2.3L ('83-'97) '88 2.3 weird fuel pressure readings

[Shran]

I am kind of at a loss on this. 1988 Ranger, 2.3

Back story: this truck has run weird for as long as I've had it (about 6 years.) It spits and sputters when it's cold and runs a lot better after it's warmed up.

It has been getting progressively worse. Now it has an obvious miss even when warm on occasion. I threw a timing light on it and checked fuel pressure while I was at it and found something weird - key on, engine off it would build up to 35psi and then drop down to about 32 and stay there indefinitely. Running, it would drop down to around 25, and would briefly hit low 30s when you crack the throttle. Way out of spec.

I had it loaded full of scrap and risked a trip to the scrap yard where it died. Thought it was out of gas as it was very low, put some in, would not start. Left it, came back later, cranked for about 30 seconds and it came to life so I drove it home. I pulled the bed, and tested both pumps for function. Both work. Next I removed the sending unit, high pressure pump, and frame mounted reservoir. The fuel filter came after that and it appeared to be clogged - weird because it's fairly new, the tank is new, and inside the tank looks very clean.

At this point, I decided to do a second gen pump conversion. I swapped in a high pressure Kemso pump, modified the fuel lines so that the the sending unit feeds straight up to the (new) factory fuel filter, eliminating the high pressure pump and reservoir. Put it all back together, fired it up, aaaaaaaand.....

I still have the same fuel pressure reading. Still runs weird.

What gives? I replaced the regulator recently... is it bad? My pressure gauge is fine, I just used it on a couple other trucks.

 

[Shran]

Never mind. I fixed it, the regulator was apparently bad. I haven't seen one fail like that before.

Runs way better but still is quite rough till it warms up, at least it's drivable now.

 

[scotts90ranger]

Did you reset the fuel trims (unplug battery)? It could have some spots still learned in the weeds.

Working on engines at work over the years I've learned not everything makes sense, I've had to think outside of the crate the box is in... when a machine breaks down in the middle of a factory making cans for food or cars they get cranky...

 

[Shran]

I didn't do that yet, my battery terminals are filthy and need to be cleaned up so I'll let it sit a while and reset while I do that.

Something is still off. It was really running bad this morning and sounded like it was pinging when I went up a hill. Very high idle at a couple of stop lights too.

 

[scotts90ranger]

Intake gasket at the cylinder head is my best guess on that, if one cylinder is running lean it can do odd things, had that happen on my turbo 2.3L once...