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Discussion Starter · #1 ·
I'm trying to troubleshoot a fuel issue and need some information. I have a pressure gauge hooked in line between the fuel inlet hose and the fuel pressure regulator. If I keep the pressure relief valve on the gauge depressed when I energize the fuel pump I get no pressure at all and no fuel going through the discharge hose coming off the pressure relief valve. If I don't depress the pressure relief valve when I energize the pump I do get a pressure that is up to specs after a few cycles. When I then push the relief valve I do get a shot of fuel than nothing else. My thinking is, if I have the discharge valve depressed while the pump is energized shouldn't I get a constant flow of fuel out of the discharge valve?

I know this is not a normal test procedure but I think it will help me.

2000 Beetle 2.0 Auto trans.
 

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Hey, I agree with your logic; as a matter of fact, the factory "volume" fuel pump test... uses the valve to pump fuel into a graduated cylinder. This volume test; is to see if the pump is capable of delivering enough fuel to the engine; sometimes, the fuel pressure can be good but the volume is not, causing fuel starvation.

I would stick with the factory testing procedures and fuel pressure specs; from what you are saying, i would say it is possible the pump is bad. However, confirm using the manual; here is a link below, to the testing procedures. (hit "next"; to go to the other pages showing all the steps)

http://workshop-manuals.com/volkswa...essure_vacuum_and_temperature_specifications/
 

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Discussion Starter · #3 ·
I'm trying to understand the fuel pump a little better. Just out of curiosity, If I was to undo the fuel inlet hose just before the regulator. Would the fuel pump run constantly if it was energized? What shuts the pump off once it has reached the proper pressure before the engine starts?

I can't do a full system test as I would like to because I can't hook my gauge near the fuel filter like the manual says to do. I am trying to find a different gauge but no luck so far.
 

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Any auto parts store; should rent you one for free. I used the cheap one from harbor freight with good results:

http://t.harborfreight.com/fuel-injection-pump-tester-92699.html?utm_referrer=direct/not provided

I just put the gauge right before the fuel pressure regulator; testing there, was good enough to confirm my pressure and confirmed my pump was bad. The manual; attempts to isolate each section, to confirm possible restriction in the system (e.g. Before fuel filter etc.). You could replace the fuel filter first and see if. It makes a difference.
 

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Discussion Starter · #5 ·
The gauge that I get from the auto parts store doesn't have the proper connector that I need to do what I want it to do but I may try the one mentioned.

I still need to know what shuts the pump off after it reaches pressure and the engine is not running. I assume it does not run constantly.
 

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Hey, good question. Maybe these would help: here is a VW self study program; that goes over the OBD II system and shows schematics of each system (including the fuel system). On the early VW New Beetle; it is a return based system (two lines) but later models, seem to have been upgraded to a returnless (one line).

http://vwts.ru/injector/obdii_eng.pdf

Fuel system schematic:

http://workshop-manuals.com/volkswa...agram_information_and_instructions/page_2696/

This video; has some good info:

https://www.youtube.com/watch?v=Ei31evIvRcU
 
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