Oil Pressure Gauge
Thread Starter
Advanced
Joined: May 2004
Posts: 93
Likes: 0
From: In the valley
Oil Pressure Gauge
My 1988 convertible's oil pressure gauge is showing 80psi most of the time. Occasionally it will drop into the 60s. Methinks it is the gauge oil pressure sender. There are 2 senders, correct? One for gauge and one for ecm? Which one is the one for the gauge? Is it available aftermarket or should I get it from my friendly neighborhood dealer? Also, in looking at the location, back of engine, how do you access it to change it? Do I have to r/r distributer? Looks awful tight back there!!!!! Any advice would be appreciated. Have a great day. 
Thanks, in advance,
Charlie
Thanks, in advance,
Charlie
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
One oil pressure sender. The ECM does not get oil pressure information. It is screwed into the rear of the block to the left (car's left) of the distributor. The ARE available in replacement. Any auto parts store should be able to supply one. I got to mine by removing the ww motor. That seemed like less work than the distributor.
RACE ON!!!
RACE ON!!!
Last edited by CFI-EFI; Jul 8, 2004 at 06:49 PM.
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
There is only one oil pressure sender.
You can test the dash read out by doing the following.
Disconnect the Tan wire at the Oil pressure sender which is
near the distributor driver side, back of the engine block.
With the ignition on engine not running.
One end of a 90 ohm resistor to ground with the other end to the tan wire which goes to the digital dash. The reading should be 80 psi +- 3 psi.
45 ohms should read 43 psi +-3 psi
20 ohms should read 12 psi +-2 psi
With the tan wire grounded, the reading should be 0 psi.
If the readings are correct, the sender is bad.
If the readings are wrong, the dash is bad.
Note: The oil pressure sender and oil pressure switch are built in to
the same unit.
You can test the dash read out by doing the following.
Disconnect the Tan wire at the Oil pressure sender which is
near the distributor driver side, back of the engine block.
With the ignition on engine not running.
One end of a 90 ohm resistor to ground with the other end to the tan wire which goes to the digital dash. The reading should be 80 psi +- 3 psi.
45 ohms should read 43 psi +-3 psi
20 ohms should read 12 psi +-2 psi
With the tan wire grounded, the reading should be 0 psi.
If the readings are correct, the sender is bad.
If the readings are wrong, the dash is bad.
Note: The oil pressure sender and oil pressure switch are built in to
the same unit.
Last edited by Hooked on Vettes; Jul 8, 2004 at 10:40 PM.
Thread Starter
Advanced
Joined: May 2004
Posts: 93
Likes: 0
From: In the valley
Thanks guys. I'll look for the tan wire and check the readings. I am confused though. On rear of engine near distributer, there are what appear to be 2 senders/switches on a fitting coming out of the rear of the engine. (My mistake on ecm, I read that one of them is for fuel pump, not ecm, sorry). When I looked in the shop manual, the component location page shows 2 components back there. Oil pressure switch and oil pressure sender. One is larger than the other. I am sorry to appear obtuse, but is the sender for the gauge the larger component back there?
Thanks very much for your kind replies and help. Yes it appears easier to remove wiper moter. Thanx for the heads up.
Regards
Charlie
Thanks very much for your kind replies and help. Yes it appears easier to remove wiper moter. Thanx for the heads up.
Regards
Charlie
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
Well I looked in the micro fiche and your're correct. The 88 used a seperate oil sender and oil switch.
My fiche is a little blurry but the part number for the sender appears to be 14078954 and sells for $22.00.
The sender should only have one wire going to it. The metal body is the ground for the sender. The oil pressure switch should have two wires going to it. The info. I gave you was for an 89 but I would think the testing of the sender with the different resistor values would be the same.
My fiche is a little blurry but the part number for the sender appears to be 14078954 and sells for $22.00.
The sender should only have one wire going to it. The metal body is the ground for the sender. The oil pressure switch should have two wires going to it. The info. I gave you was for an 89 but I would think the testing of the sender with the different resistor values would be the same.
Last edited by Hooked on Vettes; Jul 9, 2004 at 11:15 AM.
