GPz Oil Sensor Issue

No eBay APP ID and/or Cert ID defined in Kunena configurationMy 1985 GPz750 build has a bug with the oil sensor. On the bench the oil sensor changes state from continuity to open as it should. The oil sensor provides ground to the oil light to complete the circuit. When oil flows it raises and internal magnet and opens so the light goes out since there is no path to ground. With the sensor mounted (in the bottom of the oil pan) I can start the bike while I monitor the continuity with a digital volt meter. It does not change state. Furthermore I swapped the sensor with another GPz 750 I've got in the garage and it too doesn't change to an open state.
The sensor just sticks up into the oil pan, there isn't any special passage or tube it ties into. This puppy pumps oil though. I bought a low quality cam cover that didn't fit well. Oil poured out of the cam cover like a waterfall. The oil pump is delivering good circulation. The bike has run for 30 plus minutes at up to 7K rpms. If there were oil delivery issues, they would have surfaced. Here is a picture of the sensor. Any thoughts as to what could cause this problem?

Not familiar with the gpz but If I were in the same position, I would play around with the oil level, within it's limits. It seems like an overfilled or underfilled motor may have something to do with it, if the bike shows no signs of oil starvation.

Another thought that crosses my mind. How did you test the sensors? Using the same oil, with the sensor in the same position as it would be?

Pretty sure it's just an oil level sensor, not a flow or pressure sensor of any sort. That leads me to think that perhaps the "float" isn't as bouyant as it's supposed to be (or that the oil level is actually lower than intended). I'm assuming your bench test didn't actually test that aspect.

If you want an oil pressure sensor it looks possible to install a pressure switch via in the port near the igniter pickups. The KZ750s use that port/switch, but on the GPz it's got a plug installed. Obviously you'd have to modify the wiring if you want the LCD to indicate the status of that switch rather than the oil level switch. I've considered doing it on mine, but decided to trust the oil pump and worry about more important things in life (like financing my retirement, or what to have for dinner).

I would clean the sensor in a big white bucket so that you can see if there's any crud that might have been causing the float mechanism to hang up. As a last resort, I would also consider opening the thing to take a look. by bending the 3 tabs on the top.

Partzilla has them in stock Not cheap but www.partzilla.com/parts/detail/kawasaki/KP-27010-1057.html

maybe they do. but maybe not. I'd be surprised if they did. Their parts availability listings aren't always correct.

ThatFiveOhTho wrote: Not familiar with the gpz but If I were in the same position, I would play around with the oil level, within it's limits. It seems like an overfilled or underfilled motor may have something to do with it, if the bike shows no signs of oil starvation.

Another thought that crosses my mind. How did you test the sensors? Using the same oil, with the sensor in the same position as it would be?

The oil is right in the center of the site glass and as this is plugged into the bottom of the oil pan the oil would have to be extremely low.

As for testing I removed both sensors, placed the on the bench. Set up my DVM for measuring resistance. Simply turning the sensors upside down causes them to go to an open state as the magnet slides towards the top of the brass cylinder you see in the picture. At rest position (gravity pulling it down) it has continuity which completes the circuit to light the oil light like when you first turn the ignition key on.

martin_csr wrote: I would clean the sensor in a big white bucket so that you can see if there's any crud that might have been causing the float mechanism to hang up. As a last resort, I would also consider opening the thing to take a look. by bending the 3 tabs on the top.

I did disassemble it and clean it Martin. I had to resolver the connection at the top to do so but it works well and behaves exactly like the one that has not been touched.

riturbo: Correct on the part numbers (not that you need me to validate) Using Partzilla I was able to determine all GPz 550s and 750s 82 through 85 use the same sensor. The Spectre 550 and 750 do as well. Surprising to me, the LTDs of the same vintage and size do not.

That Five OhTho: See comments above about my test process and side by side comparison with another 'unmolested' unit from another bike.

ayeckly: The sensor sits right in the bottom of the pan and the intake ports are at the bottom. If you look at the eBay pic you can see part of one of them at the top where the brass meets the aluminum.

As usual you all got me thinking. In the wiring diagrams the sensor is listed as "oil level sensor". I cannot find an oil pressure sensor shown anywhere in the Kawasaki service manual wiring diagrams for the GPz's.
If I'm not mistaken it also shows it as a normally open switch. I can tell you both show continuity to ground at rest. Very odd to me.

When they went to the oil level sensor, they got rid of the oil pressure sensor. Obviously, if you are routinely in the habit of checking your oil level, in the sight glass (bike upright and level, not running), then you don't really need the sensor.

On the 550's, I think you have to change the oil pan to an older type to be able to use the oil pressure sensor.

Basically, the motors break down to the older type that have more rounded castings, and the newer squared-off castings. The newer type more often got the oil-level sensor, while all of the older types got the pressure sensor.

On the 550's, the shaft drive LTD models had newer style motors, while the chain drive LTD's had older style motors.
I *think* the oil pans can be swapped, but I'm not positive.

I've often wondered if you could just drill and tap a port in the newer oil pan to use a pressure sensor, then you'd have both.

My 83 GPz1100's are stock with only oil LEVEL sensor, no oil PRESSURE sensor. This is shockingly silly design. I would rather have the low pressure warning, but seeing as how all my 81 and up stock KZ's and GPz's burn up copious amounts of dead dino's, having both would be the best plan!

On the 550 - 750 plain bearing cranks, you should have an aftermarket oil pressure warning light or gauge installed! The big fours are a little less critical of low pressures with roller bearing cranks. No oil pressure will spell rapid engine destruction, especially with plain bearings, even if there is adequate oil level. Hence why I would choose pressure monitoring over level monitoring on any engine, if I had to choose.

On all KZ fours, if the oil sensor is in the oil pan, it is likely a level sensor and not a pressure sensor. The only location on the oil pan that sees pressurized oil is inside the oil filter cavity. The later 1000 / 1100's with oil pressure sensor switches / warning lights have the sensor / switch located on the main oil gallery just behind the cylinder block between no. 2 & 3 cylinders, just below and to the right of the cam chain tensioner.

It would make sense that the GPz's oil level sensor should be normally closed with no oil present for a regular instrument light or gauge to work properly, but the GPz's electronic warning panel might work the opposite (I don't remember off hand). Either way, the sensor has to switch when the float rises off the bottom to the top of its travel, and that should be easy to check by submerging it in oil right side up with the meter attached to the lead and the sensor body (ground). The oil pan (sump cover) in turn gets its ground source from the pan bolts and maybe from the oil filter bolt. Paint could keep the bolts from grounding properly, causing the sensor circuit to malfunction.

Even if the level sensor works, I like to install an aftermarket wet / direct fluid sensing oil pressure gauge on all my high performance engines. Tapping off the main oil gallery usually works well enough. On stock or mild engines I at least install an instrument panel mounted pressure warning light (6-8 psi on plain bearing cranks, 2-3 psi on rollers) with remote electrical sensor.

Remember, pressure in the oil galleries only indicates the bearings are getting supply oil and has nothing to do with operating pressures inside the bearing, which are much higher. So don't be worried if your oil pressure gauge seems low when the engine gets hot. That is the oil thinning out and is normal. A good thing to remember is a TRW poster that used to be on the wall at the race shop I worked at - it said "pumps don't create pressure, they only create flow. Only restriction to flow creates pressure".

-Scott

The low oil light strikes me like an 80's idiot light in a car. "Here is the reason your patient died" If there isn't enough oil to flow through the bottom of that sensor in the bottom of the pan, you are already completely screwed. It is the posthumous announcement of a problem.