Fuel Pressure / Check Valve
11-15-2015, 02:56 AM
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Fuel Pressure / Check Valve
I have a question about fuel pressure and the check valve, I have a pressure gauge on my fuel rail, when the car is turned off after running it holds pressure for some period of time at the 50psi area. However after a period of time, the pressure drops back to zero psi.
Should the pressure hold at 50psi? Or is it normal for it to drop, and if so how long should it hold pressure for prior to dropping?
After a quick run, about 5 mins, I came back home. Shut it off, checkedgauge it was at 54psi.....is climbed to nearly 60psi in the first 2 minutes or so after it was shut off, and has held there for about 5 minutes so far......
Should the pressure hold at 50psi? Or is it normal for it to drop, and if so how long should it hold pressure for prior to dropping?
After a quick run, about 5 mins, I came back home. Shut it off, checkedgauge it was at 54psi.....is climbed to nearly 60psi in the first 2 minutes or so after it was shut off, and has held there for about 5 minutes so far......
11-15-2015, 07:44 AM
#2
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To hold fuel pressure you need tightness in the fuel pressure regulator and injectors that are well sealed. There is no reason for fuel pressure to increase other than heat soak that may conceivably increase fuel pressure a tad after shutting down.
As to how long fuel pressure should hold I do not know a definitive answer to that one but I would expect some pressure decay over a period of days. If the pressure is holding starting should be a doddle, if there is significant pressure decay then it will take a second or two to pressurise the fuel rail after turning the key.
Perhaps other listers can be a bit more definitive about the pressure decay situation.
Rgds
Fred
As to how long fuel pressure should hold I do not know a definitive answer to that one but I would expect some pressure decay over a period of days. If the pressure is holding starting should be a doddle, if there is significant pressure decay then it will take a second or two to pressurise the fuel rail after turning the key.
Perhaps other listers can be a bit more definitive about the pressure decay situation.
Rgds
Fred
Last edited by FredR; 11-15-2015 at 10:52 AM.
11-15-2015, 11:14 AM
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I normally see it drop on my cars after a few hours or overnight.
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928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."