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Low Oil Pressure, then Stall
#1
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Joe
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Hey everybody,

I'm made some progress on my model 2372. I've reverted the car back to 6v/positive ground, new voltage regulator, though I did replace my points with a Pertronix ignition. Running into the following issues and need some help troubleshooting.

When I first start the car up in the day, it runs great. It starts immediately, it's quiet, relatively smooth, and the car moves well. As it reaches operating temperature, I see my oil pressure (which starts at 40) begin to drop as I decelerate, eventually stalling out. It's then a little dicey starting back up (though it eventually does). In neutral, the oil pressure bounces right back up to 40. In high or reverse, it drops to 35, then to 30, and so on, and the idle is slow and rough. But again, this is only when the engine is hot.

I did notice that I'm down about a quart of oil, so I'm going to fix that when I get back home, but I'm sure I have an issue with worn piston rings, and the new spark plugs may already be fouled from oil leaching into the cylinder. I'm running "Classic Car Motor Oil" 15W-40. I haven't done a radiator flush yet, but it's on my to-do list.

What else should I be looking for in terms of the engine losing power/stalling when it's at operating temperature? Thanks in advance, everyone!

Posted on: 8/5 12:44
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Re: Low Oil Pressure, then Stall
#2
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HH56
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Worn bearings could also be the major reason you are losing oil pressure. As the oil heats and thins, more is leaking thru the bearings and dropping the pressure. Adding heavier oil or a viscosity enhancer might help a bit but is not a cure all. In the era a can of STP at every oil change could be a worn engines best friend but no idea if the STP product available today is the same as the thick honey like product available then.

Pertronix ignitions are somewhat finicky when used on 6v systems. Unless the wiring and charging system is in top notch condition any voltage drop could be severe enough to start the module misfiring. If you are using the old original coil, those have also been known for breaking down or becoming erratic when they heat up.

If you are running the original fuel pump with modern gasoline, some of the old rubber components are not compatible with ethanol and will break down. Sometimes they fail entirely, others just swell and restrict flow.

If the flex fuel line near the bottom of the radiator between the pump and metal gas line is the original, those get hard and inner lining can crack. A loose section of lining could, because of fuel pump suction, be dislodged and a flap like portion move out in the bore to restrict fuel flow. Often an engine will idle fine but more flow needed for faster speeds is enough to cause the issue. Same with the old ceramic fuel filters. Varnish could be partially clogging the filter element allowing a minimal amount to flow thru but not enough to supply the engine at speed.

Posted on: 8/5 13:22
Howard
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Re: Low Oil Pressure, then Stall
#3
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kevinpackard
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Like Howard said, fuel system could be part of the problem with stalling. Fuel filter, rubber line, carb, etc. Has the carb been rebuilt? If not, that wouldn't be a bad idea. I had to replace my ceramic filter with a modern paper one (couldn't clean the junk out of my ceramic). Rebuilding the carb and fuel pump solved everything else for me.

No experience with the Pertronix system, but I've heard mixed results from others. The stock components work fine for me, especially after I replaced all wear items....points, condenser, rotor, cap, wires, plugs, etc.

-Kevin

Posted on: 8/5 14:05
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Re: Low Oil Pressure, then Stall
#4
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Joe
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Thank you, both. This is super helpful. I wonder, too, if this might be vapor lock. I noticed the fuel line is actually touching the radiator as it loops around to the carburetor. Chance this might be my demon as well?

I did top off my oil with viscosity enhancer and the oil I used to the change to bring it back to full. Initially ran great... then lots of stalling, hard starting, running rough. I'm going to try to adjust the fuel line so it's not contacting the radiator and see if that makes a difference.

Thanks again!

Posted on: 8/6 11:22
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Re: Low Oil Pressure, then Stall
#5
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Fish'n Jim
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If you haven't cleaned and dropped the pan it needs to be done or flush out with kerosene (not running)
Partial or no oil filter motors accumulate sludge in the pan, and can block up the inlet or plug up the pump or channels. When it starts things get stirred up and whammo, not enough flow.
Change the oil again after 500 miles or so after it's cleaned out fter you get it clean down under.
My mantra is to get each system: fuel, electrical, lube, vacuum, etc working as it should before attempting to start these old cars, that way there's no playing hundred questions what could be wrong or causing harm.

Posted on: 8/6 11:52
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Re: Low Oil Pressure, then Stall
#6
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kevinpackard
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Great advice from Fish'n Jim. Definitely drop the pan and clean it out. Mine had thick sludge at least an inch thick. The pick up screen for the oil pump could by clogged by junk. Better to get it cleaned out and start fresh.

Definitely go through the fuel system and electrical (ignition) for the stalling and rough running. Something in those two systems is causing your problem.

Posted on: 8/6 14:48
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