EVAP Vent Valve Test?
Posting Guru
Joined: Feb 2002
Posts: 1,534
Likes: 2
From: Warren, MI
Electrically, it doesn't matter. It can be anywhere in the circuit as long as it's in parallel with the coil. It's there to protect the driver electronics from spikes when the coil's electrical field collapses and induces "back -EMF" into the circuit. The diode shorts that spike to ground.
Hotshot
Joined: Jan 2004
Posts: 19,768
Likes: 1,082
From: St Louis
The key is that it must be across the coil. Of course, coils can be energized by switching the "Hot" ala the AC clutch coil or they can be energized by providing a ground to the "low" side of the coil.
Since there's no diode apparent in this circuit, one of two things would be assumed: 1) Any diode used is internal to the PCM or 2) there's no diode, so don't worry about it.
Since there's no diode apparent in this circuit, one of two things would be assumed: 1) Any diode used is internal to the PCM or 2) there's no diode, so don't worry about it.
Posting Guru
Joined: Feb 2002
Posts: 1,534
Likes: 2
From: Warren, MI
The key is that it must be across the coil. Of course, coils can be energized by switching the "Hot" ala the AC clutch coil or they can be energized by providing a ground to the "low" side of the coil.
Since there's no diode apparent in this circuit, one of two things would be assumed: 1) Any diode used is internal to the PCM or 2) there's no diode, so don't worry about it.
Since there's no diode apparent in this circuit, one of two things would be assumed: 1) Any diode used is internal to the PCM or 2) there's no diode, so don't worry about it.
A search found the following:
To minimise the antenna-like radiation of this electromagnetic energy from wires connected to the inductor, the flyback diode should be connected as physically close to the inductor as practicable. This approach also minimises those parts of the circuit that are subject to an unwanted high-voltage — a good engineering practice.
A closer look my '09s diagrams showed all solenoids have polarity markings.
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5th Wheeling
Joined: Aug 2012
Posts: 32
Likes: 0
Can someone tell me why the following is happening?
Every 3rd day (like clockwork) my escape throw a po 455 code.
It doesn't matter how much gas is in the tank.
I clear the code, drive it to work the next day, no code.
Drive it to work the following day, no code.
Drive it to work the 3rd day, and I can tell you almost the exact mile/time the emission light will come on!
What gives!?!?!
Does the EVAP system only cycle every 3 day or what?
Thanks!
Every 3rd day (like clockwork) my escape throw a po 455 code.
It doesn't matter how much gas is in the tank.
I clear the code, drive it to work the next day, no code.
Drive it to work the following day, no code.
Drive it to work the 3rd day, and I can tell you almost the exact mile/time the emission light will come on!
What gives!?!?!
Does the EVAP system only cycle every 3 day or what?
Thanks!
Posting Guru
Joined: Feb 2002
Posts: 1,534
Likes: 2
From: Warren, MI
Can someone tell me why the following is happening?
Every 3rd day (like clockwork) my escape throw a po 455 code.
It doesn't matter how much gas is in the tank.
I clear the code, drive it to work the next day, no code.
Drive it to work the following day, no code.
Drive it to work the 3rd day, and I can tell you almost the exact mile/time the emission light will come on!
What gives!?!?!
Does the EVAP system only cycle every 3 day or what?
Thanks!
Every 3rd day (like clockwork) my escape throw a po 455 code.
It doesn't matter how much gas is in the tank.
I clear the code, drive it to work the next day, no code.
Drive it to work the following day, no code.
Drive it to work the 3rd day, and I can tell you almost the exact mile/time the emission light will come on!
What gives!?!?!
Does the EVAP system only cycle every 3 day or what?
Thanks!
I was reading in my manual that certain EVAP test was run when the engine was OFF. It tests how long it held the vacuum.
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5th Wheeling
Joined: Aug 2012
Posts: 32
Likes: 0
I vacuum tested the purge valve today.
I took both inlet on outlet hoses off the valve
Put vacuum to the canister side of the valve first (8 hg), put a 12V source to the electrical connection and nothing happened.
Next, I put a vacuum to the manifold side of the purge valve, put a 12V source to it and nothing happened on that side either!?!
Is the purge valve bad? I thought that at least one side of the valve shouldn't hold vacuum while the other side should.
What's wrong?
I took both inlet on outlet hoses off the valve
Put vacuum to the canister side of the valve first (8 hg), put a 12V source to the electrical connection and nothing happened.
Next, I put a vacuum to the manifold side of the purge valve, put a 12V source to it and nothing happened on that side either!?!
Is the purge valve bad? I thought that at least one side of the valve shouldn't hold vacuum while the other side should.
What's wrong?
Posting Guru
Joined: Feb 2002
Posts: 1,534
Likes: 2
From: Warren, MI
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5th Wheeling
Joined: Aug 2012
Posts: 32
Likes: 0
I have had the vent solenoid valve off already and it held pressure and dumped after 12v was put to it.
I've checked everything else, so the last thing to check is the purge valve and the was the process of checking it I found on the web.
How about the tank's vent vapor valve
Or the (simple) check valve by the canister?
I've checked everything else, so the last thing to check is the purge valve and the was the process of checking it I found on the web.
How about the tank's vent vapor valve
Or the (simple) check valve by the canister?
Posting Guru
Joined: Feb 2002
Posts: 1,534
Likes: 2
From: Warren, MI
I have had the vent solenoid valve off already and it held pressure and dumped after 12v was put to it.
I've checked everything else, so the last thing to check is the purge valve and the was the process of checking it I found on the web.
How about the tank's vent vapor valve
Or the (simple) check valve by the canister?
I've checked everything else, so the last thing to check is the purge valve and the was the process of checking it I found on the web.
How about the tank's vent vapor valve
Or the (simple) check valve by the canister?
Thread Starter
|
5th Wheeling
Joined: Aug 2012
Posts: 32
Likes: 0
When I tested the vent solenoid valve with a 12V source today, it closed fine.
But I notice when I blew air back up through the valve, I felt and hear air leaking out around the electrical connection (pins)?!?!
Should this happen? Is this valve bad then?
But I notice when I blew air back up through the valve, I felt and hear air leaking out around the electrical connection (pins)?!?!
Should this happen? Is this valve bad then?
Posting Guru
Joined: Feb 2002
Posts: 1,534
Likes: 2
From: Warren, MI
What about in the other direction or vacuum? It is a vent valve so it might not seal in one state although that doesn't sound right.
Posting Guru
Joined: Feb 2002
Posts: 1,534
Likes: 2
From: Warren, MI
It's open then so it shouldn't matter.
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5th Wheeling
Joined: Aug 2012
Posts: 32
Likes: 0
When I put a vacuum on the solenoid valve today, out of the car with power (12V), to close it. I hear the vacuum leaking around the electrical plug.
When the car's computer runs the leak test, it close the vent solenoid valve and puts vacuum to the system and sees how long it take the vacuum to decay. To short in time it would throw a po 455 code.
So I'm thinking the vent solenoid it bad.
When the car's computer runs the leak test, it close the vent solenoid valve and puts vacuum to the system and sees how long it take the vacuum to decay. To short in time it would throw a po 455 code.
So I'm thinking the vent solenoid it bad.