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jjlutz
New User
Dec 29, 2010, 6:34 PM
Post #1 of 5
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Oil Pressure gauge
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I have a 1988 GMC 1500 4WD with a 5.7 engine. When the engine starts up I have a little better than 30 lbs oil pressure. I plow with the truck, and after about 20 minutes, the pressure falls to a level that lights the "Check Gauges" light on the dash when it falls to an idle. Just today it would not come back up and turn out the light when engine speed was raised. I had just changed the oil before this started happening. There is plenty of oil in the pan, and the lifters don't seem to be starving for oil. The engine seems to be running well, but it is disconcerting to see that light on. Is it possible that the sending unit is bad, or is it more likely the oil pump?
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Hammer Time
Ultimate Carjunky
/ Moderator
Dec 29, 2010, 6:54 PM
Post #2 of 5
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Re: Oil Pressure gauge
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I would first try changing the oil again and use a different brand this time. Some vehicles just don't like some brands of oil. If the problem still persists, then your going to have to verify the pressure with a manual gauge to see if the sender is accurate. It might be even cheaper to just replace the sender to see if it helps. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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jjlutz
New User
Dec 29, 2010, 7:21 PM
Post #3 of 5
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Re: Oil Pressure gauge
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Thanks; Another issue may be that I put in 10-40 instead of 10-30 to try and boost the Oil Pressure. I live in Maine and it is COLD. I should try and go back to 10-30?
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Hammer Time
Ultimate Carjunky
/ Moderator
Dec 29, 2010, 7:24 PM
Post #4 of 5
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Re: Oil Pressure gauge
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It won't be too serious with a truck that old but that would be a real problem on a later model. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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jjlutz
New User
Dec 30, 2010, 3:33 PM
Post #5 of 5
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Re: Oil Pressure gauge
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Thanks Hammer Time . . . . I pulled the sending unit off and hooked up a mechanical gauge and it blew the gauge to its highest mark. I put in a new sending unit in and it seems to be working fine. I'm glad it wasn't the oil pump. That would have been a big replacement job, especially with a foot of snow on the ground. Thanks again.
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