Novak Conversions Jeep Wrangler YJ engine mounts

Oil In The Fuel Tank

UPDATE: POSSIBLY SOLVED

I didn't want to leave everyone hanging without a followup, so here it is (with photos).

Today I pulled the old fuel injectors, dropped the tank, and found the issue (or I hope I did). Two of the injectors for cylinders 3 & 4 (rear two) had oil inside the injectors, as well as the fuel rail on that end...plus some sludge buildup which I assume was a mixture of fuel and oil. As soon as I pulled the injector for cylinder 4 fresh oil (from the recent oil change) was dripping from the injector on the fuel rail side. I cleaned the fuel rail out to the best of my ability before installing the new injectors and reinstalling the fuel rail.

The new fuel pump was placed inside a new bucket with fresh fuel, and the return hose was placed into another new bucket so I could keep any contamination from going back into the system. I primed the fuel line a couple times and she started right up. None of the original symptoms were present, and I let the engine run for only 30-45 seconds before shutting it down to check the fuel rail for leaks as well as to ensure my fuel system was functioning properly. I fired her back up and let the engine run for another 90 seconds. At that point I checked the return bucket (see photo for results). I should have swirled the fuel in the bucket before putting it into the clear cup because I noticed a lot of carbon buildup and chunky oil sitting on the bottom of the bucket that did not make it into the clear cup.

I removed the fuel rail and injectors to ensure oil was not going back into the fuel rail, and was pleased to see nothing but "clean" parts. Happy with the results I fired her back up and let the engine run for another 90 seconds. I assume I was pushing roughly a pint (16oz) of fuel per minute through the system based on what I saw in the return bucket, but I did not measure the results other than the clear cup that you see in the photo. The fuel that was coming out was MUCH cleaner at this point.

Now for the fuel tank.....after dropping it again and draining the remaining 1/2 gallon (64oz or a "growler" of fuel) I took a peek inside with a bright light. I was absolutely amazed at the "berg of sludge" that was inside (see photo). I truly have ZERO idea how so much crap got into the tank since it was fully cleaned out prior to all of this. When I say fully cleaned I mean hand-scrubbed on the inside with some grease destroying soap, rinsed out multiple times with hot water, and left to air dry upside down for nearly two weeks before being reinstalled. Today, I did the same thing and it is now drying once again. There is NOTHING inside that tank that shouldn't be there. I didn't measure the "berg of sludge", but my best guess is around 10-16oz, and it was thick & slow moving like bearing grease. It was kept away from the old fuel pump due to the slosh box around the pump, but the amount of other crap was what clearly caused the failure.

RESULTS:
This problem has never come up before, and I have never seen oil get into a fuel tank like this. I've asked quite a few people about this and not a single person has heard of this. Best guess is the fuel injector(s) failed and some cylinder blow-by was pushed into the fuel rail, or something crazy happened and there is no simple answer for this issue.

I am going to let the Jeep sit for the next few days with fresh fuel in the system before I run another gallon or two through it and check the results. If clean fuel is coming out the return line I will get everything buttoned up and update this post if the issue continues.

Thanks All!

Patrick
 

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Would love to see the photos, but am unable to view .HEIC images, which I believe is an Apple phone protocol. Be that as it may, I became confused with the description that "fresh oil (from the recent oil change) was dripping from the injector on the fuel rail side". if this crankcase oil reached the fuel rail by getting past a bad injector, where is all that oil coming from? The respective cylinder? Are you burning oil? And then, what path did this oil take to get back into the fuel tank?

You earn my prize for the strangest Jeep problem ever! Imagine... something new after 30 years of YJ experience.
 
I noticed water remaining in my tank after washing it out and shaking it upside down for a few minutes. The vent and filler tubes do extend down into the tank a little so not all the water came out from what I expected to be the lowest spot. I had to use a towel and reach inside to soak up the last few cups of water with the tank rightside up.

I wonder if there's any of that gunk caught up in your filter now.
 
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I'm still trying to Sherlock out where it came from.
But I'm just not familiar enough with FI systems to speculate mechanically anymore than I already have.
Very strange..Very strange indeed!
The only other thing I can think of is that a load of goo came out of very low filling station tank.
I hope you do indeed have it solved, You've busted your ass for for it!
I hate mysteries...
 
