TEDA

i have a 90 f150 4.9 liter. recently when the engine warms up, the oil pressure drops to zero at idle.

when cold the pressure is normal and when the rpms are up it is normal.

i suspect the oil pump is bad, i just dont look forward to replacing it.

any advice would be appreciated

aliens8mycow

Is it making any noise, like a ticking sound or similar? Have you tested oil psi with a manual guage instead of the one in the dash?

marko56

Another crappy Ford sending unit??

DixieDarkhorse

its not crappy, its 20 years old!!!
if it was like chevy fuel sending units it would have been out after 5 years!

penick000

Not to hijack your thread but I have a 5.0 with erratic oil pressure. Engine purrs like a kitten and only has 56,000 miles on it.

I was just about to ask if the oil pressure sending units are a common fail point. I figured if they were i'd go ahead and replace it and see how things are before I went through the trouble of hooking up a manual gauge.

Any suggestions about buying a new sending unit? Any to avoid? Is it the same for the 4.9, 5.0 and 5.8?

All I can find is an oil pressure switch from autozone.com for about 8 bux. Seems pretty cheap. I would have suspected a switch for an idiot light, but figured the gauge would need a sending unit. Maybe it is just the way they are listed.

Thanks,

pen

penick000

Any recommendations for or against these?

Autozone Oil Pressure Switch

Advance Auto Parts Switch/Sender

pen

TEDA

it doesnt make any noise, just the check engine light comes on when the pressure drops. i dont have a gauge, never thought of the sending unit.

smp501

I've tried changing the switch on mine and it didn't do any good. With mine a bearing in the engine is worn out. However yours is a 4.9 and mine is a 5.8, so it might be something completely different

TEDA

i replaced the sending unit, no change. i did notice, when the pressure drops to zero, it's idling at about 700 rpm, but no noise no rattle. if i increase the rpms to say 900 then the pressure is fine.

is this just the beginning stage of oil pump failure? or some other issue? also i'm suprised i dont get lifter noise or anything.

any suggestions would be appreciated

Good old Bill

I remember lifters making noise and oil pressure is good. Al;so can have an indicator problem with no lifter noise. Was mentioned earlier to install a direct reading gauge and report back. Yes, oil pumps go bad, so do other things. Please help us to help you.