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Oil has gas smell

I have a '98 Jeep Grand Cherokee 4w with a 5.2l, it has approx 145,000 miles. It leaks a little oil and when i recently checked it (level was good), it smelled of gas. It starts easy and runs great with no smoke and no knocking when shut down. I’ve read it could be anything from rings to a stuck injector. I drive it on short trips now, only occasionally going out of town. It is due for an oil change but I would like to have a solution before driving it more or getting the oil change. Any help would be appreciated.

If you smell gasoline on the dipstick it might be advisable to drain and refill the crankcase immediately, if not sooner.

Have a mechanic hook up a fuel gauge. Rapid fuel pressure drop off after engine shut off could be due to a dripping injector.
Specifically, have that mechanic perform an injector balance test. That will tell him if one particular injector is plugged or dripping.

Cold weather + short trips = low oil temp, preventing boil-off of gasoline blow-by. I’d check the oil, then take it for an hour drive on the freeway in above-freezing temperatures, see if the smell goes away and the oil level drops. A friend had that problem, was able to light his drained oil with a match!

But the safer option might be to follow Rod Knox’s advice and change the oil first, then take an hour drive once every week or so and see if the problem (gas smell) comes back.

+1 for Rod Knox. Get that oil out of there ASAP.

The problem might caused from a leaking fuel pressure regulator diaphram.

When the engine is shut off, the residual fuel pressure can force gas past the leaking diaphram in the regulator into the vacuum hose where it ends up in the engine.

Start the engine for a minute. Shut it off and then remove the vacuum hose from the regulator to see gas leaks out of this connection. If it does the regulator requires replacement.

Here’s what the fuel pressure regualtor looks like.


I had a friends vehicle do the same thing and it turned out to be an intake gasket. It didnt have a miss either which what was so confusing to find. I would have all the stuff the other guys said checked first before doing the intake gasket though.

Try and light the oil on the dipstick with a match…If it bursts into flame, there is a problem. If it will not ignite, it’s not worth worrying about…

db … just curious, how is an injector balance test done?

@GeorgeSanJose with a fuel pressure gauge and one of these.

Ok, I think I see. That tool allows you to fire the injectors one by one. Without the ECM doing anything I mean. It can be done with the engine off. So you install the pressure guage in the rail, pump up the fuel rail to pressure, turn off the fuel pump, then fire one injector with that tool, and record the drop in pressure. Repeat on the other injectors; the drop in rail pressure due to each injector firing should all be the same if each injector outputs the same amount of gas after commanded to fire. Seems a pretty efficient way to test for uneven fuel injector problems. Thanks db for the good info.

That tool can be very enlightening but in the years that I have owned it I don’t recall it being decisive in diagnosing an EFI problem more than a dozen times. At the price shown in the link the tool might not be worth the cost to DIYers. It might be surprising to many just how often a leaking injector is found by feeling each and comparing how distinct the pintle closings feel and a digital red/green test light is faster than a set of noid lights in diagnosing power and Quad driver grounding at the injectors. For anyone wanting to jump head first into OBD II EFI diagnosis a live data scanner and a 4 channel lab scope and fuel pressure tester might come ahead of the pressure balance tester. But opinions vary, as they say.