gerg

Hi guys,
Recently ran a fuel pressure & vacuum test (hoping to solve a random skipping under hard acceleration/hard start/no start situation). Wanted to share results for your comment.
NOTE: '90 GXE has NEW (not reman.) injectors (1.5 yrs old), new fuel filter/plugs (NGK)/wires/cap/rotor/engine temp. & coolant temp. sensors.
RESULTS:
.*Key on: 47psi for 5 sec., dropping to 38.5psi (consistently). Fuel pump priming?
*Started car: 36psi at idle consistently (factory manual= 36.3psi, w/vacuum lines on/connected).
*Revving engine, quick bursts sees fuel pressure rise to 46-47psi consistently.

I measured about 4psi drop per 1 hour after I shut everything down and 0 psi overnight. Seems normal. I decided to do the fuel pressure test several times so I could clamp off “supply” & “return” lines to check fuel inj./fuel reg. leakage and fuel pump check valve leakage. These are results:
Clamp on Engine/supply side (testing fuel pump):
Car turned off & clamped: 36psi
½ hr: 37psi
1 hr: 37.5psi
1.5 hrs: 38.5psi
2 hrs: 39.5psi
*removed clamp & pressure dropped to 23psi
**Ambient outside temps were 81 rising to 87 degrees

Clamp on Return/Tanks side (testing injectors, pres. regulator):
Car turned off & clamped: 30psi
½ hr: 32.5psi
1 hr: 29.5psi
1.5 hrs: 29psi
2 hrs: 29.5psi
*removed clamp and pressure stayed at 29.5psi
**Ambient outside temps were 87 rising to 90 degrees

My last check was with a vacuum pump on the fuel pressure regulator vac. line. Manifold side plugged, cold engine.
The results:
Engine idle: 46psi (*factory manual says with vac. hose OFF manifold [plugged], fuel press. should be 43.4 psi.)
5 lbs vacuum = 43.5psi
10 lbs. vacuum = 41psi
15 lbs. vacuum = 38.5psi
20 lbs vacuum = 36psi
*Because all these readings held steady vacuum for at least 5 min. each and did not decrease, I did not remove the other vacuum hose from the pressure regulator to see if gas came out. Seems like regulator is fine (but is 46psi ok with vac. hose off manifold /plugged)? I get a correct 36psi reading when vac. line is connected properly. Also, fuel pres. readings are decreasing about 2-2.5psi when vac. is increasing, so that’s good. Does anything seem out of whack here? I have not removed rear seat to electrically check fuel pump against factory manual, but doesn't it seem like it's functioning properly from the above data?