Oil Pressure Problem Solved.

Big Mac

New member
Hi Guys,
Several months ago, posted a problem I was having with my JD750. The oil pressure light wouldn't go out for several seconds, after start up after setting for a week or so. I thought I had the problem solved, but sometimes wishful thinking just doesn't work out. As I have used the tractor this spring, the light was staying on longer and longer. Last month it was taking 25 to 30 seconds to build pressure. I knew I had to park it or find the problem. I removed the oil pan, to check the sump pick up, it was clean as a whistle. I thought maybe the pick up tube may have a crack or be loose and drawing air instead of oil. When I put the pan back on, the problem was still there. I then removed the gear cover on the front of the block, to get to the oil pump. I removed the pump for inspection and discovered that the casting had a crack running half way around the housing inline with milled area for the inside of the pump. I believe that the crack was allowing the pump to draw air instead of oil. However when the pump ran for awhile oil would eventually block the crack and the pump would operate till the engine was shut down. After shut down, the crack would allow air into the vacume inside the oil pump and the oil would drain back to the pan, causing the problem to reoccur.
I have ordered a new pump and gaskets and will post the results when I get it back together. Also I should mention that I consulted my local JD dealers service manual as to how to remove the gear cover on the 750. I was worried that the injector timing would be upset as the injector pump is located on the top of the cover. The manual said nothing about the injector pump in the removal of the gear housing. I tried several times to pull the cover, and could only move it about a quarter of an inch. I desided to remove the injector pump to get a look inside, to see what was holding it up. With the pump removed, the gear case almost fell off. The injector pump has lifters that ride the cam shaft lobes, and the lobes were blocking the back lifters from moving. Seems that the service manual should have talked about this, even the shop supervisor was surprised about this. Will let you all know the outcome!
 

Big Mac

New member
:wave::respect:Hey guys, I got the old John Deere back together today. I had packed some vasoline in the new oil pump as I assembled it, and even though it didn't start because I had to bleed the injecter pump, it developed oil pressure while cranking the engine over to bleed the fuel system. Once it was running, the oil light would go off almost at the sound of the starter turning, I mean real quick! Problem solved. The lesson learned here is, if your engine is slow to pick up oil pressure look for air getting into the system between the pick up sump and the oil pump.
Thanks for all the help, I really appreciate it!
 

Doc

Admin
Staff member
Gold Site Supporter
Glad to hear you got it fixed. Good job! :thumb:
And good tip for all of us tractor operators. :D
 
Top