I have a 1988 F150.. unknow miles. It was running ruff at times ...so I put in new plugs, wires, and fuel filter. Tried to put rotor and cap on but the bolts broke off holding distributor cap. So I had to replace distributor. All was well but now it will not start. I have no real spark. Replaced coil. And still a very weak spark that really only seems to fire when you turn the key off? And ideas?

Did you place it with the correct dizzy? Does the rotor turn inside the cap, and if so, does it have the same harness hookup in the cap?

Sounds like the ignition module is not getting voltage in the "run" position, OR the system ground is weak (this would explain a weak spark in "start" and none in "run" as you get more coil voltage in start than in run.

I am going to try to replace the guts of the new distribitor and check the ignition module..

thanks