Fuel in oil- what can cause this? the FPR? Bad injector?

So, I have about 3.3% fuel content in my oil according to blackstone labs, everything else checked out good. they said this was quite high. Could have been from taking the sample cold, but everyone on the trail said it seems like my jeep runs rich, got any ideas on the causes?

FPR or a leaky/stuck injector are my forest two things to go? Could it be something else?

All engines have "some" blow by. A healthy engine (fuel, spark & blow by all within norms) will boil the gas out of the oil, provided the oil gets & stays up to temp long / often enough.

So three things could potentially be causing this.

One, rings are shot / blow by is excessive. This, I kind of doubt. It makes sense hypothetically, I guess, but I don't really expect it's the issue.
Two, ignition is incomplete. Again - possible, but if you have a decent idle quality & the engine runs down the road & you've done maintenance (you have, haven't you? cap / rotor / wires / plugs?) then it's probably not the problem either.
Three - fuel leaking from injector or FPR. I've replaced more FPRs than injectors.
Put a fuel pressure guage on it, turn the key on. Observe if it holds steady or leaks down a bit.
If you want to get right to it, pull the air cleaner off & have a wiff of the open throttle body. Smell gas? You shouldn't. If you do, pull the FPR & look for wetness. If none, pull injectors next. Connect everything, turn the key on, watch for anything dripping.

Thanks thats good to know. Compression is pretty good and I do plugs/cap/rotor/o2/filters/wires around twice a year so the thing is always tuned . always replacing sensors.
Ill probably do FPR, the injectors are newer, but I don't trust them 100%, got them on ebay as flow matched injectors, but who knows if they are sticking open. they said it could have been from being a cold engine too.

Make sure to properly gap the plugs. no matter what brand or packaging tomfoolery.

I dont know how many times at work, we have a happy homeowner slap a set of plugs in to their car only find its not running any better.

good call on the plugs . but they always get gapped to .035.

you're on the right track with FPR or injectors, fuel is a solvent and if it leaks into the combustion chamber it dissolves the oil on the cylinder walls then flows right past the rings.

personal experience here, if you take the FPR off be prepared to replace the bigger o-ring on it. every one ive taken off has been rock hard and either cracks or crumbles. even a tiny crack will make it dump fuel all over the #1 exhaust tube. that's bad, lol.

Or, after shutdown. an injector isn't staying closed, allowing the pressure in the rail to bleed into a cylinder or more.

OK thanks guys . So it seems injectors and FPR to start . Where is a good place to source the bigger O rings? I am trying to find a way to do a leak down test too.

blondejoncherokee said:

OK thanks guys . So it seems injectors and FPR to start . Where is a good place to source the bigger O rings?

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Bigger o-rings?

Where are you planning getting your injectors? Stock motor?

GrimmJeeper said:

you're on the right track with FPR or injectors, fuel is a solvent and if it leaks into the combustion chamber it dissolves the oil on the cylinder walls then flows right past the rings.

personal experience here, if you take the FPR off be prepared to replace the bigger o-ring on it. every one ive taken off has been rock hard and either cracks or crumbles. even a tiny crack will make it dump fuel all over the #1 exhaust tube. that's bad, lol.

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The ones grimm is talking about of the FPR? I know the new FPRs come with the Orings I think.

I got my last set on ebay for 40$/8 injectors I think.

Leak down should be just watching the fuel pressure after shut down. I think the spec is no more than 5 psi in 5 min.

Checking the individual injectors will require fuel rail removal. But im sure you knew that.

If your jeep is running rich, check map sensor (including vacumn line to throttle body) and o2 sensor.