For my new engine, im using a 325lph single pump, which has a threaded on 1 way valve, how important is it to have that valve? Id imagine the fuel would loose prime and take a while to start without it right? J/w because im having a heck of a time finding fittings to fit it.

 

It's not needed. The EEC primes the pump for ~2sec when the key goes to RUN, and then it stays on whenever the engine is turning (even on the starter).

 

i dont mean to steal this thread but ive been wondering and since the subject came up i thought id ask.now i recently changed my fuel pump (i have a 4.6) so i bought the pump for my engine. what im wondering is could i have bought a pump for a bigger engine as long as it fit in the tank? i just ask cause i always thought no matter how big the pump was its the injectors that made sure the right amount of fuel was there.an if say i ever got crazy and needed a bigger injector would i need a new pump? sorry if i stole this thread just something ive been wondering about.

 

Stan 2973,when you ask if you could have put a larger pump in your tank,you mean one that flows more fuel(gph) and more pressure,the size of the pump in the tank is the same unless you go to a pump you mount outside your tank.Your pressure regulator is what controls the fuel pressure,the injectors simply inject the fuel into the engine @ the pressure they set at(i.e.19#,32#etc.)The only reason you would change your injectors is because your engine requires more fuel to operate at its maximum performance,like a supercharger or turbocharger application.the supercharger kit will either supply the new injectors or give you the p/n of the correct injectors for your partiular application if they are required.Hope this helped on some of your pump questions.

 

I need to jump in here and add some info about pump sizes.
On a stock motor or one that has mods that don't raise hp requirements very far should run on the stock sized pump capacity without a problem.
Capacity is a rating of fuel flow (volume) vs HP as long as the injector size also matches a bit more than the HP produced, for reserve.
An example is a 5L efi motor with 19 lb injectors running a 40 psi fuel pressure making just over 200 hp W.O.T. only requires an 88 l/ph pump the have a safe reserve. An 88 l/ph pump will supply at least 285 hp, far above the rating of the engine in stock configuration.
The injectors are usually flow rated at 40 psi for Ford motors and pump flow matched to that parameter with some reserve.
If one tries to raise fuel pressure to achive greater fuel from the injectors, it does work within limits but fuel pump volume is a direct inverse relationship to pressure meaning when pressure is forced to rise, volume goes down.
Installing larger pumps against a relitive stock or little modded motor provides no benifits because the injectors still flow the same, at the same rail pressure as dictated by the regulator.
To go a step further, there are supercharger installations that do raise fuel system pressure by over riding the stock fuel regulator. This is done to force the injectors to flow additional fuel to cover the extra forced air the blower makes.
However there is a limit to this as well before a larger fuel pump is required because again as the pressure goes up the flow volume goes down until a point is reached that the fuel is no longer enough to cover the peak HP requirement and the injectors are now too small to meter enough fuel.

 

Bluegrass,thanks for your post on pumps and injectors,it is very interesting reading.I understand the basics of pumps and injectors but you made it plain and simple.I just recently replaced my pump in my 2000F-150,I installed a Walbro,the guy on the phone was talking pressure and volume,now I understand the relationship of the two and how one affects the other.I have often wondered if I go to a larger injector if I would see an increase in performance,like putting a bigger carb on your car,but after reading your post I can see I should look else where for more performance.Thanks again for that insight into pumps and injectors.

 

alright.... so back to my question. I understand that the pump runs for about 2 seconds, but will that be enough to get the fuel right ther every time even when I just put the key in and start it without waiting for a second with the ignition on?

 

Probably. At worst, you'd have to hold it in START for a fraction longer.