88 GMC 1500 troubles

Hey, I was hoping that someone could help me out on this one. I have an 88 GMC 1500 with 166k. I bought it a few months ago. A few weeks after I bought it I was driving and everytime I would hit the brakes
or let the engine idle, the check guages light would come on due to the oil pressure dropping off to Zero. I figured maybe it was a bad connection at first. I gave the engine an oil change and the problem seemed to go away for a bit. Then after a few weeks, same problem again. Only when I idle or hit the brakes taking power away from the engine. As soon as I hit the gas, the oil Pressure comes back up again. It used to run at about 100 Kpa. Now it seems that the oil pressure is running a lot lower, and when I take my foot off the gas, the oil pressure drops to zero. When I hit the gas again, sometimes it doesnt even come up. Does this sound like a bad pump, guage, faulty wiring, or Worse? I dont know these engines very well, so I am asking for help. It seems also when Im running it for a while and the oil pressure is up again the check engine light will come on for about 20secs. then extinguish, this has only happened over the last couple days. Anyone know how to get the codes of this thing. Any help would be appreciated. Thanks
--
Posted at author's request, using moderated http://www.AutoBoardz.com interface
Thread archive: http://www.AutoBoardz.com/88-GMC-1500-troubles-ftopict248489.html
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I'd be inclined to replace the sending unit.

Not related to the oil pressure reading.

Turn the ignition on, jumper pin "A" to pin "B" in the ALDL, the check engine light will flash out a binary two digit code, i.e., blink <pause> blink blink is a code 12 blink blink blink<pause> blink blink is a code 32
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sep 4, 2:08pm, "Stormin Mormon"

I'd also try a thicker viscosity like 20-50. jimmy
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

----------
This is a sending unit problem. Not sure what motor you have, but the 5.7 has it on the drivers side of the motor with a little 'Whitch' hat looking thing over it to protect it. It spins off, and is easy to replace. There is a pin hole inside the unit that is easy to clog, and the reason for the low pressure reading.
HDS
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.