Loss of fuel pressure

[Bucky5.0]

I have a 1988 ranger 2.9 5 speed 2wd i have been fixing up. All new plugs wires cap coil both fuel pumps and a filter plus a pressure regulator. Fires up and idles fine but at about 2500 rpms it acts like it wants to die and back fires. Put a fuel pressure g on and when you turn the key 40 psi then slowly drops. Any suggestions?
Thanks

 

[svtcards]

Have same problem on my v8 swap 1st gen ranger now.after testing a few things i figured it wasn't fuel injectors leaking by.i narrowed it down to check valve in in tank fuel pump.i will find on for sure if I chose the correct part to replace.i turn key to run position.it jumps to 33 psi ish.then I lose about 15 psi instantly.then It sits at around 15 psi for about 2 hrs then drops to 0.if it was an injector leaking it would drop to 0 psi instantly.and you d smell gas after u shut engine off from running.

 

[RonD]

1997 and earlier Fuel pressure regulators(FPR) are set for 43psi, and have a vacuum hose attached
When engine starts intake vacuum reduces the fuel pressure to about 30-35psi, thats normal
This allows for a more stable pressure for computer to calculate injector open time, i.e. air/fuel mix
When you floor it, vacuum drops, pressure goes up AND fuel use goes up, so pressure doesn't go up much, when cruising or slowing down vacuum is high and pressure remains stable
The point of the FPR

At 2,500rpm if engine is struggling if could be clogged exhaust
But yes if fuel pressure is stable 30-40psi at idle and then is slowly dropping when you hold engine RPMs above 2,000 then you have a flow issue, most likely a bad filter or bad High pressure pump

New now means "Never ever...............ever, tested", you are the very first human to touch it, lol
30+ years ago there was a thing called Quality Control, its now in the "I remember when.........." category

Everything comes with a warranty now, use it, "we" are now the Quality Control for any new parts


If you ever wondered why Ford(Motorcraft) or GM(ac/delco) parts are so expensive, because car makers pay for Quality Control on all parts, its cheaper in the long run to pay people to test the parts before they are installed into a new car/truck
But there are still Recalls, lol

 

[vigness]

Only thing I will add, is what I ran into when firing my '03 up for the first time in almost a year.

I was hunting gremlins couldn't find one to save my life. I limped it along for over a month with shit for power. Then I stuck my hand in the bottom of the air filter box. The damn mud daubers had built a nest and was blocking 80% if the incoming air. The engine was trying, but the vacuum on the intake side of things was causing all sorts of things to do LOTS of weird things. Popped the head light out and put a long extension back through the air box inlet and I had my truck back.

The lesson being is that the computer is only as smart as it's inputs. Screw any one of them up in a way it can't compensate for and it will tell you a hundred different things wrong and none of them are. It's the old GIGO principal.