ttAmerica RoadsterAWD

Went on a 4hr drive yesterday and noted my oil pressure gauge flickering at the top end even tho throttle was constant. Then the pressure would peg to the top with just a little off idle, now at idle it's pegged beyond upper numbers.....like if there was a short or something. Could this be a bad sender, bad gauge, short?

Jaime

garrett376

You need a new sending unit. It happens all the time - well, on two of the 4 964's I've had! It's a pain to reach, but not if you undo half of the intake manifold assembly as I covered in a post somewhere!

cjansen

Jamie,

I had a similar problem a while back but my oil pressure would peg high or low and appear to get stuck for several days then would work normal for weeks at a time. I figured that it wasn't the sender unit because the central informer should have went off if it detected a loss of oil pressure and it is on the same circuit as the pressure gauge. So i started looking at the gauge itself and found that i could get it to fail by tapping it. So I took of the connectors and cleaned them but I still had an issue. Then I found that on the back of the guage there are some large pin contacts with these triangular shaped sockets and I squished the sockets a bit to get a snug fit and problem was solved. Sorry I don't have a picture but I'd start at the gauge end and look for something intermittent.

But if yours is only reading high and then normal it may be a genuine sending unit failure. Maybe someone has a procedure for diagnosing the sending unit?

ttAmerica RoadsterAWD

Hi guys. thanks for the support and info. Now the oil pressure immediately pegs beyond 5 with only the ignition key on, not even turning the engine. Does this give any more clues as to what it could be? Any electrical guru's out there??

Jaime

DaveK

I'd still agree it's the sender.
When I repaced mine, it was because I could often get 1-2bar on the gauge with the ingition on but without starting the engine.

robbed666

Central informer doesn't monitor the oil pressure gauge, only the switch unit built into the sender. They are separate (electrically) from each other.
BUT! The gauge works by a variable resitance to ground. Any additional resistance, say from a poor connection will cause the gauge to read incorrectly.

Apart from the connection to the back of the instrument panel. There is only one other inline connection (according to the wiring diagram). That is connector T30. This is located in the engine compartment. LH side, near the rear control box. The wire is green with a red tracer.

HTH

Jeremy Pinsly

Sounds like the sending unit to me....I had mine replace too.
If you attempt to do this yourself by removing the manifold to access the sending unit, take good care to ensure you seat the manifold back perfectly, otherwise you'll have air leaks.....

jimq

if the ground is bad or lose to the sensor it will peg.

Indycam

The old test is to unplug the sender and watch the gauge . Then ground the wire and see what the gauge does . The sender is a variable resistor , so unplugging it the gauge sees infinite resistance and grounding the wire causes the gauge to see zero resistance .

If you have a decade resistance box , you can use that to dial up and down a gauge .

The other test is to hook a dvm on the sender and watch the resistance , it should change smoothly up and down with the rpms .

ttAmerica RoadsterAWD

You guys are awsome! Where abouts in the engine is the gauge? Is it close to the air filter? next to the??

Jaime

JasonAndreas

replacing the oil press/temp sender o-ring: the "hemi-manifoldectomy" technique

ttAmerica RoadsterAWD