Thread Starter
Advanced
Joined: May 2004
Posts: 93
Likes: 0
From: In the valley
Thanks for your help guys, I picked up an oil pressure sender, non AC but a direct match for the 14078954. Before installing I remover wiper motor to access (thanks again CFI-EFI) and pulled the tan wire. With it open gauge read 80psi and grounded read 0psi. I did not have access to any resistors by the time I got around to this Friday nite. Sooooooo...I went ahead and installed the sender, and now have oil pressures on gauge other than 80. They seem high though. Hot idle is 45psi, when I get on the throttle it goes up into the 70psi range. Perhaps the gauge is flukey as well. Anyway, sorry for the long post. BTW, what are the average oil pressures for this car. My Blazer idles at around 35psi. Do vettes have high oil pressure?
Thanks so much, again.
Keep the faith
Charlie
Thanks so much, again.
Keep the faith
Charlie
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
I'm glad if I was a help. The resistor tests weren't necessary, as you discovered. The 0 and 80 readings proved it was the sender. Oil pressure of 45# hot and idling sounds suspiciously high. You could double check it with a known, good, mechanical gauge, but I see another sending unit in your future. You didn't use Teflon tape on the sender threads, did you?
RACE ON!!!
RACE ON!!!
Thread Starter
Advanced
Joined: May 2004
Posts: 93
Likes: 0
From: In the valley
No, no teflon tape. The sender had what appears to be paint on the threads. Seems to have sealed well, no leaks. What are the stock pressures? As I said, my Blazer 4.3 Vortec runs at about 30-35 hot idle. Could this be an indicator of a mechanical issue? I changed the oil last week using Castrol 5w30 and a K&N filter. Again, thanks for your help.
Charlie
Charlie
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Advanced
Joined: May 2004
Posts: 93
Likes: 0
From: In the valley
I do not know if it is correct. It seems high to me, as well. I did not know if vettes oil pressure ran high as a rule. I'm getting the impression that my pressure is high, or the gauge or new sender is wacky. I guess I need to find a mechanical gauge and chech it. Can anyone tell me the "factory spec" for oil pressure for a 1988 L98? CFI-EFI, again, thanks very much for your help.
Regards
Charlie
Regards
Charlie
Instructor
Joined: Apr 2004
Posts: 240
Likes: 0
From: St. Louis MO
Originally Posted by Corky52
I do not know if it is correct. It seems high to me, as well. I did not know if vettes oil pressure ran high as a rule. I'm getting the impression that my pressure is high, or the gauge or new sender is wacky. I guess I need to find a mechanical gauge and chech it. Can anyone tell me the "factory spec" for oil pressure for a 1988 L98? CFI-EFI, again, thanks very much for your help.
Regards
Charlie
Regards
Charlie
Team Owner
Joined: Sep 2001
Posts: 62,160
Likes: 1,733
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Factory spec for Oil Pressure is 45-60psi at cruise, dropping to the 30's at idle. Cold idle can surely stay in the 40's and 50's.
If its really hot, it can get to the 20's.
If yours is jumping into the mid-60's at WOT, thats just fine.
If its really hot, it can get to the 20's.
If yours is jumping into the mid-60's at WOT, thats just fine.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Corky52,
I'm not concerned that your pressure is too high. I'm concerned about the accuracy and usefulness of your gauge. 88vettelover's 28#-34#, is cold pressure and seems more realistic.
Your higher, hot idle pressure, especially with that thin oil, is suspect. My concern is that if the pressure ever drops to "normal" numbers your inaccurate(?) gauge may lull you into a false sense of security, where you may actually have little or no pressure. If the gauge is correct...Great!
RACE ON!!!
I'm not concerned that your pressure is too high. I'm concerned about the accuracy and usefulness of your gauge. 88vettelover's 28#-34#, is cold pressure and seems more realistic.
Originally Posted by 88vettelover
...my 88 runs about 28-34psi when I first start it.
RACE ON!!!
Last edited by CFI-EFI; Jul 12, 2004 at 12:27 PM.
Thread Starter
Advanced
Joined: May 2004
Posts: 93
Likes: 0
From: In the valley
Okay, thanks for all of the responses. To do a mechanical pressure test, what do I need? An oil pressure test kit from Snap On runs 120.00+-, or can I get a mechanical gauge from say Advance Auto and thread it in where the sender goes to observe and compare? I really do not want to go to Mr Goodwrench if I can help it. We have a new shop that supposidly specializes in hi end cars that I could call.
Thoughts, opinions?
Thanks
Charlie
Thoughts, opinions?
Thanks
Charlie
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Corky52
...or can I get a mechanical gauge from say Advance Auto and thread it in where the sender goes to observe and compare?
Thanks
Charlie
Thanks
Charlie
RACE ON!!!
