Author Topic: Oil pressure switch (Read 6019 times)

Patrick · « **on:** October 16, 2007, 06:39:57 PM »

When the oil pressure switch on the crankcase goes bad, does the light stay on or off? My oil light doesn't come on, but the bulb is good in another socket and a test light shows juice to the bulb and juice to the connector from the pressure switch to the wire harness. I figure it's a bad ground. The oil pressure switch is the ground, right? I pulled the switch when I painted the case. Could I have painted away the ground? Or is the switch just bad?

Patrick

scondon · « **Reply #1 on:** October 16, 2007, 06:48:57 PM »

Good question. I've never had one go bad, so I don't know the answer. I do know that if you disconnect the wire leading to the switch that the light will stay on. If the bulb in the instrument panel burns out, well then it's always off

Is your light staying on/off?

Patrick · « **Reply #2 on:** October 16, 2007, 07:04:33 PM »

My light is staying off, but I have juice with the test light at the little bolt that screws into the switch. Since this is a new rebuild I'd really like to be sure I have oil pressure before I do anything. I plan on installing an oil pressure gauge in the oil galley, but I don't know how well that will read with the kickstarter. I'm actually hoping for another explanation because with the top end on it's going to be a bear to get that pressure switch out. There isn't any clearance....

scondon · « **Reply #3 on:** October 16, 2007, 07:14:41 PM »

I'm not sure if you would get juice at the switch if the bulb was burnt, but it's easy enough to swap instrument bulbs just to confirm that it's not the bulb.

The main oil galley cap/plug(the one where you intend to install the pressure gauge) is easy to remove. You can take it off and use the kickstarter to confirm that oil is circulating. Watch out, it can get messy quick

If you need to change the pressure switch, I'm pretty sure that the large nut spins independent of the switch, allowing you to remove or install with the engine in the bike. Garage is too messy at the moment to dig one out to confirm this so hopefully someone else will chime in on this.

Klark Kent · « **Reply #4 on:** October 16, 2007, 07:20:08 PM »

i had this happen to me. my oil light would come on when the bike (550k1) was hot. turned out to be the oil pressure sensor. when the sender is working right apparently a diaphram is filled to the point of triggering a disconnect-ground fault- in the oil light circuit. my sender went bad and when the oil was thin enough the diaphram didnt do its job, and the oil light would come on. i.e. the sender actually breaks the oil light circuit when all is well.

so i think if you have an oil light that doesnt come on and the bulb is find you should be looking for a ground fault in that circuit.

good luck
-KK

Patrick · « **Reply #5 on:** October 16, 2007, 07:29:23 PM »

The bulb is fine. I actually tried three other bulbs before I finally switched with the bulb in the neutral light, which was working fine. All the bulbs work in the neutral socket, none work in the oil light. I have traced the wire all the way from the sender unit to the bulb and I have juice with the test light every place two things meet. So there is juice there, but no light. I figured the system must work by pressure from the oil disconnecting the ground, making the light go out. I don't really know what goes on inside the sender, so I'm guessing.

Until August this bike had sat since 1991. It's unknown how long it sat before then, so there was plenty of time for anything semi-delicate to encrust itself in whatever position it happened to find itself in.

The sender unscrews as a unit, but the clearance around it doesn't allow for a standard Craftsman 1/2-inch drive socket to get around it. It must take a thin wall socket.

Or maybe I just need to look at it some more.

Patrick

scondon · « **Reply #6 on:** October 16, 2007, 07:35:38 PM »

Sitting since '91? I can imagine the switch getting a little crusty

I've got to take off now, but I can check in the garage tomorrow night. I've got a few switches and I'll see if I can't remember which tool I've used to remove them, although you'll probably have it figured by then. Once you get it out it may be possible to clean/refresh it. If not, send me a PM and I can mail you one if you're in the US.

Patrick · « **Reply #7 on:** October 16, 2007, 08:05:18 PM »

Thanks, Scondon, but I've got a parts bike that has already been a generous donor of small parts, like the shifter mechanism and a cleaner kickstarter and such. If I can figure out how these come out I can try the sender from that bike. I think it's sat idle only since the later 90s sometime.

I just went out and pulled the wire from the sender unit. When I ground that wire to a crankcase bolt, the oil light comes on.

