After I installed an under-hood fuel pressure gauge, abou two months ago, I adjusted the fuel pressure regulator so the gauge would show 28 psi. Yesterday, halfway through a longish trip, I noticed that the gauge showed 24 psi. Thirty miles later it showed 20, but when I got home, 5 miles further down the road, it showed 29. Despite these fluctuations, I noticed no change in performance. This morning I checked a see-through filter I have between the tank and the pump, and there are a few grains of debris in there, but not enough to obstruct the filter. I started the car. Pump sounds normal. Fuel runs clear through filter - no air bubbles. Gauge showed 29-30 at start-up and fell back to 24 after warm-up. I tapped the gauge with the handle of a screwdriver..., no change. Tapped the pressure regulator..., no change. Question 1: Can a D-jet function normally with 20-24 psi? Question 2: Could fluctuating pressure like this indicate a fuel pump on its way to failure, even though it sounds healthy? Question 3: Could this be a malfunctioning pressure regulator, and should I change that first, before I tackle the fuel pump? BTW, the main filter is basically new and was put in at he same time I put in the see-through filter. At that time I also flushed the fuel pump.
Bob S.