I was able to put the fuel pressure tester on the vehicle, here's how it reacted:

Initially, the pressure shoots up quickly to about 6 bars, then the regulator seems to bring it down to about 3.5 bars. If I continue to crank the motor, the pressure slowly rises.

I tried it with the return line both connected, then disconnected and fed to a gas can, the results were the same both times, so I am assuming that there is not a clog in the return line.

The system pressure seems to hold for several minutes after the ignition is turned off, but I can see fuel dripping inside, beyond the air sensor .

The "lower chamber" pressure seems to be near the .4 bar difference that is mentioned in the shop manual.


With good fuel pressure numbers and wet plugs, perhaps I have to look at the possibility of a weak spark? Keep in mind, the engine WILL idle smoothly when the fuel pump relay is removed, or the fuel inlet line is disconnected. So there is enough spark to ignite whatever it's burning under that circumstance.

Another question I have regards the auxiliary air pump. My understanding is that it provides the extra air necessary when the air sensor is in the resting position. If the air pump is not functioning, would this have the effect of choking out the engine during start up ? I tried cranking the motor with the sensor plate slightly depressed, but the it reacted the same.

Anyone test their auxiliary air pump lately?