oil pressure switch jump?

[mattsoltesz 0]

Please be nice...im a novice....is it possible to jump the oil pressure switch? I have a 93 520-H.....and the oil pressure switch has to leads off it? How does it work? Does it just complete a circuit when working correctly?

[kpinnc 16,234]

Matt (I assume), most oil pressure switches that I have seen are very simple. They are normally a closed switch, and the wires run between the coil and a ground source. When the oil pressure reaches a pre-determined PSI, the switch opens, removing the ground source from the coil. This of course allows proper ignition, but will ground the coil in the event of a loss of oil pressure while running. It is a VERY good thing to have working correctly, as it protects your engine. I would say it protects your engine more than any other safety feature you have.

Again, I am assuming here- you may be looking into bypassing this feature, which I would discourage. It would be far better to repair or replace the issue you may be having. Keep in mind that the switch may be working fine, and you actually have an oil pressure problem. You will destroy an engine designed for "full pressure" lubrication if it does not maintain the desired pressure.

Good luck!

Kevin

[mattsoltesz 0]

I definately dont want to permantly bypass the switch...just to see if thats part of the problem.....also Im having a hard time getting the flywheel off...i need that off to get the oil pressure switch out..

[Duvall 0]

Not sure if you are thinking that the oil pressure switch is part of the engine cranking problem ....

The oil pressure switch would not cause the engine to not crank.

[04fxdwgi 1]

Please be nice...im a novice....is it possible to jump the oil pressure switch? I have a 93 520-H.....and the oil pressure switch has to leads off it? How does it work? Does it just complete a circuit when working correctly?

If I'm not mistaken, the oil pressure switch controls the "idiot light" on the dash and activates the hour meter only. If the oil pressure switch controlled the cranking / ignition, you would never get it to start after an oil change.

[kpinnc 16,234]

If I'm not mistaken, the oil pressure switch controls the "idiot light" on the dash and activates the hour meter only. If the oil pressure switch controlled the cranking / ignition, you would never get it to start after an oil change.

Do what???????

I have several small engines with full pressure oil systems. The oil pressure switch only opens after the pressure reaches 4psi, which is easily achieved when the starter turns the flywheel- providing the full pressure oil system is working correctly.

Operating engine oil pressure is obviously higher, but the switch ensures the system is working BEFORE damaging the engine while cranking with no oil.

And my hour meter on the 518-H works with only the key switched on. The engine need not be running to accumulate hours, and the oil pressure switch has nothing to do with it.

Kevin

[04fxdwgi 1]

Do what???????

I have several small engines with full pressure oil systems. The oil pressure switch only opens after the pressure reaches 4psi, which is easily achieved when the starter turns the flywheel- providing the full pressure oil system is working correctly.

Operating engine oil pressure is obviously higher, but the switch ensures the system is working BEFORE damaging the engine while cranking with no oil.

And my hour meter on the 518-H works with only the key switched on. The engine need not be running to accumulate hours, and the oil pressure switch has nothing to do with it.

Kevin

The oil pressure switch does indeed control the hour meter on the 520H..... See diagram.

Attached Image (Click thumbnail to expand)

[04fxdwgi 1]

Do what???????

I have several small engines with full pressure oil systems. The oil pressure switch only opens after the pressure reaches 4psi, which is easily achieved when the starter turns the flywheel- providing the full pressure oil system is working correctly.

Operating engine oil pressure is obviously higher, but the switch ensures the system is working BEFORE damaging the engine while cranking with no oil.

And my hour meter on the 518-H works with only the key switched on. The engine need not be running to accumulate hours, and the oil pressure switch has nothing to do with it.

Kevin

I just checked all the wiring diagrams for the '93 520H (which I have also) and the oil pressure switch indeed only controls the idiot light and hour meter.

The switch is a double pole / single throw switch, meaning one normally open and one normally closed contact with the common being the grounded body of the switch. With the engine not running (no oil pressure), the normally open contact goes to the hour meter (black wire) and the normally closed contact goes to the oil pressure light (dark blue wire). Both these circuits use the common contact of the switch which goes to ground internally.

Switch has nothing to do with the start or run circuits of the '93 520H.

