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No oil pressure

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=47074
Printed Date: 30 Aug 2025 at 1:05pm
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Topic: No oil pressure
Posted By: 2900
Subject: No oil pressure
Date Posted: 11 Mar 2012 at 3:22pm
Hi, working on a turbo 2900 that has been stored 3+ years, added new oil and antifreeze, bled fuel system, freed up shutdown solenoid arm and it starts and runs with no issues except the minor detail of no oil pressure. I have a trusted mechanical gauge installed in place of the sender, if gauge is unhooked it is flowing a very weak stream of oil. I have had the pressure valve behind the pump out, oil pump looks new, screen on pump is clean, relief valve on oil pump is free and clean, drive gear on cam is fine, oil cooler is not leaking, and I do not know what else to check. I do not believe this to be a problem that had been ongoing with this engine because the rods and mains all look like new, however I have no history on this engine. What did I miss?



Replies:
Posted By: tbran
Date Posted: 11 Mar 2012 at 4:05pm
MUST HAVE MASSIVE DUMP POINT - REINSTALL EVERYTHING - INSTALL AIR PRESSURE TO THE PORT WHERE THE SENDER IS - LISTEN AND YOU WILL FIND THE DUMP POINT.
KEEP IN MIND THERE IS A PLUG IN BACK OIL GALLEY FOR OIL COOLER BLOCKS AND THERE IS A DRILLED ALLEN PLUG IN FRONT FOR OIL SPRAY ON GEARS WHICH IF IS MISSING WILL BE A DUMP POINT.   FINAL THOUGHT - HAVE SEEN OIL PUMP SHAFT SPIN INSIDE GEAR THAT BROKE INSIDE PUMP.  
 


Posted By: DrAllis
Date Posted: 11 Mar 2012 at 4:07pm
Sounds like it's a pre-1972 version with a camshaft driven oil pump and single oil filter, correct?? Oil flow goes like this......oil sucked thru the oil pump strainer screen and discharged thru the steel tube into the block. Cold oil relief valve on the pump only opens when pressures exceed 80 to 100 psi and returns oil to the pan.....should be able to check that with 150 psi air compressor I'd think.....it can't have anything stuck inside it holding it open. From the oil pump discharge tube, oil flows up thru block passages and out to the oil filter base. Oil flows thru the correct P/N ? filter and back into the block and travels rearward about six inches and then out again thru an elbow to a large metal tube that carries the oil around the back of the block to the eng oil cooler. Oil into the rear port of the cooler and out the front port thru another short tube into the RH side of the block. It enters the block there and fills the main oil galley which runs from the very rear of the block all the way to the front of the block. At the rear of the blocks main oil galley there is a threaded plug....and at the front of that same main oil galley there is another threaded plug, EXCEPT it has a small hole drilled in it, to let small amounts of oil lube the timing gears. IF THIS PLUG IS MISSING, YOU'LL HAVE NO OIL PRESSURE. Someone had to have the engine apart and left the plug out to have this scenario. So, assuming the oil pump is OK fine and moving oil, the only three possibilities are the cold oil relief on the pump.....the pressure regulator behind the injection pump (missing parts) or the front main galley plug missing. Where is your oil pressure gauge plumbed in?? the RH side on the main oil galley??


Posted By: 2900
Date Posted: 11 Mar 2012 at 4:16pm
Thanks for the excellent info, oil pressure gauge is installed on RH oil galley behind fuel filter. Pressure regulating valve on front RH side was clean and free with no obvious defects, swapping with another relief did not help.


Posted By: Ky.Allis
Date Posted: 11 Mar 2012 at 5:52pm
If I recall correctly,when I did an overhaul on my 200 several years ago,the rocker arm assembly has a plug on each end of it. I'm thinking they are cork? I forgot to put them back in during reassembly and engine had very little oil pressure because oil was flowing out of each end of rocker arm. Only ran it a few minutes,but with no pressure building up in rocker arm,it scorched rocker arm. Found a used one and replaced plugs with new ones and it worked fine. 



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