What determines a 1 or 3 pin oil pressure sensor?

454cid said:

Ok so you all are speaking of the 3 wire part..... is my one wire just for the gauge then? Just in case you haven't looked at my signature, this is a 99 454.

I'm not really understanding why GM would power the fuel pump with two circuits.

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someotherguy said:

Reason for redundant fuel pump circuit on the GMT400's is backup in case your relay fails. At least that's the way I take it...

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Schurkey said:

No, not really.

If the fuel pump relay is turned on, the oil pressure switch CANNOT turn the fuel pump off.

If the oil switch has pressure so it's turned on, the fuel pump relay CANNOT turn the fuel pump off.

EITHER ONE can turn the pump ON if the other one fails.

BOTH have to turn OFF to kill power to the pump.

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someotherguy said:

I think your late model with the 1 wire sensor may be a '99 "classic" anomaly, but I haven't had time to do much research on it. It does seem the GMT800 stuff operates differently, so at the end of GMT400, they may have changed more than we've realized just yet. On a GMT800 (at least on our 2006's), pull the fuel pump relay and that engine isn't starting regardless of how long you crank it to build oil pressure.

Reason for redundant fuel pump circuit on the GMT400's is backup in case your relay fails. At least that's the way I take it...

Richard

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454cid said:

Hmm, the 800's seem to be all 3-wire, when I look on Rockauto. I suppose my 1-wire could be some sort of stop-gap solution. I was kind of assuming that 1-wire was TBI, and 3 wire was Vortec, but obviously that assumption was wrong.

I suppose what matters is that I get the correct part.

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454cid said:

I climbed on top of the engine today and while I could not actually see the oil pressure sensor, but I could feel it. I unplugged it, and the pigtail only had one wire.... I thought for sure it would be a 3-wire. I'm glad I didn't order it before looking. I did not feel any oil down there, so it must not be leaking, but the gauge is squirrelly.

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PlayingWithTBI said:

How about a 2 pin for the fuel pump and a 1 pin for the gauge? This is on an 88 vin H or K. Just throwin it out there.

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alpinecrick said:

My Lisle socket won't fit in the limited space on my 96 with the 5.7.

Pizzes me off somethin' fierce..........

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someotherguy said:

Yep, that was my recollection on the "older trucks" - had the large can-style one-pin sender down by the filter, for the gauge. Up top on the block the other one for the fuel pump circuit.

Richard

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