Fantabox said:
UPDATE: POSSIBLY SOLVED

I didn't want to leave everyone hanging without a followup, so here it is (with photos).

Today I pulled the old fuel injectors, dropped the tank, and found the issue (or I hope I did). Two of the injectors for cylinders 3 & 4 (rear two) had oil inside the injectors, as well as the fuel rail on that end...plus some sludge buildup which I assume was a mixture of fuel and oil. As soon as I pulled the injector for cylinder 4 fresh oil (from the recent oil change) was dripping from the injector on the fuel rail side. I cleaned the fuel rail out to the best of my ability before installing the new injectors and reinstalling the fuel rail.

The new fuel pump was placed inside a new bucket with fresh fuel, and the return hose was placed into another new bucket so I could keep any contamination from going back into the system. I primed the fuel line a couple times and she started right up. None of the original symptoms were present, and I let the engine run for only 30-45 seconds before shutting it down to check the fuel rail for leaks as well as to ensure my fuel system was functioning properly. I fired her back up and let the engine run for another 90 seconds. At that point I checked the return bucket (see photo for results). I should have swirled the fuel in the bucket before putting it into the clear cup because I noticed a lot of carbon buildup and chunky oil sitting on the bottom of the bucket that did not make it into the clear cup.

I removed the fuel rail and injectors to ensure oil was not going back into the fuel rail, and was pleased to see nothing but "clean" parts. Happy with the results I fired her back up and let the engine run for another 90 seconds. I assume I was pushing roughly a pint (16oz) of fuel per minute through the system based on what I saw in the return bucket, but I did not measure the results other than the clear cup that you see in the photo. The fuel that was coming out was MUCH cleaner at this point.

Now for the fuel tank.....after dropping it again and draining the remaining 1/2 gallon (64oz or a "growler" of fuel) I took a peek inside with a bright light. I was absolutely amazed at the "berg of sludge" that was inside (see photo). I truly have ZERO idea how so much crap got into the tank since it was fully cleaned out prior to all of this. When I say fully cleaned I mean hand-scrubbed on the inside with some grease destroying soap, rinsed out multiple times with hot water, and left to air dry upside down for nearly two weeks before being reinstalled. Today, I did the same thing and it is now drying once again. There is NOTHING inside that tank that shouldn't be there. I didn't measure the "berg of sludge", but my best guess is around 10-16oz, and it was thick & slow moving like bearing grease. It was kept away from the old fuel pump due to the slosh box around the pump, but the amount of other crap was what clearly caused the failure.

RESULTS:
This problem has never come up before, and I have never seen oil get into a fuel tank like this. I've asked quite a few people about this and not a single person has heard of this. Best guess is the fuel injector(s) failed and some cylinder blow-by was pushed into the fuel rail, or something crazy happened and there is no simple answer for this issue.

I am going to let the Jeep sit for the next few days with fresh fuel in the system before I run another gallon or two through it and check the results. If clean fuel is coming out the return line I will get everything buttoned up and update this post if the issue continues.

Thanks All!

Patrick
Click to expand...
I'm still trying to Sherlock out where it came from.
But I'm just not familiar enough with FI systems to speculate mechanically anymore than I already have.
Very strange..Very strange indeed!
The only other thing I can think of is that a load of goo came out of very low filling station tank.
I hope you do indeed have it solved, You've busted your ass for for it!
I hate mysteries...
 
Gary747 said:
Would love to see the photos, but am unable to view .HEIC images, which I believe is an Apple phone protocol. Be that as it may, I became confused with the description that "fresh oil (from the recent oil change) was dripping from the injector on the fuel rail side". if this crankcase oil reached the fuel rail by getting past a bad injector, where is all that oil coming from? The respective cylinder? Are you burning oil? And then, what path did this oil take to get back into the fuel tank?

You earn my prize for the strangest Jeep problem ever! Imagine... something new after 30 years of YJ experience.
Click to expand...
I don't have a perfect answer, or the "ah-ha" moment, with this issue, but my best guess is the bad injector(s) were allowing oil to enter the fuel rail, and then into the fuel return line. I am attaching JPG photos to this post.

IMG_3660.jpg


IMG_3665.jpg


IMG_3661.jpg


IMG_3662.jpg


IMG_3664.jpg
 
Well after seeing the pictures I went back to your original post and see you said "The Jeep had not been running for nearly 5 years,".

