Hey guys, got a weird problem. I've had my van parked because the engine hesitates when slowing down and until not I haven't had the time to work on it.

Idle pressure is fine, 30 psi with vacuum to the regulator, 40 psi without vacuum. However, when putting the key in the on position, the pressure only goes to around 5-9 psi. Is that normal? We run fuel system cleaner or injector cleaner fairly regularly (about every 6-8 refills).

 

Your '99 should have a 5.4 in it.
I'm not 100% sure if this fuel system works the same as it does on the older trucks but I suspect it is similar and the pump will only run for a second and stop if the starter isn't engaged. So you may have to cycle the key several times to get any pressure.
Does the pressure bleed off at all when you are doing this? If it does that could suggest a leaking injector but that would cause some running problems, does it have running problems?

 

Weak battery or otherwise low voltage to the FP?

 

Ah sorry, it does have the 5.4, my bad. It maintains pressure when of though I haven't tried holding pressure for an extended period. We'll be taking it for a test drive as it's been parked. Again, only just got time to work on it. We didn't know what the issue was (still don't) and didn't want to risk damaging it further or having a part fail while we're out. As for running problems, it's sometimes rough on deceleration.

 

I'll have the battery tested. I just had to clean the terminals and battery posts as it wasn't keeping a charge after being parked. I suspect I was managing to start off the boosting car's battery and running off the alternator. As for the fuel pump, I haven't tested the voltage on it yet. Need to find a way to get to the right cables with the fuel tank still in place. I'm planning on cutting an access panel to the fuel pump next time I drop the tank.

 

The pump access can be cut without removing the tank. I have a couple of pics that accurately shows location that I can send you.

There's a couple of threads on the subject somewhere on here (or another forum).

If you haven't done so already and since it's a '99, you may want to replace the fuel filler hose and vent and that is easier to do with tank dropped. There are a couple of threads on that subject,too.

https://www.ford-trucks.com/forums/6...ller-neck.html