Gas in oil. Rings? Compression vs. Leak Down Test

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Back story. I've been slowly bringing a 98 DSM back to life. A year and a half ago, I swapped engines into this car. The engine was a parts car engine that I drove once and didn't spend a lot of time on. 
 

After getting the car running and not a lot of driving, I've noticed a really strong gas odor and thinned oil. Somehow, gas is getting into the engine oil. It has somewhat of a hard start condition, but not terrible. Otherwise, the car runs well from what little driving I've done with it. 
 

I posted on the DSM Facebook page my issues and get a lot of one word answers "rings" "rings are shot". The car, on a cold engine has 150psi compression consistently across the board. I did buy a leak down tester and that is showing 30-45% Leakdown on an ice cold engine. 
 

With all this rambling, what I'm getting at is could the compression test be good, but the rings still be bad? Should I throw in the towel and replace the engine? Or should I press on to find out why I'm getting so much gas in the oil? Or is the answer right in front of me? 

Both tests should be done with the engine at op temp. Throttle open on the comp. Are the tools you used in good condition? 

Check the fuel delivery and make sure it's not too rich.  Especially cold.

You can have a good compression test and still have worn out oil control rings and have mixing.

For a good test, engine should be warm and the throttle propped open.  On an EFI car you can pull the fuse to the fuel pump.

If a cylinder is testing low, you can put a little oil in and re-test.  If the compression comes up it's the oil sealing the rings.  If it doesn't come up it's likely a leaking valve seat.  

If you're doing a leakdown test you may be able to identify the leak by sound.  Do each cylinder at TDC on the compression stroke for consistency.  Intake = intake valve seat, Exhaust = exhaust valve seat, dipstick or oil fill cap = rings. 

Compression test is a good basic test, but a leak-down test gives more detailed info.  You can have a car that's still running well with marginal compression.  The last 3 engines I've taken apart had the oil rings all coked up, likely from not changing oil when needed.

Make sure the injectors are holding pressure and not dribbling fuel into the intake track, which could drain into the crankcase.

In reply to L5wolvesf :

I will do the tests warm this weekend. Compression tester is old but in good shape I suppose? LD tester is brand new. 

I've also been told that because I don't drive the car, but occasionally start to keep the battery charged and short drives around the neighborhood, that the rich fuel may not have time to burn off and is leaking into the crank case. Any merit to that? 

alfadriver said:

Check the fuel delivery and make sure it's not too rich.  Especially cold.

Here's the thing, even with low compression, all of the fuel should burn well enough,  If you are getting liquid fuel into the crank, it's coming from somewhere.  Even if you have good rings right now, if liquid fuel continues to get past the cylinder walls and into the oil- you will have to replace them sometime.

Find where the fuel is coming from.

Scotty Con Queso said:

I've also been told that because I don't drive the car, but occasionally start to keep the battery charged and short drives around the neighborhood, that the rich fuel may not have time to burn off and is leaking into the crank case. Any merit to that? 

yes.

Get a trickle charger for the battery.

Ian F said:

Make sure the injectors are holding pressure and not dribbling fuel into the intake track, which could drain into the crankcase.

I did try this quickly one night. Pulled the injectors and jumped the pump. Nothing seemed to leak but I guess it could leak down over time? Maybe I should leave them out of the engine overnight just to see if they leaked at all? 

Scotty Con Queso said:

I've also been told that because I don't drive the car, but occasionally start to keep the battery charged and short drives around the neighborhood, that the rich fuel may not have time to burn off and is leaking into the crank case. Any merit to that? 

It could be contributing. Carburetors used the choke and EFI runs rich at start based on coolant temp.  Ideally once the engine is running, you should drive it until it's up to temperature.

If you are putting gas into the oil from worn rings, it is so pig rich it shouldn't even run. Stand behind the car with it running.  Are your eyes burning? Change the oil, then drive it properly, and see what happens.  

I have experience with some extremely beat up engines and I can say I never have had this happen to a point where I could quickly find gasoline in the oil. You either have a leaking injector or a *massive* misfire.

Scotty Con Queso said:

I've also been told that because I don't drive the car, but occasionally start to keep the battery charged and short drives around the neighborhood, that the rich fuel may not have time to burn off and is leaking into the crank case. Any merit to that? 

This was my first question. Short run cycles, especially in older cars that enrichen the mixture a little less precisely than new one, will wash down the cylinder walls and thin the oil considerably. The only way you can prevent that is drive it for longer distances, get it to temp and keep it ther e for a bit to burn off the fuel. 

I'm in the camp that says you either have leaking injectors or are running VERY rich and just don't know it. 

alfadriver said:

Scotty Con Queso said:

I've also been told that because I don't drive the car, but occasionally start to keep the battery charged and short drives around the neighborhood, that the rich fuel may not have time to burn off and is leaking into the crank case. Any merit to that? 

yes.

Get a trickle charger for the battery.

Or at least make sure the engine spends some time at full operating temperature on your short charge-up drives.

Bad ring are usually the result of fuel diluted oil not the cause.  Starting the car occasionally and not driving it is much worse than just letting it sit and could be the whole issue but it seems like you've got something else going on.  I'm not familiar with those cars but I'd take a look at the evaperative control system.  In some cars a bad canister purge valve can suck raw fuel into the intake resulting in exactly what you're experiencing.

Vigo said:

I'm in the camp that says you either have leaking injectors or are running VERY rich and just don't know it. 

Me too.  Even if your rings were toast, 99% of the gasoline gets burnt before it pushes blowby to the crankcase.  You'll burn oil way more than you'll get gas in the oil.

Leaking injector, bad FPR.  That would also explain your rough starts.

That's not to say you don't have bad rings... we are talking about a DSM. :)

GameboyRMH said:

alfadriver said:

Scotty Con Queso said:

I've also been told that because I don't drive the car, but occasionally start to keep the battery charged and short drives around the neighborhood, that the rich fuel may not have time to burn off and is leaking into the crank case. Any merit to that? 

yes.

Get a trickle charger for the battery.

Or at least make sure the engine spends some time at full operating temperature on your short charge-up drives.

I don't care how short your drives are, or how bad the rings are, you won't dilute the oil with gasoline unless there is an over-fueling issue.  You could take a car with trashed rings, start it once in the morning for one minute every day for three years and it won't dilute the oil with gasoline.  EFI or Carb.... unless it's dumping too much fuel

Fix the fueling.