Sure, I can help. I actually did take pictures showing the hole and the valve just in case. Is it easy to upload a pic here? Let me try later. I could also mail you one if you give me an email address.

I basically just cut from the fuel pump access hole up towards the back seat using sheet metal shears. I wouldn't want to do this on a new car, but the procedure for dropping the tank looked daunting. I think it will survive structurally. Patched with sheetmetal, screws, and silicone sealant.

Before you go and do that though, there is much you can do to test the ORVR valve. **Do that first** I would be happy to help you with the testing.

You have p1457, which means leak on the canister side. I believe it also means p1456 has passed, since it appears p1456 passing is necessary for the p1457 test to be interpreted based on how the solenoid valves are arranged in the circuit. If 1456 is passing, you don't have the leak I had.

To do any tests you need a vacuum/pressure pump. Do you have one? 35-55 on amazon. Buy or borrow that first.

Do you have the shop manual and tech bulletin updates for 1457?

There is only one hose from the canister to the ORVR valve, and you can easily disconnect it and plug the port to test.

What have you tried already?

 

rjpjnk, I have a MityVac, AutoXray 6000 & a multimeter. Check out MY THREAD HERE to see what I've done already.

Thanks!

 

Ok. I read it. Here are a couple of initial comments:

(1) The 2 way valve is complicated. The operation you observe is correct though. It should hold vacuum on the lower port when the solenoid is *not* energized. The solenoid when energized provides a passageway to bypass the normal path between the upper port and the lower port. That's why it is called a "bypass solenoid" btw.

The upper port of this wretched valve from pluto is actually designed to open to pass vacuum or pressure to the lower port when the vacuum or pressure exceeds a certain threshold (a kind of hysteresis effect). The slight resistance to flow is what allows a certain design pressure to remain in the fuel tank. Once this is exceeded, the excess pressure (fuel vapor) bleeds over to the canister side. At any time, the ECM can force this to happen by activating the bypass solenoid. It does exactly this during the p1456/p1457 diagnostic tests. The upper side port is always connected to the top port (the third leg of this beast) which is connected directly to the FTP (fuel tank pressure sensor). Did you know the FTP is not in the fuel tank? ;-)

(2) You can easily measure the FTP from this sensor using an ordinary volt meter connected to two pins on the ECM. I drove around like this for a couple of days during my investigation. The pin numbers are in the service manual. Do you have it?

(3) There is an essential tech bulletin you need for this. It is 99-075. Do you have it? I can send a pdf to you. I can't upload it here because it exceeds the 19KB limit. It is 256KB.

 

Sorry, no manual. I'm a little confused about the connections required to read voltages at the pin-connectors on the ECM. If I've got those connectors off, how can the ECM operate? Is this voltage measured on the connector/car side of the connection or directly off of the ECM pins?

.

I have 99-075, but it assumes that the user has Honda diagnostics equipment.

 

Took me several days to understand what the manual was telling me to do too. Here is the answer.

(1) Activating a particular solenoid can be done with the ECM connector unplugged from the ECM (And the car switched on but not running). You simply ground the proper pin on the wire harness. You *DO NOT* touch the ECM pins at this point. The solenoids already have +12V routed to them by other means, you just need to supply the ground. You can also do this by just climbing under the car with a 12 volt battery and two little wires with alligator clips. I used a 12 battery from my cordless drill, but I found that a simple 9V battery from a smoke detector worked fine too. (NOTE: You could also activate the solenoids with the ECM connector plugged in, but you run the risk of grounding some pin you shouldn't be and burning something out.)

(2) To measure the FTP sensor voltage you must have all the ECM connectors plugged in and the car ignition switch on (car can be running or not running in this case). The reason for this is that the FTP sensor gets its supply voltage (5V?) from the ECM through the harness connectors, so you can't unplug them. It's all in the service manual btw. (PS. I have one for sale if you want it). You get the reading by slipping two short lengths of bare wire into the terminal connectors right next to the existing wire from the car. So you are sampling the voltage without disturbing the circuit. Be very careful here. You do not want to short out your ECM. This procedure is also described in the SM.

 

You have 99-075. That's great! Perhaps if I talk you through what each step is doing you can find the problem. I just looked at the p1457 procudure. What they are doing is basically eliminating one section of the vacuum circuit at a time until the system holds vacuum.

Do you see the hose they first crimp off in Step 8? This is the hose that goes to the fuel tank. The reason the test crimps this off is that p1456 passed, so the fuel tank side is NOT suspected to be leaking so you simply remove it from the test with vice grips. (Much better idea is to unplug the hose and cap both ends using those little rubber plugs that came with your vacuum pump kit.

