[Spit]

I may have this fixed!! went to a Dodge Dealer and had them pull a pump out of stock abd checked it with a volt ohm meter, they want $135 for it!! I found out the one I had put in from a junkyard was bad. Then I went to a junkyard and got another pump checked it with my volt ohm to make sure it worked like the new one at the dealership...Put it in Saturday and no codes thrown as of yet..(knock on wood). I did learn somethings about how this pump is supposed to work and how you can test for electical problems with the internal reed switch.

FYI
1st postion terminal/wire 12 volt common (12v in to pump)

2nd position " " ground for vacuum solenid this grounding is controled by the PCM..the PCM only grounds the solenoid when it wants to pump pressure in evap system to check for leaks and in fact it pulses the ground on and off fairly quickly to make the diaphram in the pump rise & fall and build up pressure.

3rd position " "12v from the pump back to the PCM..this is controled by a reed switch in the pump and is normally closed...So that when the pump is in it's normal un-energized state the 12v going into the pump is going back to the PCM. Once the pump has pumped up some pressure the reed switch opens and the PCM knows that the system is pressurized and it monitors how long it takes for the system to leak down... too fast and it throws a minor leak code, way too fast and it throws a major leak code

So if you test your pump with a meter...between 1 and 2 should be a small resistance. and if you put 12v on 1 and a ground on 2 you should hear the solenoid click If you test between 1 and 3 there should be continuity.


My pump did not have continuity between 1 and 3...I don't think that the 12v that needs to get back to the PCM was getting there and hence the P1494 code.
Spit