Since there's no specific expedition section and it's the same engine/chassis, I figured I'd post this here. I have a 2002 expedition. 4WD 5.4. It's losing fuel pressure when it sits. Sometimes quickly, sometime it takes a while. For instance, the other day I took it to pick up some parts and while I was in oreiley it lost all the fuel pressure in the rail. Had to cycle the key about 15 times to get pressure back and then it started. It runs fine once it gets going. Once I got it home I parked it in my driveway, which is on a decent incline, with the front end angled downhill, and let it sit for about 2 days.
The next time I tried to start it, it worked fine. So the next time I parked it uphill thinking maybe having it downhill kept the fuel in the rail. Sure enough, I tried to start it today and had no fuel pressure. Cycled the key about 15-20 times, finally got fuel pressure, and it fired right up. So I went about my diagnostic work and here's what I got:
Fuel pressure with engine idling and vacuume line attached to regulator- 30psi
Fuel pressure with engine idling and vacuume line off of regulator- 40psi
Using a hand vacuume pump attached to the regulator:
No vacuume applied- 40psi
Vacuume applied- pressure drops as vacuume is applied and falls to a lower limit of 30psi.
Because these are the same numbers as above, and because the drop in fuel pressure was gradual as vacuume was increased manually, this leads me to believe the regulator is fine.
I also believe the fuel pump, itself, is fine because once it's running, it doesn't give any drivability issues.
So now I'm down to figuring out whether it's a leaking injector or a bad check valve in the pump. I'm leaning more toward the check valve, but it seems like if that were the issue it would be a more constant and consistent issue, rather than in intermittent one. I left the fuel pressure gauge on the rail after I shut the engine off the last time and waited 5 min and it held pressure at about 37psi. I had to go somewhere and when I got home about an hour and a half later, the gauge was back down to 0. I'm going to run this test again and see exactly how long it takes for the pressure to start dropping, but can anyone give me a good way to check for leaking injectors?
The next time I tried to start it, it worked fine. So the next time I parked it uphill thinking maybe having it downhill kept the fuel in the rail. Sure enough, I tried to start it today and had no fuel pressure. Cycled the key about 15-20 times, finally got fuel pressure, and it fired right up. So I went about my diagnostic work and here's what I got:
Fuel pressure with engine idling and vacuume line attached to regulator- 30psi
Fuel pressure with engine idling and vacuume line off of regulator- 40psi
Using a hand vacuume pump attached to the regulator:
No vacuume applied- 40psi
Vacuume applied- pressure drops as vacuume is applied and falls to a lower limit of 30psi.
Because these are the same numbers as above, and because the drop in fuel pressure was gradual as vacuume was increased manually, this leads me to believe the regulator is fine.
I also believe the fuel pump, itself, is fine because once it's running, it doesn't give any drivability issues.
So now I'm down to figuring out whether it's a leaking injector or a bad check valve in the pump. I'm leaning more toward the check valve, but it seems like if that were the issue it would be a more constant and consistent issue, rather than in intermittent one. I left the fuel pressure gauge on the rail after I shut the engine off the last time and waited 5 min and it held pressure at about 37psi. I had to go somewhere and when I got home about an hour and a half later, the gauge was back down to 0. I'm going to run this test again and see exactly how long it takes for the pressure to start dropping, but can anyone give me a good way to check for leaking injectors?
