Zero Oil Pressure

[kyken]

Here's my first little problem since getting my truck going.

Truck started right up as usual but I immediately noticed I had no oil pressure. So, I turned it right off. I started the truck again and the needle did not budge, not a fraction. Yep, checked the oil, it's good.

The indication was never perfect as I usually had a pegged needle, +60 and sometimes it would read normally.

Just went out to the truck and found a loose wire, fixed it hoping that was it but still no pressure.

What does this sound like? Gauge, sending unit, oil pump, hopefully nothing bigger?

Thanks!! Ken

[rboltz]

Only way to know for sure is to put an analog guage in where the sending unit goes. I had the same a year ago or so and it was the sending unit. This after I replaced the pump.

[kwai]

Probably the sending unit. Put a real guage on it and check it. You can also check the sending unit.

The oil pressure guage sending unit should read 0-1 ohm with the engine off. If the ohmmeter does not indicate this or in excess of 1 ohm replace the sending unit.

With the engine running the ohmmeter should indicate a higher reading. If a higher reading is not indicated replace the sending unit.

[kyken]

My Brother should have an ohm meter. If that's the case, does NAPA or local auto parts store have them? There is one on ebay, specifies for 60 spi. Is this the one?

http://cgi.ebay.com/ebaymotors/ws/eB...%3AMEWAX%3ABIN

Thanks all!!
Ken

[moose3d]

Assuming the wires are good (you can do a continuty check if questionable), unplug the wire from the sending unit and turn on the master switch. The gage should max out and then ground the sending unit wire, the gage should go to zero, if it doesn't do both, the gage is bad. If it does what I just said it should, the sending unit is bad.

This is what I did in the motor pool everytime I had an operator say the gages were not working. Worked everytime.

[brute4c]

Follow the above advice to test the gauge and sender...I just want to add that I had my gauge peg out once while I was driving...dont know why but I just happened to see it happen...needle dramatically went full right all of a sudden...stayed there for about 5 seconds, then the needle fell to 0...the sending unit AND the gauge were bad by then...I am guessing the sender fried and then took the gauge out.

Just sorta sounds like what I had happen...when I read your incident that is...so maybe both of yours are bad.

[kyken]

Thank you all, will try it today!

Is the above ebay link the correct sending unit or can they be purchased elsewhere?

[militarypotts]

That above sending unit does not list the M715 as one of the vehicles it's used for. Need to check that out.

[brute4c]

The mil sending units come set for a specific gauge range...not a specific gauge.

Not the best wording but basically...if the gauge reads 0-60 then the sender needs to be the 0-60 sender...like this one linked on Ebay is.
There are also 0-120 gauges and they need a different sender set for 0-120...

So the sender scale has to match the gauge scale and then you are good to go.

[kyken]

Thanks Moose3d, MP and Brute4c.

I just pulled the lead off, master on and got no change at all on the gauge. Flat dead, not a wiggle at all.

So, I am leading to believe what Jon said, if I understood him correctly, that there is a problem with the sending unit therefore damaging the gauge. Guess I'll order both. Also, if I checked this earlier and replaced the sending unit, I most likely would still be using the original gauge. Live and learn!

Thanks a lot guys!!