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| This is the part that caused the failure. The oil pump relief piston was loose in its bore and hanging up on the sharp edge of the relief port sticking it open. We did not blueprint this pump and we should have. |
Unfortunately the folks at JWT reported that the car had completely lost oil pressure on their dyno and they feared that the engine was severely damaged. They confirmed the zero oil pressure with their own reference oil pressure gauge. The engine started to rattle and squeak on the dyno and they feared the worst.
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| The valve was sticking about here. That is a big hole for your oil pressure to be blowing off through! |
We tore down the engine to assess the damage fearing a near total loss and we can report that we were pleased to find minimal damage to the engine and were able to trace the root cause of the loss of oil pressure.
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| We were expecting to find crankshaft carnage but like the bearings, our crank was in great shape! |
The oil pump relief valve was jamming intermittently due to a combination of excessive clearance in the bore, a sharp edge on the valve piston and a sharp edge on the relief port. The valve was cocking in the bore and getting hung up on the port bleeding off all of the pump’s pressure.
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| The only damage we could find was that the milky appearance of the WPC treated journals was burnished shiny in some spots. The crank surface and dimensions did not change, only the appearance did. This was the worst journal. |
This engine had run on zero oil pressure several times during the race and for a few minutes at low speeds and idle before ultimately being diagnosed at JWT. One of the reasons why we thought that the issue was a bad sender was that we thought that if the engine was really getting that low of oil pressure it would have failed!
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| This was the second worst journal. We could just put the crank right back in! |
