Measuring Frequency valve Duty Cycle

Hi Carl,

the FV DC is check

Hi Carl,

the FV DC is checked at the FV by hooking the 2 wires from the old timey Analog Dwell Meter set on 4 Cylindersetting, one DM wire to one each of the FV wires by slipping the protective rubber boot back on the FV wiring connector and inserting small adapters into the plug that can be reached by the DM wire clips. Once connected start engine and once closed loop condition is reached a properly tuned engine would read a Duty Cycle of 45%-55% needle gently swinging back and forth...if the Duty Cycle is out of spec...it will be neccesary to access the Mixture Control Screw at the Fuel Disttributor...for rich condition the MCS would need a CCW turn for correction, if the Duty Cycle indicates Lean Condition the MCS would need a slight CW adjustment...each time replacing the FD access port screw to plug the air leak which will cause erroneous readings. Each time an adjustment is made the 02 sensor should be unplugged, make corrections at MCS as necc. , replug 02 sensor..check DC.

To perform this test properly the engine should be warmed to open loop, O2 sensor connected.

All adjustments should be in small increments, access port replugged after each adjust and 02 sensor unplugged while adjusting and replugged after adj. and before rechecking DC.

Is any of this clear???

Regards, JRV

Hi Carl,

I brought the Bosc

Hi Carl,

I brought the Bosch book home in case you need any clarifications, so I'll have the reference material handy.

But perhaps I should clarify how a FV works...as we know the Bosch CIS FI system works by metering air flow and with fuel held at a constant but specific pressure controlled by the Aux. Pressure Reg. K-Lambda works the same with the addition of a release valve (FV) inline with the pressure side...by opening and closing this injector called a FV,,the mixture can be minutely & rapidly controlled by raising & lowering the System Pressure - High Pressure = valve closed=lean mixture, to Lower Pressure = valve open-richer mixture. This Valve (injector) is called the Frequrncy Valve. Thru electronics controlled via computer the readings of a heated 02 sensor are converted to signals sent to the FV opening it more rapidly allowing pressure to escape, or more slowly holding more pressure. In this manner the actual fuel muxture can be richened or leaned depending on the Frequency the injector operates.

This system cannot or does not compensate for faulty system pressure or many other possible malidies.



Regards, JRV

Thanks for your insightful exp

Thanks for your insightful explanation JRV. This is actually how I have been checking the FV. I see the 50%DC(according to my analog dwell meter) non-fluctuating at cold, them once warms moves to 75%DC once warm, also non-fluctuating. Very strange (I was expecting the 50% figure)but Mr. Foley sees same numbers (factory settings) that I do.

Have exchanged protection relay, jetronic ECU, both relays, tested diode, O-2 sensor. Any thoughts on why we *both* would see these numbers? Are the cars set extremely lean from factory?

Thanks once again for your time & help JRV. the board & members are a superb resource.

Carl

Hi again JRV,

Wish I could

Hi again JRV,

Wish I could tell you I did this the "right" way. Using my Gastester CO machine, adjusted to 1.2% CO very close to current setting. Then (shade tree time!) turned mixture "rich" CCW until popping in exhaust almost resolved (about 1/4 turn)...this corresponded to CO about 2.8% but idle sped up. Ran fine except now cold-starts (until warm) very rugged wants to almost die.

Turned further until idle speed dropped (about 1/4 turn CCW more) then returned to baseline. Turning "lean" (CW) from baseline get about 1/8 turn before engine begins to falter. Reading DC while doing this, it decreases to about 70% then cannot turn further without stalling motor. So physically cannot achieve the 50% DC.

So no, did not set properly (smile). And I know you can't really help much without knowing proper data and I respect your professionalism in refraining.

But interestingly, turning CCW (rich) increased DC to 82%. Why would this be?

Carl

PS All of the above with O-2 sensor connected

Thanks JRV - shall do all of t

Thanks JRV - shall do all of this (was going to reply yesterday for some odd reason my ISP server was down).

Removed cam covers to check camshaft alignment (correct) ordering gaskets will post results once reassembled.

Thanks again JRV,

Carl