Author Topic: Forester XT won't start when hot  (Read 439 times)

November 24, 2017, 09:43:03 AM
Read 439 times


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Thought I'd post this up in case someone else experienced this problem.

For a while now my Foz has been giving issues when trying to start whilst hot i.e. engine at temp; shut down the engine and leave it for a while; then when I tried to start it up it would just crank but not even try to fire up. It seemed to be characterised by a funny sound from the left bank like "lugluglug" before shutting down and the throttle response was odd, not bad just a bit unpredictable.

Anyway, after much google mechanicing, I thought it may be the fuel pressure regulator going bad, which is apparently pretty rare. So off I went to WHPerformance to diagnose it.

OK, a little about how a FPR (fuel pressure regulator) works. It's job is to maintain a static fuel pressure when out of boost and raises the pressure on a 1-1 ratio with the boost i.e. if you boost to 1bar, you will get idle pressure of 3bar plus 1bar, making the pressure 4bar.

We hooked up Wayne's fuel pressure gauge and turned on the ignition > Fuel pressure went up to 3.5bar. Bear in mind, the normal idle pressure of 3bar, so it was a little high but not too bad. So I fired up the engine and just hear Wayne shout "Kill it, Kill it!!". Thinking WTF, I shut off and go round the front... Fuel pressure shot up to over 7bar when I blipped the throttle and blew the gauge's hose off!!

So in summary, the FPR was sticking and causing extremely high fuel pressure, basically flooding the spark. It only happened when the engine was hot (who knows why). So many people out there replaced part after part hunting this issue down so hope this helps someone out.
« Last Edit: November 24, 2017, 09:44:42 AM by Garrsie »
2006 Forester XT, Wiseco pistons, 18"Koya lightweight wheels, Bridgestone re002, Custom 20g turbo, STi IC, 76mm exhaust, Walbro 255, Custom turbo inlet, intake spacers, Gizmo Boost Controller, TGV deletes. BC RA Coilies, Brembo big Calipers, PB RS Discs, Coolboost WMI, Intent Performance Tuned

November 27, 2017, 06:08:40 AM
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2007 2.5XT Manual (and boy did I have to search for manual one)