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1994 Chevy oil pressure guage

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1994 Chevy oil pressure guage

sassyjeri40 sassyjeri40
New User | Posts: 1 | Joined: 11/12
Posted: 11/29/12
04:06 PM

My gauge has run bout 40 now its going almost all way over Hi.Y?  

waynep71222 waynep71222
Enthusiast | Posts: 448 | Joined: 03/12
Posted: 11/29/12
06:03 PM

well...   there are a lot of things that come into play...

i am taking this is a Throttle body injected motor..  it will probably have a 3 wire oil pressure sending unit...

do you have a hand held digital volt meter????  if so.. try this first.. as the oil pressure sender circuit is completed by the ground wires...

start the engine.. turn on the headlights..  set digital volt meter to 20 volts DC..
1.   test between the Negative battery post and the Positive battery post..
2.   test between the Negative battery post and the engine block.
3.   test between the Negative battery post and the body/firewall...
4.   test between the Engine block and the firewall.  

if you get more than 0.04 volts on tests 2, 3, 4.. then you have a bad ground between those parts...

don't take this lightly.. i have tested a 98 chevy pickup that had 8.5 volts between the engine and the body... thats a bad ground issue..

can you get in and unplug the oil sending switch.. clean the threaded area of the switch to remove any dirt from the area..    use the special oil pressure sending switch socket then remove and replace  the sending unit..  they are not cheep but they do fail...

if you want to invest .. mechanical oil pressure testers...  140 Psi gauge with adaptors on a long hose can be screwed into the oil pressure port... so you can get a mechanical oil pressure reading..

you could also have an electrical issue..   shorted wire... issues in the dash board.. but starting in the engine compartment is easier..


3 wires on the oil switch.. the CENTER WIre is for the gauge..

the outer 2 wires are for the fuel pump... the orange wire has LIVE BATTERY VOLTAGE on it.. that has a fusible link.. NOT a fuse.. these blow slowly. the other wire goes to the fuel pump fuse and then to the fuel pump..

i will come back and put up some images later..

the oil pump pressure relief valve could have jammed shut and forced the oil pressure way high also...  the some brands of oil filters have had pleated media failures where they have gone deep into the oil galleys..  

waynep71222 waynep71222
Enthusiast | Posts: 448 | Joined: 03/12
Posted: 11/29/12
07:37 PM

here are some pictures.. this is the oil pressure switch.. i took the cover off.. these are usually not removable..  please don't try to remove the cover on yours.. this is just for a visual.

the center lead is for the gauge... the bridge and the 2 contacts inside the cap are for the fuel pump power circuit


pepsi1 pepsi1
Guru | Posts: 1718 | Joined: 09/11
Posted: 11/29/12
10:49 PM

I'm not sure if this sensor also lets your transmission go into OD. Have you noticed the tach. higher then normal, at cruising speeds? Has the gas mileage been worse lately?

Theres a quick way to check it the sending unit.

1.With an OHM meter go across the (2) polls if there is no value or no resitance,the sending unit is no good. When you remove it recheck the sending unit.
2.When the engine is cold. With an OHM meter see what you get for a value on the (2) polls of the sending unit.
3. Get the engine warm, and With an OHM meter see it the values have changed. Then the sending unit is working. If it doesn't change value then the sending unit is NO GOOD...Replace the sending unit.


waynep71222 waynep71222
Enthusiast | Posts: 448 | Joined: 03/12
Posted: 11/30/12
02:13 AM

let me help bobs post with some resistance values for the wells PS220 oil pressure switch

the fuel pump pressure Switch contacts opens when pressure falls below 2-7 PSI
the fuel pump pressure switch contacts are the outer 2 terminals..

the oil pressure terminal is on center.. and is connected to the shell of the sending unit..
80 PSI - 60-96 Ohms
40 PSI - 48-70 Ohms
8 PSI - 20-35 Ohms
Less than 2 PSI - 5 Ohms max

here is a look at the connector pigtail


pepsi1 pepsi1
Guru | Posts: 1718 | Joined: 09/11
Posted: 12/01/12
02:57 AM

I can always count on you for the help