Oil Pressure Switch

[kulle]

Still trying to track down why my boat runs for a few mins then shuts off. I have spare at coil and from distributor when it shuts off. Thinking of checking oil pressure switch and if i can get it running, voltage at fuel pump. I had a small amount of oil on the underside of the oil switch...was thinking about pulling it off to test, does anyone know if I remove that switch, will oil drain out completely or is it high enough on engine block that it wont? Mercrusier 4.3 L V6 ( 1993)

 

[Scott Danforth]

Oil pressure switch is in the oil galley. It would leak a small amount.

Its never the coil

Check all your harness connections

 

[thumpar]

If you suspect the oil pressure switch just bypass it for a test. DON'T leave it like that of course. Only to test.

 

[achris]

... does anyone know if I remove that switch, will oil drain out completely or is it high enough on engine block that it wont? ...

I know. Pulled many out... Only drains out if you do it IMMEDIATELY after the engine was running. And only a small amount... It's way higher up the block than the oil level in the sump...

But as thumpar suggested, just bypass it for testing. Much easier. If it proves to be the problem, yeah, replace it... If it's not, you've saved yourself some work.

Chris......

 

[kulle]

Thanks all, did further testing....
- confirmed 12V to oil switch with key on, nothing to fuel pump as designed
- get 12v to fuel pump with engine cranking/started
-pulled fuel line to carb inlet off, fuel pump is pumping fuel( tested both- supply pump with 12v and through the connector plug)

I'm at a loss, the damn thing starts right up runs for a little then shuts off. Only thing seems weird-

when i manually move the throttle with engine off, i can literally see the spray of gas in the carb, but when engine is running if i look, not seeing the same fine spray, but the fuel pump is pumping gas???

Guess i'll have to take it in.

 

[kulle]

So took it to shop, They did a few hours diagnostics and then bypassed the oil pressure switch and said he ran for like 20 mins ( not water tested though). Picked it total $400 later, before i took it out on the lake, I fired it up and let it idle a few mins ( previously it would stall out soon after the fuel burned off in carb- 4.3 mercrusier v6 gen1 ) Got it fired up on slip, docked it, shut it off until eveyone boarded, fired it up and went out...soon as i got outside no wake, i gave it a little throttle nothing crazy- but it sounded like it was sputtering, so i gave it more and it took off, planed and was cruising for about 5 mins, then it stalled out! got it restarted and stayed close to docks and it stalled again, then would not restart ( same symptom as before switch was replaced. They also replaced the water/fuel separator, but i'm at a loss and frustrated as to what it could be.

 

[Maclin]

when i manually move the throttle with engine off, i can literally see the spray of gas in the carb, but when engine is running if i look, not seeing the same fine spray, but the fuel pump is pumping gas???

You may be confusing the Fuel pump outside the engine with the Accelerator pump inside the carb. The accelerator pump inside the carb is actuated by moving the throttle forward, squirts fuel out during that motion (forward). It does that to cover up a huge lean condition as the throttle plates are opened up. Stop the throttle movement and the squirt of fuel stops. Move it fast and a bunch comes out, move it slow and the squirt is less. If you looked down the carb throat with it just idling and did not move the throttle then no squirt happens.

 

[kulle]

yeah the mechanic explained that to me as well, thanks. i'm just trying to understand whats wrong....seems kind of fuel related. looks like orig pump., might clean dist cap and replace pump. anyone have any other thoughts of what to check?

 

[kulle]

oil pressure sending unit

So even after taking it to shop, they installed a oil pressure safety switch, my 1993 4.3 v6 ran in idle longer and even for about 6 mins on lake before it stalled out again. could i have a bad oil sending unit? oil pressure on gauge was about half-40, is that normal? might start replacing parts...i tested coil, spark,battery, fuel pump pumps, but looks original...idk help

 

[Docdealer]

oil pressure sending unit

So even after taking it to shop, they installed a oil pressure safety switch, my 1993 4.3 v6 ran in idle longer and even for about 6 mins on lake before it stalled out again. could i have a bad oil sending unit? oil pressure on gauge was about half-40, is that normal? might start replacing parts...i tested coil, spark,battery, fuel pump pumps, but looks original...idk help

Did you ever get this sorted?