Author Topic: Oil Gauge showing some odd stuff???  (Read 7308 times)

Offline silvrbreez

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Oil Gauge showing some odd stuff???
« on: May 26, 2009, 07:50:49 AM »
Background
83 SWB stepside purchased from 2nd owner in September 2008.  The truck has a 350 in it that isn't original to the truck.  Pulling numbers shows it to be from either a mid-70's truck or a late-70's Camaro.  Odometer shows 37,186...could be 137,186 but likely it's 237,186.

What's up
The truck seems to be running fine but my oil pressure gauge is acting funny.  Here are the three situations I'm dealing with...
1. When cruising highway, gauge now reads about 15 psi or so where is used to (few months back) run around 30-45 psi when cruising.
2. When I stop at a light or cruise slow (think city driving) the oil pressure gauge jumps all over.  When I stop it drops to 0 psi, when I push the gas it jumps up to 15-30 psi, when I brake it jumps up higher and then drops back down to 0 psi.
3. Whenever the gauge drops to 0 psi as described above, it is almost always accompanied by the "CHOKE" light coming on.
4. After I finish cruising for awhile (think arrive at my job) the oil pressure sits nicely at around 15 psi and will stay there as long as the truck is on and with several restarts and revs.

Questions
I'm I making something out of nothing?
Could my oil pressure sending unit be going bad?
Could I have a problem with my oil pump or pickup?

Any help is much appreciated.

Offline Captkaos

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Re: Oil Gauge showing some odd stuff???
« Reply #1 on: May 26, 2009, 11:42:49 AM »
Check the oil level and state first.
If everything look ok, check the gauge for a short or something.

Offline silvrbreez

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Re: Oil Gauge showing some odd stuff???
« Reply #2 on: May 26, 2009, 12:35:29 PM »
It's about that time for an oil change.  I think while I'm at it I'll just swap in a new sending unit since it will all be drained down already.
I also have a new wiper switch I need to install, while I've got the dash off I'm going to check my wires leading to the cluster and the condition of the printed circuit.

Offline ccz145a

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Re: Oil Gauge showing some odd stuff???
« Reply #3 on: May 26, 2009, 09:46:00 PM »
The choke and the sender use the same hot wire, so I can see how the choke light comes on if there is a prob in the sender or the wiring.
1975 C10 Silverado LWB, 454CID, TH400, 10bolt 3.42
11MPG Downhill w/tailwind (but there ain't no hills here)

Offline silvrbreez

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Re: Oil Gauge showing some odd stuff???
« Reply #4 on: May 30, 2009, 09:05:27 PM »
Think I've confirmed it's the sending unit and I'm ready to swap it out.  As usual when this noob gets into it he has some questions...

Mine looks like this as it is installed now...



The part I bought from the local parts store looks like this...


I'm guessing the part I bought just fits within that brass bulb shown as it's installed now?  That brass bulb has a 3/4" nut fitting on top that the electrical connection of the sending unit fits through.  Should I turn that nut or the smaller nut below the bulb shown in the first pic?  I'm turning and turning on the one up top and while it is spinning, it doesn't seem to be coming out.  If someone could explain to me how these pieces fit together that would help me figure out how to get this thing off.

Offline user85

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Re: Oil Gauge showing some odd stuff???
« Reply #5 on: May 31, 2009, 11:11:23 PM »
I think the sending unit you are trying to install is for a truck with just an oil light not a gauge. the sending unit with the bulb is for a truck with a gauge. I have an 85 and it has 2 units 1 for the gauge and one for the choke light(2 prongs) they are right next to each other. Turn the bulb from the bottom, sometimes the bulb just spins on the base and won't come out.

Offline silvrbreez

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Re: Oil Gauge showing some odd stuff???
« Reply #6 on: June 01, 2009, 08:24:44 AM »
The one on the truck now only has one prong and I have a gauge.  I was thinking this I bought the right sending unit and that it fit inside the bulb.  If I'm wrong I'll need to swap out the sending unit I bought for another one.  Should I return it to the parts store and find the right one that already has the bulb included like in the pic above?  I wasn't sure I could get it like that.

Thanks for the tip about turning from the bottom.  It definitely feels like the bulb is just spinning on the base.

