Question about Ford Ranger
1996 Mazda B2300 SuperCab. Replaced canister purge solenoid and fixed leak in vapor return line. Check engine came back on. How do I test the flow sensor and is there a fuel tank pressure sensor in the tank, and how to test. Also, the "Fuel Vapor Vent Valve" on top of tank, how does it work, how to test, how to remove? I did have a defective purge solenoid (replaced) and a leak (fixed) but still have check engine light. Larry
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Posted on Jan 02, 2017
Change the evap vent solenoid canister located near the master cylinder on the right side of the engine or your hoses may be cracked. Good luck!
Posted on Mar 12, 2009
SOURCE: 1997 malibu / I had faulty code po440 . I Replaced Purge valve behind engine, canister valve solenoid, gascap from dealer, charcoal canister, smoke test. 1 week later check engine light on again wit
Diagnostib Test Code (DTC) P0440 is defined by SAE J2012 simply as "Evaporative Emission System".
This code is what I call a "catch-all" code for the evap system. This is the code that sets when all the other EVAP codes do not apply and there is a malfunction detected in the EVAP system.
It is not really hard to diagnose this code if you have the correct equipment and understand how the EVAP system operates.
How DTC P0440 sets:
The system is tested when there are no electrical problems with the Purge Control Solenoid Valve (PCSV) or Canister Vent Solenoid Valve (CVSV) circuits and the Fuel Tank Pressure (FTP) sensor voltage is within the operating parameters. The Powertrain Control Module (PCM) commands the CVSV to close and the PCSV to open and apply vacuum. It then looks for a change in the FTP voltage to indicate that there is a vacuum being drawn on the fuel tank. If there is no change, DTC P0440 sets.
If there is a change in FTP voltage, the PCM draws the vacuum to a predetermined set point and closes the PCSV (leaving the CVSV also closed) and looks for decay in the vacuum in the tank as evidenced by the FTP voltage. If the predetermined set point cannot be reached, DTC P0440 sets. If the set point is reached and the decay is faster than allowed over a predetermined time period, DTC P0440 sets.
It should also be noted that the monitor for this code is a "type B" DTC, meaning that it must fail on two successive drive cycles before it will turn the check engine light on. So, if it fails on the current drive cycle, then the conditions for running the monitor are not met on the next drive cycle, the code will not set on the second or third drive cycles. All conditions must be met and the monitor must fail two drive cycles in a row. This explains why it may take a week or two before the check engine light comes back on.
This code is very easy to diagnose using a scan tool that is capable of performing "purge and seal" tests and graphing the FTP voltage over time. The technician can actually "see" the vacuum being drawn on the fuel tank and the vacuum decay by doing it this way. Repairs can be verified this way without having to drive the vehicle several times to get the EVAP monitor to run.
By running the evap purge/seal function on the scan tool and using hose clamping pliers, different parts of the system can be checked by clamping off the hoses that connect the components and watching the FTP voltage graph. If there is no change in the FTP voltage when the system is commanded to purge, a vaccum gauge should be used to verify that the purge solenoid is actually working and that vacuum is being applied to the rear of the vehicle There could be leaks in the line between the purge solenoid and the canister.
For an example of how this works:
Possible rust holes in the filler neck and/or a defective fuel cap can be determined if there is no change in the FTP sensor voltage or rapid decay upon the initial test that goes away when the filler tube hose is clamped off between the filler tube and the fuel tank. A sticking CVSV can be determined in the same fashion by clamping off the hose between the charcoal canister and the CVSV.
Holes in the hoses themselves can also be diagnosed the same way by disconnecting them from the vacuum source end and plugging the source tube. Example, remove the vent hose from the canister and plug the hole in the canister. If the problem goes away, it is either the hose leaking or the CVSV leaking. So, reconnecting the hose to the canister and disconnecting it from the CVSV and plugging the end of the hose will tell you if it is the hose or a sticking CVSV.
This may sound really involved, but it is very easy to diagnose this way once you know how.
Posted on May 11, 2012
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