1991 Chevy 350 With oil pressure problems?

I have a 1991 Chevy K1500 with a 350 in it. The block is from an '81 and the truck has been run hard. I fixed a problem with my fuel pump a few days ago and it has been running like never before. But now, every time I let off the gas, the oil pressure gauge drops to 0 and my ';Check gauges'; light comes on. It also stays a little low, especially when I get on it. I'm thinking maybe the sending unit, oil pump, clogged filter, or maybe a messed up bearing. Any ideas?1991 Chevy 350 With oil pressure problems?
If it has been run hard, as you say, I'm not one to agree with a faulty gauge or sending unit. Rather, it sounds as though, depending on the miles, the oil pump may be getting weak or the strainer on your pickup could be clogged.


With that said though, I am a believer in starting at the cheap end and working up.


The following information assumes that your oil level is correct.


Purchase or borrow a manual oil pressure gauge, and a length of tubing and install in place of your sending unit. Make sure the threads are the same as on the sending unit.


You can now start you engine cold and check the pressure both at idle and at i higher RPM of say, 2000. Then let it warm up, and check the pressures at idle and 2000 RPM again. I t is normal for your pressure to range between 40-80 cold and 15-80 when it is warm. If it is less, see below.


To pull your oil pan and check the strainer, only the replacement gasket and some time are lost. While your there, now you can have access to your oil pump. To determine if this is your problem, you will need some expertise to check tolerances with a feeler gauge. The shop manual for the ';81 is where to find this information.


It will also help you in going through these steps.


Good luck1991 Chevy 350 With oil pressure problems?
You have to determine if it's a mechanical problem with the motor or just a bad sensor. Remove the oil pressure sending unit and install a shop oil pressure guage into the same hole. Run the motor and see what kind of pressure it is running at. I would be looking for around 15-25 psi at idle when the motor is hot. If that's okay, it is the sending unit or possibly the cluster which you will have to diagnose.
Sounds like the oil pump is going or clogged...


Have you tried using any cleaners in the oil then draining and refilling it with a quart of marvel mystery oil and top it off with what ever oil you use?


Good luck!
Sounds like the oil guage maybe bad or it could be the oil pump. If, this is still the oridgnial from the 81 model. But since, the check guage lite is coming on. I'd look @ the oil guage first and go from there.





Good luck!
My '89 Chev had a similar problem - it turned out to be the oil pressure sending unit. Easy to replace and it was only about $30.