Ranger code P0456
 

Hey guys my trucks check engine light came on and it's throwing a P0456 code and saying the truck has a minor evac leak somewhere, any idea where this would be? My truck has always had a problem starting right away and I know it's losing pressure in the fuel system somewhere, could this be the cause.

No, P0456 would be EVAP system code so not related to fuel or fuel pressure, or even engine opration

EVAP was added to vehicles years ago to stop gas fumes from escaping the gas tank when you were driving and fuel was sloshing around in the gas tank, its a form of pollution, so its an "emissions" system
There is a charcoal canister in the engine bay or behind gas tank depending in the year of the Ranger
The canister is hooked to the gas tank via a vent at the top
When engine is running an EVAP solenoid hooked to the intake manifold and controlled by the computer, will put some vacuum(low pressure) in the canister so it sucks any fumes out of the tank and back to the intake to be burned like gasoline from injectors.

There is a EVAP pressure sensor on vacuum hose running to the gas tank or on the gas tank itself
The sensors tell computer how much vacuum is being applied to gas tank, it isn't much
When you shut off the engine, the tank should hold pressure for a bit, this is a test that there are no leaks in the gas tank or EVAP hoses, your code means pressure didn't hold

You may remember prior to this when you stopped for gas and loosened the gas cap you would hear a "whoosh" of air, that was because of EVAPs negative pressure in the gas tank that hadn't been released yet
With a leak in the system you probably don't hear that any more

What year Ranger and what engine?
It matters as to where you should look for the leak
It could be the Filler tube or its vent is cracked a bit, common issue on vehicles, and so common air leak point
Can even be a bad gas cap, not sealing well any more

Thanks for the reply Ron! You are correct I don't hear anything escaping when I open the gas cap but I believe the truck has had this problem since I got it so I never did or at least I don't remember hearing that before. My truck is a 2002 4.0, I looked up the code last night and from what I found it looks like there are four possible causes.

Evap system hose, I'm guessing that's the rubber hose on top of the fuel pump assembly judging from a video I found online, his Ranger was also showing that code.
Gas Cap allowing pressure to escape
Vapor Canister purge valve
Fuel tank sending unit gasket may have gone bad from drying out
Fuel filler neck gasket may have gone bad from drying out

I know this is kind of a heard one with out taking it in and having a smoke test done. Is there anything else that I don't have listed that you can think of that might be causing this code? Also do you know of a way to test the gas cap to see if it's gone bad?

If you have a helper you can do your own test without the smoke

Get a short length of hose and a damp towel/rag
Take off gas cap
Put end of hose in the filler and wrap damp towel around it to seal it
Have some one blow into the hose while you listen for air escaping
The tank should hold pressure when you blow into it, but there is a vent solenoid on the canister, so try turning on the key, engine off, that should close the vent

DO NOT use an air compressor for this, you WILL BLOW OFF EVAP hoses and fittings
Human lungs can generate 2psi MAX pressure, no air compressor can be turned down that low, lol

In 2002 your canister will be behind the gas tank, that's where most of the EVAP hoses will be, with just 1 hose running to the front engine area

This thread has pictures of EVAP canister and parts:https://www.ranger-forums.com/genera...t-part-151001/

If there is a leak there then pull the bed off to work on it, just 6 bolts and unplug the tail light wires

I found a video online telling me how to test the gas cap. if that doesn't work I'll try the way you told me about. I'm taking the bed off soon anyway to grind and coat the frame so I'll have a chance to look over everything under it. Thanks again Ron!

Good idea

Also look at rear leaf spring hangers, when bed is off, they rust out on ALL pickup trucks, not a Ford thing, a pickup truck thing, lol, way easier to change them with bed off

Thanks Ron! I'm planning on giving everything a good looking at when working on the frame.