Hi forum, after months of chasing my problem with acceleration (didnt want to go above 2-3k when warmed up, and popping sound from intake )
shame on me only as the last step i did test a fuel pressure

Behaviour is quite odd, and i cant do proper analysis

Cold
Idle Pressure - 34 PSI, vacuum disconnected - 42PSI
Throttle up with pressure connected - falling briefly to 28ish, after release goes up to 40ish, and immediately back to 34

At operating temperature on idle - 30 PSI, vacuum disconnected - 35
No loss of power and popping yet

Took car for a very good drive, loss of power appeared, checking fuel pressure immidiately

Idle - 20 ish, throttle up - falling to 5-10 and huge missfire with popping sounds from everywhere

took me a minute to close a return line, pressure 60

next minute again with return open, pressure is still 20-ish , but now when i revv it up , it goes up to 30 and car sounds good.

What i mean, that there is a very straight correlation between engine temperature and fuel pressure behaviour. Thats why it was so hard for me to find where the problem was and thats why i thought its crank sensors. (now they are new)

What does it say? FPR or pump?

Thanks

 

I recall your inquiry on my post about a similar running problem on my 92. First thing I'd say is fill the gas tank up, and see if it changes. The other idea i have is, and correct if I'm wrong, are there differences between fuel pressure readings when the car is still versus moving ?

 

When was the fuel filter last changed?

Doug

 

Thats for sure not the fuel level, as tank was 1/2 full , but i can feel it up even more. I cant verify that, i have liquid gauge right on the feed line, cant check it while driving =/

 

literally 20 miles ago, and year ago i was fixing evap system and tank, intank filter and the rest did look good.

 

The fuel pressure regulator should be kept constant between 35-45lbs. The fuel pump delivers approximately 31.7gal @43.5psi (120l/min @ 3 Bar).
Assuming all the fuel in the tank is of recant freshness and doesn't look like orange juice and smell like varnish. What you are describing is a failing fuel pump, fuel starvation -clogged filters or an internal leak in the fuel system - inside the tank or the regulator is leaking. At the moment I would rule out any bed sensor inputs to the fuel or the ignition ECU. Do you have any codes stored on the center console message display?

The easiest test that could be done before you go further:
Pull off the vacuum hose from the fuel pressure regulator and check for raw fuel in the hose or dripping out of the regulator.
The other test is pulling off the the fuel supply hose from the fuel rail and extend it with some hose into a container large enough to hold fuel. Then,hot wire the pump at the connector at the EVAP loss flange on top of the tank or at the fuel pump relay, behind the hockey puck support on the right hand side next to the support. There should be a significant fuel flow come out of the hose with pump energized. Do the math to come up with a fraction of amount over time.

WARNING!
ANY TIME YOU DO WORK WITH FUEL AND ENERGY SAFETY IS OF HIGH PRIORY. DO THIS TEST AT YOUR OWN RISK AND IN A VERY WELL VENTILATED AREA AND KEEP ANY SOURCE OF IGNITION AWAY. HAVE A FIRE EXTINGUISHER NEAR BY.

 

Thanks!
Let me quickly get through some additional points you mentioned

1. Fuel is fresh and clean ( i was there when fixed evap flange)
2. fuel filter is new
3. no leak in fuel lines - it even holds pressure as it is
4. No errors and all sensors either new, or checked
5. no fuel from FPR vacuum spigot