1988 GMC 1500 troubles

[aarcuda69062]

In article <1208241_e7bc72092cc084caa345945a3c8ea291@autoboar dz.com>,
vader <none@000.com> 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

[HDS]

vader <none@000.com> wrote in news:1208241_e7bc72092cc084caa345945a3c8ea291
@autoboardz.com:

> 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
>

--

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