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  #1  
Old 07-11-2015, 08:48 AM
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Default Fuel pressure drop.

At moment I'm trying to figure out why I'm losing fuel pressure once engine bay heats up(10-15 min driving)It's only small decrease 5-6 psi but enough to change Afr.
Plus doesn't hold fuel pressure after priming system.just drops to zero quickly. But car starts fine.
I've only just ran new fuel lines,injectors, rails, fuel pressure reg, fuel pump, fuel filter.
There's no fuel leaking anywhere. Doesn't sound like any vacuum leaks and manifold pressure looks about right.
I've changed pump back to old walbro. Still same.
I'm thinking fuel temperature is getting higher than normal, dropping pressure but that's just a guess. Fuel lines does have aeroflows silcon protection tubing.

Has anyone had this problem before. ???
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Old 07-11-2015, 02:07 PM
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Fuel pump duty cycle is 100% at start. Drop to 33% after like one min later, so fp will drop 6psi accordingly, but not to zero psi! Maybe u have a faulty sensor, or u mount the sensor on the supply line (should be on the return side)?

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Old 07-11-2015, 02:26 PM
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Faulty FPR more than likely - not holding pressure - drifting with temp changes.

What brand is it?

Try another FPR - that's known to be working.
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Old 07-11-2015, 02:48 PM
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doesn't hold pressure when fuel system is primed.
not sure about fuel pump duty cycle. i have 99-00 wrx, i don't think it has fuel pump controller, just relay?
It's brand new 1200 turbosmart reg. I've got sard standard reg ill try tomorrow, it's smaller and perhaps better for my setup.
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Old 07-11-2015, 06:16 PM
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Quote:
Originally Posted by nwt1976 View Post
doesn't hold pressure when fuel system is primed.
not sure about fuel pump duty cycle. i have 99-00 wrx, i don't think it has fuel pump controller, just relay?
It's brand new 1200 turbosmart reg. I've got sard standard reg ill try tomorrow, it's smaller and perhaps better for my setup.
Pre bugeye has no variable speed fuel pump system.......That's just Gordon going off half cocked.........again.

Are you sure you haven't mixed up the FPR inlet & outlet ports?
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Last edited by Rossco; 07-11-2015 at 06:17 PM.
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Old 07-11-2015, 06:40 PM
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Quote:
Originally Posted by s20525xxx View Post
Haha, very funny. I just happened to have fuel pump controller issue on mine, so thats the first thing came to my mind. No idea GC8 runs relay. Sorry, OP.

Ps: so u found out power reading is always the same on dynos yet regardless gear ratio settings, and cross over point is not at 5250rpm if graph is rescaled?
P.s no one cares - & you said it was because of an incorrect final drive ratio = potato.
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Old 07-11-2015, 07:18 PM
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Connected correctly . 1200 turbosmart reg has two inlet ports and return line.

Anyways i've connected sard reg. but not mounted, primed fuel system and bang pressure holds. Ran engine through warn up cycle and base pressure stable. Happy days.

i'll need to do test drive tomorrow.
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Old 07-11-2015, 07:20 PM
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Quote:
Originally Posted by Rossco View Post
P.s no one cares - & you said it was because of an incorrect final drive ratio = potato.
Sorry, for the hijacking, OP. Hopefully u get it fixed soon.

Edit: good to c sard fpr fixed the problem. I had a tomei fpr, it wasn't holding perfectly stable at high boost but sard is.

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Last edited by s20525xxx; 07-11-2015 at 07:25 PM.
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Old 07-11-2015, 07:42 PM
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Quote:
Originally Posted by nwt1976 View Post
Connected correctly . 1200 turbosmart reg has two inlet ports and return line.

Anyways i've connected sard reg. but not mounted, primed fuel system and bang pressure holds. Ran engine through warn up cycle and base pressure stable. Happy days.

i'll need to do test drive tomorrow.
Open up that Turbosmart reg & see if there's any foreign material stuck in it some where, maybe it picked up something from the new lines or rails.
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Old 07-11-2015, 07:44 PM
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Quote:
Originally Posted by s20525xxx View Post
I had a tomei fpr, it wasn't holding perfectly stable at high boost but sard is.
This is because 95% of the Tomei's on the market are Chinese knock offs and hard to tell apart from the legit ones.
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