The Stovebolt Site Forums The Shop Area Engine Shop Gas Smell in Engine Oil - Causes Other Than Pump? Updated with Results.

57 3100, 235.

Newish symptom since sorting out my ignition issues recently...

After running the engine for a few test runs, I noticed that my oil was overfull, thin, and smelled of gas. Well, to be honest, it smells like some type of solvent, which must be gas since water would be the only other thing, right?

So, I drained all the oil out, replaced my fuel pump (based on advice seen all over the forums), and refilled with fresh oil. I took out the oil filter (bypass one) and cleared out that oil as well. I did not replace the filter yet while I sort the solvent smell.

The new oil has been in there for about 30 minutes of total engine running time. And now, it looks to be climbing in height on the dipstick and smells strongly of solvent again.

I also noticed that it is back to spitting out condensation from the tailpipe that includes black soot. Not oily, but the combination of soot and water makes it look like charcoal in water.

The truck still likes choke, even after warm, and dies after a short time when running at idle. I usually only run it for short "test run" periods right now. Not sure, but I think it runs worse AFTER warm-up.

This is the third fuel pump on this truck in one year. Am I chasing the wrong symptom? Does the soot signify that it is running rich or lean? Is there something catastrophic I can expect soon?

I hear "water" sounds as [what I assume to be] oil is draining back down into the crankcase after shutoff. Could this sound be from gas draining out of the carb and into the intake instead? If so, what could be causing it?

I don't want to run it right now for fear of launching the top of my engine.

What should I be looking for?

Thank for the help,

Jim

I doubt you would have gotten 3 bad pumps or had 3 go bad in a short time of little use .... the drainback you hear is oil from the filter and particularly from the top end, not gas, but yes it's running way rich - don't know if that would send a lot of gas into the crankcase, but definitely some would be washing down the cylinder walls ... not a good thing to be running it repeatedly at idle even if you think you're warming it up, you really need to drive it to clear the moisture from inside that's condensing on everything each time you shut it down .... the fact that it needs choke to run then dies says you have a carb/fuel problem, check for vacuum/intake leaks

Bill

If the volume/level of your oil is increasing more than just getting warm, I'd be looking for the source of the increase. If you don't have a garage fairy adding oil, look at the fuel system.

If it is significant I'd also be concerned with washing out the cylinders, like Bill mentioned, from extreme richness. I can't imagine it would run very well at this point though, expecting it would behave more like repetitive flooding and not want to start.

You need to eliminate any possible cause. Start here.

Look for any fuel coming out the carb vent tube while running or after shutting it down. If there is an overflow you may have a needle seat/float problem.

Next, I don't know your carb, but check to make sure the bowl is not somehow draining into the intake after shut down.

Okay Gents,

Thanks for the thoughts. hd4unm, it's a Carter YF 2100S that was very recently [professionally] rebuilt and otherwise functions perfectly.

Bill, I took the top off my oil canister after a short test drive tonight and subsequent long idle. It idled this time after the test drive and warm-up without dying. I have no idea what to expect. I did get the soot and condensation at first start-up, but I had it choked to the max and opening the carb up stopped the soot this time.

However, when I dipped my finger into the oil in the canister, it ran off like Kool-aid on a Mississippi mid-summer day. Definitely getting fuel (and lots of it) into the oil.

I could try closing the mixture screw and backing out 1-1/2 turns so that I know what it is set at, but I need to change the oil again first. I have not changed any settings on the carb since I bought it.

After I change it again, Chris and I will do a compression test, another fuel pump test, and post the results.

I should have bought stock in Chevron oil...

Jim - are you sure the carb is correct for Chev? here's a note on the 2100 from CarbKing from another forum:

"Most of the YF production was for Ford engines, especially the 300 CID 6 cylinder which require more fuel. MOST (not all) of the current aftermarket repair kits contain a fuel valve designed for the Ford engine which has an orifice of 0.101 inches. The fuel valve as used in ALL of the YF carbs for Chevrolet had an orifice size of 0.081 inches. If you do the math, the valve for the Ford has an orifice size which is seventy percent larger! Using this valve in the Chevrolet carburetor will cause at best an over rich condition at idle, and at worst flooding and fuel leakage."

I'd suggest you try a different carb and see if the problem goes away

Bill

Bill,

No, I am not sure. The YF was sold as a replacement for the Rochester B, which I already had and had nothing but trouble with.

You might be on to something here though. I don't have specs on my carb, but looks like I need to start researching this size issue.

I would hate to think I am back at square one with the carb, as the Carter YF cleared up a years' worth of frustration I had with my Rochesters, but I can't begin to discount it as a possibility.

