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I have G.A.S.
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I've been out of town for a month for work. We got home & found that the neighbors grandson had not actually earned his extra credit towards some kind of merit badge. He had promised to keep our front yard cut & trimmed. He did it once, 3 weeks ago. It rained nearly everyday for the last 3 weeks but the old $20 MTD did a good job. Then I just HAD to get the L out & cut 4 weeks of bale-able grass in our 1 acre back yard.
All went well, I worked it hard for an hour & headed to the shed. As I let it cool at idle, I lifted the hood & blew it all clean when I noticed there was no oil pressure on the gauge. I upped the throttle & still no pressure at all!
After it totally cooled down, I re-started it & the gauge went to it's "normal" 1/3 of scale.
What the heck? No rattles or knocks, how can it keep running so well?
 

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how can it keep running so well?
Because it's a Gravely of course!:D

I'd be looking for a more stable straight viscosity oil. Heavy engine use heat probably lowered the vis but was still lubing. What weight/type/multi or straight weight oil are you running in it? Oil been in the engine all Winter? Might have picked up some condensation that thinned the oil out. Change it!!!!
 

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I periodically open the oil filler cap and shine a light down in there while it's running. If oil's flowing, you'll see it squirting out the return line, just down inside the filler neck.

And like Harold said, make sure what's in there is fresh; now that the weather's warm, single-weight is probably a good idea too.
 

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Gravely Fan
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It sounds like your gauge might be bad. After an hour of running if it got no oil your engine would be toast. Do like JRD said start the tractor and take off the oil filler cap and look for oil flow. If you see oil change your gauge. - Kris :rauch10:
 

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I have G.A.S.
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Discussion Starter #5
Thanks for the replies gents.
I bought this jewel a few months ago & even though the oil looked & smelled pretty good, I changed the oil & filter before I 1st started it. I was told it wouldn't run when I bought it, they'd tried "everything". The main issue was valve adjustment.
It's been run about 10 hours since then, mostly rough brush hogging.
I put Castrol 20/50 in it thinking it would help due to age & obvious heavy usage in the past. So far it hasn't burned or leaked any.
I did look at the flow under the cap awhile back but I didn't think of that last night when it was hot & tired. I'll check that today.
 

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do you have dipstick or just the petcock check at the bottom?

On mine with a numbered gauge ill get about 25lbs cold but often will tail off to almost nothing when its hot (ie the oil thins out)
 

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Gravely Fan
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On mine with a numbered gauge ill get about 25lbs cold but often will tail off to almost nothing when its hot (ie the oil thins out)

It shouldn't do that. All of my machines pin the gauge all the way to the right off the scale. - Kris
 

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I wondered about that too. My LI doesn't have a gauge, but the L8s do, and both of those do the same thing, peg the gauge at the top of the scale. Both of the gauges are pretty old and the faces are dirty, so it's hard to tell for sure, but they don't seem to have numbers on them, just a "low" scale on about the bottom third of the scale and "normal" on the rest.
 

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Gravely Fan
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If it pins the gauge it means the oil pump is good and strong and the pick up is free of sludge. - Kris
 

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I have G.A.S.
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Discussion Starter #10
It has a dipstick & I have a new pressure gauge on the way. With PSI numbers on it....
Too busy in the depths of a rental house plumbing in the crawl space from **** project today & for a few more days possibly before I get to run it hard again. :banghead3
I'll update you'se all asap when I get home.
Thanks again.
BTW, is the 20-50 oil a good choice?
 

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Gravely Fan
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When oil gauges became an option in the early 1950s they did have PSI markings at first (0-15 PSI because those were the days of the old low-volume pump which has a maximum pressure of 10 psi). If you're not sure which pump you have, get a flashlight and look behind the pulley on the rear of the engine. On the high-volume pump the oil pipes connect to the sides of the pump body. For the low-volume pump the pipes connect to the rear of the crankcase right next to where the oil pump cover is bolted on. Gravely switched to the more common Low/Normal type soon after. The post-1958 Gravely engine (high-volume oil pump) with correct bearing and oil pump clearances and a correctly-working pressure relief valve will run at about 30 PSI. The pump is capable of a lot more output than an engine in that condition needs, so a lot of the output goes out the pressure relief valve to help lubricate the forward/reverse planetary. That excess capacity means you will continue to see about 30 PSI for a long time as the bearings wear. When the running pressure begins to drop, it means the bearings have worn to the point where the pump's output is no longer able to keep up with the amount of oil escaping from the enlarged bearing clearance. Once this deteriorates to the point where the needle stays in the "Low" range on the gauge, it's time for a bottom end overhaul. It is possible (if you're lucky) that the pump has lost its prime and is sucking air instead of oil. This can happen when the oil lines have been disconnected, or when the tractor has sat for a very long time. Sometimes you can prime the pump by simply tipping the tractor as far back on its tail as possible with the engine running. Or you can disconnect the far end of the pipe on the output (left) side of the pump and use a pump-type oil can to force oil into the pump. By the way I did forget to mention in my post above for checking for oil flow under the filler cap, even if you can see the flow all it proves is that the oil pump is working. The oil line that feeds the engine could be completely blocked, but you'd still have excellent flow below the filler hole.



