intermitent oil pressure

dangerous06

dangerous06

diesel tech
Just replaced an engine and have an oil pressure situation that's driving me nuts! Start up Gauge reads 40psi one or two minutes later drops to zero check gauges light comes on!? Restart and same thing all over again! What could be the issue ? Going to put a gauge on it tomorrow don't have a 1/4" fitting for the port on top of the oil filter. I believe the gauge it cost me a turbo Sheared a shaft on a good turbo "Stock" Tight no play to boom in 3 miles!
WTF?
 
I fill the filter and the engine then crank like crazy till the fuel system is filled then it fires oil pressure is always up by that time! And it was also with this motor but it drops to zero after a few minutes but not always. I drove it 40 miles this morning and no drop also at idle it stayed up when I got to work! test it again in a while to see what it does!
 
dangerous06 said:
I fill the filter and the engine then crank like crazy till the fuel system is filled then it fires oil pressure is always up by that time! And it was also with this motor but it drops to zero after a few minutes but not always. I drove it 40 miles this morning and no drop also at idle it stayed up when I got to work! test it again in a while to see what it does!
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Buy a Moroso 3 QT accumulator get a chunk of -6 hose and fittings. Use this to charge the system and you will have no more zero pressure start ups.

I put 1.5 gallon in the pan, fill the filter up and charge the whole system with this.
 
I figure all the assembly lube is enough to go thru first crank! But I will look at that system hook it up at the filter fitting I assume!
 
Is it the factory gauge you're going off of? The stock cluster will show oil pressure for 30 seconds on startup whether there's pressure or not. So when you say "after 2 mins it sometimes drops off", that scares me into thinking those startups might never have had oil pressure.
 
fatgraderman said:
Is it the factory gauge you're going off of? The stock cluster will show oil pressure for 30 seconds on startup whether there's pressure or not. So when you say "after 2 mins it sometimes drops off", that scares me into thinking those startups might never have had oil pressure.
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Holy crap now that is scary! That is one stupid set up!
 
dangerous06 said:
Holy crap now that is scary! That is one stupid set up!
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You weren't aware that the factory "gauge" is a dud? It's just a Hobbs switch, 7 psi. The gauge shows "customers expectations" for oil pressure. Another words, it's an idiot light with a needle. And for some reason, their algorithm shows oil pressure instantly (customer expectations), but if it doesn't see oil pressure after 30 seconds, then the gauge needle drops to zero and the lights come on. That's why I wonder if a couple of those start ups had oil pressure. I like the accumulater setup. Never tried that.
 
Yeah I'm going to order one or build one asap! I have a bleeder ball laying around that will work also! At 250+ for a Moroso it's a basic hydraulic cylinder.
 
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dangerous06 said:
Yeah I'm going to order one or build one asap! I have a bleeder ball laying around that will work also! At 250+ for a Moroso it's a basic hydraulic cylinder.
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You can find them on racing junk for a few buck, and Moroso has replacement orings in case they fail.
 
Had this same thing happen to me after i built my engine but i also had a mechanical gauge on and it read good pressure. It was just the sending unit that must of got wrecked from the parts washer. Get a mechanical gauge on there before you worry to much about it.
 
DodgeDude55 said:
Had this same thing happen to me after i built my engine but i also had a mechanical gauge on and it read good pressure. It was just the sending unit that must of got wrecked from the parts washer. Get a mechanical gauge on there before you worry to much about it.
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^^^^^^^ I think that's most likely what has happened. Or a bad connection. But those switches are fairly well known for doing that.
 
My engine builder came to me for my first start up. He uses a stainless steel fire extinguisher. We put a couple of qts in the can and then charged it with an air hose. Then he hooked it up and filled the block. Worked like a charm.
 
I've seen this before and had a talk with the builder turns out he had no clue about the round torque screw by the oil pick up. He put a standard bolt there and I assume the pickup didn't seal properly and is sucking air! the truck is a 4x4 and pan removal for inspection is almost impossible I had the builder start another build asap in case this motor dies before I fix it. It loses prime after shut down which is bad if you start and stop a lot! Of course customer was in a hurry and left before I figured it out now I have to get him back here! I hate these situations!
 
I would find a new builder. What kind of engine builder doesn't visually check every single surface when bolted together to make sure its sealing properly. Obviously not I one that pays attention to detail. I understand mistakes happen but when it's something that, makes you wonder
 
I usually build them but time constraints made me have the machine shop put it together he's been doing it for 40 years but all kinds not just cummins and some things only a cummins guy knows and when someone else takes it apart it's a gamble I lost!
 
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