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Oil pressure

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bm1665

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late 1990 350 crusader at star

late 1990 350 crusader at start up the gauge shows 42 psi after a few minutes the gauge bcomes eratic and begins to lower to 0 eraticly
 
"If I had to guess, its the oi

"If I had to guess, its the oil pressure sender, located on the left side (odd cylinder) of the engine. If you want to analyze it, disconnect its single wire, and hook an ohmeter to it and the block. Watch the ohms during this warm up period."
 
"I'd guess sender, too. I&

"I'd guess sender, too. I'd also suggest verifying the gauge and wiring are functional while you are checking the sender. poor man's check is to leave the sender wire off and the gauge should show MIN peg with key on. short the sender wire to ground with key on and should peg at MAX. More ellaborate check uses appropriate valued resistors."
 
To be really sure go down to y

To be really sure go down to your el chepo auto parts store and buy a cheap oil pressure gauge - under $10. I keep one on the boat all the time. My 2007 8.1L has lost three senders so far.
 
Yep. I think they must have h

Yep. I think they must have had a bad run. I finally bought one from a Crusader parts dealer online. The Crusader dealer in Morehead City must have had a stock of bad ones. I tried to find out if the GM vehicles used the same one but none of the dealers had any in stock.
 
"JOe...If this one goes, I&#39

"JOe...If this one goes, I'd start looking at another cause for it like a short in the lead running to the helm. Those are terrific odds to acquire three units X amount of time apart and they all fail, even from the same manufacturing lot."
 
"Al:

With the 8.1L, I think

"Al:

With the 8.1L, I think they use the ECU's sensor and drive the gauges thru the CAN Bus. Same basic operation (rheostat) but it has the third leg tied to Vref."
 
The short cut method is to remove the wire from the sender. turn the key on. Gauge should show min reading. clip sender wire to ground. needle show show max reading (full scale). if the gauge behaves correctly, get a mechanical pressure gauge to make sure the oil pressure is OK.
 
i tried that, i removed the sending wire turned on key and it read 80 psi, the max. but when i reconnect the wire turn on engine let run it reads 0 psi
 
i removed the sending wire turned on key and it read 80 psi
Click to expand...

assuming that was with the sending wire grounded, it sounds like the sending unit.

See post #4, above, for extra info.
 
The later 8.1L engines do drive the gauge thru the ECM. It outputs a signal that's the same as if it were coming from a standard pressure sender. I have lost 3 sneders but the last one I ordered came from a different supplier (batch probably) and wasn't painted blud as if it came from Crusader. It's been working fine for two years now.

I still carry my el cheapo mechanical oil gauge that I can hook up if it goes out. I thought about permanently hooking up a second gauge off the block as a backup indicator.
 
i have a 1994 mercruiser 5.0lx alpha one, 305, can anybody recommend a dealer or parts store that would possibly carry my oil pressure sender. i have tried numerous places by my home and nobody has my part
 
it was brought to my attention that the part i have may be the oil pressure switch, is this the same as the oul pressure sender, if not can somebody explain what each does, and where my sender may be located
 
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