Fuel Tank - Limp Mode

[Legoman1985]

So this morning I filled up my tank and started to drive. My car then went into limp mode...something similar happened a few weeks ago so I changed my fuel filter and checked the cam follower (which thankfully is all good).
After a few days my car went back to normal, and it wasn't until I filled up today that I'm thinking there's a faulty sensor in my fuel system somewhere? Anyone else had such problems at all? I drive a 2007 Mk 5 GTI
Thanks

[mjmallia]

I would be plugging it into VCDS to see what fault codes are flagged.

Checked for leaks/ along the system?

If could be a cracked Fuel Pressure Regulator Valve (N276)........the big one above the HPFP as they can crack in half.  Usually caused by people pressing too hard on the engine cover in that area, and the connector side applies too much levering force and then CRACK!

Even a hairline crack would mess things up and superglue can be used as a temp fix.

[Legoman1985]

Thanks mjmallia...I shall give that a look. It's strange that it does it when the fuel tank is filled above halfway. It then goes back to normal if I restart the car when it's below half a tank. Never had this before 🤔

[bobby_fodge]

Could it be the fuel level float attached to the intank pump if the issue only appears when the tank is a certain level full?

Not sure how you'd test that without inspecting the existing one or swapping in a known good one.

Access is easy, under the rear off side seat base.

[Legoman1985]

So...it turns out that the HPFP was on its way out as during my service they found fuel in my oik. They've checked the cylinders for leaks etc and they are all good. They didn't know the exact reason for the weirdnesswhen filled over halfway other than maybe a fuel pressure issue. I've had it for a week now and no faults or issues...Including when on a full tank of fuel