Patrick

750essess · « **Reply #8 on:** October 17, 2007, 05:40:14 AM »

With the engine running you should have 12v at the terminal screw on the sensor and when it is off you should have ground turning on the light, so yes your sensor is probably bad. It comes out with a pair of channel locks.

OldSchool_IsCool · « **Reply #9 on:** October 17, 2007, 05:58:17 AM »

Quote from: Patrick on October 16, 2007, 08:05:18 PM

I just went out and pulled the wire from the sender unit. When I ground that wire to a crankcase bolt, the oil light comes on.

Patrick

That proves ll circuit components are working except the pressure switch. Swap it out with the one from your doner bike. Hopefully that one works better.

Patrick · « **Reply #10 on:** October 17, 2007, 07:24:19 AM »

Channel locks. Bingo. I replaced the switch with the donor bike. I now have an oil light. I just hope that it goes out when I get to the point where I'm ready to start the bike.

Patrick

bender01 · « **Reply #11 on:** January 22, 2008, 05:15:20 PM »

I need to replace my switch too but I dont want to waste my new oil. Can the switch be changed out without draining the oil? All the looking around on this site leads me to believe that those switches arent too reliable. My bike is a 75 550k1 with 11k miles. My problem is same old comes on at an idle when hot.

Bodi · « **Reply #12 on:** January 22, 2008, 05:25:49 PM »

If the pressure switch is above the oil level in the sump, then there won't be a massive oil leak. Some may come out but not a lot. The 750 should be pretty dry too, the oil tank is above there but very little oil should ooze through the pump when stopped.

scondon · « **Reply #13 on:** January 23, 2008, 10:08:57 AM »

Quote from: bender01 on January 22, 2008, 05:15:20 PM

I need to replace my switch too but I dont want to waste my new oil. Can the switch be changed out without draining the oil? All the looking around on this site leads me to believe that those switches arent too reliable. My bike is a 75 550k1 with 11k miles. My problem is same old comes on at an idle when hot.

Not familiar with the 550's, but if your light comes on at idle when engine is hot I would be checking the oil pump, rather than the switch, to see if it's pumping at adequate pressure. Oil pressure goes down as oil heats up and is at its lowest at idle.

bender01 · « **Reply #14 on:** January 23, 2008, 11:32:02 AM »

there isnt a way to put a guage on it like the 750 without Drilling and tapping.With the bike idling at 1k I look in the tappet covers and see oil but it wont splash out unless it revs up to 12-1500. Seems alot if people have had this problem. I would love too here some others opinions too. the switch is 30$ a pump is 200$. I even bought a carb sync tool hoping that it was just out of sync. It was but still no dice. Ive also switched to 20w 50 oil. with no difference but being real cold blooded now.Does anyone rebuild these pumps? The bike runs like a top too me. What if my tach is off and it was actually idling at 800. My speedo is off by at least 5 mph. if it idles at 1200 no light!! ANY advice or opinion will be welcome. Thanks

Deltarider · « **Reply #15 on:** January 23, 2008, 11:48:48 AM »

First check if your bike's 1200 isn't actually 1000 rpm. Is your tachometer the ND or the Seiki type? I've seen a ND tachometer that showed 1300 where my DMM electronic tachometer read 1000 rpm!
Test is easy to do and can save you a lot of work.
I would not recommend an idle lower than 1050.

TwoTired · « **Reply #16 on:** January 23, 2008, 11:58:46 AM »

The switch is supposed to activate at something like 5-7 PSI, I'm told.

If the Pressure is really below that, then the oil pump is leaky, or the main and rod journals have more clearance than they should and leak more oil than the pump can keep up with.

If the switch is bad or dripping oil, then it may indicate low when it really isn't. You can change the switch without draining the oil.

Your choices are to replace the switch and hopes it fixes the indication. Or, instrument the actual pressure to see if the switch is lying to you. You could also remove the switch and apply pressure to it and test just what pressure it takes to open the switch.

Cheers,

Deltarider · « **Reply #17 on:** January 23, 2008, 12:12:35 PM »

Still I would first verify that tachometer.

