1985-1998 [Subscribe to Daily Digest] |
I've been working on a 1995 9000 CS.
I've got an EVAP valve CEL. It blinks 8 times.
I've done searching on here and someone sent me the EVAP valve section from his "Service Manual: Engine Management System, Trionic
OBDII" Thanks Street.
Lets start with mechanical:
Symptoms:
I've pulled off the line on the manifold that comes from the EVAP valve.
I can suck on the line (no resistance) when the ignition is off, and when the ignition is on but engine is off. I can not suck on the line (I get and maintain vacuum in the line) when the engine is on and the valve is not ticking for a brief period of time right after startup. When the valve starts ticking I can suck in pulses concurrent with the valve ticking. I can not blow though line at any time.
With the line that comes from tank I can suck on it (no resistance). I can not blow though it (I can pressurize and maintain pressure in the line).
My Analysis:
I have read that the valve has a safety where if it failed it would remain open. The results I've gotten from my tests confirm this by the fact that I can not suck on the valve when it is powered. I noticed that with the ignition on (engine not running) the valve is not powered. Is that correct? It also makes since that I can not blow though the valve ever, because that would be a boost leak. The line does not leak.
As to the line from the tank. The one way valve at the filler neck is working properly and the line does not leak.
On a side note: Townsend has some things hand written on the ELCD Valve page he has posted on his site. One of which says "Open 12V" and "Close 0-.1V" I have found the exact opposite. With the valve unpluged and in my hand I can suck threw it, thus being open, and when powered I can not suck though it.
Electrically:
Everything says that the valves should have a 26 ohm resistance. I have three used valves and they all share a mid-40s ohm resistance. I've even tried weiring up a 20 ohm resistor on the ground side of the valve. It changed nothing.
I have read from Townsend's site and Street's manual that the EVAP Valve is "activated by being grounded via pin 27 on the ECM" and that pin 27 is connected to pin 21 "in order to permit diagnosis"
I checked my ECU connector. If I go by my connectors indication of pin 21 and 27 I find that I have no pin 21. I went and probed my ECU connector for continuity on to the evap valve. On the wire that gives the valve +12 I find varying degrees of continuity to pins 48, 49, 31, 32, 1, 3, 4, 5, and 6. On the wire that gives the valve it's signal from the ECU I find connectivity to pin 27 only. I have not found any disconnected wires.
When properly installed my valve does exactly what I've read it supposed to: be closed on start, start ticking after a little bit, stop ticking every 4 minutes for 30 seconds.
Any insight as to what is going on here? Should I "add" a pin 21? I did have problems with the pinout in the book being wrong. I had to "shift" all the pins over two in order to make it accurate. Is the book wrong for my model year? Did they change OBD1 vs OBD2 EVAP valves? What about the whole 12v open 0v closed issue? Should I crush this car?
I havn't even touched the ABS light yet :P
posted by 24.10.98...
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