Which Fuel Pump? 😬

[TheShadow]

Hey all,

I'm new to the site. I just bought a 2005 3.2 Quattro and I'm having an issue where my fuel is draining back to the tank super quick when I park. I can't use the push button start because it takes a while to crank. I have to turn the key to get the fuel pump going and then she starts right away.

My question is, can one replace only the fuel regulator valve or do I have to replace the whole high pressure fuel pump? I am having a hard time finding the part for just the valve.

Best I can find is that it's an "N276" valve. I'd rather not have to pay another $250 for the whole pump assembly.

[SinCityA6]

When you open the driver door after it has been sitting for a bit, do you hear the fuel pump priming the system?


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[TheShadow]

It's way more faint than on my VW, but I do. Is that the pump in the tank priming the system?

[SinCityA6]

It's way more faint than on my VW, but I do. Is that the pump in the tank priming the system?

From my understanding, yes. The low pressure fuel pump in the tank primes the system and then the high pressure pump in the engine bay feeds the system once started.
Mine is very prominent when opening the door. If yours is barely audible, there may be your issue. If the pump is not priming the system properly, that would explain the longer than normal crank time.


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[TheShadow]

Thanks for the reply.

Sorry to take a while to respond. I finally got my VCDS scanner though.

So my rail pressure stays steady after start up at around 4.80 to 5.00 bars at operating temp. When I turn off the engine though, from what I understand, pressure should actually increase due to heat sink.

My pressure actually drops at a little more than .01 bars per second though. I'm thinking that is pretty telling of the fuel pressure regulator. I've heard the injectors can leak into the head sometimes too, but wouldn't that cause a really rich mixture upon starting from extra fuel being in the cylinder?

Any other thoughts about causes?

[95blkmax]

Thanks for the reply.

Sorry to take a while to respond. I finally got my VCDS scanner though.

So my rail pressure stays steady after start up at around 4.80 to 5.00 bars at operating temp. When I turn off the engine though, from what I understand, pressure should actually increase due to heat sink.

My pressure actually drops at a little more than .01 bars per second though. I'm thinking that is pretty telling of the fuel pressure regulator. I've heard the injectors can leak into the head sometimes too, but wouldn't that cause a really rich mixture upon starting from extra fuel being in the cylinder?

Any other thoughts about causes?

1- Pressure should momentarily increase due to heat sink if the engine is already at operating temp. If you're looking for that condition on a cold engine, it's not going to happen.
2- Yes! if you had a leaky injector when engine is off, it would certainly leak with full pressure behind it from the engine being on, so yes you would be rather rich on one bank (but keep in mind, if it's minor enough you will not see a code pop up from a rich condition the richness is still within the parameters of a given RPM)
3- Do you have any codes come up at all?

[TheShadow]

1- Pressure should momentarily increase due to heat sink if the engine is already at operating temp. If you're looking for that condition on a cold engine, it's not going to happen.
2- Yes! if you had a leaky injector when engine is off, it would certainly leak with full pressure behind it from the engine being on, so yes you would be rather rich on one bank (but keep in mind, if it's minor enough you will not see a code pop up from a rich condition the richness is still within the parameters of a given RPM)
3- Do you have any codes come up at all?

Thanks for the info. Unfortunately, sort of, there are no codes at all for anything. Do you know what in VCDS might tell me if it is running rich on startup?

I will probably just end up getting a new high pressure pump but if it's easy enough to do some more diagnostics, it's probably worth it.