88 GMC 1500 troubles

Joined: Aug 11, 2008 Posts: 1

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 doesn't even come up. Does this sound like a bad pump, guage, faulty wiring, or Worse? I don't know these engines very well, so I am asking for help. It seems also when I'm 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

External Since: Nov 12, 2004 Posts: 808

In article ,
vader wrote:

> 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
> doesn’t even come up. Does this sound like a bad pump, guage, faulty
> wiring, or Worse?

I'd be inclined to replace the sending unit.

> I don’t know these engines very well, so I am asking
> for help. It seems also when I’m 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.

Not related to the oil pressure reading.

> Anyone know how to get the codes of this thing. Any help would
> be appreciated. Thanks

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