Fuel Injector Differences

[speedracer0626]

98 Explorer returnless fuel system and 98 with return. The injectors are the same between both systems is what I'm gathering.

 

[410Fortune]

No injectors are different!

The 4.0 injectors are rated at 16 lbs of fuel delivery per hour
The v8 is 19 lb/hr

The return fuel 91-1997 runs at 36 psi fuel rail pressure and the injectors deliver 16 lbs / hr

The 98-04 returnless fuel runs at 68 psi fuel rail pressure and the injectors deliver 16 lbs / hr

The injectors are not the same
They have same delivery rate but with different pressures behind them

The wiring plugs changed also
The pcm does not know which fuel rail/ injectors you have it simply turns the pump on and off

Using return style injectors with a returnless rail will deliver too much fuel because of the increased pressure behind them and vise versa

 

[speedracer0626]

Ok makes perfect sense and a perfect reason to have a dead spot at WOT. Return pump on a returnless system. Right now I'm in the process of doing the heater core and all that extra that comes with the job. Will run it here soon with a gauge and see what pressure we are running. Thank you kind sir.

 

[410Fortune]

No problem!
A return style pump may not make enough pressure, it is designed to run at 34 psi not the 64psi you need!! and the 64 psi is regulated in the tank not at the rail. Fun fun