Injector problem???

[Timberline]

I need some thoughts on my truck.

I was cruising about 85mph (running with traffic) with the tach at 2300-2500rpm and I started to hear a higher pitched clatter (similar to a lifter noise) that would come and go it would do it for maybe 10-20 seconds and instantly quit and sometimes for only 1-5 seconds. It would come and go as if it were triggered electronically. When the new sound would hit the truck would surge slightly.
The only place that I could get the sound to repeat itself was at the 85mph speed. I tried to run the truck in a lower gear at 50 mph at 2500 but couldn't get it to repeat.

Is this an injector problem or.....???

Let me know your thoughts.
Thanks in advance.

[Jim Brzozowski]

If I'm remembering correctly, your pilot injection shuts off at 2400 rpm.

[More Power]

SoTx may be on the right track. The engine rattle produced when pilot injection drops out is both RPM and pedal position (fueling) dependent. You probably aren't into the pedal as much in a lower gear, so the pilot injection issue isn't as apparent.

MP

[Timberline]

That makes sense. The truck is running flawlessly and I have not heard that particular sound before.

I did drop by the dealership and let them check for codes and the only code that came up was low fuel pressure and I am about due to change the fuel filter which they felt might possibly be the cause of that code. I had a fuel filter setting on the shelf ready to put in, which I have done. I will have the truck back on the road this weekend with a load behind it and will see if I can repeat the noise.

Thanks for your input.