long standing problem with a truck..

[Nephets]

Okay, we have a chevy silverado, 1995 vintage. 216k on the clock.
the problem we have is that when the fuel tank starts to empty out (roughly 3/8 of a tank left) the truck will have issues staying running. It seriously acts like starts to run rich. Visually watching the two injectors (5.7l V8 TBI

)when its having the problem, it almost appears as though the injectors are wide open. (push the linkage back to open the throttle and at like ~10% it acts like you just shoved the thing to wide open)
So far, we've replaced the fuel pump, fuel pump relay, fuel pressure regulator, fuel filter, map sensor (4x) tps sensor (2x), IAC 3x, and a new PCM. We verified voltage at 13.4v on the fuel pump, (its a pita to take the bed off a truck just to make sure the fuel pump is plugged in). also had the ignition module checked and that came back okay. plugs and wires all appear fine. what i dont get is the fact that at 3/8 of a tank you have an issue, but at a full tank you don't
This is the truck that the gf ran the motor 3qts low. so you can see my concern with fuel dilution problems.

 

[mechtech2]

Those vehicles had problems with the fuel pump 'O' rings. They would leak and I hope you got the improved ones.
You should be throwing engine codes, at this heavy state of fuel injection.
But maybe what you think is too much is normal.
Coolant sensors are a huge factor. If yours is out of range, it may be calling for more fuel because it thinks the engine is still too cold.

 

[Boomer]

Very true about the temp sensor. Had an 83 Cavalier that started to do this with the TB injectors and it was indeed the temp sensor. It died and the car thought it was -80F or some such. New one cured the problem.

 

[eljefino]

Do you have an o2 sensor on each bank of cylinders? Wonder if one side is going lean due to low pressure, air, whatever, flooding out the other side.

Pull & check all the plugs for differing levels of soot?

 

[HyperJinx]

Its sounds like a temp sensor issue but the low tank thing is confusing me.