1986 Ford F-150 oil pressure

BIGRUSTY1984

MEMBER
1986 FORD F-150
V8
4WD
AUTOMATIC
97,000 MILES

When I start my truck it has 40psi but when it warms up goes to 0 so then I put a high volume oil pump in changed the pick up tube and screen changed the oil pump shaft changed the main Bearings, rod Bearings installed a new wet gage nothing changed no knock no tick truck runs great but no oil psi but when I step on the gas in park the gage goes to 20 psi idle 0 driving up the road 0 also the Bearings I took out were still good and the oil pan had very little build up in it.

5 Replies

BLUELIGHTNIN6

MECHANIC
16,542 POSTS

Suspect faulty oil pressure switch

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Saturday, February 14th, 2009 AT 8:24 PM

BIGRUSTY1984

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6 POSTS

I have a manual gage

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Saturday, February 14th, 2009 AT 8:26 PM

BLUELIGHTNIN6

MECHANIC
16,542 POSTS

Sorry thought it said 1994 not '84.

When was last oil change? Is the current oil the correct type?

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Saturday, February 14th, 2009 AT 8:52 PM

BIGRUSTY1984

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6 POSTS

Today valvoline 20/50 mobil 1 filter and IM sorry its a 86

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Saturday, February 14th, 2009 AT 8:56 PM

RASMATAZ

MECHANIC
75,992 POSTS

Possible causes include:

Excessive main and rod bearing clearances (someone may have installed the wrong-sized bearings or standard-sized bearings on a reground crankshaft). Only 0.001" of extra clearance in the main bearings can reduce oil pressure by up to 20%!

Excessive camshaft bearing clearances (a bearing may have slipped out of place when the cam was installed).

Excessive clearances inside the oil pump.

Leaks between the oil pump and engine.

Oil pump relief valve stuck open or installed backward.

A loose or mispositioned oil pickup tube (too high in the oil pan).

A defective oil pressure sending unit or oil pressure gauge.

Low oil level in the oil pan.

Cracks or leaks in the oil galleries or gallery plugs.

Cracked oil pump housing (improper installation).

Oil viscosity too thin for hot weather.

Oil viscosity too thick for cold weather.