Oil Pressure Switch for Fuel Pump - Strange Happenings

[DougIndianLake]

I have a 1996 Mercruiser 4.3 LX Gen+ in a Donzi 182 Medallion (bowrider) that has been working great since I have owned it, which has been 2.5 summers. Yesterday, after running great for about 20 minutes, it stalled. After that it would start really well but then sputter out after 30 seconds to a couple of minutes. If I put it in N and revved the engine it would run longer than if it was in D.
Thanks to other threads on iBoats I diagnosed it as an issue with the oil pressure switch for the fuel pump. When I went to check it out I saw that the wires that would ordinarily connect to the leads on the oil pressure switch had been removed from the switch and were connected to one another.
On a hunch, I disconnected the wires from one another and attached them where they would have been originally, on the leads on the oil pressure switch. The engine ran great for the rest of the day yesterday.
My first question is: What's the scenario that would have prompted someone to bypass the switch, then at least 2 years later make that fix no longer work, but make the "factory setting" work again?

And my second question is: What's the recommendation from here to ensure it all continues to work as it should?

Thank you. Glad to have found this forum.

 

[tank1949]

I have a 1996 Mercruiser 4.3 LX Gen+ in a Donzi 182 Medallion (bowrider) that has been working great since I have owned it, which has been 2.5 summers. Yesterday, after running great for about 20 minutes, it stalled. After that it would start really well but then sputter out after 30 seconds to a couple of minutes. If I put it in N and revved the engine it would run longer than if it was in D.
Thanks to other threads on iBoats I diagnosed it as an issue with the oil pressure switch for the fuel pump. When I went to check it out I saw that the wires that would ordinarily connect to the leads on the oil pressure switch had been removed from the switch and were connected to one another.
On a hunch, I disconnected the wires from one another and attached them where they would have been originally, on the leads on the oil pressure switch. The engine ran great for the rest of the day yesterday.
My first question is: What's the scenario that would have prompted someone to bypass the switch, then at least 2 years later make that fix no longer work, but make the "factory setting" work again?

And my second question is: What's the recommendation from here to ensure it all continues to work as it should?

Thank you. Glad to have found this forum.

My best guess is that someone jerry-rigged it in order to get it to work and come home but then didn't fix it to CG specs. Go to adult section for how to install the proper oil switch and wiring. There are safety concerns!!!!! I hope electric pump is not an automotive type. I owned 2 alphas whose former owner had auto pumps and direct wired oil switches installed. NOT GOOD!

 

[Rick Stephens]

The oil pressure switch is a (legally required) safety device. At some point, someone had an issue that made them wonder if the switch was the problem and they bypassed it. Apparently you still have that issue. Returning the wires to proper location on the switch did not *fix* whatever was wrong during yesterday's trip. It had no effect at all. So you have another issue somewhere. A guess would be a dirty connection that you god to working when you were moving wires around.

 

[Rick Stephens]

And my second question is: What's the recommendation from here to ensure it all continues to work as it should?

I added a relay switch to my wiring to improve oil pressure switch longevity. As wired from Mercruiser, the oil pressure switch sustains the load to the fuel pump. It is just enough power to introduce arcing carbon to the contacts in the switch. By using an inexpensive relay you can take the load off the oil pressure switch and put it on the relay instead.

Here's achris's drawing of that modification.

 

[DougIndianLake]

I added a relay switch to my wiring to improve oil pressure switch longevity. As wired from Mercruiser, the oil pressure switch sustains the load to the fuel pump. It is just enough power to introduce arcing carbon to the contacts in the switch. By using an inexpensive relay you can take the load off the oil pressure switch and put it on the relay instead.

Here's achris's drawing of that modification.

