How to test oil pressure sending unit

[slalomdude]

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When you say ignition on, do you mean that you've entered the security code, then pressed start, then pressed start AGAIN to actually put the boat in IGN ON mode?

yes, that exactly how it is. Power to all gauges and perfect pass boots up.

[CradGen2]

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S Dude. It is ever work correctly? I read the whole threat and seems you have wiring issue or loose connection. I had a 2000 Sport with a GT40 and never had this issue. Looking forward to the final outcome. Did you change the gateway out? Not even sure I know what that is.

[dwsa]

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Yes, Ignition on as in guages come alive, fuel pump powered.

[dwsa]

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HI, was at my boat today and can confirm the oil transducer measures 250 ohms with engine off, no oil pressure. Removing the wire and grounding the wire causes guage to peg at max deflection.

[slalomdude]

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Ok, thats the same as mine then. So if my gauge is pegged, maybe its a bad gauge issue. At 250ohms, with 0 oil pressure thats 0.048amps. Once pressure increases, resistance must decrease and so current will increase and gauge will deflect accordingly. If I am seeing full gauge deflection, it must be seeing a high current flow, ie short to ground. If its not in the wire to the sender, it has to be shorted in the gauge. Thats my thinking anyway, anyone chip in if you think I am wrong!!

[dwsa]

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Remove the sense wire off the guage if still pegged its the guage, if it does not peg out then as you said before the sender wire is shorted to ground somewhere. Is might be what drains your battery. I got a new guage for mine from Correct Craft.

[slalomdude]

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Removed it at gauge and needle goes to zero. This one is bafling, because as someone pointed out earlier, if the wire to the sender was grounded, it woulnt make any difference when the wire is disconnected at the sender, it would still be going to ground and pegging the gauge.

[dwsa]

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The wire that you removed must be grounded somewhere between the gauge end that you removed and the oil pressure sender (transducer). Therefore with wire reconnected to gauge and other end at transducer removed, your gauge should remain pegged because of the ground somewhere in between. You will need to trace the wire from the gauge down to the oil pressure transdcucer. You can disconnect the main engine harness near the starter motor and measure ohms to ground to determine if the short is in the engine harness or the cabling/harness to the dash. Your gauge will unpeg when you disconnect the engine harness because that removes the supply volts to the dash, that is why you must measure ohms, you can even do it with battery disconnected, look in the diagrams to determone which pin in the harness plug is the oil pressure. Good Luck

[slalomdude]

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Again spoke to Woody at SECC, he said the gauges are renowned for going bad and he he has rarely seen a sender go bad. I think for $30, I will buy a new gauge. I will test the wire to the sender and at the gauge and ring it out to ground , just to verify the wire is good. Thanks guys

[slalomdude]

Ok, got the new gauge and works great. I learned a lot over the course of troubleshooting this one, especially to call Woody at SECC first!!!. I now have a spare sending unit from skidim if any needs one cheap!!

[DanielC]

Cap and rotor, plug wires

I know this is the oil pressure thread, but cap and rotor was mentioned in this thread somewhere.
My 1997 Ski with GT-40 , with 1967 hours, was running a little ragged at the end of last (2007) season. I replaced the rotor, the distributer cap, and the spark plug wires, and it is running great. It is smooth again, the engine sings a pure song, and it will run right up to 5200 rpm, quickly.
Take the plug wires off one at a time, and compare the length when you are changing the wires.

[EchoLodge]

RE: Cap and rotor, plug wires

I have a 90 sport with the same issue. I guess I need to swap out my gauge. Anyone have a suggestion for a place that sells vdo white gauge?

I found this one!

http://www.egauges.com/vdo_mult.asp?...eries=OL_WH_BL