jcarter13

I have a recently bought 1988 F-150, 300 inline, 4WD. I very recently fixed some issues with the cooling system but today I noticed the Oil Pressure Gauge is jumping all over the place at higher speeds. It only caused the red ENGINE light to flicker for half a second. Here is a video of what the gauge is doing (55mph interstate audio volume by the way):


Is this more likely the oil pump or oil pressure sending unit going out?

hawthorne90250

As far i as know at least on my 4.9s the oil pressure switch is a simple on/off. the gauge just reports that u have oil pressure and moves to about the center. i not sure what psi the sender makes at. so your gauge/wiring/sender is probably the problem.

joe mcmillan

The oil pressure sending units are on/off only so only indicate some pressure or no pressure. These fail frequently so either replace the unit or better yet, install a manual guage so you will know exactly how much pressure you have.
The next most likely possibility is the screen on the bottom of the oil pump. The holes in these plug from carbon buildup over a period of time and will eventually restrict the oil flow to very little. There is not an easy fix (solvent or motor flush will not clean the holes by just running it through) so you must drop the oil pan to see. Once the pan is off. the clean up is easy - just scrape off the sludge and open the blocked holes. If your pressure is really low, this is the most likely cause.

lksmith95

have you checked your oil? because if your oil gets pretty low it'll do that..

87f-150

Have you put a manual oil pressure gauge on it to see what the oil pressure really is ? Alldata has a article 88-5-14 on oil pressure gauge - erratic or low reading. Vehicle built before 10/01/87 . On the 4.9 I6 you will need the oil pressure sender #e8.tz-9278-a
And the next part is a resistor wire
#e6.sz-9f291-a
On the v-8 the part numbers are
E6.sz-9278-a. Oil pressure sender
E6.sz-9f291-a the resistor wire

I had low and erratic reading and check with a manual gauge it had oil pressure so I order this part numbers from bob Allen ford phone number is
1-888-865-0764 they said they had them in stock . I hope this helps