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Re: How to tell if your fuel pressure regulator is (archive)

[ Follow Ups ] [ 5-series (E34) Message Board ] [ Msg. Board FAQ ]

Posted by Richard V on April 03, 2000 at 21:14:45:

In Reply to: Re: How to tell if your fuel pressure regulator is posted by Paul H. on April 03, 2000 at 02:59:31:

: : Does anyone know how to tell if the fuel regulator is bad? I realize the fuel economy has to be 1st sign, but I have a hesitation conditions on my '92 535I 5 speed, more noticeable when cold, but also noticeable (not as much) when warmed up, and I am suspecting the fuel pressure regulator. I can disconnect the 02 sensor, and the problem goes away. I have surmised, that I may have a rich fuel mixture and the 02 sensor is telling the system to "lean out" consequently, the hesitation.

: As far as I understand, the O2 sensor, when unplugged caused the DME to enter an open loop state, which slightly enriches the mixture.

: Just as an experiment, try plugging the hose from the carbon canister to the inlet manifold. I have long been suspicious that this may be contributing to a similar hesistation condition on my '91 535i 5spd.

: I experimented with this recently, and am convinced that drivability improved. I have now installed a "restrictor" orifice in the hose, which allows the canister to be purged, but in a limited way.

: I have an electric purge valve, but don't know what is correct operation for it. I do know that it operates, in a pulsed manner, all the time. I'd have thought that it should be not operating at high manifold vacuum ie. idle and part throttle.

: Anyway, food for thought.

: Paul.

Paul, I tried what you suggested. I can not notice any change in idle quality when removing (& plugging the vacuum line to the FR. On, Off, on, off not change. I did remove the purge valve & plugged it. Drove around the block and could not tell much difference. With or without the FR hooked up. Any other suggestions?

BTW, the purge valve doe pulsate about 1-2 times a second

Thanks, Richard V.

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