Bodi · « **Reply #18 on:** January 23, 2008, 12:25:43 PM »

Honda supplied internal pump parts for very few models, if you check the parts fiche (cmsnl.com or powersportspro.com and others) you will see if the rotors are available - if there's only a part # for the complete pump then that's all they would ever sell you (and probably discontinued long ago).
Rebulds are possible but rather difficult, if internal parts are n/a. If there's a rotor set from a current bike that fits, sweet... but there's no cross refernce for these parts. A new rotor set can be made by a trochoidal pump manufacturer or someone with a CAD EDM system but the cost would be pretty disturbing. If the housing is worn, the pump is pretty much junk - a better used one looks like the answer.
The pump can be disassembled and inspected, the service manual has clearance specs I think. There will a gasket of some sort, if it's an O-ring it should be reuseable. Check the relief valve, I've seen pumps where this is damaged or sticking open slightly which drops the oil pressure a lot.
The most worthwhile test would be with a pressure gauge. I think the 550 switch is on the side (ie top) of the oil pump. It has a 1/8" NPT pipe thread, so by getting a pressure gauge and a street elbow you should be able to remove the switch and install the gauge in there well enough to check the pressure; the cover will obviously not go on with the gauge but you should be able to ride it a bit to see the pressure as the engine heats up. You should get minimum 40psi at idle and 60 - 80 psi revved up cold (the relief valve opens to limit the max pressure) and about 20psi at idle when hot, minimum about 40psi hot at higher RPM - higher is better. If it's really low then hope the oil pump is bad, the alternative is usually a full teardown for crank bearings.
Just an idea - is the 500 prone to having a loose cam chain wear into the main oil gallery? That would cause an oil pressure problem.

mrosso · « **Reply #19 on:** January 23, 2008, 02:31:24 PM »

I was thinking about removing the wires to the pressure sensor or plugging it all together and just going with an oil pressure gauge attached to the side of the case. Anyone doing this? Is there anything that would get screwed up if you go with a guage and ditch the sensor?

Patrick · « **Reply #20 on:** January 23, 2008, 03:24:58 PM »

I have a pressure gauge on the oil galley of my 750s, but I still have the oil sender switch. If, for some reason, I lose oil pressure I would prefer to have an idiot light telling me that right away. The pressure gauge lets me monitor the pressure so I know it's good, but I only want to look at it when I want to.

bender01 · « **Reply #21 on:** January 23, 2008, 05:23:05 PM »

Tach is a seiki. Ill see if my 350 tach can slip on there to compare. Im going to pull the switch and check for crud . If i can figure out how to trip the switch with pressure i will. But will probably get a new one. My honda shop looked and said I can still get an oil pump.Ignoring the sensor and getting a gauge would be ideal to me but I dont want to alter the bike to make it work. The relief valve inspection is going to require pulling the pump?! So if the it isnt the tach or the New 30$ switch, Ill then ditch the 50w to inspect it and go from there.That would be a good reason to get the gauge set up Bodi mentioned as im sure that will come in handy down the road. I hope its the switch. Im out to try my tach. if its ok Ill order the switch tommorow and Ill let eveyone know my outcome. Thank You for the advice.

bender01 · « **Reply #22 on:** January 23, 2008, 07:30:01 PM »

ok my 550 seiki tach reads 1200 on the 550 and thats where the bike seems to sound and idle very well. pulled my 350 tach over to the 550 and it read 1000. I did this 3 times to be sure. When i start the 550 the tach takes awhile to catch. Maybe thats my problem.thanks Ill know this weekened when i get out on the highway.

Deltarider · « **Reply #23 on:** January 24, 2008, 01:56:28 AM »

Still I would verify your tacho by comparing it to the reading of an automotive DMM. I consider such a DMM (with Dwell- and Tachofunction) a good investment. They are not that expensive anymore.

Idle should be at least a true 1000 rpm. Lower rpm may endanger the minimum required oilpressure.

Happy motoring

Bodi · « **Reply #24 on:** January 24, 2008, 07:27:04 AM »

The relief valve cap screws out from the lower right of the pump unit - it retains a spring and the valve piston. It will come off with the pump in, maybe... if there aren't any other parts in the way. Removing the pump is no big deal, just keep track of the dowels and the O-rings. The 3 screw round cover is the rotor cover, if you remove that you can check the rotor condition without removing the pump body. Just be careful to not damage the large O-ring I think is on that cover. To remove the whole pump, do not remove those 3 screws, just the 3 or 4 that are not on that round cover. It just pulls straight out, can be removed with oil in the bike just dripping whatever oil is actually inside the pump.

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Author Topic: Oil pressure switch (Read 6019 times)