I use this car to go to work so I am hesitant to take off parts that I have never taken off before. Because of that, I would like to be able to do as much testing as I can with the parts still installed on the car. I would also like to test as much as I can without the engine running.
It is even better if I can test with the ignition key in the off position. I cannot do all of the testing that way, as testing the fuel tank pressure sensor appears to depend on having the ignition key on, and using a volt meter, but the engine does not need to be running.
I think I could do much of the testing with the ignition off. I need some tools, one being a hand vacuum pump (Mityvac, which I have not yet bought). I also need something to activate some of the solenoids. I do not know of a tool for that, so I might make something using a 9 volt battery, but wish I could find a real tool for this purpose.
For example, if I want to test the purge control valve (#24), I think I can do that with the ignition off. I can disconnect the vacuum hose from the manifold that leads to the purge control valve. I can connect the hand vacuum pump to the hose and create a vacuum. I would expect the purge control valve to be closed since the ignition is off, and I would expect the vacuum to hold unless the purge control valve leaks. I am not sure how much of a vacuum I will need, but assume I can figure that out. I think that if the vacuum holds for two minutes or so, the purge control valve does not leak. I would also want to be sure that the purge control valve opens when it is supposed to open. If I disconnect the two pin connector from the purge control valve solenoid, I should be able to test it by applying power from a 9 volt battery to the solenoid. I do need to figure out which side is positive (+) and which is negative (-) on the solenoid. If I find the vacuum holding at some level just before I apply power, I would expect the vacuum to immediately drop when the 9 volt battery power is correctly applied to the solenoid. I can do that test without even looking under the car. If the purge control valve is good, I would reconnect the vacuum hose between the purge control valve and the intake manifold. I would also reconnect the two pin connector to the purge control valve solenoid to make sure I put things back the way they started.
I understand that manifold vacuum pressure (perhaps negative pressure) gets to the EVAP canister via the purge control valve. If the purge control valve appears to be doing its job, I could then move testing to the other side of the purge control valve by disconnecting the vacuum hose from the purge control valve that leads to the EVAP canister. I would connect the hand vacuum pump to the open end of that vacuum hose, where I disconnected it from the purge control valve. This places the vacuum suction past the purge control valve, but for the rest of the system suction would appear to be coming from the intake manifold. If I try to create a vacuum, it should fail because, as I understand it, the EVAP canister vent shut valve is normally open. Doing that test shows that either the EVAP canister vent valve does its job when no power is applied to its solenoid, or some other leak is occurring.
The EVAP canister vent valve closes when power is applied to the EVAP canister vent shut valve solenoid. If I disconnect the two pin connector from the EVAP bypass solenoid valve, I could apply power from a 9 volt battery to that solenoid. I think I should be able to create and hold a vacuum in this condition, because the rest of the system appears to be a closed system. However, my supposedly closed system seems to have a leak, which means it is not truly closed. I could then try clamping shut the all of the hoses that connect to the EVAP canister except the line that leads back towards the purge control valve (or hand vacuum pump when configured for this test). With the 9 volt battery attached to the EVAP canister vent shut valve solenoid, I should be able to create a vacuum with the hand pump. If I cannot create a vacuum, I have a leak in my canister (#22), a leak in my evap canister vent shut valve (#25), or a leak in the vacuum hose or purge joint (#32) on the route back to the purge control valve (#24). I can test the vacuum hose part by placing a clamp on that hose near where it attaches to the canister and trying to create a vacuum using the hand pump.
If the vacuum hose is good, that indicates that either the (#22) canister or (#25) vent shut valve leaks. In that case, I probably need to remove the canister to try to isolate which has failed. At that point, I might want to replace both unless I can figure out how to test the vent shut valve by itself. Or as you suggested quite some time ago, I could plug holes in the canister and check it for leaks, but I would have to remove the vent shut valve first. After replacing either or both, I would clear the code, put things back, and test drive until I get through at least a tank and a half of gas to see if the p1456 comes back.
If instead the above tests indicate working equipment, I need to figure out how to test the (#26) two-way valve, the (#27) eval bypass solenoid valve, and the (#29) ORVR valve. I suppose my new gas cap could also be at fault, which would be a real shame after all of this! I do not quite understand how the two-way valve (#26) is supposed to operate. I think vacuum applied to one of its connections causes it to either connect to the canister or bypass it. Is that correct? What does the eval bypass solenoid valve (#27) do?
Monday, July 23rd, 2018 AT 7:40 PM