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oil pressure sending unit |
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mstrcrftr
Supporter of TheAMCForum Joined: Jul/12/2010 Location: houston Status: Offline Points: 2066 |
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Posted: Oct/07/2017 at 8:44am |
something funky is going on with my oil pressure gauge. this is a new install on a new engine. i have a tee fitting on the block for the sending unit. one side of it goes to a mechanical gauge on the engine and that works fine. the other side goes to an electrical sending unit for the dash gauge and its not working. when i jump the sending unit wire to ground, the gauge works. i tried replacing the sending unit and it still does not work. any suggestions on what to do?
thanks Barney |
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6768rogues
AMC Addicted Joined: Jul/03/2007 Location: United States Status: Offline Points: 6241 |
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Did you use some type of thread sealant or teflon tape on the threads of the sending unit or Tee? If so, it might electrically isolate the sending unit from the block. That won't matter for the mechanical gauge. Otherwise, I would guess that both sending units are bad or wrong for the gauge.
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mstrcrftr
Supporter of TheAMCForum Joined: Jul/12/2010 Location: houston Status: Offline Points: 2066 |
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i thought of that and tried grounding the case of the sending unit to the block, no change. do you think its possible that i have two new bad units? both were ordered for 80 psi gauge. i was wondering if the unit was different for an 80 psi, but you would think that the gauge would at least move if it was for a 40 psi gauge.
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Airdrie AMX
AMC Nut Joined: Aug/08/2010 Location: Alberta, Canada Status: Offline Points: 329 |
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Do you have a good ground strap from the engine to chassis?
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72 amx javelin 401 4spd
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rockAMX
AMC Addicted Joined: Sep/16/2011 Location: Lethbridge AB Status: Offline Points: 985 |
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By the dash gauge, do you mean the oil light or a gauge?
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DWR
1968 AMX |
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mstrcrftr
Supporter of TheAMCForum Joined: Jul/12/2010 Location: houston Status: Offline Points: 2066 |
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battery cable goes directly to the block and yes the dash has an actual 80 psi gauge.
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rocklandrambler
AMC Addicted Joined: Feb/09/2013 Location: Nanuet, NY Status: Offline Points: 3953 |
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Could it be the mechanical pressure line is siphoning off enough pressure that the electrical sending unit can't sense any pressure? Does the electrical gauge work OK when hooked up by itself?
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Past AMC's
1974 Hornet X (new) 1975 Gremlin X (new) 1964 Classic 660 Cross Country 1965 American 440-H |
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mstrcrftr
Supporter of TheAMCForum Joined: Jul/12/2010 Location: houston Status: Offline Points: 2066 |
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mechanical gauge reads 60 at idle. not a pressure bleed thing.. its gotta be two bad sending units. everything else works..
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mstrcrftr
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still having issues with this. can someone look at the drawing below and confirm that this is how the circuit actually works?
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304-dude
AMC Addicted Joined: Sep/29/2008 Location: Central Illinoi Status: Offline Points: 9082 |
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It is possible that the instrument panel circuit is damaged.
You can test with the engine running, by ohming the output on the switch directly. You may need someone to increase the engine RPM to show resistance change from idle to 2500 RPM. If you see the resistance change, it is possible the one of contacts where the oil pressure gauge has a broken trace or wire. |
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71 Javelin SST body
390 69 crank, 70 block & heads NASCAR SB2 rods & pistons 78 Jeep TH400 w/ 2.76 Low 50/50 Ford-AMC Suspension 79 F150 rear & 8.8 axles Ford Racing 3.25 gears & 9" /w Detroit locker |
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