- Kris:rauch10:
 

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Huh. I didn't know there was a pressure relief valve in there. Is it integral with the pump itself?
 

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is there a specific service PDF that just addresses the oil pump?

Ie how to take it apart clean service etc. Or is it a simple cam/gear driven afair off the crankshaft.
 

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Gravely Fan
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Huh. I didn't know there was a pressure relief valve in there. Is it integral with the pump itself?

The Model L and C relief valve is directly downstream of the filter. In other words the pipe that comes from the output port on the filter goes to the pressure relieve valve below the oil filler cap. - Kris :rauch10:
 

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Gravely Fan
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is there a specific service PDF that just addresses the oil pump?
Ie how to take it apart clean service etc. Or is it a simple cam/gear driven afair off the crankshaft.

I don't know if there is a pdf. I don't think there is one. The oil pump is a cam/gear driven affair. If you look at the illustrated parts lists you can see the gears. - Kris :rauch10:
 

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The Model L and C relief valve is directly downstream of the filter. In other words the pipe that comes from the output port on the filter goes to the pressure relieve valve below the oil filler cap. - Kris :rauch10:
Ah! That's that fitting that looks like it's bigger than it needs to be, eh? So the valve is effectively keeping the filter and the line to the front main bearing at regulated pressure, and dumping the excess back into the filler neck.
 

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Gravely Fan
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Ah! That's that fitting that looks like it's bigger than it needs to be, eh? So the valve is effectively keeping the filter and the line to the front main bearing at regulated pressure, and dumping the excess back into the filler neck.
Yes. - Kris :trink40:
 

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Gravely Fan
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There is a simple (but messy) test by checking for oil flow downstream of the filter. If you have the original bypass filtration pipe layout, disconnect the filter to relief valve pipe. Which end doesn't matter. (On the original low-volume setup a pipe goes from the output (left) side of the pump to a tee fitting on the side of the crankcase. One side of the tee feeds the engine. A pipe from the other side of the tee goes to the input port on the filter. The final pipe goes from the output port on the filter to the pressure relieve valve below the oil filler cap. This provides bypass filtration, where only oil in excess of the engine's needs goes through the filter and from there back to the transmission, so the engine receives unfiltered oil). If you have the later full-filtration pipe layout (On the high-volume setup a pipe goes from the output (left) side of the pump to the input port on the outer diameter of the filter adapter. If there is a pressure gauge it screws onto a tee fitting inserted between the pipe and the filter adapter. Another tee is screwed into the outlet port in the center of the filter adapter. One pipe goes from the tee to an elbow fitting on the side of the crankcase. Another pipe goes from the tee to the pressure relief valve. This provides full-flow filtration, where all oil from the pump goes through the filter so the engine receives filtered oil). It doesn't matter which oil pipe layout you have as long as it matches one or the other described above. Disconnect the filter to crankcase pipe. Start the engine. Oil should spurt out. If it does, your oil pump and filter setup is fine. If it doesn't, reconnect that pipe, disconnect the one next closest to the oil pump, and try again. If you get all the way back to the oil pump and still don't get spurting oil, then either the pump is bad or has lost it's prime. If you get spurting oil before you reach the pump, check the last pipe you disconnected for clogging. While testing this way never let the engine run for more than a few seconds. If this testing shows that oil is circulating but you get no pressure reading on a 0 - 15 PSI gauge or can't see oil flowing by the filler opening, then your engine bearings are probably shot and it's time for a bottom end overhaul. Kris:rauch10:
 
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