help with light & oil pressure

[tryinghard]

Here we go....89' Chevy 1500 4x4 305' 130k

 

First of all oil pressure drops to nothing when stopped after engine warms. Erratic pressure guage readings in dash. The brake/gas combo has sufficed so far, but i am looking for a more permanent solution. I replaced oil pressure switch...no dice. I suspect oil pump....any thoughts?

 

Second of all the service engine light has plagued me for years, although the truck runs great. I had been losing substantial coolant so I just replaced the intake manifold gaskets(my biggest job so far) and decided to do what i could about the light during the overhaul. In the past I was able to ground the connectors under the dash and get codes which i thought were EGR and TPS related according to the book. For the past year or so the grounding trick wouldn't work and the light is always on even when trying to get codes. During the intake overhaul I relaced the EGR and the vaccum lines looked ok.

NOW THIS IS THE WIERD PART...I start the truck after re-connecting everything..it runs..great...and the light is out out..BONUS, BUT then i touch the brake and it comes back on, then on/off as i press and release the brake. By the time i pull the truck out of the garage the light is on again permanently...d**n

So could there be some sort of issue with the power brake booster messing with the vaccum of the emmission system? i am stumped...anyone shed some light on the issue?

[redvett]

Here we go....89' Chevy 1500 4x4 305'  130k

 

First of all oil pressure drops to nothing when stopped after engine warms.  Erratic pressure guage readings in dash.  The brake/gas combo has sufficed so far, but i am looking for a more permanent solution.  I replaced oil pressure switch...no dice.  I suspect oil pump....any thoughts?

 

Second of all the service engine light has plagued me for years, although the truck runs great.  I had been losing substantial coolant so I just replaced the intake manifold gaskets(my biggest job so far) and decided to do what i could about the light during the overhaul.  In the past I was able to ground the connectors under the dash and get codes which i thought were EGR and TPS related according to the book.  For the past year or so the grounding trick wouldn't work and the light is always on even when trying to get codes.  During the intake overhaul I relaced the EGR and the vaccum lines looked ok.

NOW THIS IS THE WIERD PART...I start the truck after re-connecting everything..it runs..great...and the light is out out..BONUS, BUT then i touch the brake and it comes back on, then on/off as i press and release the brake.  By the time i pull the truck out of the garage the light is on again permanently...d**n

So could there be some sort of issue with the power brake booster messing with the vaccum of the emmission system?  i am stumped...anyone shed some light on the issue?

 

<{POST_SNAPBACK}>

 

 

 

The low oil presure is probably cam bearings since you have oil presure when you rev. it up. The lack of codes could be 2 things, poor grounds or ECM is bad. Did you fix the EGR & TPS problems? Have you ever changed the MAP senser? If not do it.

[budhayes3]

Check the circuit for the service engine light, if the ECM's OK, the wiring to the light might be grounded keeping the light on, and you wouldn't be able to get codes. Certain grounded sensors will cause the same problem. Jump the A to B in the diagnostic connector like you usually do, and start unplugging sensors, if the light starts blinking or goes off, you've found your problem. Be aware that you might have a ton of codes after that process!!

[Shaners]

I had an '89 G20 Conversion van. The oil pressure gauge was erratic when it got older...

 

The cure was a loose wire on a dirty connection at the sending unit.