Hello we hit a weird failure mode of gasoline in the motor oil and cannot detect any mechanical issues.

Our 73 2.0 was recently restored and engine rebuilt using NOS, refurbished, or new parts. After the car was together, we spent several months shaking out the bugs by driving->identifying issues->fixing (repeat), until it was running very well.

That said, once the car was mechanically sound, I switched focus to deep cleaning and waxing the car for the first time and found a small flaw in the paint that required a visit back to the body shop.

We dropped the car off before the lockdown and it sat for more than two months, before it was fixed.

The problem: The body shop inadvertently left the ignition on and the new Optima battery drained out, but after charging the car it would not start. We pulled the plugs and they were soaked in gas, which lead us to check the oil. The oil was full of gas.

We towed (carrier) the car to our friends shop who could not find any obvious mechanical issue, so we cleaned the plugs, replaced the oil and filter, ran the car. The car ran perfectly. We drained the oil and replaced the filter for good measure. The car is running well, no signs of injector or seal issues, and lots of power.

Any theories?

I thought that it could be the pump cycling on and off as the battery starts to fail / recover, but this should not cause the injectors to fire.

Cold start injector.
Remove it, bypass the injector and unplug it.
Leave the injector in place to plug the hole.
They are old, they leak.

That would dump gas into the intake plenum but not into the cylinders, unless a really big leak. I would suspect the fuel injectors or pump before that.

Thanks. The injectors were NOS and then rebuilt before install and appear to be operating as expected. We will pull the cold start valve and pressure test it.

Note that unless you plan to start the engine with outside temps below freezing (literally, 32F) then the CSV will never engage. Just leave the hose disconnected and plug the fuel rail fitting (914Rubber sells the screws and washers to screw into the fuel rail fitting.)

Thanks. The car is very stock, so I’d like everything working and in place, but if we cannot address then disconnecting and capping.

This is odd.

The only entry point for fuel into the engine is via the injectors,the cold start injector being the easier/more common mode of failure, however in either case (cold start injectors or main injectors) even if stuck open you would still need fuel pressure to push fuel through them which even with the key on shouldn't be occurring (unless you have the pump relay jumpered)

I dont see how this could have happened without there being multiple points of failure. one impacting an injector circuit and one impacting the pump circuit.

Agreed, the theory is that when the Optima was dying and reviving, the ignition circuit was periodically activating the pump.

It’s easy enough to check, put the cold start injector into a baby food jar.
Turn key on, turn key off
Watch injector keep dripping.

Our mechanic tested the value this morning under pressure and it appears to be working well. The car is also running perfectly.

Any other things to check?.

Well, you have five injectors. That is all you have that places fuel into the motor, so one of them is the issue.

I hear you

I would pull all 5 injectors, disconnect the electrical connectors on each and pressurize the system and inspect for leaks thru the pintles. If you do 1 at a time, don't stop when you find the 1st one leaking because there may be others. This will probably solve your problem unless it's running extremely rich washing out the piston rings...
Good luck.

Thanks, we are pulling the new injectors to see and will report back.

Thanks everyone for the help, we figured it out. After a deeper look at the timeline, we discovered that the newly rebuilt motor on first startup ran rich for the first hour or so, but during this period an injector seal was working it’s way lose from a missed step during install. I drove the car for another hour and it was running good but rich, so back to the shop. At this point the head mechanic/owner (a friend) stepped in and fixed the injector seal, reduced the gas pressure and it was back to running well. I took the car home, noticed the flaw in the paint, and off to the body shop where this story began.

... nobody thought to check the oil, but thankfully no damage we can detect.