So I have a 1998 Ranger 4.0 that I got about 2 years ago and it's always had a lot of issues but it got me from point A to point B. It's always ran pretty rich and about 3 months before it stopped running it would run very rich and chug at idle to the point where I could not even go through a drive thru without it dying on me. After browsing around and looking through various threads I landed on the fuel injector pressure regulator may need to be replaced. I ordered a new one through rock auto and after I installed it the truck will not start. I noticed the regulator had came with a thicker o-ring and decided to try reinstalling the regulator with the thicker o-ring and still no start. The starter turns and it seems like its making spark but I haven't pulled any plugs yet and when I turn the key to the on position I can hear the fuel pump engaging so I feel like I should have fuel pressure but I still need to get a gauge to confirm. At this point I'm just kind of trying to figure out how replacing that part would cause it to suddenly not start and also where to go from here and what the best course of diagnosing the problem would be.

I do not have a code scanner right now but getting one soon and will update with all codes it throws out.

 

The fuel pressure regulator on a 1998-2011 Ranger is in the gas tank with the pump
So is that what you changed?

If not whats the part number or model number of the part you did change?

O2 sensors last 12 years or 100k miles, after that engine starts to run richer and richer without setting codes
So how old are your O2 sensors?
Won't cause a no start, just the richer and richer thing