With this hose plugged, and the vent solenoid energized (closed) you canister should be leak tight. So they've got you pulling a vacuum at the purge valve and testing that it holds by measuring 1.5V at the FTP (1.5V equivalent is too small to measure on your mighty vac gauge btw, don't try). And if you try to pump the vacuum up higher so you can see it on the gauge, you'll likely damage the FTP which is not designed to be exposed to high vacuum or pressure. Did you already do this? ;-(

If vacuum does not hold they then have you crimp off the air hose to the vent shut valve. Basically, if it holds after this the valve was not closing properly and is defective.

If it still doesn't hold they then have you shut off the path to the ORVR in the same manner.

If with all these dissconnected it still does not hold vacuum they conclude a canister leak.

All of these tests require you to have access to the FTP signal on your volt meter.

If you don't feel comfortable tapping into these wires on a live ECM I have an alternative method I can show you. It will involve simply dissconnecting the 2 way valve from the system and plugging that hose (that's the lower one). THen you can pump up as much vacuum as you like since the FTP is no longer in the loop. THen you could maybe watch the vacuum gauge. Your call.

Btw, the 2 way valve is not a suspect in p1457 as long as vacuum holds on the lower port, which you already verified.

Well, I've probably written too much at once. Let's take it one step at a time. Do you want to use the actual FTP signal to proceed or not?

 

Not to jump ahead or generalize, but since I've already verified the electrical/vacuum integrity of the VSS, Purge Vlv and Bypass (it's the same as the two-way, right?) Vlv, I was just going to yank out the canister from underneath the car (easy to do), plug up all the holes but one and pull a vacuum on it. That would tell me if the canister is good. Depending on what's involved, I may be interested in tapping into the signal wires. I'm an aircraft mechanic of 26 years, so I "ain't too skeered".

 

Jeff

You should definitely test the canister as you mentioned. No need to remove it from the car though. Just plug 3 of the 4 ports and apply vacuum to the 4th (I suggest using the purge valve port for this).

From reading your other post it was not quite clear to me that you have really verified these other valves are not leaking. You didn't provide details of how you performed each test.

Basically, the canister has 4 ports, and each one is connected by a hose to a valve, and each of these valve can be leaking, or the canister itself can be leaking.

Here is how I would test each valve.

(1) Purge valve.
WIth engine off purge valve should be closed. Go under car and pull purge valve hose off canister. Apply vacuum to this hose. If it holds, purge valve and entire line connecting to it are air tight.

(2) Two-way evap bypass valve.
This is tricky. One part that fails is the O-rings between the bypass valve and the 2 way valve. To test this it is not sufficient to just observe that vacuum holds until you engage solenoid. You need to unplug the hoses from the top (FTP) and upper side (Tank) ports and plug both these ports. Then engage the bypass solenoid and then pull a vacuum on the lower side (canister) port. If the O-rings are leaking the vacuum will not hold. This vacuum should now hold regardless of whether the solenoid is engaged or not. Now open up the top port (FTP) and you should then see that the vacuum holds only when the solenoid is engaged (as you already determined). THis is because the solenoid connects the lower port to the upper and top ports. You need to test the O-rings in between.

(3) Canister vent shut valve. remove the ORVR and two-way valve hoses from the canister and plug the respective ports on the canister. Then remove the purge valve hose on the canister and attach your vacuum pump to that port. Then energise the vent shut solenoid and try to pull a vacuum on the canister. If it holds, both the vent shut valve and the canister itself are good so go to Step 4. If it does not hold, crimp or plug the big hose from the vent shut valve to the air filter can and try again. If if holds now valve is bad. If it doesn't canister is bad (or outer shell of valve is cracked where hose attaches).

(4) ORVR valve
There is a detailed test procedure for the ORVR valve and float test described in the service manual. IT requires two vacuum pumps (or one pump and a second vacuum gauge). Basically it says you should be able to pull a vacuum on the hose leading from the canister to the ORVR, and this vacuum should hold until you then pull a second vacuum (only one pump) on the vapor signal hose (the small one of the three going to the filler neck) The first vacuum should immediately break then. Since it is hard to connect a pump to the quick connect hose from the canister to the ORVR they suggest you leave it connected to the canister, plug two of the other ports and pull vacuum on the fourth.


That's all there is to test other than the ECM itself.

 

rjpjnk; Thank you very much for your time and effort in helping me out! I've been working long hours this week and haven't had time to pursue any of the procedures yet. I'm off for the next few days though and will proceed with troubleshooting.

I'll report back here with my findings. Thanks again for the help.

 

Well, rjpjnk, I've bookmarked this thread, printed all the info and filed it away. Thanks again for all this valuable information!

As for my P1457 problem, the world may never know what the real issue was. This is actually my daughter's car and she drives the wheels off of it. She's now gone through probably over a dozen drive cycles now and the light hasn't come back on. Go figure.

The only clue I have is that last week, when I was checking things out, when I pulled the electrical connector off of the Vent Shut Valve, there was a small amount of rust/dirt that fell out of the connector when I took it off. I looked at the harness end and the plug on the valve itself, didn't think much about it, then plugged it back in after I finished my tests. Looking back, that may have been the problem.