View attachment 365874

Thanks Rick. I am a real novice but I have enough gumption to do anything provided I have a great diagram like the one you provided or a YouTube video. That said, could you provide specifics about the inexpensive relay? I have no idea what that is. Thanks man, Doug

 

[DougIndianLake]

The oil pressure switch is a (legally required) safety device. At some point, someone had an issue that made them wonder if the switch was the problem and they bypassed it. Apparently you still have that issue. Returning the wires to proper location on the switch did not *fix* whatever was wrong during yesterday's trip. It had no effect at all. So you have another issue somewhere. A guess would be a dirty connection that you god to working when you were moving wires around.

Thanks for this too Rick.

These wires were dangling out there in plain sight. On another post someone mention a purple wire and a purple/yellow wire that lead to the switch. They were right there in front of me so I attached them with a jerry rigged coupler. I hadn't done anything between my last attempt at starting it and attaching the wires to the switch, which resulted in the engine running flawlessly for the next 6 hours. When today's rain stops I will look and see where those wires lead to and where I could have knocked around some dirt or something, but considering how little I handled those wires, I'm skeptical that that is what got things going.

Could condensation have caused my stalling issue? I ask b/c the issue occurred at around 9:30am. Everything was dewy when we got to the dock. Boat started right up and ran great for 20 minutes but then the stalling issue happened. After the issue happened I looked around the engine, topped off the drive lube which was really low, and tested it a bunch more time. Same issue. Then, I came inside for about an hour to have some breakfast and do some research on the issue during which the sun was shining and the temperature went up. That's the only other change in condition I can think of between the issue and messing with the wires.

 

[Rick Stephens]

Strictly to give an example, as I am not a big fan of Amazon, here is a relay that you can walk into your local Napa store and pickup. Wiring is not difficult, although neatness is important and having the right connectors for the wires is crucial.

Corrosion on connectors, loose connectors, mis connected wires. Corrosion in the main wiring plug. That there are many such possibilities is why electrical diagnostics and repairs can be spendilicious.

 

[nola mike]

I added a relay switch to my wiring to improve oil pressure switch longevity. As wired from Mercruiser, the oil pressure switch sustains the load to the fuel pump. It is just enough power to introduce arcing carbon to the contacts in the switch. By using an inexpensive relay you can take the load off the oil pressure switch and put it on the relay instead.

Here's achris's drawing of that modification.

View attachment 365874

Of course, my relay went out and left me dead in the water. Switch is cheap enough and easy enough to swap that I probably would just go that route if I did it again. That said, I did just get this relay from Amazon, that looks waaay more waterproof than the last one. Cheaper than anything local and seems much nicer.

1 Pack 5-Pin 12V Bosch Style... https://www.amazon.com/dp/B01N66W2XF?ref=ppx_pop_mob_ap_share

 

[Rick Stephens]

Of course, my relay went out and left me dead in the water.

Not all that many boaters sink their boat in salt water either

 

[DougIndianLake]

Strictly to give an example, as I am not a big fan of Amazon, here is a relay that you can walk into your local Napa store and pickup. Wiring is not difficult, although neatness is important and having the right connectors for the wires is crucial.

Corrosion on connectors, loose connectors, mis connected wires. Corrosion in the main wiring plug. That there are many such possibilities is why electrical diagnostics and repairs can be spendilicious.

Thanks Rick. And I too am not fond of Amazon so I will get it locally.

 

[nola mike]

Not all that many boaters sink their boat in salt water either

Brackish water. And plenty of people sink them, just not many get them running again

(We're now working on the mangled stereo, AKA "fun stuff")

 

[achris]

When connecting new wires into an existing circuit please solder and wrap with self-amalgamating tape or adhesive lined heatshrink. Do not under any circumstances use those horrible Scotch-lok things. (The person who invented those things needs to be put in prison!)

Chris....

 

[Rick Stephens]

When connecting new wires into an existing circuit please solder and wrap with self-amalgamating tape or adhesive lined heatshrink. Do not under any circumstances use those horrible Scotch-lok things. (The person who invented those things needs to be put in prison!)

Chris....

