1999 Mercruiser 5.0L oil safety switch

gdc0581

Seaman Apprentice
Joined
Jul 23, 2009
Messages
43
My 1999 5.0 L is doing the start - run 5 seconds- die thing. When it runs, it runs beautifully and has good oil pressure showing on the gauge. I have disconnected the fuel line at the carburetor and find I get good fuel flow while cranking, but none while running. From other threads, I suspect that it is the oil pressure safety switch. When I buy a new machine, I always purchase the service manuals. Unfortunately, my dealer who is now out of business sold me the manuals for a 1997 unit and mine is a 1999, which I think is very different. I didn't determine this until it was too late. Looking at parts lists, I'm pretty sure I have an electric fuel pump and not the mechanical pump mentioned in my service manual. What I really need to know is everything about the safety switch. Most important, exactly where is it. What does it look like. What color wire is connected to it. Theory of operation, is it normally open or normally closed.

My engine is model 4-M11025LS, serial number 0L060754. Any help would be greatly appreciated. With the engine in my Bayliner 2452, I can't see anything on the bottom half of the engine hence why I want to know exactly what I'm looking for and where it is.
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,319
https://webapps.brunswick.com/literature/literaturePartsInfo.do its located just above the oil filter
IMG_1953.jpg
 

wrench 3

Commander
Joined
Aug 12, 2012
Messages
2,108
The switch is normally open. It's closed by the engine oil pressure to connect ignition feed to the fuel pump.
 

gdc0581

Seaman Apprentice
Joined
Jul 23, 2009
Messages
43
Thanks. I can't ask for much more than that. I'll check it out tomorrow.
 

gdc0581

Seaman Apprentice
Joined
Jul 23, 2009
Messages
43
Thanks to all. I cleaned the connections and I'm back in business.
 
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