There were two complaints. A stored P0440 engine code and the customer had a difficult time filling the fuel tank. I thought it would be best to check the P0440 problem first. EVAP faults can cause refueling problems. When the EVAP monitor begins on this system the engine control module opens the purge control valve. With the valve open the engine intake manifold vacuum can draw vapor or air from the canister. The ECM expects to see a change in short term fuel trim. If there is no change the weak vacuum test will be run. The vent valve will be commanded closed and the purge control valve pulsed open. The ECM is looking at the fuel pressure sensor for an indication of vacuum in the tank since the system should now be closed to the outside atmosphere. If this does not happen after two attempts a P0440 code sets.
A leak in the system could cause this problem and it would certainly not be unusual to find an EVAP leak. The most common leak points are at fuel caps or near connections of rubber hose to either metal pipe or plastic tubing. Usually on this particular make and model the leaks are at the canister hose. I gave the system a pretty good look and there were no obvious leaks. Not seeing an obvious leak certainly does not mean there are no leaks but before getting too involved with leak checks it would be a good idea to see that the purge valve actually has vacuum to it, that it does open when commanded and that the vacuum can get to the canister. I did a test of the vent valve that it did close when commanded before I lowered the car.
There was a pretty obvious problem at the purge valve. The vacuum hose at the valve had been replaced and the replacement hose was kinked shut. No engine vacuum was actually reaching the valve.
After replacing the hose, I let the initial EVAP load test run just so I could let you see what the ECM is looking for at that time. It wants the short term fuel term to give an indication that the system is working.
I said there were two complaints. I had not found anything to cause the tank to be difficult to fill. After checking for venting problems or restrictions and even dropping the tank for better access, we found nothing. I tried to fuel up at the station normally used by the customer and I could only add fuel slowly or it would kick the pump off. I went to two other stations and had no problem even at full flow. The fix for the hard fueling problem? It's like the old joke. Doctor it hurts when I do this. Well don't do that.
Kenneth Hayes
aka Deranger
