High pressure fuel regulator relay location?

[RPMtech147]

09 A4 CAEB

My alldata wiring diagram doesn't give me the relay location. It feeds fuse #5 in the engine (plenum) fuse box. Not getting 12 volts to the fuse. When I apply 12V the hpfp stops squealing. (Had this issue for months, just haven't had time to chase it)

Anyone have the relay location in the engine fuse box?

[RPMtech147]

I believe its the big main relay, A - Engine Component Power Supply Relay -J757- (2) (3) Can anyone confirm?

Whats odd is the test plan makes no reference of checking this relay but the factory Audi block diagram and the Alldata wiring diagrams show this relay feeding fuse #5 then off to the regulator valve.

[RPMtech147]

I did confirm this was the correct relay.

Just to add to the archives here, the issue was a really loud squeeling noise coming from the fuel pump and a fault for the regulator valve. The car having 150,000 miles, I just assumed the regulator was bad so Id just replace the entire pump, and while I was in there, and since I had a brand new one, replaced the leaking vac pump. To my surprise replacing the HPFP made no difference in the squeeling noise that was most obvious using a stethoscope on the fuel rail.

After kicking myself for not diagnosing the issue properly, I pulled out my DVOM and started actually checking for power and signal @ the regulator. Signal from the DME is good but no 12V. Of course, when I apply 12 volts to regulator, the noise stops. Once I narrowed down and replaced the relay, obviously this fixed the issue.

I can only guess the loud squeeling noise is caused by the fuel pump going full pressure and hitting some kind of internal pressure relief.

[Smac770]

Wow, really no one else around to answer these kinds of questions?

Yes, battery feeds the J271 relay, which is activated by the J623 when the engine is spinning (cranking,running). The J271 relay feeds a number of devices, including the J757 relay, which is also in the ECM box and also activated by the J623 when the engine is spinning. The J757 with the 2.0T CAEB engine powers only one thing, the fuse 5 in the ECM box which then feeds the N276 HPFP regulator valve, which is selectively grounded by the J623 to control the pumping volume. The J757 powers four devices, iirc, on the 3.0T engine.

[old guy]

Wow, really no one else around to answer these kinds of questions?

Smac770: You really should not be allowed to take a week off from AZ. As you can see, without you it tends to all fall apart

[RPMtech147]

Wow, really no one else around to answer these kinds of questions?

Yes, battery feeds the J271 relay, which is activated by the J623 when the engine is spinning (cranking,running). The J271 relay feeds a number of devices, including the J757 relay, which is also in the ECM box and also activated by the J623 when the engine is spinning. The J757 with the 2.0T CAEB engine powers only one thing, the fuse 5 in the ECM box which then feeds the N276 HPFP regulator valve, which is selectively grounded by the J623 to control the pumping volume. The J757 powers four devices, iirc, on the 3.0T engine.

Good to hear from you Mr Smac. I've been sucked into the darker, darkside with my Late 2010's Range Rover so I haven't been on the forums much. Funny enough I had issues with my own junk lately.

[Smac770]

Yeah, makes for quite a stack to work through when I get back from a trip. Be doing it again in a few weeks. With not as much new to learn it seems these days, it's more of a chore. But still interesting, while I have the free time for it.