[73chevelle423]

We have a 1989 f150 4x4 6cyl 4sp. I was coming down interstate last nite and engine lite came on and oil pressure guage drop to zero,(engine was pecking like a lifter not knocking) pulled over and at idol guage came back up and lite went off, pull out got back up to 55 and lite came back on guage dropped, pulled over checked oil and it was full,lite off and guage up.Any ideas what might be going on.

 

[Mr Mac]

Sounds like the oil pressure sensor might be going bad or the connection is loose.

 

[Mr Mac]

By the way, welcome from Southern Illinois!

 

[Takeda]

Welcome to F-150 Forumz!

I agree, it's probably the oil pressure sending unit. Keep in mind, it's a dummy oil pressure gauge. It doesn't show variations in oil pressure. When the oil pressure reaches about 7 PSI, the sending unit "switch" closes, and the gauge reads about half scale. When the oil pressure is below the 7 PSI, the gauge
reads ZERO.

 

[73chevelle423]

Thanks for the replyies.

 

[Nicodemus]

Hey;
I read your post and I agree with the bad sending unit, as it's the most likely problem. Since you haven't updated the post I'll toss a few other ideas out there. IF the sending unit doesn't correct the problem. It could be one of the following, A dirty pickup tube screen on the oil pump causing pump cavitation at higher RPM's, an oil filter with a collapsed filter element, the bypass valve and/or weak bypass spring in the oil pump allowing the bypass to open and dump oil pressure back into the oil pan or excessive clearances in a worn oil pump. Just ideas in case the sending unit is not the problem. The "ticking" sound you hear leads me to believe the engine is actually be losing oil pressure.