Chern889 Posted March 27, 2015 Posted March 27, 2015 Just doing some diagnostics on my 05 LGT, trying to chase down a high AF correction at idle. Having a hard time finding good info on fuel pressures! What is it supposed to be at idle? Currently my car is about 40psi on Initial prime(100% duty cycle), then drops to about 36psi while running(100% duty cycle) then drops again to about 32psi when the pump goes down to 33% duty. When you rev it up it will climb with duty increase as well as when into boost. Leaning away from a bad FPR as it holds rock solid for hours after shutdown(and after initial prime). Does this sound like a failing fuel pump to you? I upgraded the wiring to 12GA throughout with no improvement. My current never ending issue is a high AF correction(up to 10%) At idle and slow speed cruising(33% duty cycle) but goes away with rpm increase. I have ruled out an air leak(I think) with pressure/smoke testing, new intercooler, intake/TGV gaskets, new hoses throughout, thorough inlet checking, new PCV valve, new MAF sensor and new front 02 sensor. Any thoughts? Starting to run out of ideas!
spec.B Dream Posted March 27, 2015 Posted March 27, 2015 Sounds like your fuel pressure regulator is generally doing its job. If you pull the vacuum line between the intake manifold and the FPR, you should get about 43 psi (correct me if I'm wrong here). The FPR should the increase and decrease fuel pressure 1:1 with boost and vacuum.
Chern889 Posted March 27, 2015 Author Posted March 27, 2015 Just tried it out, with FPR vac hose OFF I get 46psi (@100% duty) and about 44psi (@33% duty). Pop the hose back on and instantly 32psi(@33% duty)
travrach Posted March 27, 2015 Posted March 27, 2015 Spec is 41-46 with FPR hose off, and 33-38 hooked up.
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