Oil pressure gauge high all the time

[toupee]

Hi everybody.  I'm having gauge issues.  My oil pressure gauge was non functional so I got a new sending unit.  Now once the key is turned on the gauge stays on high all the time - ignition on or ignition off.  Any ideas?  I thought the gauge should read high with the wire disconnected from the sending unit, but when I tried that my gauge reads nothing.  I thought the gauge should offer more resistance as the pressure builds up or do I have something backward here?

[Plumcrazy]

Sounds like you have the wrong sending unit.  It should be a fairly large bell shaped unit.
The ones for the warning light are much smaller

[toupee]

Got the one I have from autozone.  It looks just like the one that came off.  It is the bigger bell type you mentioned.

[John_Kunkel]

Sounds like you got a sender for an idiot light, it will ground the light at low pressure and ground with a gauge is full scale.

[craigandlynda]

it is grounding out somewhere...check the wiring in that area carefully...also, it is possible its a faulty unit...pull the wire off the top and see if the needle goes back down..if it goes down, its a faulty sender...if it stays hi, its along the wire somewhere

[toupee]

Tried pulling the wire earlier and it drops to low.  must be a bad unit i guess.

[craigandlynda]

let me know how that works out...

[toupee]

Got a new sending unit.  Seems to be working... kind of.  At idle the needle sits all the way down at the L mark.  It is moving now... just not where I think it should move to.  When I hooked up a mechanical gauge I got close to 30-35 psi on it.  That was with the idle up a bit, but not a bunch.  It is idling at 550 warm (which i intend to up to 700-800).  It was at 900-1000 when I got the 30-35 psi reading on my mechanical gauge.

[craigandlynda]

good progress....here's a few ideas...1) get idle up where it should be. 2) is oil in good shape? have a decent oil with a 10-40 or better viscosity? proper level? 3) if there are a lot of miles on this motor, realize the bearings or the pump may be a little tired..4) i assume its a big block...an easy idea to boost the pressure a little is change the spring in the pump housing..easily accessed and changed, there is a higher pressure spring available (or at least there was) which will boost pressure some...a friend once boosted the pressure by taking out the standard spring and putting a small slug under it, to boost the pressure...just some ideas...personally, i like higher viscosity oils in the summer...20-50, or even straight 50 for racing...

[moparjohn]

OK, I have the opposite problem, new wire harness, new correct send unit, no O/P on guage. Sometimes a little gauge movement early (first couple miles) then falls flat to left. Ground the wire and it shoots right up. Where do I look?

[Plumcrazy]

OK, I have the opposite problem, new wire harness, new correct send unit, no O/P on guage. Sometimes a little gauge movement early (first couple miles) then falls flat to left. Ground the wire and it shoots right up. Where do I look?

Assuming the other gauges read correctly and that you have good oil pressure, try another sending unit.

[craigandlynda]

try another unit...if that fails, try this...remove the sending unit. grab a handful of towels, and have someone start the motor.oil should squirt up thru the hole. shut motor down asap to prevent a larger mess...

[moparjohn]

This is the second sending unit, so I'm guessing it's good. I know I have O/P I did a mechanical test (test guage)

[craigandlynda]

hmmmm....does guage work first few miles, then pressure drops flat? hook your mechanical guage in, and drive a while watching that guage...does it stay up, or drop under 20 pounds?i would be very concerned if your pressure  :scratchchin:starts ok then drops that much...change oil AND FILTER and try things again...if you lose pressure under those circumstances, there is strong possibility of engine problem...weak pump, clogged returns thru the heads, worn bearings, weak bypass spring in the pump....etc

[moparjohn]

The whole problem started with a bad alternator, it fried the fuseable link, and then the O/P guage stopped working.

[moparjohn]

also the engine wa rebuilt Oct 06. all new internals including oil pump

[craigandlynda]

hmmm...started when fusible link went? oboy....do you have schematic for your wiring? check to see if you have a voltage limiter in the dashboard area...if i remember right, some cars have these to limit maximum volatge to soem of the guages to 9 volts...this is an unusal problem