Hi All,
I’ve been lurking for a bit while I slowly fix up this 1998 Discovery that I acquired. The big issue right now is a P1447 code “Evap System Purge Valve Open or Short Circuit Fault”
that is preventing me from passing smog here in California. I’ve tested the purge valve; it opens and closes when voltage is applied and it has the same resistance measurement as a few others that I had an opportunity to check (43ohms). I have 14 volts coming on the brown/orange wire that ties into the multifunction relay just to the left of the charcoal canister and good continuity all the way to the ECU on the gray/yellow wire. I’m taking a huge guess that the ECU should complete the circuit at a given RPM to open and allow vapors into the intake manifold?? At this point I’m stumped and my electrical trouble shooting skills suck.
If the ECU is bad what are the chances I can grab one off FleaBay and swap without having to flash it? Are the ECU’s incapable of adapting to the vehicle while driving? The gas cap is a new Discovery Series I 1994-1998 Advanced Evaporative Loss (AEL) model from Rovah Farm. Any help would be much appreciated!!
Thanks
John

 

Has anyone had their ECU re-flashed and if so do you have a ball park cost or are there places where I could reliably order re-flashed set?

 

Cheaper and easier to buy a used one from Paul Grant. Do a search on this forum for him. He sells on Fleabay too. Match your part numbers so you get an AEL unit.

Beyond that read this;


EVAP canister closure valve performance: P1447

EVAP Canister Closure Valve Performance Test
The test compares the value of fuel tank pressure against a threshold, during normal purge operation. If the value of FUEL TANK PRESS VOLTS is
less than CLOSE VALVE BLOCKED PRESS, then an appropriate fault counter is incremented up to a limit of close valve blocked diagnostic fault
limit. Otherwise the fault counter is decremented down to a limit of zero. If the fault counter reaches the limit then an EVAP canister closure valve flow
fault is present.

The fuel tank pressure is measured at the fuel pump (it has a sensor), check the connector at the top of the pump by removing cover under load space floor carpet/rubber.

 

Thanks ihscouts!! So I pulled up the carped/foam and found the fuel pressure sensor connector has a red, black (ground) and green/pink. Red and black terminate at C1033 on the ECU and pink/green at C1017 on the ECU and red has 5.1 volts with the key on. For continuity I had .2 ohms on the red, black and pink/green from fuel pressure sensor connector to ECU and the same from black to ground at the battery. Seems pretty consistent with everything being in order although I’m wondering about the 5 volts on the red.

 

5V is the fuel float to gauge reading.

Pink/Green is fuel pressure sensor.

.2 ohms is pretty good.

Black is always ground on a Rover.

What you'd have to do is measure resistance changes on the pressure sensor leads as the truck is running. Can you do this?

 

I"ll have to rig up something, maybe careful insertion of pins into the wire and check resistance that way.

 

I inserted sewing pins into the green/pink (high tech , I know) at the pressure sensor connector at the fuel tank and at the ECU connector. I ran my test lead from these to the multimeter and got .9 ohms with the key off. With the engine running I was getting a .1 ohm fluctuation and the meter was beeping like I was loosing continuity (voltage pulse??) and that may have accounted for the .1 ohm fluctuation. Not sure if that was a valid test or not.