Noisy auxiliary fuel pump

A couple of weeks ago I noticed a sound I hadn't noticed before when I started my tiguan - 2.0 tdi engine cbab.

Initially, I thought nothing of it, and put it down to the usual diesel engine noises.

The noise in question, was an electric pump type sound. Continuous, with the same frequency, irrespective of engine speed. I could only hear the noise from inside the cabin, though when outside the vehicle, it might have been drowned out by the usual diesel clatter.

Furthermore, I noticed that the noise would start roughly 3-4 seconds after starting the engine.

The sound itself, when sat in the vehicle, appeared to be coming from the front of the vehicle.

Once I had decided that there definitely was an issue which needed to be investigated, I stuck my head under the bonnet when the vehicle was running, nothing other than diesel clatter appeared to be present.

So I hit the internet, and some of the things mentioned were water pump, both the main mechanically driven item and the auxiliary coolant pump which is electrically driven... the radiator fan(s)... cam belt cover rubbing... cam belt riding over tensioner shoulder... high pressure pump...turbo pipework... egr... and so on and so forth. Needless to say that it gave me a few pointers, but I really needed to be a bit narrower in my search.

So, I decided to try and find the general location of the sound within the engine bay.

So, with the engine running, being very careful of any moving parts, and with the top engine cover removed I listened within various areas of the engine bay. I believed that I could just about hear the sound, but it was difficult over the usual diesel sounds, and it seemed to be (standing at the front of the vehicle, facing towards the rear) coming from the left side of the engine, around the general area of the cam belt, high pressure pump etc.

So using a long screwdriver as a stethascope, I proceeded to see if I could isolate the sound. Bingo!!

The sound was coming from a part which I had no idea what it was, but it was between the fuel filter and high pressure pump.

A bit of google-fu and it turned out to be the auxiliary fuel pump.

Once I knew that, I did a bit more googling, and various posts seemed to state that it should be changed and it cured the sound. Some stated that the sound was still present when changed... one said that his main dealer tech said to ignore it as some are just noisy and there's no need to worry... one said that he changed the fuel filter, and this sorted the noisy pump...

So, I thought that I would change the filter first, and if it didn't cure the noisy pump, then I would change the pump. I didn't want to just leave it, as it definitely was a new noise, and I didn't want to risk failure and potential damage to the high pressure pump and/or injectors.

Anyway, I changed the filter this evening, primed the system using vcds, started her up... and no more noise! Yay!

Yooj