Mower Engine oil pressure gauge failure

[WhinYett]

My Honda sit-on mower refused to start the other day. I had been replacing a drive belt bu hadn't disturbed anything on the engine. Following the procedure for checking the various interlocks which can stop the engine it turns out to be the oil pressure detector (no gauge). In investigating the problem I discovered I had been measuring the oil level wrongly over the last year or two (I usually check it once before the cutting season starts). So its been running low on oil for a while - but not that low. I emptied 0.75 litres of old oil when the capacity is

1.1 litres.

What does the oil pressure consist of? Is there any possibility that it could be "reinvigorated" somehow? Otherwise I have to remove the engine. Meanwhile the grass grows and how!

Frank

[Muddymike]

Its some fancy mower engine if it has an oil pressure detector. Most mower engines do not have pumped lubrication just splash. Honda generators I have had dealings with have an oil level cut off built into the safety systems, are you certain its not one of those?

Either way, if the engine was running quite happily with the low oil level it could just be a faulty sensor. Try finding and by passing it.

Mike

[Tim Lamb]

In message , WhinYett writes

Don't know the Honda engine. Oil is generally pumped around various engine parts that need a constant supply. Crank shaft bearings etc. The

*oil pressure* is created by the resistance to the flow of oil; bearing wear will gradually reduce it over the engine life.

Does your engine have an oil filter? Could it be that the protective shut down is caused by a blocked filter rather than lack of oil?

[Nthkentman]

My Honda sit-on mower refused to start the other day. I had been replacing a drive belt bu hadn't disturbed anything on the engine. Following the procedure for checking the various interlocks which can stop the engine it turns out to be the oil pressure detector (no gauge). In investigating the problem I discovered I had been measuring the oil level wrongly over the last year or two (I usually check it once before the cutting season starts). So its been running low on oil for a while - but not that low. I emptied 0.75 litres of old oil when the capacity is

1.1 litres.

What does the oil pressure consist of? Is there any possibility that it could be "reinvigorated" somehow? Otherwise I have to remove the engine. Meanwhile the grass grows and how!

Most Honda engines have a low oil level sensor that prevents starting or cuts the engine when oil is low or on a too high angle tilt. What engine type is it?

Oil checking is done on level surface, unscrew dipstick, wipe clean and then place on top of the hole without screwing back in to give correct level indication. Replenish to between the marks or hatched marking area

[Road_Hog]

Ah, but you did touch the engine by empting all of the oil out of the sump.

I take it by the oil pressure detector you are referring to the 'oil alert' which is a low level cut out system. It's basically a float and switch type protection system and cuts the engine out. Not seeing it or seeing how you removed the oil or the history, it's difficult to say exactly what happened. What can happen if the oil isn't changed on a regular basis as per the schedules AND the machine is old, dirty oil can 'grease' up and when you refill it with new oil the float doesn't rise again.

It is unlikely that it engine wear by lack of oil as Honda engines are quite tolerant to that.

You can get pdf copies of all the engine manuals from their engine centre website.

Just click on service and then service information.

The spare parts list is also there.

And it should have exploded picture of all the parts

Or you could talk to power equipment technical service dept - they used to speak directly to customers when I worked there.

01753-590500 is the main reception number.

[harry]

The oil pressure is caused by the small clearances in the various bearings on the crankshaft. Surplus oil is bypassed by a relief valve. So as the clearances increase through wear, oil pressure falls. Normally large clearances result in mechanical noises which indicates repair work is needed.. Or the oil pump could be buggered. Or the relief valve. (Both quite unusual) Or oil filter (if fitted) needs changing.

Normally the switch just brings on a warning light.

Check if you have a spark first.

It can only be lack of spark or lack of fuel stops it from working. Try shorting this switch out & see if it works.

Without actual repairs,the only way to "reinvigorate" oil pressure is thicker (more viscous) oil. Not recommended.

[Muddymike]

I disagree with that. It could be any number of other factors such as;

Sparking at the wrong time. Too much fuel. Poor compression. valve timing wrong.

But as Frank has checked the interlocks and found the oil sensor to be faulty we are assuming that is the only fault.

Mike

[Gazz]

Plus the info about it never having had an oil change, or keeping it topped up, it's most likely the oil level finally got low enough to trigger the interlock, possibly due to tilting the mower to fit the new belt.

Then as mentioned, due to the shitty gummy oil that's been in it for so long, the level sensor is now stuck open, simple enough to test... bypass the sensor and see if she starts, but if she does, go out and buy a new sensor and wire it back in the circuit, or the next time you 'forget' to change or check the oil level, it'll be the con rod making a rapid exit through the crankcase that alerts you to the problem.

Of course, if this was the first start of the season, then it could well be a stuck open valve, stuck carb float, rats nest in the air filter housing, shit in the fuel tank etc, but i believe he mentioned it's run fine this season, until he replaced the drive belt,

[WhinYett]

Sorry - "gauge" was just the wrong word. What I have is some sort of float switch which is definitely NOT working. I have the relevant mower details. There are several interlocks on the mower to ensure safe operation plus the low oil indicator. I could check that all the others work - by operating the various micro-switches.

Road Hog thanks for the above. I will try to short out the actual device and see if the engine will start - which would definitely identify the problem.

That's tomorrow's main activity determined.

Frank