99 Explorer hard start problem

[GT86]

I've got a 99 Explorer with the SOHC 4.0 V6 that has developed a hard start. Had a CEL that was coming back as lean operation on both banks. Hooked the fuel pressure gauge to it, and saw I had pretty low pressure (40-ish psi), and it would drop back to 0psi within 5 seconds after shutting it off. So, I replaced the pump and that brought the pressure up to 63 psi.

The CEL is gone, and the truck runs better now, but it still has the hard start. Pressure is still dropping to 0 psi within seconds after turning the engine off. So, I'm thinking I've got a bad FPR or leaky injector(s). On the 99 SOHC, where is the FPR? Haynes shows it by the rail, but it's not there. Of course, Haynes usually generalizes a bit too much and tries to cover too many models/years in one fell swoop. Is there any way to test whether I've got leaky injectors vs. a bad FPR?

 

[BrooklynBay]

Welcome to this forum! It might have a leaking injector, but it's hard to determine which one it is. Did you replace the fuel filter when you replaced the pump?

 

[GT86]

Yep, changed the filter when I changed the pump.

 

[Cobraguy]

I actually built a set up for checking for leaking injectors. It can check either the pump check valve or the injectors. You just plumb it in between the supply line and the rail. I built this because I was having the exact same problem on my son's Lincoln LS8. I isolated it to a leaking injector. But what injector? You should be able to pull the spark plugs after trying to start it and see which one(s) are wet. But what I did was pull the fuel rail and leave it attached to the fuel system. I zip tied the injectors to the fuel rail so they wouldn't blow out under pressure. Then I pressurized the system. It was obvious very quickly. I had two leaking injectors. I just bit the bullet and replaced them all.

There may be better ways, but this is what I had to work with.