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  #1  
Old 08-07-2010, 11:52 AM
Galazza Galazza is offline
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Post Oil Pressure Gage indicates zero

My Oil pressure Gage in a 4x4 1999 Ford Ranger 4.0L indicates no pressure. It started doing that in the last couple of weeks. I changed the oil pressure-sending unit on the engine driver's side (accessing it from the wheel well lifting the rubber flap) but did not fix the problem. There is lots of oil in the engine and I use the truck regularly with no problems. When I started the engine the oil gage needle goes from bottom (out of scale) position to just below zero position or around there(in other words the needle moves up a bit). Strange, isn't it! Any idea on what may causing that ?
Gabe

I changed the pressure sending unit and I also rotated the niddle anticlockwise to the stop (peg) position. It works great. Thanks
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Last edited by Galazza; 10-21-2010 at 07:18 PM. Reason: found problem
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Old 08-07-2010, 11:59 AM
FireRanger FireRanger is offline
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Default Re: Oil Pressure Gage indicates zero

It's a wiring problem somewhere between the sender and the gauge. The sender is only a switch. When oil reaches 7psi, the switch closes. There is a resistor on the gauge pod that pegs the needle at the middle. So it can only read 0 or middle.
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  #3  
Old 10-14-2010, 05:55 PM
art47 art47 is offline
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Default Re: Oil Pressure Gage indicates zero

I have wondered about this oil pressure gauge. Mine pegs to the center right away and stays there. When the ignition is turned off, the needle stays centered. When the ignition is turned on it goes all the way left. Start up and it goes back to center. Sooooo. . . this thing is just an idiot light with a needle?
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Old 10-14-2010, 06:14 PM
FireRanger FireRanger is offline
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Default Re: Oil Pressure Gage indicates zero

Yep.
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Old 10-14-2010, 06:23 PM
EMB1230 EMB1230 is offline
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Default Re: Oil Pressure Gage indicates zero

And it's not just the 95-03 cluster that does it, 89-94 ones are the same way. Tach or no tach, makes no difference
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Old 10-14-2010, 07:52 PM
art47 art47 is offline
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Default Re: Oil Pressure Gage indicates zero

So,
to have a gauge that displayed true oil pressure you would need a sender unit that actually measured a range of pressure, say 0-100 psi?
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Old 10-15-2010, 04:24 AM
FireRanger FireRanger is offline
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Default Re: Oil Pressure Gage indicates zero

Yes, you would need a sender that is made for vehicles that actuality use them. Then you also need to open up the gauge cluster and bypass the resistor that pegs it at the middle.
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Old 10-15-2010, 04:45 AM
crowdpleazer crowdpleazer is offline
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Default Re: Oil Pressure Gage indicates zero

^^ or put an actual oil pressure gauge in there...
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Old 10-15-2010, 09:57 AM
FireRanger FireRanger is offline
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Default Re: Oil Pressure Gage indicates zero

Are you talking about an aftermarket add-on guage?

The OE gauge nor the circuit it is attached to will not indicate a variable pressure until you replace the switch with a sender and bypass the dummy resistor.
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  #10  
Old 10-17-2010, 08:39 AM
Rocky Mountain Ranger Rocky Mountain Ranger is offline
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Default Re: Oil Pressure Gage indicates zero

It would be nice to have functioning oil pressure gauge, without trying to find space for an add-on. Someone mentioned by-passing the 20ohm resistor and replacing the OP sending unit with a variable output OPSU. I have been behind the dash twice... bypassing the resistor should not be hard (with a multimeter). What oil pressure switch would be needed to replace the OE? Would the gauge's electromagnet still function within the appropriate range (showing standard operating pressure about mid-scale of the dummy gauge and low pressure near the "L")?
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  #11  
Old 10-17-2010, 08:58 AM
Rocky Mountain Ranger Rocky Mountain Ranger is offline
'02 EDGE 3.0L 2wd auto
 
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Default Re: Oil Pressure Gage indicates zero

I just finished reading another thread and sounds like converting my OP idiot gauge to a functioning gauge wouldn't work on my '02.
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Old 10-17-2010, 09:17 AM
FireRanger FireRanger is offline
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Default Re: Oil Pressure Gage indicates zero

Why not? I don't think the design has changed since the early 90's
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  #13  
Old 10-17-2010, 10:58 AM
rwenzing rwenzing is offline
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Default Re: Oil Pressure Gage indicates zero

Quote:
Originally Posted by Rocky Mountain Ranger View Post
... bypassing the resistor should not be hard (with a multimeter).
97~2003 do not use a resistor in series with the gauge. The resistor bypass is necessary only for the earlier gauge clusters that have it.


Quote:
Originally Posted by Rocky Mountain Ranger View Post
What oil pressure switch would be needed to replace the OE?
The correct SU for the 97-back OP gauge is the common Standard Products PS60 or Motorcraft SW1547B or equivalent.


Quote:
Originally Posted by Rocky Mountain Ranger View Post
Would the gauge's electromagnet still function within the appropriate range (showing standard operating pressure about mid-scale of the dummy gauge and low pressure near the "L")?
For 97~2003 Rangers, the gauge itself is rewound to read about 40% of full scale at full battery voltage. Simply substituting a variable resistor sending unit would cause the needle to operate very low in the available scale and not be much more useful than the factory "idiot light with a needle".

Fortunately, it is possible to substitute the 95~96 OP gauge guts into a 97~2003 cluster. Make that change and use the PS60 or equivalent and the gauge will read actual pressure.

I have a 95 gauge in my 2003 cluster and a variable resistance sender an it works great. Clearance for the PS60 style sender is an issue with the 4.0 SOHC but it can be done. Not sure about the other engines but it should be possible.
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  #14  
Old 10-17-2010, 11:22 AM
FireRanger FireRanger is offline
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Default Re: Oil Pressure Gage indicates zero

^^^ The man.
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How to: Aux light wiring, relays, & fuses
Info: 300+ intake threads here on FRF
Info: HID Projectors
How To: NO HEAT Troubleshooting Guide
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  #15  
Old 10-20-2010, 09:52 PM
Rocky Mountain Ranger Rocky Mountain Ranger is offline
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Default Re: Oil Pressure Gage indicates zero

Thanks for the advise! My oil pressure gauge just broke so I have installed an under-the-hood mechanical OP gauge until I track down a 2002 OE gauge or do the '95-'96 switch over.
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