A couple days ago I went to change the battery in my is350 with what seemed to be a battery with a low charge, we jump started to see if it would charge. Shortly after the car started I noticed a new strange sound from the engine that I have not heard before at the top of the engine near the throttle body. I am used to the normal ticking from the injectors, this kind of sounded like that but noticeably louder. It comes and goes at idle and seems to go away with some rpms. Any idea what it could be?

 

It's normal, it's the direct injection. Just noisy by nature.

 

Yes I am familiar with the noise from the direct injection, the concern is that this noise sounds different than the normal noise from the injectors. I would just like to address the noise if possible to prevent any problems that may come up.

 

There is high pressure fuel pump on the right side of the car mounted to the valvetrain cover which makes the ticking noise. The sound is similar to diesel engine fuelpressure pumps, but it's not that loud. It is normal.

 

^And to add to that, that pump is right below the TB; so the noise right there would be louder than normal because of close proximity.

 

So it seems the noise is right around where that pump is so it is likely the pump. I had never heard this noise before and it bothered me. Is it normal for the fuel pump to be intermittently noisy? I just don't want to ignore this so easily it if what I heard is a symptom of a problem.

 

^Yes. You won't hear the thing upon initial start-up. It'll start making its normal noise after 15-30 seconds after start-up (if just letting it idle).