Onemoparnut

I went tonight to look at a truck he wants to buy. The truck is a 97 3500 drw 4x4 auto. when the truck is idking there is a buzzing sound that cycles on and off every few seconds. Sounds like it is comming from the injection pump. Is this normal?

funcruise

Wouldent be the compressor for the air conditioning cycling on and off would it?

Hercules

Does it quit after cycling several times? Does it occur after start up, or, does it do it all the time after the engines at operating temp? If it's only for a short time after start up, cycling on and off makes me think of the grid preheater in the intake. I've never heard one make noise before and would think it could only make noise if it's shorting somehow, but, the current draw from those are pretty large and that might be effecting something else causing the noise. If you look at the volt meter on the dash, it will drop every time the grid heater turns on, and return back to 14+ volts when it cycles off just after start up. It may be something to watch to see if the noise comes and goes when the volt meter indicates a voltage drop every time the grid heater cycles and that may lead you to what's causing the noise. Especially since not much in the engine bay uses electricity on a 12 valve.

Onemoparnut

i didn not notice the volt gauge moving but I was not inside the truck I was mostly under the hood. It ran about 10 minutes and was still making the noise when we shut it down. it is very quiet and hardly noticable.

Hercules

So, it made the noise with the engine off, too? Was the key in the on position w/engine off, or, was it literally in the off position and ready to be pulled out?

Onemoparnut

No it only made the noise when the engine was running