One step forward, three steps back...

I'll tell you, though, this would sure beat an engine replacement!

More to come...

Thanks,

Jim

Go find a rochester monojet 1 brl off of a late model 250. It will bolt up in place with no modifications, they are on swap page often. Makes a world of difference over model B .

one thing I have learned on this website is to listen to Jon (carbking) on carburetor matters. Also "professionally" rebuilt means very little to me, we occasionally send out some of our equipment at work to the factory when there is major buildup/repair work to be done. And nearly every time we get back some piece of ##@@* that we have to rebuild correctly after we get it back. I mean the big major machine work that we aren't equipped to do is done, but the assembly as far as I can tell was done by trolls with drinking problems. The last rebuild cost 225,000 taxpayer dollars, which we had to tear apart almost immediately upon receipt and correct several glaring errors. Just because you paid someone a good chunk of money doesn't mean they did it right.

One problem using a monojet on a 235 is the dis. vac is wrong on a 235 it's port vac and on the 250s it's manafold vac. There are alot of mod.Bs around I have three sitting in the garage now all rebuilt and ready to go and they all work just fine. I have a 2100s carter on my 52-3100 and get easy starts and better MPG so I use that.I would see if there is a fellow Bolter near you that can let you use a "B" for a couple of weeks and see if that clears up this problem.

Pete

Let me understand this.

You have to apply the choke to get it to run when cold?

As it warms do you slowly open the choke?

Once the choke is fully open will it idle okay? If not is there black smoke coming from the exhaust indicating flooding?

How is the oil pressure when it's running and hot?

How much does the oil level come up after the engine has been run a while and is at operating temp?

How long at a time do you run the engine? A few minutes at a time?

It's pretty normal to get condensation out the tail pipe. Especially if you are only doing short runs. The exhaust doesn't sound like it is getting hot enough to get the moisture out before the engine is shut down. So even more condensation happens. You can get quite a bit of water out the tail pipe from short hops.

Pete, Bill, and All,

Thanks for the thoughts. I may see if Chris can bring his spare Rochester over this weekend and let me use it for a bit. If that fixes things, I will revisit my aversion to using one. Maybe send several of mine to Larry Isgro to try and get a bebuildable one...

Bill, is it possible to replace the fuel valve in the YF to make it perform to GM specs, or would this be the start of more dominos going over?

Jim

You said in one post it's still getting fuel in the oil and "lots of it".

I just can't see a carburetor doing this unless it was poring gas in while the engine is running. It would have to be going over the top of the vent tube and running down inside the carb.

The engine would hardly run (if at all) with that much fuel going in through the carburetor. I highly doubt you could drive the truck with this much fuel going in at once.

I would highly doubt you would have 3 fuel pumps bad in a row. But that's about the only way the oil can pickup "lots" of fuel in a very short run.

Even the 300 Ford carb wouldn't put that much fuel through it.

Thanks Roy...

I have the same doubts, especially since it runs really well right now. I've had flooding issues before that kept me from being able to properly time the engine and it just doesn't seem that bad to me right now.

I need to consider the possibility that I am dumping fuel past the rings prior to combustion. And, as my 235 is already sporting .060 over pistons, I may not be able to afford to rebuild it.

It's possible that I have reached its service life, though I have only owned it a year. May be why the previous owner parked it in the field around 1991. Who knows?

Exploring everyone's thoughts, ideas, test procedures, and gut instincts here. And I appreciate yours.

Best,

Jim

I don't know about modifying the YF, but swapping on another carb would be where I'd start in order to eliminate the carb being the problem .... like Roy, I'm also puzzled how enough gas could be getting in the crankcase as to make a real difference in volume and viscosity, if via the carb I'd expect it to run poorly under any condition, if via the fuel pump I'd think the pump couldn't keep up to the carb at more than idle, particularly under load, although I guess you haven't been really loading it

Bill

You're right...not really loading it. As for volume:

-I changed the oil 10 days ago when I changed the fuel pump, and the crankcase showed dead on the full line when done. I had drained it completely prior to that and DID NOT refill the oil filter or put in a new oil filter.
-On Sunday morning, I checked the oil and it again smelled of solvent. But, the level was still at the full line, or just a hair above. Test warm-up but only for ten or so minutes.
-On Monday afternoon, drove it for about ten minutes and warmed up more after that. Ran just fine (even on the very steep hills that I used while chasing the condenser gremlin).
-Checked the oil after letting it cool for twenty minutes. Oil cannister is now filled with VERY thin (but clear) oil, and crankcase reads above the full line by about 3/16 inch.

