Pb sensors (what are they)


Information and questions on GL1200 Goldwings (1984-1987)
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Bray20
Posts: 15
Joined: Fri Sep 24, 2010 8:42 pm
Location: Norman, Oklahoma
Motorcycle: 1985 GL1200 Ltd.

Pb sensors (what are they)

Postby Bray20 » Sun Jul 08, 2012 8:21 pm



I have an 85 Ltd and my problem is, sometimes when I start it the rpms drop off to about 200. After I start driving it runs okay but the rpms fluctuates and I can feel it surging. I found a vacuum hose loose on the pbl sensor. I have not started it sense hooking the hose back up. I would like to know what the pb sensors do. From looking on the internet I saw where it was mentioned that they are parking brake sensors. But being a goldwing why would it have a parking brake sensor. Would that cause the motor to surge as I mentioned and why is there a vacuum hose hooked to them. Thanks for any help you can give.



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thrasherg
Posts: 1837
Joined: Tue Oct 20, 2009 11:21 am
Location: Plano, TX
Motorcycle: 2004 GL1800, 2005 Honda Shadow 750, 2008 Yamaha R6 with RG500 engine, CRF450X, CRF230, CRF250X, XR200, CR500

Re: Pb sensors (what are they)

Postby thrasherg » Mon Jul 09, 2012 11:44 am

I think you have misunderstood something.

The only things connected to the inlet manifold should be a carb and a timing advance unit (Other bikes might also have a vacuum operated fuel tap). If the unit is the timing advance unit, it will cause your idle to vary if it is misbehaving (They can get very stiff, or the rubber diaphragm inside can split (Potentially causing a lean condition (Not good)). Others will chime in, but I don't think there is anything else connected to the vacuum/inlet side of the carb.

Gary

Bray20
Posts: 15
Joined: Fri Sep 24, 2010 8:42 pm
Location: Norman, Oklahoma
Motorcycle: 1985 GL1200 Ltd.

Re: Pb sensors (what are they)

Postby Bray20 » Mon Jul 09, 2012 1:50 pm

Thanks for the feed back. The 85 Ltd is a fuel injected motor. I got a feed back from another forum and found out the Pb stands for Plennum Barometric sensor. The sensors are similar to the map sensor on an auto. They regulate the fuel mixture in the banks of the injector banks. With the vacuum hose discounted the sensor registered no vacuum on that bank and the fuel mixture was not regulated properly.

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thrasherg
Posts: 1837
Joined: Tue Oct 20, 2009 11:21 am
Location: Plano, TX
Motorcycle: 2004 GL1800, 2005 Honda Shadow 750, 2008 Yamaha R6 with RG500 engine, CRF450X, CRF230, CRF250X, XR200, CR500

Re: Pb sensors (what are they)

Postby thrasherg » Mon Jul 09, 2012 2:05 pm

Sorry for the bum steer, i forgot that some of the older wings had fuel injection.. The pressure sensor is connected to the air box plenum (Before the throttle butterflies) and is used to detect changes in atmospheric pressure and correct the fuel/air mixture as you go up and down mountains and other tall obstacles!! I thought from your description the PB sensor was after the butterflies/carb.. If this sensor is bad it will cause some rough running, but your symptoms don't sound like I would expect if this sensor had failed!! I suspect you are looking for another problem.. Hopefully other more knowledgeable people can chip in..

Gary

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virgilmobile
Posts: 7660
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: Pb sensors (what are they)

Postby virgilmobile » Mon Jul 09, 2012 2:34 pm

The sensor connection fine tunes fuel delivery.there are 2 of them,and it will overload the engine when unhooked.
The sensors expect about 9" of vacuum at a idle and report a corresponding voltage to the ECM.It uses that voltage along with the throttle position sensor voltage,ambient air temp and engine temp sensor to determine the pulse duration of the injectors.




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