99 4.0 ohv low fuel pressure

[alyakhim]

hello everyone. i am new to this forum and first i want to thank everyone for collaberating together to make a great explorer resource such as this. i have a 1999 ford explorer xlt with the 4.0 ohv engine and the returnless fuel system. since i purchased the vehicle in october i have been struggling with a lean condition on both banks and the cel with codes p0171 and p0174 that i just cant get rid of. i have ruled out any sort of vaccuum leak i have changed all the intake and plenum gaskets fuel injector o rings and every sensor on the intake assembly as well as the gaskets on the sensors that require them. however after doing all of that i looked into the fuel pressure and discovered that i measure only 27 psi at the rail and that is when the ignition is only in the on position and running. i have yet to monitor any major leakdown but i do know that after 10 minutes their isnt any pressure loss. i will do a longer test this evening. i have replaced the fuel pump and sending unit. the fuel filter and have recently ordered a new fuel pressure dampener but am not confident that will fix the issue because recent research led me to find this is a returnless electronic fuel system and when i purchased the dampener i thought it was a regulator. but what the hell i have already replaced everything else. the pressure measurement did not change between the old fuel pump and the new one. i am uncertain of where to go and look next as i dont really have many more parts in the fuel system for suspect. the vehicle suffers from hard starting. it may take up t0 5 to 6 seconds to start. and when veh icle is driven to become hot and it is shut off and restarted after approximately 20 min to half an hour of waiting it will run very rough and act as though it is starved for fuel and the only way to clear it out is to rev the engine for a slight amount of time and it will run and idle normal. i conclude that the engine is trying to build pressure at this time and clears up once achieved even though it only ever gets what i assume to be a bare minimum. if the vehicle were to be started after sitting say overnight. normally it will fire in only a few cranks. its normal idle speed is 1500 rpm which i believe to be very high. i do not have a fuel leak in a line and am tearing my hair out and spend every free second working on this issue. anybody with an idea on where to go next will be my hero. thanks - mike

 

[buckwill]

i keep hearing about problems with fuel pressure regulators problems,, could yours be dumping fuelor pinching it off, find where its at and check it out, just an idea,

 

[alyakhim]

the fpr in the 99 ohv returnless system is integrated in the fuel pump assembly and i just replaced the few pump without change in my low pressure reading. on the rail where the fpr is located in pre 99 models is just a dampener on mine. i already have it ordered and changing it because whats 75 more dollars right? hahahaha

 

[alyakhim]

off topic question. can a leaky valve cover gasket cause a vaccuum leak? especially the drivers side where the pcv valve plugs in?

 

[buckwill]

i cant see how a vlave cover gasket can call a vacuum leak, spray carb cleaner or wd40 lps2 at fittings or around manifold base wi engine running, if u hear rpm change then u know u have found leak,, on fuel pressure,, if u start at source and diagnose from there, then u are more likely to find problem, soo, start at fuel pum,, put fitting in line off pump with fuel going noplace but guage, does it have pressure?? if the pump is making pressure then problem is obviously someplace else,, if some device is dumping fuel then that must be fixed, but u will have pressure or not but start at the source and work downhill,, pump then bypass, then regulator etc etc,

 

[ranger7ltr]

Question for you...

Have you changed the fuel filter yet? When you pulled the filter what did the fuel on the inlet side look like...Was it dirty/rusty??? This would be an indication of a rusty metal tank and the restriction on the inlet sock of rust or dirt would restrict the supply of fuel to the pump...

And the fpr is integral to the fuel pump assy...And the fpr actually only releases pressure when the fuel pressure gets over 80 psi...Did you change the whole fuel pump assy or just the pump itself?

The fuel system on the 99 is very simple; a fuel pump provides high pressure fuel to the filter then into the fuel rail...The damper is there to even out fuel pulsations in the rail to the injectors...There are no electronics to modulate the pressure or anything controls like that...The pump outputs pressure at a constant rate and the engine uses it as needed...

The only other possible issue would be a major leak in one or more of the injectors and I think you would see an extremely rich running engine or one that is hydrolocked with fuel... Or possibly the high pressure rubber line from the pump to the output fitting on the pump assy has a split in it...

 

[alyakhim]

thanks ahead for your replies gentlemen, i'm going to make a liar out of myself by sayin i don't have a leakdown at the rail. i just discovered my pressure will bleed down to 10 psi in the matter of 5 minutes. So I'm thinkin that I have a leaky inject(s). I thought the same thing, that i would have a rich condition if my injector was leaking so I didn't put a whole lot of faith in checking for a leak down. rookie mistake again. been crash coursing myself since Ive been dealing with this issue. I'm not quite sure how to go about pin pointing exactly which injector and new is quite expensive perhaps I'll go to the local boneyard and pick an entire fuel suppy assembly with injectors but i dont wanna risk being put in the same boat :/

 

[buckwill]

jus pullem out an leavem on top of the engine the leaky one should be obvious

 

[alyakhim]

looking to get an adapter tee for my fuel pressure tester so i can pinpoint what has pressure and what doesnt. the fuel pump i replaced mine with came from the bone yard however the rail fuel pressure didnt change one iota between the 2 so i very much doubt the check in the fpr is bad on both. as soon as i get this tee adapter i'm gonna test this theory as i dont wanna throw any more unecessary cash at this p.o.s. if everything checks out with my fuel pump than i must have multiple problems as i have a lean fuel system and a potential leaking injector which would explain the ease of starting after sitting a fair amount of time.