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96 x90 revival
my guess is
you fix cars. but?
no fuel pressure gauge
no hand vacuum pump with gauge.
then wonder why you cant test FPR ? 50 is wrong!
buy a new FPR, save on gauges, sure. (and 5 times cheaper than rebuilt ECU)
no full scan data presented, all sensor readings with 02 stuck at 1vdc high,rich, and hot engine and closed loop failing
no data, no way to help you at all, I am sorry.

the FPR must do as post 6 shows, my graph is off a 1996 same as yours, and is correct.
keyon is not 50 PSI , it is not in spec,
so that confuses the H3LL out of the ecu and the injectors over inject hugely
9 PSI more that mine, huge over pressure, huge.
Off hand I'd say yet again, 1 more stinking FPR, after 22 years of use,. ( no shunt test done so..... no savvy answers lacking that)
and 30 gas pedal pressings per day for 22 years, 250,000 times the FPR had to move and regulate. what more do you expect from this poor old FPR?
I'd say 1million times giving weekend usage trips etc.
The POOR FPR has worn parts side, it sticks now. in a queer and odd and totally un reliable way, known as CHAOS.
gee get new one? $60
example , 10 years back , only FPR sold in town was $200 each.
so we installed fuel pressure sender on the front rail (adpator)
and gauge in car. (electric SWarner, fuel pressure gauge)
drove car, learned that fuel pressure changed, in wrong ways, incongruous to vacuum , very odd, and random or temperature cold worse, and well random at times.
intermittent. (it was sticking inside)
stuff happens, no FPR made lasts forever NOT ONE.
think this way
if pressure (fuel) is wrong
the 96 ECU can not fuel trim wrong pressure if out of spec, that is what the spec includes, this ability to trim.
and at wot THERE IS NO TRIM, only MAF and FPR.
you fail to note, and I repeat (post 6 ) see this and read all words there, and learn how FPR works on 16v 1996

the max pressure spec, is 43 PSI spec (happens key on, sealevel is max max)
and that 50 psi is 7 PSI more than MAX MAX. so is grossly wrong,, not just tad BIG time WRONG.
is this not clear, if not say why, please.
then fail to note the idle pressure is off too
you said 40
but the 800rpm hot fuel pressure is 30-37 PSI
not 40, mine is 30, mine is 30 because vacauum is 19"hg, and hot engine 800rpm and the 30 includes low altitude.
so yours read 10 PSI higher than my 96 and 97 (had do cars same EFI)
the 30 like mine, would be 10 PSI higher on yours.
but to be fair and only reading the spec, your FPR is 3PSI over spec, a hard cold fact
and skipping full vacuum testing at 26" i bet it reads high too, (mine reads 21psi fuel) Yes I test the FPR and all points. at least 3, or more,
the older the car and FPR the more carefully I test, if flush in cash a new FPR lands here,
all you can do is test, or throw parts, your call, your cash.
the FPR also prevents flooding here.
yes , one high road 18k, and super low air pressures, and if fuel pressure is too high here, the engine fuel floods fast for injector rates.
ATM air pressure here is 0.51 bar(1/2 normal) so if fuel pressure was stuck high (40) the injectors flow 2 time normal and flood, did you know that? Knowing this helps you learn to test cars EFI.
We do the mountain test too, after all cars drive ANYWHERE. ( 1bar is seal level below is 1/2 that) so pressure FUEL drops 1/2. if not it floods.(fuel ) your altitude is zero, so is the best place to be to test any FPR. (1 bar air pressure ATM)
[Image: 3_11_12_18_8_24_31.jpeg]
the fuel pressure gauge you HAD was top grade, SNAP-ON tools not some cheap crap china cloned trash.(C4 trash)
so I take the 50PSI as fact, all we can do as a tech is trust our tools, in fact I have duplicates so I can cross check readings, (and cross check me)
the tools make the man, working on cars, if no tools all we do is guess, (or like you did, cause vacuum leak see 02 wake up and is text book example that is super good test)!!!
all it proved was,. injectors are over injecting, 1 or all 4.
you can also use and IR gun (1 more $15 tool) point it at exhaust tube, 1 ,2,3,4, (mid point top shields off) see if all 4 run the same temp. (this is EG Temp test, exhaust gas temp test)
just like all carb piston air craft engines have for setting fuel mix and not burn up the engine, lean. (see dash enrich knob? " Cessna?))
IF, we see all 4 same, that tells me all 4 injectors are doing the same thing, done on a hot engine , at idle , or at 2500 rpm, held there, for 1 full minute to let it stabilize
(aimed as same distance down from exh. ports)

if all 4 are same then what makes all 4 injectors over inject and not ECT stuck at 150f. if one port super cold the injector may leak.(or spark bad or other causes compression related)
FPR. we know the MAF reads right. so..
Have a new set of injectors on order. We will see what happens my next is a FPR. Left that as a last resort. You have me sold on that. Thanks.
Got the new injectors in runs better but still over fueling, bought a new FPR hopefully it will be two bolts and two hoses away from fixed.
Changed FPR and same problem, I was thinking that maybe when I changed the fuel pump that I may have reversed the two rubber to metal fuel lines. So I swapped them over and no deference, I’m assuming one is a return and one is vent , or goes up to the EvaP system?
Well, after a month or so of throwing parts and fixes at her I think I scored, I must have had the the fuel return line one the evap and evap on the the return. As it seems to be clearing up the o2 sensor is now bouncing and fuel trims are trying instead of pegging and giving up. Also no more soot from the tail pipe and scanner says it’s staying In closed loop at idle.

Stupid mistake,
anyhow she is sporting new injectors, new pump, regulator and filter. So the fuel system is in top shape not really money wasted. Also thermostat, ECT .I’m thinking the only part besides my time that I really got burned was the $100 ecu. May be able to put that on eBay and recoup some loss.

Thanks for sticking with me on this. Now on to the fun part Modifications and adventures.

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