Hello all!
I'm new to the forum(obviously). I moved along to Dodge Rams for a long time, though I was raised in a Ford family. However, I came across a deal I couldn't pass. I got my hands on a 1991 F150 Supercab, 5.0, with only 83,000 original miles on it fairly cheap. It has a couple problems to fix, but otherwise it's gonna be beautiful once cleaning is finished. Two of the main issues are ones I have never encountered, at least to this degree, are...
1) It's running very rich. That on its own has been a mystery. I'm not sure if it's the computer at this point or what. One thing I'm wondering is, the cat has a decent sized rust hole in it, roughly 1"x4" located on the side. I'm curious if the rich fuel may be due to the hole causing the O2 sensor to go nuts? I hadn't noticed the hole initially, just knew it had an exhaust leak. While tending to the second problem of running a little hot, plus not wanting to restart while hot, I was watching and topping the radiator, as we were purging the air after replacing hoses and flushing the system when the exhaust suddenly took on a deeper rumble. I looked around and saw the cat was full of fire and the sound was flame puffing out the hole. That, I figure, should indicate how rich it's burning. I have seen cats in meltdown,but this was a new one lol. It looks like it's probably pretty much hollow after however long it's had the rust hole.
I debated on how to pursue the next step. I do have another converter from a 92 that I thought about putting on to see if that fixes the rich problem. Another thought was to delete the cat.
2) As mentioned, when up to temperature, if the truck is shut off, it doesn't want to restart. I'm familiar with this problem on the rangers, where the starter was placed where the heat effects them. One issue with running a bit hot was we found the lower radiator hose was likely the original and was very soft and nearly sucked closed at higher RPM. I know there are 2 temp sensors on these too, the one that feeds the computer is new. When it was shut off, the cat fire died immediately, but still didn't want to restart. My brother was messing around and flipped the switch from the front fuel tank to the rear, which supposedly wasn't working, and it fired up. Shut down, front tank, no start, rear tank, started up again. When running, if you switch back to the front tank, it doesn't run as well. I'm really baffled lol.

 

Welcome to
Check fuel pressure with gauge(fuel filter changed?), attempt to get to temp, then check for codes, most use the Innova 3145 OBDI code checker, but if your good at counting flashes, and dont get distracted easily, then you can use paper clip.
see link-->Fuel Injection Technical Library » How To Run a Self-Test

how to vid-->(16) How to read a check engine light code on a Ford 1983-1995 EEC 4 system - YouTube

 

Pretty sure the guy I got it from changed the filter, but definitely worth a look. I really need to just get an OBD1 reader, been relying mainly on an OBD2 tablet, obviously not useful here lol. I do have a jumper somewhere in my toolbox I made up years back to count off CEL codes. I'll give that a try first.