no oil pressure??

My dad gots a 88 1500 2wd witha 305 auto n 140k miles.. for prolly the last two years whenever you first start it up it reads some oil pressure.. but then the check gauges light will come on and the oil pressure gauge reads a big fat 0... im guessing its the gauge or whatever reads it cause hes put about 20k miles on the truck since this started and im not sure but i dont think the engine woulda lasted that long if it had no oil pressure... n e input or tips on what to look at would be helpful.. thx

sounds like a bad sending unit, it should be mounted down by the oil filter with 1 wire coming off it or maybe that wire just came off?

There is also a sending unit mounted right by the distributor. I have seen quite a few of these go bad, both the one by the oil filter and the distributor.

My 1988 K1500 350 just started doing the same thing! Gauge reads near 50 upon startup and idle and maintains this pressure for the first few minutes in gear, then drops to 30 and then when I come to a stop, the pressure had dropped to about 10 but today it dropped to that big fat zero! Shut the truck off and let it cool down, started it up and sure enough...back up to good pressure again. And I just drove it home from the shop for a check engine problem that was unresolved.

these trucks use a dual purpose sender on the main feed by the dist. it is a fuel pump switch and oil pressure gauge. the check gauges module will light up if there is tach signal and the pressure drops....replace the sender for $26ish frmo advance auto (you may need to pull the dist to get to it)

and while in there, put a T in and hook up a real gauge

almost every older chevy truck i have driven from an 81 to my 88 k5 have the same problem it almos always is the sending unit

Ya its also the electrical guages read so inaccurately because ur oil pressure is actually around 10 or so but i had that problem, when the oil warms up it thins out and makes it just read flat zero. Just replace the guage, my sending unit and wiring turned out to be fine

I wish to modify my last post - SOME of these trucks use the dual purpose sender. On the ones with the separate sender by the filter, it is so close to the exhaust manifold that it gets fried and does goofy things. replace with a real sender for a mechanical gauge but put the plastic tubing in some 1/4-5/16 brake line to protect from the heat (I just did one of these over the weekend)