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2.8 oil pressure

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Old 01-01-2004, 11:58 PM   #1
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2.8 oil pressure

my 1987 blazer has got some oil pressure issues. whenever i amm idling my check gages lite comes on. but sometimes when i'm idling it doesn't. couold it just be my gage or my sending unit. does this happen to anyone else. i only got like 120,000 miles on the engine. but my blazer has been rolled. so lots of things could still be messed up. thanks for the feedback.
Old 01-02-2004, 10:46 AM   #2
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Maybe the connector at the sending unit has become loose. That would account for the now and again check light. I would check the connection first, then move on to gauges or sending unit.
Old 01-03-2004, 09:18 AM   #3
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But know that sending units are really common to go out of whack...

Replace it with a true GM unit for best results.
Old 01-03-2004, 04:40 PM   #4
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yeh i'll probly check all the connection and then replace sending unit if necessary. but what are common oil pressures for those 2.8 at idle?
Old 01-03-2004, 07:39 PM   #5
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yes,my 87 did this too. I upgraded to a 3.4 and now things are great. my oil pump was worn out in the 2.8 and i had alot of crud/sludge in the heads that may have been restricting the flow of oil back through the return passages. take a look through oil cap into the valve covers to see if yours is sludged up too.
Old 01-04-2004, 06:54 PM   #6
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the normal are about 40, but i had on my 86 project i have, i had it bored to a 3.1, and a racing oil system and now it gets over 60, go that route, its better to have more oil
Old 01-04-2004, 08:16 PM   #7
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The Chiltons Manual states the oil pressure should be at 45psi at 2000rpm, but does not have anything listed for idle.

The Haynes manual shows oil pressure should be at 10psi at 500rpm and 50-55psi at 2000rpm. I have an '85 2.8, and mine gets to 45psi at 2000rpm, though shows around 10 or 20psi at idle, which is around 700-750rpm.
Old 01-05-2004, 09:52 PM   #8
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You might want to get a mechanical gauge and double check the pressure readings...my 87 had the same problem with the check engine light flickering, and the gauge bouncing around. I swapped in a junkyard sending unit, for no improvements, then rigged up a mechanical gauge to 6 feet of hose so I could even check running pressure. (duct taped it to the hood, drove around with it for an afternoon). Anyway, despite all of the gauge /light wierdness, I had 25 lbs at idle, and 55 at 60mph.
Old 01-05-2004, 09:59 PM   #9
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Very low oil pressure at idle is usually an indication that the main & crank bearings need to be replaced, with 120,000 miles, it might be time to consider that possibility. But check your pressure with a mechanical gauge first - it's the cheapest...
Old 01-05-2004, 11:46 PM   #10
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Smile

I "moved on up" to a 3.4 in my 1988 S10 and I have 37 psi at idle and 62 psi at cruise as veiwed by my electrical Auto Meter oil pressure gauge:
http://huryde.station180.com/gallery...aSY2932&id=ahe
HTH's

Mike Campbell

Last edited by SY2932; 01-06-2004 at 12:20 AM.
Old 01-06-2004, 05:37 PM   #11
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yeh my light is starting to flicker i dunno it just bothers me that the light keeps coming on. but i mean do the manufacturers set the oil light to come on before it even should to keep u heads up on it or what? i mean my light flickers at idle and thats at about 20 psi. maybe lil under but if u guys say 10 psi -15 psi at idle i should be alright. when goin bout 35 i get 40 psi. 65 its bout 50 psi. i dunno much bout pressures but are these good?
Old 01-07-2004, 03:00 AM   #12
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i have a 86 with the same problem the gauge bounces around at idle and then goes up to 45-60 when i throttle it. i havent had any problems with mine and i have seen other ones that do this too. i think it just a common thing with these 2.8s i do know that the sending unit is a weak spot for these
Old 01-22-2004, 07:37 PM   #13
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Re: 2.8 oil pressure

I know on older smallblocks the light came on @ around 7 lbs. In my Camaro I had that problem with my guage dropping to around 8-10 @ idle in gear, Anyway, I had trash in one of the ports that go into the filter, It was wires from a wire wheel on my rebuild, Cleaned it out, Changed the oil and she holds 20 now!
Old 02-11-2004, 11:14 PM   #14
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Re: 2.8 oil pressure

You were asking if anyone had a similar experience and I have, and still do. I have an 88 S-10, 2.8L with 115,000 miles that started doing this one year ago. I have done all the things mentioned including putting 50W oil, and the light still come on. A mechanic told me that either the oil pump is worn out or the engine is worn out. The behavior is consistent with this. the light barely came on at first, and now it comes on any time the engine is below 2,000 rpm and warm. In addition for the first time in its life, the engine is now missing consistently and does not seem to have any power. I guess I wait until a rod comes through the hood, then decide what to do. Because of this, I am seriously considering dropping in a 3.4L engine, however, I am worried about running a "rich" mixture at low speeds and not passing inspection.
Old 02-12-2004, 01:36 AM   #15
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Re: 2.8 oil pressure

[QUOTE=Hou88S10]You were asking if anyone had a similar experience and I have, and still do. I have an 88 S-10, 2.8L with 115,000 miles that started doing this one year ago. I have

As I said above, mine did that breifly...oh, about 75,000 or 80,000 miles ago, and it turned out to be a totally electrical problem. SInce the sending units and wiring are notoriously bad, check it with a mechanical gauge! You can built your own mecahnical testing gage from hardware store parts if necessary.

Frankly, after my experence, I wouldn't consider the gauge to be much better than an idiot light, certainly there is little hope that 40psi on the guage actually equals 40 psi, etc.
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