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Oil pump failure

Oil pump failure

Old 07-01-2019, 08:18 PM
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Default Oil pump failure

Put a mild built 454 in my boat for the summer while I rebuild my 496 blower motor. After the first hour on the water I lost oil pressure. It has a melling m77hv after I got it home I pulled the dist. And with my priming tool and drill can build almost 50lbs of pressure. Put the dist. Back in and cranked it and it wonít pump any. There is also a lot of play in the pump shaft now. I measured the dist. Shaft length and distance from the pump shaft to the intake mating surface and thatís correct. Wondering if anybody has any insight on what could have gone wrong before I pull the motor. Unfortunately I think the boat is done for the summer after only one trip out.
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Old 07-01-2019, 08:43 PM
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I once had a roll pin holding the cam gear break. It appeared to be fine because I could see the roll pin, but it was in 3 pieces.
And I have used many M77HV pumps, my favorite pump.
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Old 07-01-2019, 08:52 PM
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I looked it all over pretty well and couldnít seem to spin the cam gear. Iíll look it over tonight tho. Also it still turns the distributor because it still fires and will run. Thanks for the quick reply
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Old 07-01-2019, 08:55 PM
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Was the oil pick secured to pump my builder tack welded mine.
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Old 07-01-2019, 08:57 PM
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It bolts to the pump with one of the housing screws. Itís definitely a real head scratcher
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Old 07-01-2019, 10:42 PM
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If the oil primer builds 50 psi I would say pump is fine. I would think it would be cam/dist gear related
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Old 07-02-2019, 05:07 AM
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Originally Posted by Crude Intentions View Post
If the oil primer builds 50 psi I would say pump is fine. I would think it would be cam/dist gear related
Agree, remember the cams can break also, had that happen once..
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Old 07-02-2019, 05:12 AM
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Engine will still run and the distributor rotor turns so the cam is still together. I might throw a stock distributor in it and see if it will build pressure. At this point Iím just trying to figure out whatís happening because Iím gunna have to pull the motor out and apart to see what all damage came from the loss of oil
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Old 07-02-2019, 06:42 AM
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are the lifters rattling when started ?
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Old 07-02-2019, 08:14 AM
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If the engine runs/rotor spins the gear is fine.

If the priming tool builds pressure, the oil pump and it's drive rod is fine.

Must be the male 'key' in the distributor gear that's gone. Never head of it breaking but every few months it seems I run into something that I'm working on that I've never seen either.......so.....pull the distributor and turn it upside down and look at it.

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