Quote:
Originally Posted by ossiblue
Agree that you may have a problem with the bimetallic heating element, but it doesn't seem to account for your symptoms. Your numbers indicate the wur is functioning properly for a cold start and initial cold running. Even if the element has failed, the heat from a running engine would cause the bimetallic arm to adjust the pressure--unless the arm is faulty. You might do a follow up test by actually running the engine until it fully warm and then take a warm control reading. If it's still low, the arm is faulty as well.
A quick question about your test before you pursue any repairs: Did you check to see if there was current to the plug for the wur before doing the warm control test, or did you just plug in the connector? The heating element is the primary cause of failure in the wur but you should double check to see if it is actually faulty.
Back to your initial problem. I agree with Paul--it still sounds like a too lean mixture, though you still may have a problem with the wur. Could be air leaks or a leaned out mixture adjustment via the screw on the FD.
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The engine was not running when I performed the warm control pressure test, so as I understand it, the electrical connection to the WUR should be heating the bi-metallic strip in the WUR. Since there was no change in the pressure once I connected the electrical, I can only assume that:
(1) the WUR is not getting power, or
(2) the WUR is getting power but the bi-metallic strip is not heating properly
So, you are correct... I need to verify that the WUR is getting power before I assume the WUR is faulty.
Here is a link to a video on Youtube I used as a reference:
CIS Fuel Pressure Test - warm pressure test
My understanding is that at cold start, the arm of the BM strip pulls the diaphragm away from the valve which (a) increases fuel return to the tank and (b) reduces control pressure. When the BM strip heats up, it closes the valve which increases control pressure and decreases the amount of fuel return to the tank.
Under normal conditions (ie, not this bypass-starting-the-engine-but-run-the-fuel-pump-anyway test), it seems logical that the heat from the engine would cause the BM strip to warm and close.
This would seem to indicate that the strip works and explains why the car stars fine after the engine is already warm.
In my case, the control pressure never increased once the electrical connection to the WUR was made.