Oil Pressure Alarm Saved PT422 Engine

[BobRip]

As some of us know the Robin engines have an oil pressure switch, but Power Trac choose not to connect it to anything. Several years ago I connected it to a light on the dash and a Sonalert alarm. Today after mowing for 5 minutes I had a flat on my mower. I drove back to the house to reinflate it and when I restarted the engine I got a low oil beep, beep, ... and a light. I first thought the oil pressure switch had failed. I started lookin at the engine, and noticed a lot of oil on the floor of the engine compartment on the right side. I had recently changed the oil and had tried to remove the drain plug on that side of the engine. I was not able to get it out, but evidently had loosened it. It was now lying in the engine compartment. I put it back in and refilled the oil and mowed the lawn. I suggest to all that they consider connecting the oil pressure switch to an alarm. The audible one was the one I noticed first.

[Tim_in_CT]

funny (not haha) that you should mention that... (stand by for thread hijack).

because on Saturday, my engine caught fire... and I think my low pressure alarm probably saved me from destroying my engine as well.

I had added an external oil cooler, and one of the supply hoses was too near the exhaust manifold. Even though I had wrapped both with insulation, apparently exposure to heat had degraded the oil line and it finally sprung a leak... pumped the sump dry in about 10' of travel (based upon the oil on the ground).

I heard the alarm, stopped the engine, and then I heard the "whoomph" of the engine catching on fire. No fire extinguisher on my PT (that will be rectified)... I ran to the garage and grabbed a blanket and tried to unsuccessfully smoother the fire, and then remembered the fire extinguisher in the basement (we just moved two weeks ago, so I knew where nothing was). Three shots with the dry chemical and the fire was out.

Damage: half melted gas tank (another minute and I think I would have been in real trouble), slightly burned seat. Removed the oil cooler, put a new filter on, refilled the sump, and mowed another half acre the next day.

KentT propehetic utterence dogged me all afternoon on Saturday...

http://www.tractorbynet.com/forums/p...ml#post1157829

bottom line: $10 for a sonalert buzzer was money well spent. Mounting a fire extinguisher on your PT could be the difference between a $100 repair job and a $4000 repair job.

oh, and replacing the exhaust manifold is moving up on my list of must-do's.

[cqaigy2]

Wow!

Thanks for sharing your stories.

[KentT]

Ouch, Tim! Sorry to hear that, but glad you controlled the damage.

I'm glad that Rich had mounted a fire extinguisher on mine before I bought it, though I've never had to use it... I cleaned about an inch of oily sticks and leaves out of the belly pan when I brought it back from Tennessee for the summer -- no air compressor there to keep it cleaned out...

Now you guys have me wondering if my Kohler also has a disconnected low-pressure warning somewhere...

[SnowRidge]

Kent, the Kohler data sheets indicate that the "Oil Sentry" feature provides a way for OEMs to have the engine shut down on loss of oil pressure. A diagram is provided to show how to do it, but it is up to the OEM to hook it up. Power Trac did not hook any of them up, to my knowledge. I traced it on my PT-425 and it is not hooked up.

There is a wire, green if I remember correctly, that provides a ground if there is no oil pressure, an open otherwise. The wire is not connected to anything expect the oil pressure switch.

I don't know why PT chose not to hook them up, but they really should have ripped the Oil Sentry labels off of the engines if they weren't going to use the feature. Doing otherwise left owners thinking they had protection that isn't there.

[Clarke]

According to Kohler the switch is hooked up on a generator not on a wheeled vehicle. You would not want your PT shutting down on you half way up a hill. On a wheeled vehicle Kohler says the system could be used with a warning light or buzzer.

sg

[SnowRidge]

I don't think that would be a problem with our speeds and the hydraulic drive. My main complaint is PT leaving the decals on. Coupled with Kohler's advertising their Oil Sentry (at least when I bought my PT) it made it seem like the machine was equipped with an automatic shutdown. I know in the past a lot of other folks thought theirs was too.

They could have included the information in the manual, too. They just don't seem to care.

[DCWhitley]

I did a search and can't find any description of how you wired in the light & alarm into the low oil pressure switch for the Robin engine. Is it the same as the Kohler engine that when the switch activates it goes to ground? Also, any problem hooking up any 12v item like a light to the other wire that appears just to be a 12v feed?

[J_J]

Originally Posted by DCWhitley

I did a search and can't find any description of how you wired in the light & alarm into the low oil pressure switch for the Robin engine. Is it the same as the Kohler engine that when the switch activates it goes to ground? Also, any problem hooking up any 12v item like a light to the other wire that appears just to be a 12v feed?

The low oil warning switch is a grounding switch. With no oil pressure, the switch is grounded and can be wired up to a beeper or light to give warning.
It should be wired up to beep or cause a light to flash when you turn the key to on. This would be a test mode for no oil pressure. As soon as the engine builds pressure, the switch opens the grounded circuit, therefore no beep or light . The switch as used on generators, is wired to shut down the engine with low oil pressure, because it is usually unattended, therefore it should save the engine before it self destructs.

[Tim_in_CT]

Originally Posted by DCWhitley

I did a search and can't find any description of how you wired in the light & alarm into the low oil pressure switch for the Robin engine.

http://www.tractorbynet.com/forums/p...ml#post1411904

There is a gray wire with a bullet-type connector that is unused in the wire bundle by the right rear side of the engine compartment (at least true on my PT).

Alternatively, you can trace the gray wire from the low pressure switch which is on the bottom left front side of the engine on the forward edge of the oil filter mount:

http://www.robinamerica.com/media/diagrampdfs/19.pdf