Diagnose ongoing no start.
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Lead Driver
Joined: Jun 2013
Posts: 5,647
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From: north of Minneapolis, MN
The one that prevents the HPOP reservoir from draining back into the oil pan when the engine is not running. Right now I forget the engineer's term for it, but it's around just below the bottom of the HPOP reservoir and part of the oil galley that feeds the HPOP reservoir. It may be part of the front cover casting, but don't quote me on that right now, LOL.
The injectors have 200k on them. But how does that allow the oil to drain from the reservoir?
Last edited by Dan V; Nov 14, 2025 at 08:04 AM.
FTE Leadership Emeritus
Joined: May 2014
Posts: 27,350
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From: Lake Hartwell, GA
The one that prevents the HPOP reservoir from draining back into the oil pan when the engine is not running. Right now I forget the engineer's term for it, but it's around just below the bottom of the HPOP reservoir and part of the oil galley that feeds the HPOP reservoir. It may be part of the front cover casting, but don't quote me on that right now, LOL.
EDIT: https://dieselorings.com/products/8-...check-plug-kit
Lead Driver
Joined: Jun 2004
Posts: 6,326
Likes: 585
From: Amarillo, TEXAS!
That isn't really a check valve. It's called a short circuit valve. Even if oil was able to drain back via the lube oil pump, when the reservoir got oil again, ICP would climb and the engine should start.
If an upper injector oil o-ring is ruptured, it can allow oil to flow right out of the injector bore, through the oil return ports in the head and into the oil pan. It can also cause basically zero ICP while cranking, even though it's a relatively small leak path.
If a lower injector oil o-ring is ruptured, the oil would flow into the fuel system, you'd see a loss of oil on the dipstick and probably a black fuel filter element.
If an upper injector oil o-ring is ruptured, it can allow oil to flow right out of the injector bore, through the oil return ports in the head and into the oil pan. It can also cause basically zero ICP while cranking, even though it's a relatively small leak path.
If a lower injector oil o-ring is ruptured, the oil would flow into the fuel system, you'd see a loss of oil on the dipstick and probably a black fuel filter element.
Thread Starter
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Lead Driver
Joined: Jun 2013
Posts: 5,647
Likes: 891
From: north of Minneapolis, MN
That isn't really a check valve. It's called a short circuit valve. Even if oil was able to drain back via the lube oil pump, when the reservoir got oil again, ICP would climb and the engine should start.
If an upper injector oil o-ring is ruptured, it can allow oil to flow right out of the injector bore, through the oil return ports in the head and into the oil pan. It can also cause basically zero ICP while cranking, even though it's a relatively small leak path.
If a lower injector oil o-ring is ruptured, the oil would flow into the fuel system, you'd see a loss of oil on the dipstick and probably a black fuel filter element.
If an upper injector oil o-ring is ruptured, it can allow oil to flow right out of the injector bore, through the oil return ports in the head and into the oil pan. It can also cause basically zero ICP while cranking, even though it's a relatively small leak path.
If a lower injector oil o-ring is ruptured, the oil would flow into the fuel system, you'd see a loss of oil on the dipstick and probably a black fuel filter element.
Fleet Owner
Joined: Jun 2004
Posts: 25,090
Likes: 1,112
From: Rio Rico, AZ.
Not to put too fine of a point to this, but did you verify the HPOP reservoir was full before you ran the deadhead test?
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Lead Driver
Joined: Jun 2013
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From: north of Minneapolis, MN
I'm thinking the brass/bronze flecks are a sign.
CNCFAB
Joined: Apr 2020
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Interested to see the internals to see what happened.
