2000 Volkswagen Beetle Fuel Pump knocks loudly

Not sure that I can help, but certainly willing to try.

You are positive this is coming from the fuel tank area?

Does the noise ever get louder?

Does it ever increase or decrease in repetition?

When you first turn the key to the on position, before you crank it, does the noise happen as the pump is being energized?

I know some GM have a pulse dampner, not sure on the beetle.

If you have the old one, can you hot wire it to observe any anomolies?
I need to read through my tech software to see if I can pry out something to work with.

I did find a tsb that my be unrelated, but want to share it regardless because I would gather low oil pressure may continue this condition:

Engine - Rattling Noise On Start Up (Normal Condition)

Condition
Camshaft Chain Tensioner(s) or Camshaft Adjuster(s), Rattle or Knocking Noise

Technical Background
The camshaft adjustment is hydraulically actuated and controlled by the engine oil pressure.

If the vehicle has been sitting, with the engine turned off for a period of time, the oil accumulation inside the camshaft adjusters partially bleeds off and the oil flows back into the oil sump.

To ensure an efficient camshaft adjustment after an engine cold start, the oil pressure inside the camshaft adjusters must be built up as quickly as possible.

During this time a slight rattle or knocking noise may be audible.

This noise is normal at engine start and will last until the oil pressure is fully reinstated.

I found another one regard the trunk lid. I want you to open the trunk lid and keep it propped while you see if the noise is still present.

PAul

A defective pump is possible, seriously doubt a bad gas scenario.

I am thinking a restriction a line maybe in the return line. Check and monitor the fuel pressure from start up.
I would do this not only to determine the symptom source, but the reason for the runniblility issue. I would not be surprised if you find the pressure goes out of spec. As it warms up. If I am right, I would pull off the return line at each end and blow compressed air through it, replace the filter and do the same on that line as well as the vent line.

Also on the fuel filter replacement, I would question it. Any time I do a fuel pump, we do the filter. I don't care if it was done the week before. I have seen filters start to plug up very quickly in some cases.

Do you have a fuel pressure gauge?

OEM style:
VAG1318 pressure gauge
Adapter 1318/9
Adapter 1318/17

Aftermarket gauges should work, but you'll need the right adapters.

IF yes, I'll send the procedure.

Maybe I missed it, but I thought it runs, just rough.

Can you get the lines disconnected and blow air through them?
Even if you buy a small compressor, it is something that always comes in handy around the house.

IF there is a restriction, this may be why the pump goes from good to bad.

Another thing I might try is to disconnect the return line and run it into a container and visually see if the volume starts dropping off as it gets worse.

The return line is just returning the fuel that isn't used, so it isn't a problem doing so with any I have worked on.

Hey,
I was talking to the top Monkey around here on your car. DId you replace the pump with a after market pump, If so What brand? Or did you get one from the dealer? With the exception of Delphi, All the other aftermarket ones really have bad track records.

Good.
You may want to give delphi tech support a call at 1-877-go delphi.

LMAO!

I had sat there for about 5 minutes writing it out and kept getting 8 numbers too. I got it from both my supplier and the Delphi website. Finally I just copied and pasted it from the site. I was hoping it worked, but didn't ty it.
. I'm gonna dial it and see what happens.

Sorry. Didn't mean to laugh.

HEH HEH. And you doubted me! HAHA!

When you call the number, keep in mind the menu has changed on December X, 2008.

On the serious side I hope they can give some more technical logic that brings this to a close.

Did you try blowing out the lines?

Look at the fuel rail

9 is the pump
16 is the pressure line

13 is the rail