kuilima said:
HI my 93 gmc 3500 6.5L has low oil pressure, I changed to sendind unit and nothing so I changed the oil pump and still nothing when the engines cold I have 40psi at idle when it warms up I have like 20psi and when Im driving and going down a hill and let off the gas the pressure drops so low the light comes on. I just bought this truck so im not sure on the history. please can anyone help
Kuilima,
Unfortunately, I have the same exact issue! Have you learned abything new? Does this sound familiar:
I recently purchased a 93 Sierra 6.5TD. When the truck is initially started, the oil pressure is steady around 40 psi and raises up to about 50psi at 2500rpm. I have noticed after driving for about 30 miles, the oil pressure drops suddenly from about 40psi to about 25psi at 2500RPM/70mph. Every once in a while (about once every 10 minutes) it will "click back" to 40psi but will only say there for a few moments.
When the truck comes to a stop and idles at about 600RPM, the oil pressure will settle in around 10psi (a little to the left of the 1st white hash mark) and it will do the same thing as at steady spead in the way of "clicking" up to about 25psi every few moments and then go back to the lower reading. If you park the truck for an hour or so and start driving again, the above process begins all over. I checked the connection on the oil pressure sending switch and it was secure and dry. I also changed the oil to the suggested wt.
I am going to try and install an aftermarket oil pressure swith to verify the pressure is falling.