After those five years did you drive it at all and if so how far? Two miles or 2000 miles?

I've worked on many small engines and that black oil you see coming out of the injectors looks like very old gasoline that had dried up and condensed. I've found the same thing in fuel lines and carburetor bowls when people don't winterize their mowers or generators and drain all the gas out. I'm thinking that old gas got pushed into the fuel rail. Did it have a strong smell?

Still no idea about that octopus inside the fuel tank. Looks natsy.
 
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Flyer58 said:
Well after seeing the pictures I went back to your original post and see you said "The Jeep had not been running for nearly 5 years,".

After those five years did you drive it at all and if so how far? Two miles or 2000 miles?

I've worked on many small engines and that black oil you see coming out of the injectors looks like very old gasoline that had dried up and condensed. I've found the same thing in fuel lines and carburetor bowls when people don't winterize their mowers or generators and drain all the gas out. I'm thinking that old gas got pushed into the fuel rail. Did it have a strong smell?

Still no idea about that octopus inside the fuel tank. Looks natsy.
Click to expand...
My Jeep sat for 10 years, nothing like any of this was in my fuel system and it runs great.
I was a professional small engine mechanic for 11 years and whats dripping looks like filthy oil, not the varnish I've seen.
 
Fantabox said:
I don't have a perfect answer, or the "ah-ha" moment, with this issue, but my best guess is the bad injector(s) were allowing oil to enter the fuel rail, and then into the fuel return line. I am attaching JPG photos to this post.

View attachment 117369

View attachment 117370

View attachment 117371

View attachment 117372

View attachment 117373
Click to expand...
OK, after seeing that blob of goo, I'm about 99% sure it did NOT come from your motor.
There is just too much of it.
It looks like the crap I have scraped out the bottom of solvent tanks.

Old service stations, especially rural and mom & pop types, have a dirty little secret.
30 years ago I was warned by friends NOT to buy gas at our local service station, one was a mechanic there and told me why.
Before the owner would order a load of gas, he'd dump their waste oil in the storage tanks for the pumps to dispose of it.
What's 5-10 gallons of oil in 10,000 gallons of gas, right?
What doesn't mix with the gas falls to the bottom, some of it floats to the top.
What falls to the bottom may float on a layer of water.

I've never bought gas at a service station since.

I think you may have unwittingly bought your problem.
 
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jeepjoe43 said:
My Jeep sat for 10 years, nothing like any of this was in my fuel system and it runs great.
I was a professional small engine mechanic for 11 years and whats dripping looks like filthy oil, not the varnish I've seen.
Click to expand...
Huh that's strange. I'm not doubting you at all but out of the two dozen or so small engines I fixed for neighbors I'd say about half had black tar in the carb bowl or fuel line that I could scrape out with a screwdriver. Maybe the humidity near Houston does something funny. I also have a boat which sat for 8 years with gas in it before I tried starting it. New battery and a quick shot of starter fluid and it fired right up and ran well. But then I had added quite a bit of Sta-Bil to the tank.

I feel certain there would have to be a good vacuum to get any external oil on the injector up past the o-ring and into the line. I just don't see that happening when it's normally around 30 PSI unless they were submerged for a long time and it was some atmospheric condition causing it.
 
Flyer58 said:
Huh that's strange. I'm not doubting you at all but out of the two dozen or so small engines I fixed for neighbors I'd say about half had black tar in the carb bowl or fuel line that I could scrape out with a screwdriver. Maybe the humidity near Houston does something funny. I also have a boat which sat for 8 years with gas in it before I tried starting it. New battery and a quick shot of starter fluid and it fired right up and ran well. But then I had added quite a bit of Sta-Bil to the tank.

I feel certain there would have to be a good vacuum to get any external oil on the injector up past the o-ring and into the line. I just don't see that happening when it's normally around 30 PSI unless they were submerged for a long time and it was some atmospheric condition causing it.
Click to expand...
I've seen lots of tar, too.
Once worked on a Briggs that was so bad the pick-up pulled out of the carb when I pried it off the tank.
But it was tar, he's describing oil...

It's not coming from his motor.
See my reply to his pictures. Best theory I have.
 
FINAL FOLLOWUP.....HOPEFULLY:

After reading some feedback I was able to discern that the black substance was really old fuel. The old fuel had essentially congealed in the fuel lines and fuel rail, which was not checked prior to the first fuel pump swap. Thanks to everyone that offered their opinions and insights.

