Bad oil pressure switch?

[acdc96]

Started my boat yesterday for the first time this year. After putting new spark plugs and fuel filter in I turn the key to run position and the fuel pump turns on without the engine running. Obiviously it's not a good idea to have the pump running without the engine running. The engine runs fine and everything but now the fuel pump stays on when the key is in the run position. I think it might be the oil pressure safety switch that's bad. Although, the oil pressure gauge works perfectly. What's up with this?

It didn't do this yesterday before i changed the plugs and fuel filter. I've checked the wireing and everything checks out. 87 mercruiser 5.7 with a Carter fuel pump.

 

[alldodge]

Started my boat yesterday for the first time this year. After putting new spark plugs and fuel filter in I turn the key to run position and the fuel pump turns on without the engine running. Obiviously it's not a good idea to have the pump running without the engine running. The engine runs fine and everything but now the fuel pump stays on when the key is in the run position. I think it might be the oil pressure safety switch that's bad. Although, the oil pressure gauge works perfectly. What's up with this?

It didn't do this yesterday before i changed the plugs and fuel filter. I've checked the wireing and everything checks out. 87 mercruiser 5.7 with a Carter fuel pump.

If your oil switch is staying closed it would keep the pump running. Easy to check, pull the plug off it and put an ohm meter across the terminals, should be open

 

[kanteen]

I had the same problem last year, pump wouldn't shut off. For me it was definitely the oil pressure fuel shut off. Needless to say this is dangerous because your kill switch (or a stall) wouldn't stop fuel from flowing.

 

[gm280]

It could easily be the oil pressure switch, but also check the wire(s) to verify that they are not pinched to ground and allowing the fuel pump to run. Just a suggestion... :noidea:

 

[acdc96]

it's the oil pressure switch... i tested it with a voltmeter and it was stuck in the on/open position allowing the pump to run non stop.
Thanks All !!!

 

[acdc96]

one last thing i cant find a Part number on the pressure switch anyone know the P/N?

 

[alldodge]

one last thing i cant find a Part number on the pressure switch anyone know the P/N?

You engine (1988) didn't come with an electric fuel pump, so this was added. If you have a 3 prong switch walmart and summit racing has them. Put "fuel pump oil pressure switch" in google and it will come back with several items