Hi calling all pros for advice. I have owned a 1991 F-150 with a 5.0 E4OD for 7 years. I have never been able to set the timing with a timing light! Well a few days ago driving down the road the engine lost spark. After sitting a couple hours it came back and ran fine for a few miles and did it again. When I finally got it home I read the codes and got the dreaded code "hall effect pickup" After checking the wiring and connections I bought a new distributor and installed it as per the manual, no good wont hardly even crank! So one again I pulled the valve cover to check compression stroke at TDC only to confirm what I already knew, the line on the balancer is no where near the indicator as before. The old distributor was off several teeth! I went ahead and pulled the balancer thinking it had sheered the key way only to find out the key was just fine! Has any one else run into this problem? Oh btw the key is at 12 O clock at tdc, could the crank have twisted? It ran great for years!

 

I have a 91 Bronco 5.0 that I've been all thru the engine. The harmonic balancer is mounted in rubber and they are notorious for slipping making the timing marks irrelevant. I assume when you replaced the dizzy that you also got a new TFI on the dizzy. If not, your problems are not over. From the sound of your issues, the TFI was the most likely problem. It will start and run but when it builds heat, it shuts down. Then after it cools it starts and runs. Typical of the TFI which mounts on the front of the dizzy. For the harmonic balancer, you're looking for a new one if you want to fix it right. I assume you're aware of removing the spout to time it and replacing at after it's in time.
Ignition module/TFI

 

Thanks Labnerd for all your input. Yes I have had to replace the TFI in the past, and yes I know about the sprout. Well I found out my problem this morning, Please try and keep in mind I am a retired Harley Davidson tech/instructor. I have always fixed all my own stuff, I enjoy learning new skills. Well today I decided to use a dial gauge through the plug hole and just mark my old balancer, after I found exact TDC with a sharpie I removed to put a more durable mark in it with a triangular tool file. Although I had cleaned the balancers surface with a nylon pad I decided to not only use a file mark but also paint it red for my old tired eyes! Upon sanding with some 320 paper, low and behold I began seeing lines, then numbers right where I marked it! And again exactly where I had marked it! So lesson learned, my bad. The deep wide grove on the wide cheek of the balancer is NOT the timing line! Guess I;ll know better next time! Maybe after the next 372,000 miles!