7.3 no oil pressure - Diesel Forum - TheDieselStop.com
'99 & up 7.3L Power Stroke Engine and Drivetrain Discussion of the '99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.

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post #1 of 5 (permalink) Old 11-05-2011, 05:49 PM Thread Starter
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7.3 no oil pressure

i have a 99 f450 i put a motor in from wrecked truck i bought it has no oil pressure at idle can rev up a little and it has oil pressure but instantly drops when i let of it also i very hard to start
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post #2 of 5 (permalink) Old 11-05-2011, 07:15 PM
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I'm not an expert here so i could be way off. Bad pump maybe? How high do you have to rev it to get it to normal oil pressure? Not exactly sure what the signs of a bad pump on these are but I've had a couple on old diesel tractors that acted that way when they started going out....
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post #3 of 5 (permalink) Old 11-05-2011, 09:18 PM
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How and where are you measuring oil pressure? Like redneckjake said, the pump is one possibility. Others would be the bypass spring, excessive bearing clearances, or a bad pickup.

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post #4 of 5 (permalink) Old 11-06-2011, 10:13 AM Thread Starter
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i removed sending unit from top of front cover and installed pressure gauge there. i seen truck engine was pulled from it had to be running when wrecked engine doesnt have blow by or any misses it busted the oil cooler and i swapped it over from my old one i also swapped out oil pump on crankshaft. to get it to start i have to fill housing full of oil where hp oil pump mounts. otherwise it just cranks over.
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post #5 of 5 (permalink) Old 11-06-2011, 09:21 PM
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Pull the LPOP out and inspect it for wear. Use this HPOP Manual an look at page 5 for LPOP inspections. Also look at the cover for wear as it effects the pressure too.

Replace it with a Melling LPOP

Like mentioned before, if you have clearances that are larger than designed, the oil pressure will not build. A rocker that is off or broken can cause low oil pressure at idle.

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