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Old 04-06-2010, 09:25 PM   #1
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Fuel pressure

Hi guys,

Just wanting to know what fuel pressure the 2.5 986 boxster should have at the fuel rail?

Thanks,
Sam
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Old 04-07-2010, 03:36 AM   #2
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Quote:
Originally Posted by sparker
Hi guys,

Just wanting to know what fuel pressure the 2.5 986 boxster should have at the fuel rail?

Thanks,
Sam
The manual info on Cannell (although it's dated) shows 3.3-3.8 bar (+/- 0.2 bar) for fuel pressure at the rail and fuel flow should be around 850 cubic cm in 30 secs.

Also, the fuel rail caps are not reusable and need to be replaced with new ones.

Regards,
paul...
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Old 04-07-2010, 08:59 PM   #3
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Wow - that high? I wax expecting 40-45psi tops!

Anyone running a fuel pressure gaugethat can confirm these figures?
Sam
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Old 04-08-2010, 10:02 AM   #4
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Quote:
Originally Posted by sparker
Wow - that high? I wax expecting 40-45psi tops!

Anyone running a fuel pressure gaugethat can confirm these figures?
Sam
Yes and yes. And you do not need to replace the cap if you can find the small seal that goes inside it.................
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Last edited by JFP in PA; 04-08-2010 at 10:04 AM.
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Old 04-09-2010, 04:02 AM   #5
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Originally Posted by JFP in PA
Yes and yes. And you do not need to replace the cap if you can find the small seal that goes inside it.................
Do you mean that I would need to "catch" the seal from dropping if I took off rail cap off? This is good to know even though I'm not planning on checking my fuel pressure/volume.

To me, it's a waste of time buying a fuel pressure gauge that's not accurate enough to do an injector balance test and only use it to check press/vol. Gauges I can afford are things like Actron which are only +/- 2psi mid-scale (I called the company), and I'm sure you have something that's +/- 1psi full-scale (and made in US).

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paul...
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Old 04-09-2010, 05:48 AM   #6
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Quote:
Originally Posted by paulv
Do you mean that I would need to "catch" the seal from dropping if I took off rail cap off? This is good to know even though I'm not planning on checking my fuel pressure/volume.

To me, it's a waste of time buying a fuel pressure gauge that's not accurate enough to do an injector balance test and only use it to check press/vol. Gauges I can afford are things like Actron which are only +/- 2psi mid-scale (I called the company), and I'm sure you have something that's +/- 1psi full-scale (and made in US).

Regards,
paul...

No, I mean you need to pop the seal out of the cap and insert a new one. They have a bad tendancy to not reseal......

You really do not need +/- 1PSIG accuracy; most of the time, you either have pressure within range, or little to no pressure at all. I think the unit we use is also +/- 2 PSIG, and it is just fine for this type of test.
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Old 04-09-2010, 06:28 AM   #7
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The fuel pressure spec is not 3.3-3.8 Bar.
On the early cars, before the introduction of the returnless fuel systems, there are two measurements a static measurement with no engine vacuum (engine not running, fuel pump activated) that is 3.8 +/- 0.2 Bar and the second measurement with the engine idling (vacuum to the FPR) is 3.3 Bar +/- 0.2 Bar. These measurements test both the pump and the regulator.


-Todd

Quote:
Originally Posted by paulv
The manual info on Cannell (although it's dated) shows 3.3-3.8 bar (+/- 0.2 bar) for fuel pressure at the rail and fuel flow should be around 850 cubic cm in 30 secs.

Also, the fuel rail caps are not reusable and need to be replaced with new ones.

Regards,
paul...
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Old 04-09-2010, 08:26 AM   #8
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Originally Posted by tholyoak
The fuel pressure spec is not 3.3-3.8 Bar.
On the early cars, before the introduction of the returnless fuel systems, there are two measurements a static measurement with no engine vacuum (engine not running, fuel pump activated) that is 3.8 +/- 0.2 Bar and the second measurement with the engine idling (vacuum to the FPR) is 3.3 Bar +/- 0.2 Bar. These measurements test both the pump and the regulator.


-Todd
Yup, that's right -- I did a lousy job of copying this from the manual -- sorry......

Regards,
paul...
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Old 04-09-2010, 02:29 PM   #9
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Ok, so closer to 3.3 than 3.8 bar? That makes more sense I guess.

Also, about the rail you guys are talking about, is there no where else I could tee into the fuel system? No rubber fuel lines that are easily taken from?

Sam
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Old 04-13-2010, 08:25 AM   #10
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Quote:
Originally Posted by sparker
Ok, so closer to 3.3 than 3.8 bar? That makes more sense I guess.

Also, about the rail you guys are talking about, is there no where else I could tee into the fuel system? No rubber fuel lines that are easily taken from?

Sam
Not really, no.
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Old 04-13-2010, 05:40 PM   #11
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Doesn't have to be a rubber line, are there any threaded sections that I can bolt a T piece into?

Regards,
Sam
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