Offline Marc

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Re: Oil Gauge showing some odd stuff???
« Reply #7 on: June 01, 2009, 03:32:09 PM »
Oil pressure gauge sending unit should be on the top rear of the engine, kind of behind the distributor.  The oil pressure switch that controls the choke should be on the block on the boss that the oil filter mounts to.  Check your oil levelto make sure it is OK, but I unfortunately suspect since the Choke light is coming on (it's actually a low oil pressure switch and light - when it closes it allows the choke to be electrically actuated to open - think that the choke only opens when the engine runs and a good way to detect it is the presence of oil pressure) you are losing oil pressure.  It would be somewhat common for a sending unit to fail for the gauge, but odd for them both to fail.  They are probably both OK.

Offline silvrbreez

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Re: Oil Gauge showing some odd stuff???
« Reply #8 on: June 01, 2009, 03:57:14 PM »
Marc:  So you think that if I just added some more oil that the problem would be fixed?

EDIT: I know CaptKaos recommended it earlier, but I never did for whatever reason.  Just checked the oil and it's dangerously low.  I guess I'm burning oil or something.  I'm going to be running out to the auto parts store and picking up a few quarts of 10w30 to fill her back up.  I'll let ya'll know what happens.
« Last Edit: June 01, 2009, 04:29:05 PM by silvrbreez »

Offline oldwhity

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Re: Oil Gauge showing some odd stuff???
« Reply #9 on: June 01, 2009, 09:05:20 PM »
If your burning a little oil, try runnin a heavier weight oil. I did because  my 85 burns oil as a hobby and since I went with a heavier oil it's slowed a bit. Also, what kind of filter are you runnin? I used to be a diehard "Fram" user but read a couple articles and switched to "Bosch". I noticed a higher reading on the guages.
Rob G.
81 Chevy K20 4x4 LWB stepside
I enjoy long quiet walks..........in a junkyard!

Offline silvrbreez

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Re: Oil Gauge showing some odd stuff???
« Reply #10 on: June 02, 2009, 07:50:34 AM »
Wow!  I feel like a 'tard for not checking the oil from the get-go.

I had to end up adding 2 1/2 quarts to the truck.  2 1/2 quarts!!!!!

Cranked it up, the engine purred, and the gauge shows to be running the same psi as when I bought it back in September.  The needle sits between 45-60 psi depending on the type of driving I'm doing.

Thanks for all ya'll help.

Now to figure out why it's burning so much oil.

Offline silvrbreez

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Re: Oil Gauge showing some odd stuff???
« Reply #11 on: June 17, 2009, 08:15:17 AM »
Alright, so I've been rolling for about 2 weeks now with the oil pressure gauge showing signs that everything was back to normal.  Then, this weekend, my gauge starts acting funny again.

The first go'round it was very low on oil causing the gauge to dance on the low 1/2 of the scale and sometimes dropping to zero.  Adding two quarts squared me away and things are fine.  (I still need to figure out why it dropped so low.

Now the gauge is dancing at, around, and beyond the upper limit of 60 psi.  Sometimes the gauge completely clocks out and rests all the way horizontal at 180 deg!  Is this now a sign of a bad sending unit or a bad gauge?

Offline ccz145a

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Re: Oil Gauge showing some odd stuff???
« Reply #12 on: June 17, 2009, 08:34:51 AM »
guages rarely fail. sending unit.
1975 C10 Silverado LWB, 454CID, TH400, 10bolt 3.42
11MPG Downhill w/tailwind (but there ain't no hills here)

Offline HookedOnReefing

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Re: Oil Gauge showing some odd stuff???
« Reply #13 on: June 18, 2009, 06:39:55 PM »
Could it be that your truck is using a lot of oil? Since it has been 2 weeks, did you double check your oil level again? If your oil level is normal, I'd expect the sending unit is bad as suggested earlier.
'83 Chevy C20 Silverado 454 V8 28K mi
'85 GMC Sierra 2500 350 V8 84K mi
'96 Jeep Grand Cherokee Limited 5.2L V8 4x4
'98 Saturn SC1 Coupe 1.9 I4
'01 Chevy Malibu V6
'01 Ford F250 Super Duty XLT Crew 6.8L V10

Offline Skunksmash

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Re: Oil Gauge showing some odd stuff???
« Reply #14 on: June 21, 2009, 02:16:52 PM »
Anytime anyone ever says they have an oil pressure problem, or their gauge is acting funny, that's always the first thing i think. Replace the sending unit. They are cheap and i have fixed 3 vehicle's oil pressure problems by doing it.