Fuel Pump Noise Pitch?

RonnieT · July 21, 2009

Have a 1999 Sonoma, Auto, Ex cab. 2.2 , 140,000 miles, regular maintenance nothing out of the ordinary, changed trans. about 2 years ago.

Has had a hard start situation for sometime now, hot or cold engine , hot or cold days.

A few months ago I did the Fuel test pressure as per book and it fell within specs.

So I have just been driving it thinking maybe it will quit and will know what it is?

In the past few weeks I have noticed that the fuel pump while driving or idling will really speed up in rpms it sounds like.

and then after a few seconds of that it will slow to normal sound again.

and like clock work or on a timer it will do so again, never changing the rpm of the engine but in intense whine within in the pump.

seems to still drive fine.

I have been told it is the oil pressure sending unit? I know this is tied to the pump to close the starting circuit but it seems to have some extra voltage to make it speed up?

As always the best way it starts is to allow the pump to click off after turning on the key, it does not show any more pressure that it does before the key it on but seems to turn over less times this way.

It also seems to miss a few seconds after starting like it need to belch , cough and clean out just a little.

Thanks

Ron