Still very cold temps here, but it seems obvious I have something more than a bad mixture setting going on. I don't understand why it's not running poorly. Only thing I can think of is I just don't run it long periods. Glad I didn't too, because I am worried about the engine internals getting washed down.

SWEET is definitely bringing his good spare carb over this weekend, so I have a few procedures to go through. Our plan is to check compression first, then, if good, swap the carb and fuel filters again.

Thanks for the ideas. Keep 'em coming!

Jim

Sounds to me like you need to take it for a drive. Get it good and hot. Watch the oil pressure. As long as it's good, you'll be fine.

May take a while for that smell to leave the oil even with new oil in it.

3/16" isn't much. As long as it stays there you should be fine.

Could be that much hadn't drained all the way to the pan the first time you checked it.

Well,

It was the 3/16 up AND the full oil cannister. It was empty when I replaced the oil. So, it filled the cannister AND rose 3/16ths.

That's about a quart in volume increase after 30 minutes of engine time. Can't be good. But, maybe it's a really really bad float setting? Don't know, but I worry about bearing washdown and burning them up.

Jim

I can't see a float setting on a carburetor making the oil level go up a quart in 30 minutes run time without having some really bad issues with it running. It would be dumping fuel in.

You could always clean your drain pan real good, drain the oil and measure how much comes out?

If it runs okay it must be getting in some other way and not down the carb throat. Or the carb is leaking down while it sits between running attempts. Pull the carb (you're going to do it anyway) and hook it up to a bottle of gas and a tube. See what happens. If it does not leak, you might need to keep looking elsewhere.

This is a strange one...

I am no damm expert by all means but i did have 327 chevy impala 1969 fuel pump gasket that drove me crazy filling the oil pan with gas.The pump was replaced with a electric pump.That solved it .

An electric pump might be a good idea to try.

I can't see three new fuel pumps in a row being bad, but stranger things have happened. At least it would eliminate the fuel pump from the equation.

the only way I can think the fuel pump could be causing it [aside from split diaphragm, which should have been obvious when checked] is if the pump is delivering so much pressure it's flooding the carb ..... but that should give poor running

Bill

Bill,

Let me ask you this, then; Could it have anything to do with the fact that I put in a new metal fuel tank (between the frame rails) and ran all new 5/16 steel lines from tank to pump to filter then carb? About three weeks or so ago.

http://i1195.photobucket.com/albums/aa397/fourbrads/IMG_1304_zps67bd1030.jpg

http://i1195.photobucket.com/albums/aa397/fourbrads/IMG_1302_zpscf7329a5.jpg

Jim

and the problem wasn't evident before that? you might want to try a pressure gauge at the filter and see, I think it should be less than 3#

Bill

Is the new gas tank vented? What if the exhaust is heating the gas in the tank making it expand and push gas into the carb after you turn the engine off due to a plugged vent...

Mike B

I will add that to my list of tests. It's just a standard Advance Auto pump (same as Auto Zone, near as I can see).

You never can tell when you're pulling parts from the counter and the kid behind it is less than half the age of your truck...

Hmmm...Had not thought of that.

I kept the exhaust at least an inch and a half from the aluminum tank at its closest point. The tank does have a vent, and it includes a rollover feature. Maybe I need to test that vent too, to see that air can escape.

Would a closed vent not starve the engine for gas as the vacuum built though?

Jim

Bill, et al...

I called Carburetor Exchange and asked them for the specs on the fuel valve orifice for the Carter YFs they sell as replacements for the Chevy 235s. The tech told me they use a .0945 orifice, so it looks to me like they are splitting the difference between the Ford (.101) and Chevy (.081) specs to make it more economical for them to sell these things in bulk.

I also asked what initial fuel mixture setting they use. He said two turns out. This seems a bit rich to me. So, between the two specs, I think I am running very rich.

The tech also asked me if I had a PCV system or not, as this could affect (over time), the fuel blow-by amount that remains in the crankcase. I described the road draft system to him, which he knew as an "open tube" configuration, so it's at least possible the tech did not have a good feel for these old engines. But, he was trying to be helpful nonetheless.

I think that, while perhaps not the whole problem, the two rich running issues above, coupled with the fact that I drive only very short distances for testing purposes (and thus never develop a road "draft"), may be contributing to my experience of crankcase fuel contamination.

I will still be checking the fuel pressure and swapping out carbs this weekend, but may try to lean it out a bit first (set to 1 or 1.5 turns out) and see what happens.

Thoughts?

Jim

Jim,the low speed mixture is set by engine speed.and performance.

Start the old Gal and let it warm up to temp.

