Chrysler 318/360 oil pressure switches

[Bud719]

I had one of those horrible pressure switch failure and poured a gallon of oil in the bilge before I noticed it. No apparent damage to the engine as I shut down immediately ( but that oil just pours out fast). Over 2 Marinettes, This has happened at least twice.

I am wondering if I can eliminate one of these switches ( the one with 2 spade terminals). It is unclear to me what that does. I have one wire alternators, and the switch doesn’t shut anything down I can see.

Without it, I get correct oil pressure readings at both stations, engines start fine and the alarm sounds when they I shut the engine down (with the other one still running.

Picture of the oil sensor stack :
Top - red - oil sender (to gauges)
Middle - green - single spade switch
Lower - yellow- dual spade switch ( the one I want to eliminate)

I include the schematic, but it’s unclear what this does.

Any thoughts?

[jralbert]

That switch is the worst (well, one of the worst but I can't think of other candidates at the moment) features of the 318. I also lost oil but thru absolute dumb luck happened to be down in the engine compartment when it happened and immed shut down. It so cheap both in cost and manufacture. They could have done so much better with the famed "Chrysler Engineering".

Sorry, not smart enough to answer your query

[Bud719]

Thanks Joel- I believe the alarm system uses the single spade switch.

All 4 of my Chryslers (318s and 360s) had this two spade switch. I always thought it was the alarm system for two stations, but I don’t think that now.

[Bud719]

I should have said that I need other people’s thoughts on this because I don’t know if this switch can be safely removed from the circuit (but if it can, it will remove one source of a potential engine disaster).

[BlueSkye]

Do you have a mechanical fuel pump or an electric one? I don't see it on the wiring diagram, so probably a mechanical one at least originally.

I had some failures of my original (1970s) mechanical fuel pumps and replaced them with Carter electric pumps. I put a two spade oil switch in line with the fuel pump power supply to shut it down if the engine lost oil pressure, as in if the engine wasn't actually turning. The thought is to prevent a different kind of disaster.

[Bud719]

Your use of that switch makes a lot of sense as does your electric fuel pump.

In this case, however, I still have the old mechanical fuel pumps.

(I am amazed at how my F150 can shut down and restart at stoplights! My carburetor and mechanical fuel pump sure couldn’t do that).

[Fastjeff]

That's what we used to call an 'Idiot light'. (Actually, it's good idea to have a red light come on if the oil pressure suddenly drops and your eye isn't on the pressure gage.)

I too had them fail on mine, but not leaking, just giving me false a low oil pressure reading when that wasn't the case. Replaced at least two of them and always had a spare ready to go.

On the alarm system for dual engine boats being combined, that was (is) a bad idea that Marinette should have changed early on. If an engine is down for any reason the alarm system has to be shut off or EEEEEEE! I modified mine with a relay that cut out the alarm on the engine that was not running, so I could troll on one with the alarm still functioning.

Jeff

[Bud719]

Thanks Jeff.

[Jeepmanking]

i just posted a video on YouTube on this issue, go to my "Jeepmanking" channel to watch. The one wire sending unit switch goes to the alarm buzzer only, the two wire oil sending unit is the trigger wire that tells the alternator to start charging, and then the oil sending unit that has the dome style shape goes to the oil pressure gauges. The buzzer one wire sending unit is normally closed and will open when oil pressure builds and thus turning off the buzzer or light whatever you have on your boat. The oil sending unit that controls the buzzer one wire, and exhaust riser sending unit are in series along with the other engine if you have two engines. I would like to separate the circuit and have each engine sound a alarm along with a additional idiot light so I can see what engine has issues without looking at the gauges.

[Bud719]

Good video on troubleshooting the alarm system, Jeepmanking!
I will definitely check out your other videos- it’s good to see a marrinette in these how to videos!

Also, I did not know that these switches may leak oil before they massively fail. I will put that on my starting check list so I can possibly replace them before the deluge.

For One-Wire alternators I don’t think that 2- spade switch is required, as you only connect the alternator directly to the battery. I will trace the circuits when I get home next week, but I suspect I have a hanging open circuit from the old 2-wire rig (is it the orange wire I taped off?)

Do you agree?

(I really want to safely reduce these switches if I can. I am trying to get my bilge clean!)

Thanks, Bud