab with a 7.5L 351 Windsor, Duel Tank. Last week the fusible link to the alternator blew and truck went dead instantly. I replaced the link and the Ignition Control Module (which was fried). Additionally i replaced the fuel selector valve, fuel filter, accelerator pump and carb filter (have 4bbl Holey). Fuel will pump into the carb while ignition is cranking, but pump shuts off when key turns back into the run position. Anyone have an idea why?

 

You need to know if you have voltage available at the coil + terminal with the key in the on position. If not ign switch may have a problem.

 

the wire from the coil to the ignition control module was fried so i replaced it. looks like the previous owner tied into the coil hot for his trailer lights. i took that out. i took a voltage reading and it was 7.5v. shouldnt it be 12v?

 

If you haven't found the problem yet maybe you can try the following.
Check all the fuses especially one of the 10 Amp fuses.
Then locate the EEC (power) relay and make sure it has 12 volts going to it. It gets it's supply from a fusible link that comes off the starter relay, battery cable side.
If you have the 12 volts there, then with the key on and the EEC relay active confirm that you have 12 volts coming out of the relay to the coil. Let us know what you find before going any further so we don't do a lot of unnecessary steps.

 

Finally, some success! I found the external inline fuel pump and it was not pumping. Tested it it direct to battery and it was no good. Additionally found the ignition switch on sterrign column was bad, so i just put a toggle switch on the new fuel pump until I can get the replacement switch. Ran good yesterday, for a while, then died. Charged battery overnite and tested battery this morning while truck was running (to check alternator) and only got 12.7v. Shouldnt it be closer to 13.5 or 14v? Anyway, drove truck about 20 miles total with multiple stops, then it died again. The starter is working, but i'm wondering if the battery is no good from when i blew the fusible link (connected to alternator) or if the alternator is bad (just replaced it in April)? Any ideas? Thanks.

 

If you are going to check the alt put the headlights on with hi beam. blower on high then take a voltage reading at the battery. It should be higher than 12 volts. If not, alt is not putting out as required. Don't go replacing the alt just yet !!! Need to make sure voltage reg is working properly and that could not be defective also if you have poor connections or the belt is slipping.