oil pressure question

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Aug 26, 2011
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Today I replaced my starter and when I got back into the rig to start it up I noticed the oil pressure gauge was not working or I have lost all oil pressure. The oil pump was replaced about 6 months ago. I had a lot of leaks at the oil pan gasket and had the oil pump replaced while the mechanic was in there fixing the gasket. I also replaced the oil pressure sending unit. The pressure was good until today I think? Is there a gauge I can pick up and screw into the oil sending unit hole to test the pressure? I want to determine if it is the oil pump or gauge or sending unit. Any other ideas? Looking for easy way to test oil pressure! Thanks

By the way, how do you get the "NEW" tab on these posts?

"We cannot solve the problems we currently face in the same state of mind we were in when we created them"
 

brew8

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You can buy a cheapo mechanical gauge you would likly have the remove the sender to hook it up, If you go to the parts store and fool around in the brass fitting collection you can build a T so you can have both then install it in the cab so your sure. You could have grounded the gauge somehow and fried it. Take an ohm meter and lightly touch the gage terminals and see if it moves up scale they usually have a lower voltage and go through a resistive network in the meter that can keep you from shorting it out.
 

brew8

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If you do the ohmmeter check un hook the gauge from voltage and the sending unit. You could also check the voltage at the sending unit with the key on and the engine not running you should see 12 volts there, if not the meter is open or there is no voltage at the meter. If you start the motor and the voltage stays high you have no oil pressure or the sender is bad.
 
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Thanks brew8! I have no idea what you are talking about but that's what brothers-in-law with engineering degrees are for. Thank God he lives four doors down. This may sound dumb but could
I simply take off the sending unit and start the engine and look for oil? Or should I get the brother-in-law?
 

brew8

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Get the brother in law bad idea to run it you could pull the coil wire to the distributor crank it and see what happens with the sender off
 

bj40green

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Do you have a test light? A screwdriver with a light bulb inside and a ground wire with an alligator clip? Something like this?
screwdriver test light.jpg

Hook the clip to ground (bare metal)
Hold the test light aginst the oil sender prong (don't take the wire off)
Start engine
The test light should be dim / glow
If bright, the sender is faulty
If no light at all, the gauge or the wire between the gauge and the sender is faulty.

Rudi
screwdriver test light.jpg
 
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My BIL does! We will check this in the morning. If the sender and the meter check out, do I have a major issue on my hands? Does my starter shooting craps signal some engine damage? could this simply be the oil pump? Thoughts?
 

brew8

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You can put the tranny in a high gear and push to bump the engine to make sure it isn't siezed. If you can get the engine to run then get a cheap mechanical gauge and see what the oil pressure really is. I bought a cruiser years ago and it supposedly had a rebuild, I went out to start it one day and it had no oil pressure, I pulled the distributor and used a screw driver with the handle removed and a drill to drive the oil pump it had an awful time priming, so I pulled it and put in a new one no problem after that. If you have a new one it's not likely but who knows, they either didnt change the one I had or it was just junk. The oil gauge will help determine what is going on, you may also make sure the distributor hasn't move up and disengaged the pump.
 
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Ok I did the light test. I hooked up the clamp to a ground and put the tester on the post of the sender with the wire attached. I then turned the ignition on and the light was very bright white. Then I went ahead and started up the engine and I let the engine run with the tester on there and it stayed bright white the whole time. The engine sounds ok. Do you guys think this is a sender issue then? It seems like that is what the problem is, but wanted to get your thoughts for sure!
 

brew8

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I would swap the sensor should be fairly cheap at autozone of NAPA they sold ot for lot's of years.
 
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I finally found the metric fitting to hook up my gauge and the pressure at idle was 57 psi and when I give it some gas it goes to 63 psi! I ordered the sender from toyota... problem solved!
 
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I have a similar problem with my 77. I just replaced all the tubing with the proper British Standard Pipe-taper from the engine. I tubed it up so I have a tee for the new oil sending unit, and a connection for a direct-reading gauge. When I started the engine, the cluster gauge came up to ~ 3/4 pressure, the direct gauge then came up to ~ 50 psi. Then the cluster gauge slowly dropped to zero, and actually went out of sight low. The direct gauge still read a good 50 psi. Is there a check I can make to see if the cluster gauge is bad?
 

bj40green

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Hi sggoat,

You can do the test in post#10 or use a voltmeter.
Voltage on the sender should be between 3 and 10 Volt depends on the rpm's.
If 12V -► Sender is faulty / open circuit / no ground.
If 0V and gauge is in the left corner -► Gauge or wire is faulty / open circuit.
IF 0V and gauge is in the right corner -► Sender is faulty / short to ground.

For more info about the oil pressure gauge, sender and testing procedure have look here -► https://forum.ih8mud.com/40-55-series-tech/544543-clusters-gauges-odo-meters.html and go to post #7 and scroll down to FSM page 12-29

Hope this helps,

Rudi
 
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Rudi,
Thanks. I will do these tommorrow. I did check the circuit with a meter. With the ignition off, and the sender wire off I checked continuity from the gauge wire to ground--got about 48 ohms. If I check voltage from the sender connection to the battery positive post , I get 12 volts(almost sounds like the sender is grounded internally--but it's a brand new sender) Could the gauge be bad and when I started the engine, the bad gauge caused the new sender to fry?
 

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