I flushed the lines with some fresh fuel (again) along with some Seafoam, and was able to get a bunch more crud out of the fuel lines. It wasn't an incredible amount, but it took about 1.5 gallons worth of fuel and Seafoam to get it all out, or at least enough that I was not concerned. The rest was burned off once I had the Jeep running.

The Jeep has been running for the last week, and driven a few miles without any issues. I will need to make some adjustments to the lifters, and get a new gasket...but that is about it for now. At some point I will be swapping in a Hemi motor (nothing crazy), but that is a long-term project.

If anyone in Washington State, ideally Western Washington, has any leads on a low-mileage or new motor along with a transmission I am all eyes.

Thank you all!

P.S. YJ headlights rule them all!
 
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Is it possible your Grandpa knew it wouldn't be run for some time and mothballed the tank and fuel system with some sort of oil or?? I ask as I've revived a few bikes that have sat for years with the same fuel in the tank for 5 years or longer. The fuel never looked like yours but more camel colored varnish. The tank interior was coated with a thin film a few mils thick where the fuel solidified. What you have looks like permatex gasket maker in the lines. Black tar like yuk.
A current problem with the newer ethanol laden fuels is the high solvent qualities of them and the fact they will attack,dissolve and eat up fuel system parts of older vehicles. But...your year jeep should have no problem with E10 types fuels, E15 or E85, not sure what would happen. The glob in the tank is something else. Thinking out loud here there is no way engine oil could enter your fuel system. Fuel can enter the oil from a bad fuel pump diaphragm on something with a carbed engine. That's referred to as "making oil"
Just weird. In the old days we'd dump a quart of 2 stroke oil into 5 gals or gas in the moto bikes and it flowed no problem thru fuel systems. Even had a fuel guy add 1/2 a tank of diesel to a international 345 truck and it still ran.....sort of ;) smoking and knocking like the devil though.
On my 91 with TPI there is the factory fuel filter on the frame rail just in front of the drivers side tire. If yours is similar you might change that dude out a couple times and carry a spare just in case there is some more crud in the system. Cant hurt Id imagine.
 
Since getting clean fuel to come through again, have you replaced that fuel filter again? I'd highly recommend that, as that fuel rail looked terrible! I'd also peak at that fuel pressure regulator again... I'd suspect gunk would get caught up in that little guy.
 
I would have said a bad diaphragm in the fuel pump but this is a 1993 which is multi injector EFI so there's no block mounted fuel pump (like carbs used back in the day) that could have ruptured the diaphragm and caused oil to exchange with the fuel. Usually when that happened people noticed a gas smell of the engine oil in the motor and the oil was diluted or thinned out. Only YJ's that could possibly even have this problem are 4.2L 6-cylinder 1987-1990 models prior to EFI introduction. All 4-bangers had at least fuel injection from the start in 1987.

Can't be that problem so.... Dunno!

Makes sense that old gas could have turned to sludge but that's a lot of sludge. Never had even the longest stored vehicle not run in nearly 20 years do that and make so much sludge back into the tank but I suppose it could happen. Happens to plastic and rubber parts that start to degrade and turn back into gooey sticky sludge like components over time.

Hope you got it all straightened out @Fantabox !

RR
 
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I didn't see anyone else suggesting it but seems pretty possible it could have come from the last time you filled it up. Human error does extend to fuel stations. Of course, the vandalism suggestions are probably what I would lean towards. Locking gas cap would be my goto after you finish the clean up.
 
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ian.thomas said:
I didn't see anyone else suggesting it but seems pretty possible it could have come from the last time you filled it up. Human error does extend to fuel stations. Of course, the vandalism suggestions are probably what I would lean towards. Locking gas cap would be my goto after you finish the clean up.
Click to expand...
I did.
 
pacopacopacopac said:
Since getting clean fuel to come through again, have you replaced that fuel filter again? I'd highly recommend that, as that fuel rail looked terrible! I'd also peak at that fuel pressure regulator again... I'd suspect gunk would get caught up in that little guy.
Click to expand...
Since the fuel system was an open-loop, and only clean fuel was being used to flush the system, the fuel filter was fine. The old fuel pump clogged up and was unable to even prime the fuel system, and I suspect none of the old fuel was even able to exit the tank.
 
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