Damn, one of my pet peeves. I get trailers into the welding shop that from the factory came with those connecting all the wires to the brakes. A few years down the road they all are corroded and no brakes. Seems all the manufacturers use em. Almost like they can't hire anyone bright enough to strip wires and crimp heat shrink butt connectors. Shameful.

 

[achris]

Damn, one of my pet peeves...

Yeah when I see them, someone gets a sermon!

 

[tank1949]

Damn, one of my pet peeves. I get trailers into the welding shop that from the factory came with those connecting all the wires to the brakes. A few years down the road they all are corroded and no brakes. Seems all the manufacturers use em. Almost like they can't hire anyone bright enough to strip wires and crimp heat shrink butt connectors. Shameful.

I learned years ago that most boaters buy pretty and don't think about issues "down the road. "

 

[DougIndianLake]

So all was going great last week. I ordered the relay that was suggested. The boat has sat for a few days. I just started it right up. Then I turned it off. And now, it won't turn over. I turn the key the first click and all gauges read fine, including the amps. However, the oil pressure gauge is on 0, although I have no idea what it usually reads at this point. Then I turn the key to ignition and absolutely nothing happens.
This has happened a few times since the original stall I started this post with, but I have always just turned the key back to off and it then starts right up.
I am assuming this means the oil pressure switch is completely shot so I am ordering a new one, but am curious to know if there are other things I should be looking at or any way to determine if it definitely a bad pressure switch?
BTW - I already tried bypassing the pressure switch but it didn't effect anything.
Thanks.

 

[nola mike]

So all was going great last week. I ordered the relay that was suggested. The boat has sat for a few days. I just started it right up. Then I turned it off. And now, it won't turn over. I turn the key the first click and all gauges read fine, including the amps. However, the oil pressure gauge is on 0, although I have no idea what it usually reads at this point. Then I turn the key to ignition and absolutely nothing happens.
This has happened a few times since the original stall I started this post with, but I have always just turned the key back to off and it then starts right up.
I am assuming this means the oil pressure switch is completely shot so I am ordering a new one, but am curious to know if there are other things I should be looking at or any way to determine if it definitely a bad pressure switch?
BTW - I already tried bypassing the pressure switch but it didn't effect anything.
Thanks.

Op switch shouldn't affect cranking. Try wiggling the throttle while you crank (possible neutral safety switch). Next measure voltage at the small yellow/red wire on the starter solenoid while trying to crank...

Rather than reinvent the wheel, go through this guide:

HOW TO: Troubleshooting your engines starting system

So you hit the ignition switch so you can go home and either nothing happens, or you hear a click from the engine, but the starter doesn't crank......... Now what ? If you have a test light, you can find out in only a few minutes what the problem is. I like test lights because they are faster...

forums.iboats.com

 

[DougIndianLake]

Op switch shouldn't affect cranking. Try wiggling the throttle while you crank (possible neutral safety switch). Next measure voltage at the small yellow/red wire on the starter solenoid while trying to crank...

Rather than reinvent the wheel, go through this guide:

HOW TO: Troubleshooting your engines starting system

So you hit the ignition switch so you can go home and either nothing happens, or you hear a click from the engine, but the starter doesn't crank......... Now what ? If you have a test light, you can find out in only a few minutes what the problem is. I like test lights because they are faster...

forums.iboats.com

Thanks. When I was just troubleshooting it occurred to me that it is doing exactly what it does when you try to start the boat while in gear. So I played around with all the wires while turning key but it didn't work. I will check out that other thread. Thank you.

 

[Rick Stephens]

Might be as simple as a bad ignition switch.

 

[DougIndianLake]

Might be as simple as a bad ignition switch.

After at least 15 unsuccessful tries at starting it, I went to do something else. 30ish minutes after my last try and having done nothing new to it, I tried it again and it started right up.
I let it run. Turned it off. And, it started right back up.
It has got to be a short somewhere, or could it be something else?