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Oil pressure problem, need help

Tepot

Well-known member
Joined
Sep 13, 2005
Messages
307
Location
Moncton, NB, Canada
Corvette
1974 Metalic Blue L-48 Coupe 4 speed
Hi,

Went for a drive today, first thing that it even happened. The oil pressure gage read 20 all the time. Then I was in town and when in neutral stopped at a red light, I've realized that the oil pressure went down to ZERO. I had to rev the engine to bring it back up.

Then on the way back. it was reading 30 to 35 oil pressure, then got to another stop light. then got back to zero again.

Then when I finally arrived at home. On idle it got back to 30, then 20 , then 30, I don't know but it looks like that darn gauge can't make up it's mind.

Is there any known problem with those gauge or sending unit? I sure wish it's not an oil pump problem. I don't feel like removing the engine. My summer will be all fu**ck***ed !!!.

Oh and for your INFO. there is plenty of oil in the engine and it's not knocking.

Any help would be apreciated.
Thanks
Daniel
 

bossvette

Gone but not forgotten
Joined
May 19, 2003
Messages
3,233
Location
West Unity Ohio
Corvette
1968 1997
try hooking up a mechanical gage to check your actual pressure if it differs you know its the gage or sender.
 

Garagetoyz

Well-known member
Joined
Sep 20, 2005
Messages
53
Location
New Jersey
Corvette
78 Silver Anniversary 4 spd Crate engine
Those old stock guages are sometimes inaccurate. If it was truly zero you would most likely hear your lifters screaming for help;help I agree put a mechanical guage on it for a better reading.
 

Tepot

Well-known member
Joined
Sep 13, 2005
Messages
307
Location
Moncton, NB, Canada
Corvette
1974 Metalic Blue L-48 Coupe 4 speed
Ok. I'll try the mecanical gauge for sure. There's either 3 things that could be wrong right now. Either the Oil Pump, Oil pressure gauge or the the Oil pressure sender unit.

Can someone tell me where I can find the Oil pressure sender unit on my 1974 350 engine?
 

LVMYVT76

Well-known member
Joined
Apr 21, 2006
Messages
664
Location
springfield, mo
Corvette
1976 medium blue
On my 76 its down above the oil filter, its a electrical sender. Yous may be a mechanical with an oil line going to the guage like older cars.
 

76okievette

Well-known member
Joined
Jan 3, 2004
Messages
697
Location
oklahoma
Corvette
Early 1976 L-48, 2008 Victory Red
You don't have to pull the engine to change the oil pump if you decide that's what the problem is just remove the oil pan and you can change it out. I think its harded to change the gage have to remove that center consol unit.
 

L48

Well-known member
Joined
Jun 16, 2005
Messages
247
Location
Wadsworth OH
I agree that you should try another gauge to see if that is the problem. The only other place I have seen the oil sending unit is behind the distributor, but not sure if the Vette has it there.

I have had one small block Chevy that ran fine yet showed 0 psi at idle. How is this possible? Well turns out it had a previous owner installed option of 3 spun main bearings (the front and rear main were good). All the rod bearings were good. I drove it a long time like this until I figured out what was wrong. It would sit and idle quiet, and ran fine up to about 4000 RPM or so. From there the crank would start wobbling around and kill the power. I doubt this is your problem but it is a possibility, once you prove it is not oil gauge related.
 

Jim B

Well-known member
Joined
Feb 26, 2006
Messages
62
Location
Illinois
Corvette
1974 L82 Grey coupe
I had the same problem. It was the sending unit. Replaced it and it's all good now.
 

minifridge1138

Well-known member
Joined
Feb 2, 2007
Messages
908
Location
USA
Corvette
1982 Black Fastback
I'm not sure about a 1974, but on the 1982, the oil pressure sending unit is behind the distributor. It is a round sensor that screws into the block and a small wiring harness plugs into the top of it.
When i replaced my intake manifold, i had the sensor off without a problem. Although the distributor was also removed at that point.

Good luck.
 

wishuwerehere82

Well-known member
Joined
Sep 6, 2003
Messages
2,314
Location
Rochester, NY
Corvette
Red '82 Coupe,Sebring Silver '98 Coupe
I'm not sure about a 1974, but on the 1982, the oil pressure sending unit is behind the distributor. It is a round sensor that screws into the block and a small wiring harness plugs into the top of it.
When i replaced my intake manifold, i had the sensor off without a problem. Although the distributor was also removed at that point.

Good luck.

NOPE! That's the oil pressure switch for the fuel pump.
The pressure sending unit is above the oil filter.
 

yellow77

Well-known member
Joined
Jun 17, 2004
Messages
184
Location
Tulsa, OK
Corvette
1977, Bright Yellow
Pressure sender on my 77 is just above the oil filter.

:)

Richard
 

SR'71

Well-known member
Joined
Apr 17, 2004
Messages
93
Corvette
1971 Vert 454 4 speed sidepipes
Ok. I'll try the mecanical gauge for sure. There's either 3 things that could be wrong right now. Either the Oil Pump, Oil pressure gauge or the the Oil pressure sender unit.

Can someone tell me where I can find the Oil pressure sender unit on my 1974 350 engine?

I have a '71. There is no sending unit. Oil is tapped off the oil filter and routed to the oil pressure gauge thru a black plastic tube. BE REAL CAREFULL WITH THE FERRELS , I CAN'T FIND ANY REPLACEMENTS. I have the same symptoms you describe. I found my gauge reading wrong. I teed in another gauge, it never read below 35psi hot [70 psi cold] . I siliconed the innerts of my guage and it still reads wrong. I don't know?????
 
Joined
Aug 30, 2002
Messages
1,533
Location
Colorado Springs, CO USA
Corvette
84 Z51 auto R.I.P. 89 black roadster SOLD
NOPE! That's the oil pressure switch for the fuel pump.
The pressure sending unit is above the oil filter.

On the '84 the oil pressure sending unit AND the cutout switch for the fuel pump relay are both in the sender behind the distributor (three wires)...the one above the filter is oil temp. I believe the '82 was set up the same way, being the same engine and all? I wouldn't imagine the '74 would have the same setup..

Bill
 

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