Turn the mixture screw ,engine at idle, in slowly until the engine starts to lose speed ,than turn it out until the engine starts running rich .

Than turn it back in until you get a nice idle.

the two turns out or 1 1/2 turns out for the screw are only starting points.Each engine carb combo are different a little.


Pete

So, the results from this weekend...

As Most of you suspected, and counter to the premise of the original post, it was the fuel pump. Again. Third one.

While testing the fuel pump pressure (using a fuel/vacuum tester), we found the pump putting out between 2.5 and 3 lbs. But, it was also leaking gas onto the ledge of the block just above the oil pan. Went to pull it and a LOT of gas poured out of the pump from behind the pump (engine side) as we did so.

I replaced it with a pump I cleaned up that I pulled from a 261 in a junkyard a week or so ago (See ODSS Winter Junyard Tour). This was an ancient DA pump with glass bowl and gunk everywhere. But, when we installed it, it worked. Well, it has two weep holes that were leaking gas, but slow enough that it wasn't dangerous.

Truck started right up and we got good pressure from the DA.

Moved on to the compression test. SWEET and I worked at bit at understanding how the testing equipment worked, but that done, the compression test showed 120 to 130 lbs in all cylinders. Not bad...and it probably means the rings are good.

As a side note, and based on the question Red posed about the larger fuel valve orifice in the Carter carb, I backed the mixture screw down to zero and checked how many turns out it was set at. It was around two. I returned it to 1.5 for the subsequent tests. The truck started and ran (without producing soot) with no choke applied. Interesting.

After a couple of test runs, idles, and resting, we checked the oil for volume and smell. Had a hard time detecting fuel smell in the oil, but I think there was some (my pump was leaking into the crankcase while doing the compression tests and before replacement with the DA). I will check it again each day another week of running.

Thanks to everyone for their inputs. I will report back on oil volume and smell after a week or so of further testing, but I think we have found the culprit. I have a new SA glass bulb pump (because they look cool and I am hoping these specialist shops have pumps that are not already dry-rotted) on order from AmericanClassic.

Regards,

Jim

You could also try and just rebuild the one you have it's only about 20.00 for the kit and only takes 15 min.


Pete

Thanks Pete,

If you are talking about the DA, I will probably rebuild it, but the kits I have seen run from $55 - 85 each.

Or were you referring to the ones I have been buying at Autozone, etc?

Jim

Okay...final note on this one...

The newly replaced fuel pump cured the issue. I was skeptical after three 4149 fuel pumps from two counter vendors (Advance and Autozone), but all three went bad almost immediately. Maybe there is little call for these and they dry-rot on the shelves? I don't know, but three over a years' time, that seems pretty silly.

At any rate, took a very long drive this weekend. No volume increase and no fuel smell in the oil any more.

Many thanks for your suggestions and encouragement.

Jim

Always good to hear of a happy test drive.

Thanks Roy,

SWEET did a video of it and posted the link in this thread...

Jim

Just when you thought it was safe to go back in the water...

It's Baaacckk. Always sucks when your symptoms reappear after a roundly successful series of painful tests and repairs.

I have been watching the oil for the last six months. It still has a strong solvent smell, increases in volume the more I drive the truck, and now seems to be pushing out of the road draft tube (after extended running at highway speeds).

Maybe the road draft thing is normal, but the oil volume 1/2 inch above the dipstick full line is disturbing. Oil is thin but clean.

Going back to square one on this and could use some advice.

Thanks,

jim

Two reasons for fuel in oil, one, the fuel pressure overcomes the float and floods the engine, or two, the fuel pump is bad again. Carb should be easy to see, it will be running terrible. This leaves the fuel pump.

To test this, a electric fuel pump could be installed bypassing the mechanical. With a regulator set to 2.5 psi, you should be able to run your tests. If you gain no oil level, then the fuel pump was the problem.

Its not really that hard to believe you keep getting junk fuel pumps. I suspect the fuel in your area maybe eating them up. Take it apart and see where it's leaking from, that might give you a idea where to go next.

Joe

Simple solution- - - -Install an electric pump back near the fuel tank, and use a discarded fuel pump housing less the internal parts bolted to the engine with a blind gasket under it to route the fuel lines through for a stock appearance. Just install an oil pressure switch inline with the pump power to be sure the pump shuts off if the engine stalls. I can draw up the pump power circuit I used pretty often for this application if you like- - - -it involves using a pressure switch and a bypass circuit to run the fuel pump during cranking before the oil pressure builds up. Good luck!
Jerry

cletis
Tech tip

http://jbhardin-gallery.com/trucks/fuelpump.html