350 psi?

[kingdeer]

I've got a '95 1/2T suburban with 350 TBI. Got SES lite in early October driving down the highway - originally thot it was tranny issues, but apparently not. Finally got around to checking codes - they were 43 and 44. What it has been doing, and continues to do is hesitate or miss - particularly when rpm's drop below 2000 - such as highway driving in OD. So in order to drive it reasonably, I have to drive in 3rd to keep up the RPM's up.

Knock sensor was changed. Plugs are fairly recent. Spark is good. Distributor cap and rotor was just changed. Fuel filter also changed. It's still hesitating, still missing a bit - enough I don't trust it to go anywhere. No SES lites since early october.

So we're wondering if low pressure from fuel pump. It has 147K on it, and I'm not aware of fuel pump ever being changed. I'm not sure what psi reading should be on this engine. Does this sound logical to check, and if so, what should it read?

Thanks in advance,

Rick

[Borguy]

I am far from an expert on this but shouldn't the (electric) fuel pump produce a fairly constant pressure regardless of the rpm's the engine is doing?
So I would think that when there is enough fuel at higher rpm's, there certainly should be enough at low rpm's...

[2000CAYukon]

Fuel pressure specs for TBI is 9 to 13 PSI; although, you need a special tool to read the fuel pressure on a TBI engine.

The tool installs in place of the fuel filter so that you can hook up a fuel pressure gauge.

//2000CAYukon

[kingdeer]

Originally Posted by Borguy

I am far from an expert on this but shouldn't the (electric) fuel pump produce a fairly constant pressure regardless of the rpm's the engine is doing?
So I would think that when there is enough fuel at higher rpm's, there certainly should be enough at low rpm's...

That was my original thought too...and I'm far from an expert - it does miss once in awhile while warming up in the morning - I also notice it worse when idling like at a drive thru while in gear - if I throw it in neutral it settles down, but in gear it'll miss bad.........