I have a 1994 F150, 302, almost 257,000 miles, original engine, tranny, clutch, and yes....original fuel pumps! I bought the truck brand new back in 1994 so I know this to be true. Anyway, I just tested my fuel pressure at the fuel rail. just turning the key on to let the pumps prime (its a dual tank truck) both the front and the rear pumps pressure up the same to 32-33psi. I start the truck, they each maintain about 32-33psi. if I hit the gas, the front pump will pressure up briefly to about 41-42psi, and then settle back down to around 33psi. If I switch to the rear, do the same thing, rev it up, it will jump up to around 38-39psi, and then settle back down to about 33psi. Does this sound like both pumps are still operating within acceptable ranges? Is the rear a little weak? or is it just the variation from pump to pump, only talking 4psi difference for a brief time when revving up the engine. What are your thoughts? I was thinking of replacing fuel pumps, but after testing they seem to be where they aught to be (I think). Thoughts?
Thanks in advance!!

 

fine...means the regulator is work well too...

 

30-45 is the acceptable range. the rear one usually goes out first, thats probably why it a hair lower then the other.

 

So I take it that mine are in the acceptable range. Why such a big range? Just the way it is? Would I see any improvement if I were to put in an adjustable pressure regulator? It would seem to make sense that 45psi would be better than 30psi, or does it really make any difference?

 

Also, the rear isnt really lower (I dont think)... when just turning the key-on, each will pressure to around 33psi. its just when you hit the gas, the front will pressure to about 42, and then settle back down... the rear will pressure up to around 38 and settle back down. but while idling, they both come in at about 33psi.
Do they sound like they are still good to go for a while longer?

 

leave it be.... pressure should be 30-35 PSI running with the regulator plugged in and 45 with it unplugged...

running too much or too little pressure than specified can cause a lean or rich condition... the fuel tables are mapped according to that specified pressure...

 

45 isn't any better that 30 unless you modify the engine and it needs more fuel. For example, a larger throttle body, larger injectors, and a free flowing exhaust.

 

Ok, thanks guys. I cant believe that I have almost 257,000 miles with original pumps... still going strong though. Has some cancer, and I plan on working on that come spring. I went 16 years without a lick of trouble with this truck... then I went through and replaced all the u-joints, ball joints, etc... all with the ability to be greased (so now I have like 20 zerks to grease LOL) and have started replacing other things, some sensors, coil, etc... I was never a Ford guy, but I bought this truck in 1994...mainly because it was a little lower in price than a similar chevy... I couldnt have asked for a better truck. Has only left me stranded ONCE in 18 years... and that was a couple years ago when the bolt that holds the tensioner pully arm on sheared off...in the car wash of all places. And as far as driving through snow and on slick roads, its sure footed as could be, never has given me an uneasy feeling and have only been stuck to where I had to be pulled out 1 time...and that was basically my own stupid fault. LOL IF I was looking for a new truck, I would for sure be looking at Ford. But Im not at the moment, and have actually decided to put some money into my 94 and fix her up a little.
AND, this website Rocks! Really glad I found my way here!!

 

actually not true...

every 5psi is roughly 5%-10% more fuel....

with the duty cycle of the injector you can easily be 20% in 15psi.... thats alot of fuel to put out there...just to waste