# residual fuel pressure problem on digifant mk2 !



## jogtx16v (Dec 15, 2007)

I have make some test with fuel pressure gauge .. the car is jetta 92 digi 2
36 psi with the engine run ... its ok ! 
44 psi with the engine run and FPR vaccum disconnect ... its ok ! 

the problem :
and the last test for residual pressure of 29 psi after tje engine is off its not ok 
when a shut off the engine the fuel pressure go at 0 psi in 5 sec.








and when I put the key at run position .. the pressure go at 36 psi and after 5 sec it return to 0 psi








anybody can help me please


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## Schaef (Jan 26, 2008)

*Re: residual fuel pressure problem on digifant mk2 ! (jogtx16v)*

Leaky injectors?


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## jogtx16v (Dec 15, 2007)

*Re: residual fuel pressure problem on digifant mk2 ! (Schaef)*

no leak .. the fuel rail is on a fully rebuilt 16v digifant 2


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## Fat Rabbit (Nov 18, 2001)

*Re: residual fuel pressure problem on digifant mk2 ! (jogtx16v)*

Since you can't maintain residual pressure, fuel has to be leaking somewhere. Likely choices are: one or more leaky injectors, the check valve at the main fuel pump, or the check valve at the fuel pressure regulator. On Digifant cars neither the check valve at the pump nor the check valve at the FPR are individually replaceable. FR


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## jogtx16v (Dec 15, 2007)

*Re: residual fuel pressure problem on digifant mk2 ! (Fat Rabbit)*

ok ! thank alot 
and where is the main fuel pump ? in tank or under car ?


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## chois (May 12, 2000)

Under the car in front of the right rear wheel.


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## Fat Rabbit (Nov 18, 2001)

*Re: residual fuel pressure problem on digifant mk2 ! (jogtx16v)*

The main (sometimes called "in-line") fuel pump is under the car in a small black box (fuel reservoir) on the passenger side just ahead of the passenger side rear axle. The fuel pressure regulator is at the passenger side end of the fuel rail. The regulator is held on with two bolts or screws and uses the same "O" ring gasket that the injectors use where it presses into the fuel rail. Both the FPR and the FP are rather expensive new. 
Since you apparently have a fuel pressure gauge you could attach it to the fuel supply line at the fuel rail, run up the fuel pump to pressurize the line and see how the pressure holds. That would verify the fuel pump check valve. To test the injectors you could pull the fuel rail and with the injectors still clipped-in to the fuel rail pressurize the fuel system by bypassing the pump relay and look for leaks from the injectors.
Keep in mind that you will be working around gasoline so work outside away from buildings and take precautions to avoid flames and sparks. FR


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