HiWind

those who've have problems with the FRP ... any input highly valued as ever!

1. did anyone attach a fuel pressure gauge to the test point on the left bank fuel rail right near cylinder 1?
2. did you notice low pressure or varying pressure?

I did that today and while pressure is 4bar with engine off, while running the guage needle is wavering/shaking feverishly alsmot as if the pressure drops as each injector fires. Experiencing the rough start/fuel cutoff and then return sort of actions. Gauge is NOT fluid filled and this obviosuly does affect stability but it shouldn't be fluctuating/shaking as much as it is I think. Am going to check with super expensive one tomorrow tho just to ensure its not the gauge itself. Driving/irregular fuel flow feeling is real tho.

No fuel in FPR vacuum pipe (as described by thread starter) tho and fuel pump seems happy, fuel filter 1000km old and pipes not bulging (but will check for undue hardness etc..) - oddly only started today and car ran fine last week but has been sitting a bit too much of late. New oils/filters and oil tank breather can done last week (which involved removing air cleaner oil breather pipe and throttle body oil breather pipe and routing these to catch can with breather filter on top.



this is on a 924 but the 964 pressure test nut (with little steel ball inside) is just like the one shown here to left of the gauge.

Rocket Rob

I bought a fuel pressure gauge to diagnose a low power symptom but by the time I had it, the car began running well again. So I never got around to testing the pressure. I plan on putting the cars on the road again as our winter weather seems to be over so maybe I can test it soon.

If you are seeing the fuel pressure drop after the pump is off, then it can be 4 possible causes. A bad fuel pump check valve, a bad fuel pressure regulator, leaky fuel injectors or external leak. The fuel circuit is pretty simple.

Vandit

Hey, sorry I do not have experience testing the fuel pressure on the car's fuel rail or otherwise.

HiWind

Hey Rob & V - no pressure is rock steady 4b after car switched off but flickers between 3-4.5 while car running .... is that normal?

Super90

When mine failed it was pretty obvious. There was fuel leaking out of it.




The car ran poorly, but most specifically, when the fuel level was very low.

HiWind

ps - my thinking today is that the pressure gauge at the end of the fuel rail is likely to be flickering around as its the tail end of the whole system .. would likely be much better mounted above the FPR where the pressure would likely be steadier.

-nick

Here are some numbers when I checked mine a few years ago. I don't recall the fuel pressure flickering, pretty sure that it was fairly steady. This is with Wong chip ignition maps (vacuum is probably a little different than stock) and no load

Cold:
Idle rpm, ~950, 50psi fuel, 15” vac
2000rpm, 47psi fuel, 21” vac
3000rpm, 46psi, 22” vac,
4000rpm, 46psi, 22” vac
55psi @idle w/o vacuum on FPR, same with engine not running and fuel pump only, jumpered dme relay

HiWind

thanks Nick! Did you test pressure with car running on left bank fuel rail spot near the distribs?

-nick

^ Yes, exactly!