Personal note: After changing oil and filter, excessive cranking may be required to fill filter and pressurize oil system to get a start if oil pressure switch controlled ignition. There is nothing wrong with a start with zero pressure as residual oil in brearings will protect them while pressure builds with the new oil, as long as the engine isn't "rev'ed up" before oil pressure builds. Most well maintained modern engines with electronic ignition will start within a couple of revolutions of the starter, long before pressure builds and the pressure will increase as engine comes up to idle. On engines where oil pressure switch is interfaced with fuel injection, starter circuit bypasses the oil pressure switch to allow the start with low pressure.

Hope this clears up the controversey.........

[04fxdwgi 1]

Do what???????

I have several small engines with full pressure oil systems. The oil pressure switch only opens after the pressure reaches 4psi, which is easily achieved when the starter turns the flywheel- providing the full pressure oil system is working correctly.

Operating engine oil pressure is obviously higher, but the switch ensures the system is working BEFORE damaging the engine while cranking with no oil.

And my hour meter on the 518-H works with only the key switched on. The engine need not be running to accumulate hours, and the oil pressure switch has nothing to do with it.

Kevin

Kevin,

Looking at the diagram for your 518H, you are correct in stating the hour meter works with only ignition switch in on position, but I only see your oil pressure switch going to "idiot light", since there is only one lead on your switch, not two, according to the Toro / Wheelhorse documentation.

Bill

[mattsoltesz 0]

Well at least its not the oil switch....I still cant seem to get crank from turning the key. Only if I jump the two large terminals on the starter. I guess I will have to take it to someone....It only has 251 hours! Does anyone have the wiring diagrams for 93 520-H?

[nylyon-(Admin) 8,567]

Does it crank when you jump the battery side of the solenoid with the small terminal? That's how you should be jumping the solenoid, not big to big. If it doesn't work with the small terminal, you either have a bad ground or bad solenoid.

[04fxdwgi 1]

Well at least its not the oil switch....I still cant seem to get crank from turning the key. Only if I jump the two large terminals on the starter. I guess I will have to take it to someone....It only has 251 hours! Does anyone have the wiring diagrams for 93 520-H?

I have all the electrical diagrams if you need em. Mine is a '93 520H also

Have an e-mail address? File too big for here.

[kpinnc 16,234]

Personal note: After changing oil and filter, excessive cranking may be required to fill filter and pressurize oil system to get a start if oil pressure switch controlled ignition. There is nothing wrong with a start with zero pressure as residual oil in brearings will protect them while pressure builds with the new oil, as long as the engine isn't "rev'ed up" before oil pressure builds. Most well maintained modern engines with electronic ignition will start within a couple of revolutions of the starter, long before pressure builds and the pressure will increase as engine comes up to idle. On engines where oil pressure switch is interfaced with fuel injection, starter circuit bypasses the oil pressure switch to allow the start with low pressure.

Hope this clears up the controversey.........

Dunno how we got to this point, so forgive me if I confuse any further.

I didn't say the engine would not turn over, I said in SOME designs the coil would remain grounded until a minimum PSI was reached- providing the oil pressure system was working correctly. Once the coil ground was removed (the switch is pushed open by the minimum required pressure), the ignition sequence starts, plugs fire, etc...

Again, sorry for the confusion. And thanks for the clarification Bill.

[mattsoltesz 0]

No, the starter wont work when I jump the small terminal and the battery. The small terminal has the light blue wire thats attached to it. At crank there is no voltage to it. I thought that was like the saftey wire for the starter...something before the starter is bad so it wont let power through....right? Or would you just say bad solenoid?

[04fxdwgi 1]

No, the starter wont work when I jump the small terminal and the battery. The small terminal has the light blue wire thats attached to it. At crank there is no voltage to it. I thought that was like the saftey wire for the starter...something before the starter is bad so it wont let power through....right? Or would you just say bad solenoid?

Correct ..... Bad solenoid........IF no 12 VDC comes out of it going to the starter.

If 12 VDC comes come out of it and starter dosen't crank.......... Bad starter motor

Pick up a cheap Ford solenoid at Pep Boys to test if you suspect the solenoid..