Pegged Oil Pressure Reading?

MT930 · 01-31-2009, 01:42 PM

I fire the car up the last day of the month, to keep things lubed during the November to April storage period here in the frozen north. The car fires on the first turn no smoke at all. The oil pressure needle peg's the the 5 line and stays there at 900 RPM I am a little concerned no normal fluctuations at idle it should be at line 3

but I think at least it's not low oil pressure no oil light or rapid temp gain. I drive the 1/4 mile in the neighborhood then put it back in the garage needle never moves off the 5 line on the gage. It's 38F out side the garage is heated to 50 F. Could very cold oil cause this? 20W 50W Dino oil car ran great just like I had driven it for the last week. Never seen this before, Whats going on ?

Flieger · Flieger's Garage

It is probably a bad connection to the oil pressure sender. Check for cracked insulation, loose wires, as well as corrosion on fuses in the front fuse block. Beyond that, a bad ground wire or a failed pressure sending unit are possible.

JohnJL · 01-31-2009, 01:54 PM

Let it warm up a bit longer and see if it comes down.

If it doesnt, Flieger is likely right.

tonythetarga · 01-31-2009, 03:09 PM

Quote:

Originally Posted by Flieger

It is probably a bad connection to the oil pressure sender. Check for cracked insulation, loose wires, as well as corrosion on fuses in the front fuse block. Beyond that, a bad ground wire or a failed pressure sending unit are possible.

+1. wires are located in right rear wheel well. That wire gets pelted by sand and road dirt and the insulation will sometimes get stripped exposing the wire to possible grounding.

moneymanager · 01-31-2009, 03:36 PM

Short in ground or wire to the pressure sensor at the rear of the engine, or the wire has come off. I think I remember that these circuits are wired so the gauge pins if the wire is disconnected. Someone else will correct me if I'm wrong. (This sensor is not in the wheel well unless I'm reading this wrong. That's the oil level sensor on the oil tank, at least on my car.)

tonythetarga · 01-31-2009, 04:20 PM

Quote:

Originally Posted by moneymanager

(This sensor is not in the wheel well unless I'm reading this wrong. That's the oil level sensor on the oil tank, at least on my car.)

Ya, roger that. I was thinking level sensor as I had that problem last fall and just read the original post incorrectly.

BrokeMyCar · 01-31-2009, 05:12 PM

I had similar symptoms - the solution ended up to remove the connector that goes to the oil pressure sender (on the valve cover, I believe?) and clean the contact with a wire brush. When re-attaching I flipped it upside down so it would hold better. The "teeth" of the clip had worn away a matching pattern in the "tongue," so flipping made a more secure contact.

Babak

MT930 · 01-31-2009, 07:06 PM

Cleaned the contacts on the sender and the female wire contact. reconnected

No change What's my next step on tracking this down ?

JohnJL · 01-31-2009, 07:41 PM

Didja let it fully warm up? My 71 does the same thing but al is OK once warmed up.

MT930 · 03-20-2009, 02:30 PM

First good day to get the car out of the garage. I never figured it out in November.

any more Ideas? same problem Druck Pressure pegged at 5 Bars

I did clean the connector no change.

LeakProof · 03-20-2009, 02:40 PM

I believe I had the same exact problem a few months ago. (pegged at 5-bars)
Purchased a new sendor, installed in 40 minutes, started her up, and after warm, it went to 1.5 -bars.

Mike.

MT930 · 03-20-2009, 02:55 PM

I do not have continuity from the spade of the sender to the engine

Whats that mean ?

LeakProof · 03-20-2009, 02:59 PM

Sorry, can't help you on that one.

gamatt · 03-20-2009, 05:28 PM

The oil pressure sender is a varible resistor activated by oil pressing into the sender. On the 3.2L the sneder is mounted to the right of the cooling fan (passenger side) down on the block just above the engine tin. It's rather large and is mounted just above the oil temp sender.

You will not get a short to ground checking it the way you did. If the connection to the sender is lost the gauge will peg at 5. Clean the contacts, make sure the wire is attached, and if that doesn't do it, check the wire with your Ohm meter between the sender and the gauge.

A mouse ate mine. Took a while to find the break. Good luck.

Gordon

fredmo1947 · fredmo1947's Garage

I had the same problem with my 911S, gauge pegged when the key was on the "on" position.
Checked all wires for shorts, no problem. Installed another gauge I had available, same situation with gauge pegging upon turning key to on position. Bit the bullet and bought a $70+ oil sending unit from our friends at Pelecan....problem solved. PS: got a used combo oil temp/pressure gauge for sale $60 + shipping. (I'd spend the money on a sending unit first!)

Daytona · Daytona's Garage

I have a similar problem only my gauge stays at 3.75 bars with key on and with engine running at idle and acceleration. Checked all conn. as post suggests but no luck. Can the pressure sending you be cleaned ?

vreference · 03-21-2009, 11:49 AM

Key on, Engine Off ( "KOEO" Key in the run position) you should have a 0 (Zero) reading. If it's at 5 with the key on but before the engine is running then it's the sender or the wiring. If this is the case you can unplug the sender to attempt to isolate the issue. That is, with the sensor unplugged (KOEO) you still read 5 it's an issue with the gauge or the harness. If the gauge reads zero after unplugging the sender, the sender is faulty. If you only read 5 Bars with the engine running (KOEO)it could still be a gauge or sending unit failure (wiring is less likely). The other possibility is a mechanical issue such as a failed bypass valve.

gamatt · 03-21-2009, 12:06 PM

Daytona,

You can sometimes clean the sending unit. After you take it out you will see a VERY small hole in the threaded end of the sending unit. If there was some contaminate in you oil, it could work its way into the sender and block it.

Carb cleaner and air pressure. Just don't shoot yourself in the face with the carb cleaner. It's going to spray back at you since there is no exit hole in the sender.

Not likely this will work, but it's cheaper than a new unit and it only takes a few minutes to pull the sender out and put it back.

G

Daytona · Daytona's Garage

Gamatt,
How do you remove the sender, it feels as if a nut is on the bottom of the unit ,but how do you get a wrench on very limited space.

DaveE · 03-21-2009, 01:25 PM

Mine did this once. I forgot to put the cap on after checking the oil. I was driving and it suddenly pegged so I stopped the car and looked. The cap was laying against the sender and shorting it to the engine sheetmetal.