lean codes p0171 p0172

[gearhead06]

2001 ford explorer sport 4.0 v6 2 gen I believe, lean codes bank 1 and 2 I believe they were p0171 p0172, I have replaced upper and lower intake mani gaskets, checked for vacuum leaks by spraying carb cleaner on all the hoses and ext.. I also tested the fuel pressure, my local part store doesn’t list a fuel regulator for this explorer, any ideas?

 

[ranger7ltr]

From MY 1999 there is no vacuum fpr...

The fpr is in the tank and it is there to release excess pressure back to the tank. You stated you checked the fuel pressure; what is it?

Again from MY 1999 the fuel system is returnless and runs at a higher pressurethan the return type fuel system with a vacuum fpr... The fuel pressure also stays constant; it does not vary... Or rather the fuel system is designed to not vary the fuel pressure...

As far as the lean codes are concerned there are the vacuum lines going to the evap system to verify and the possible leaks at the PCV valve, brake booster, and any valve/cam cover or the oil filler neck...

 

[gearhead06]

fuel pressure was right around 36psi and was constant, but when you go to turn the key on the fuel pump does not kick in right away and you have to turn it over stop and do it a second time to get it to start...

 

[ranger7ltr]

Have you changed the fuel filter yet?

Frankly I am surprised that it runs at so low a fuel pressure...If the filter is clogged that could cause low pressure... It will also cause the fuel pump to burn up due to the excess resistance to flow...

It is already deadheading due to the returnless nature of the system and add the clogged filter to that mix the pump will have to work extra hard to gfet fuel to the engine...

I would change the fuel filter if it has been more than 6 months on the truck...

 

[ncranchero]

You DID check the PCV hose that goes around the front of the engine for a crack/split, usually on the bottom side????? Common cause of 171/174.

PCV crack

 

[gearhead06]

I changed the fuel filter and my mechanic said 36psi was perfect... whats it supposed to be?

 

[ncranchero]

Stated fuel pressure from the 01 Service manual for the 01 Sport 4.0L SOHC :
Fuel Pressure
Key on, engine off 414-448 kPa (60-65 psi)
Engine running 414-448 kPa (60-65 psi

 

[ranger7ltr]

Operational Fuel pressure...

For a Ford Returnless fuel system is 65-72 psi from model year 1999-up...I have seen 40 psi work in one before but it was definitely not happy with that low a fuel pressure...

Now at some point with the 3rd Gen Explorer and other Fords[2002-newer] the fuel pressure was modulated for load and other variables but up to 2001 in the Explorer and Mustang the fuel pressure was constant and the lower value I have seen in my manuals was 65 psi...

And the returnless fuel system has no fuel pressure regulator on the fuel rail. That is a pulse damper which is vacuum operated...It is there to smooth out the pulses from the injectors opening and closing creating turbulence in the incoming fuel supply...The fuel pressure regulator on a returnless system is in the tank on the returnless fuel system.

 

[ncranchero]

Reading wrong place. Info corrected, THANKS !!

 

[2000StreetRod]

low fuel pressure

I agree with ranger7ltr that your fuel pressure is low. Your Sport should have at least 60 psi when the ignition key is switched to Run. According to aintpersonal the 3rd Generation Explorer fuel pump driver module "is located on the passenger side behind the interior trim in the cargo area (where the third row is located) pretty much behind the rear passengers taillight. If you remove the interior trim panel you'll see it bolted (one 10mm bolt,and two wire harness clips) just below the taillight bolts." See fuel pump driver module location?

I don't know when the Sport Trac started coming with a fuel pump driver module but it is located under the truck near the fuel tank.

 

[ERUSH97XLT]

Hello,

The fuel concerns above are all valid.

Don't rule out ignition faults---unburnt oxygen due to poor spark is read by the oxygen sensors and causes overfueling.

Also consider troubleshooting the MAF (i.e., clean it, measure voltage, etc.), and IAT. The electrical signals may be within specifications, but off slightly enough to cause the computer to over correct the fuel trims.

Do you have a rough idle?