I have a 1995 F150 which keeps popping a purge valve solenoid circuit failure code. Then, I believe from the first code, HO2 to lean/Rich codes. It seems to only do it when driving more than 15 or so miles at the same speed. It has never came on in the city or on the short commute to and from work. I have checked the gas cap and replaced the purge valve. When I replaced the purge valve my MPG went from about 6 to 10 although even after a reset, disconnecting the negative battery cable for around five minutes, the code still arrives. If anyone has any other ideas it would be much appreciated.

 

It would help us help you to know more about your truck; the engine at the very least, but transmission model, 2/4WD, trim level, wheelbase, gears, tires, miles, maintenance, modifications, damage, repairs, etc. would be good, too. If you don't know, read this caption:



The gas cap has no wiring, so it can't set any circuit fault code.

The CANP doesn't affect MPG. Never disconnect the battery to clear codes - it also clears adaptions. Get a digital multimeter & a Haynes manual, and test the CANP circuit. Try to find an older blue-cover edition because the current edition has crappy wiring diagrams. The CANP circuit is always Gy/Y, and usually comes from EEC pin 31 or 11. This shows a CANP:

 

It is an inline 6 4.9L, E40D tranny 87k miles 4x4. I did notice the canister is in the front next to the battery. I have normally seen these mounted near the gas tank. I do have the dual tanks so I thought this may be why. I traced the evap lines and there is only one canister for both tanks.

If the purge valve is not sending the gas fumes from the gas tank to the engine or sending to much causing to rich/lean scenarios how could it not affect MPG?

So I should check the actual electronics that run the valve? I have a Chilton manual, just not with me or I would check, does that include a well laid out wiring chart?

 

chiltons has a good and easy to fallow electric and vacuum diograms. did you get a ford replacement gas cap or aftermarket?

if aftermarket go to FORD DEALER and get one i put after market in our grand marquis and nothing put a ford and it was fine. same with my girls cavalier except chevy replacement

 

That's the only location for the canister on these trucks, and only some larger carb engines got 2 canisters; EFIs only got 1 regardless of tanks.



The CANP doesn't end in full manifold vacuum - just ported vacuum. So it can't affect the mixture enough to cause any symptoms; least of all MPG changes. Did you read that caption? It's easy to test the CANP. The Gy/Y wire should have <5 Ohms from the CANP to the EEC, and more than 10K Ohms to anything else (wires, battery, body...). The R wire should have ~12V when the key is in RUN, just like at the injectors, TAB, TAD, EVR, & IAC.

Chilton's makes good tire chocks, and this has nothing whatsoever to do with the gas cap.

 

I read all three captions. I am ignorant when it comes to electronics. So what I should do is hook a voltmeter into the wire clip that plugs into the purge valve then to the EEC and test said things? Or is there another place I need to test it from?

 

Test the CANP power with the key in RUN, the CANP disconnected, and the meter probes in the wiring harness connector terminals. Tes the CANP resistance with the key in any position (OFF is OK), CANP disconnected, probes in the CANP terminals. Test the wires key OFF, EEC & CANP disconnected, probes on corresponding terminals in each harness connector.

If you don't understand, take it to a pro.