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oil pressure (light) revisited

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  • oil pressure (light) revisited

    the oil light on my 79 special will come on every now and then for various lengths of time. i assumed it was an electrical problem. the only thing that worried me was that it would come on for awhile, then go out - in my thinking, if it were electrical it would occasionally blink on and off quickly. the last thing it did which was odd, was that at idle it would be off, but the more i revved the motor the brighter it got. this confused me even further - the only electrical explanation i could think of here was that it was shorting out just enough to where it got brighter and brighter the more volts the alternator cranked out.

    so..... i just went to the nearest parts store and bought a $12 oil pressure guage. it reads ~20 psi at idle, and 60+ psi under throttle. I couldn't find anywhere in the manual what range this should be - i figure it can vary quite a bit but I assume I am fine with the pressure I'm getting.

    It was at one time brought to my attention that a faulty oil sender switch can give a low oil pressure reading under higher pressures. I am thinking that is probably my problem.

    Though I'm sure it's happened before, I personally have never really heard of a small engine having oil pressure problems unless the operator has run it out of oil.

    My question is this: is there any reason why i would have perfectly good oil pressure 95% of the but have an occasional ~5 minutes here and there where the oil pressure is less than adequate? I am pretty much convinced my problem is electrical, however I am still somewhat unfamiliar with small engines and would rather not burn mine up.

  • #2
    Oil pressure gauges were discussed here recently. Where did you mount it? And is it an electric gauge, or a pressure gauge?
    Brian
    1978E Midlife Crisis - A work in progress
    1984 Kawasaki 550 Ltd - Gone, but not forgotten

    A married man should forget his mistakes. There's no use in two people
    remembering the same thing!

    Comment


    • #3
      I would replace the sensor, it should not come on until oil pressure drops below 5 pounds, and they are a common thing to go out.
      CUAgain,
      Daniel Meyer
      Author. Adventurer. Electrician.
      Find out why...It's About the Ride.

      Comment


      • #4
        xssiveone - it's a pressure guage, and i didn't really mount it - i just wired it to the handlebar underneath the ignition switch. this is only temporary until i'm convinced that my oil pressure is fine - which it appears to be. what i've thought about doing is removing the instrument panel (blinker light, oil light...) and somehow replace it with miniature guages (oil pressure, oil temp). if this project happens it will be quite a ways down the road though.

        Dragonrider - thanks for the advice. the lowest my oil pressure has gotten so far is about 17 when warm & at idle. so i the sensor typically kicks in at 5 psi, I figure i'm plenty good with the pressure i have and will try to find a new sensor.

        Comment


        • #5
          apparently my trip to work was not sufficient to get the bike up to operating temperature. while i am convinced my oil light problem was electrical, it seems that my oil pressure is indeed low. driving down the highway at 60 mph (around 3000rpm??) it was running about 30 psi. at idle, the guage barely registered (something like 2 or 3 psi) - and since the light is apparantly supposed to come on when pressure drops below 5 it would seem i have a problem.


          any thoughts?

          Comment


          • #6
            clogged oil line... oil pump.

            U can get to it if u take off the oil pan and remove the 3 bolts that hold it on...

            U should be able to do it without pulling the engine... just don't wear your sunday shirt

            When u dissasemble the oil pump, look for grooves in the mechanism. Clean it with a degreaser and assemble... shake it to check it for rattles... there shouldn't be any, or at a minimum. Oil the pump before assembly and turn it by hand, placing your finger over the oil hole on the top... u should feel at least a little compression.. barely noticible... if not, change the oil pump, since the oil pump housing gets scratched too...
            Sure beats the repairs of a seized engine.

            LP
            If it doesn't have an engine, it's not a sport, it's only a game.
            (stole that one from I-dont-know-who)

            Comment


            • #7
              Make sure OIL is all it handles..


              if its a 79sf, it also handles the warning for the brake/tail circut on that bulb ... and mine was giving me occasional fits too..

              turned out to be a bad tail light connection.... after I had oil everyehwere.. i found it...

              try the brake/tail light stuff .. much cleaner and easier.. just in case
              jeff "Wags"
              Bothell, Wa

              79sf mongrel
              79sf rusty
              79 partsbike almost complete

              Comment


              • #8
                If you just bought the oil pressure gage at an auto parts store, please give us the name of the store and part number/stock number of the gage. Also any manfacturer part numbers. Were any special adapters needed? If so list them as well. Gotta picture? I am sure other guys would like to go get one.

                As for the problem, I would pull of the oil pan and check the pump as strom recommended, possibly you just have something blocking the screen. Here is what you will find when you get inside:

                Gary Granger
                Remember, we are the caretakers of mechanical art.
                2013 Suzuki DR650SE, 2009 Kawasaki Concours 1400, 2003 Aprilia RSV Mille Tuono

                Comment


                • #9
                  sixtysix, while u're at it, could u check the neutral switch for me... where is it?

                  Couldn't find it... really... stop laughing!

                  dunno where to connect the wire... it should go to the pick-up cluster of wires... but I don't know where the switch is located...

                  LP
                  If it doesn't have an engine, it's not a sport, it's only a game.
                  (stole that one from I-dont-know-who)

                  Comment


                  • #10
                    Originally posted by strom
                    sixtysix, while u're at it, could u check the neutral switch for me... where is it?

                    Couldn't find it... really... stop laughing!

                    dunno where to connect the wire... it should go to the pick-up cluster of wires... but I don't know where the switch is located...

                    LP
                    Just a guess with out actually looking but is it the light tan wire in the bottom left corner of this photo?

                    Gary Granger
                    Remember, we are the caretakers of mechanical art.
                    2013 Suzuki DR650SE, 2009 Kawasaki Concours 1400, 2003 Aprilia RSV Mille Tuono

                    Comment


                    • #11
                      Gary's digital pictures

                      Gary - Your digital pictures kick a__! They make repairs much easier. Thanks for your contributions to the mechanical art!
                      Robert
                      79 SF

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                      • #12
                        Thanks!!
                        Gary Granger
                        Remember, we are the caretakers of mechanical art.
                        2013 Suzuki DR650SE, 2009 Kawasaki Concours 1400, 2003 Aprilia RSV Mille Tuono

                        Comment


                        • #13
                          well, Gary, where are the pix of the rest of the oil pump assembly?
                          Mike * Seattle * 82 F'n'XJ1100 *

                          Comment


                          • #14
                            Well, 66... there IS a bolt there, no wire...

                            According to the microfiche, it should be a... well, to hell with what should be... it isn't anyway.

                            I guess a simple test should do it... connect the tan wire to the ground (frame, engine etc...), and if neutral light comes on, that's it. If not... it aint it.

                            Where does the tan wire go? Perhaps to the pick-up coil wire cluster? If so, it's definetly the neutral light switch wire... and I don't have the original switch...

                            Will check some more...

                            Thanx!

                            LP
                            If it doesn't have an engine, it's not a sport, it's only a game.
                            (stole that one from I-dont-know-who)

                            Comment


                            • #15
                              sorry i haven't gotten back to you sooner
                              sixtysix.... there's nothing special about
                              the oil guage i bought. just a plain pressure
                              guage bought at the local parts store.

                              i didn't know for sure if the fittings would work -
                              i was actually planning on having to find an
                              adapter but it screwed in there just fine.

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