After a weekend with a bunch of MIT friends in Las Vegas, and then a Sunday morning trip to see the Hoover Dam, I found myself back in Vegas filling up for the ~300-mile trip home.  However, the car did not want to cooperate, and the gas pump would shut off within 1-2 seconds of starting, sometimes leaving a small puddle above the flap in the filler tube.  I moved to a second pump at the same gas station and had the same issue.  No matter how slowly I tried to add gasoline, it would stop within a few seconds.  After about 15 minutes, I had only added about 2 gallons of gas -- that's almost as bad as charging an electric car!

What's the big idea here?  The gas tank is a fixed volume and is not under much pressure, so when I push a gallon of gasoline into it (which takes < 10 seconds at a typical gas pump), a gallon of air and gasoline vapors has to be pushed out to make space.  If the vapors don't move, then the pressure inside the tank builds, which forces the one-way fuel fill valve between the tank and filler pipe to close.  The gasoline then builds up in the filler pipe and touches the nozzle, which forces it to shut off.  (Click here to see more details and illustration of the automatic shutoff gas nozzle.)  Similarly, if no fresh air can enter the fuel tank as the car is driven, then the pressure would drop and would create a vaccum relative to atmospheric pressure.  So to summarize, air needs to be able to enter the tank slowly while driving (at a rate of at most a few gallons per hour), and air needs to be able to exit the tank rapidly while refilling (at a rate of a many gallons per minute).

Nowadays, the air/vapors exiting the tank are cleaned in order to prevent hydrocarbon vapors from simply being emitted to the atmosphere -- "Onboard vapor recovery" has been mandated by the EPA since 2000.  Now, the path looks something like this (from the Hyundai service manuals website, linked from this helpful forum post):

In fact, this shows less than half of the "plumbing" involved around the fuel tank, so this diagram was a bit confusing as we tried to attack the problem.

On this car, the gas tank filler hose is on the driver's side.  Below is the view from under the left rear tire, which shows three connections.  The left (small) tube goes to the small ports around the main filler pipe.  The middle is the main filler pipe which carries gas to the tank.  On the right is a odd-looking unit which happens to be the "liquid-vapor separator".  I can't be 100% sure, but the hypothesis is that it's just a physically-higher unit which ensures that if one were to really over-fill the tank, liquid fuel would still have a hard time crossing to the canister.

And below is the view of the same thing from underneath the car.  The large pipe on the left is the main filler pipe, where gasoline goes when refueling.  The liquid-vapor separator is the long rounded object parallel to that pipe, and in this photo, the bottom connection to it is coming from the fuel tank's vent valve (at a point high up on the fuel tank), and the top connection is going into the box on the right of the photo.  The box on the right of the photo is the charcoal canister which collects fuel vapors.  This serves two purposes: one is that during vehicle operation, those vapors can be purged into the engine intake and combusted, which prevents the release of hydrocarbons.  Second is that this is the path for air intake/exhaust for the fuel tank.  The upper (thicker) hose in this photo going to the charcoal canister from the liquid-vapor separator.  The lower (skinnier) hose in this photo coming out of the canister is for the purge system, which sends those vapors back into the engine.

After a little bit of work, we removed the canister assembly, as shown below.  This involved removing two bolts for the canister holder, disconnecting the two vapor hoses, removing an electrical connector, and loosening the zip-ties.

The canister assembly is composed of three primary elements: the canister itself, an air filter which is open to the atmosphere, and the canister close valve, which connects or disconnects the air filter from the canister.  The last two photos in this gallery show the canister separated from the air filter+CCV.

Well, after all of that, we didn't find anything wrong.  No kinks or obstructions in the hoses, no significant back-pressure or other issues.  Since most people on the forums described finding hoses filled with little carbon pellets, we knew that that sort of thing should be obvious enough, and it wasn't.  So we put everything back together, drove to the gas station, and guess what -- it filled up just fine!

An unsatisfying conclusion!  Still, that fill-up in Vegas was the hottest the car had probably seen in its lifetime, which makes me wonder whether it may have been related.  Or it could have been the two pumps I tried, or any number of other things.  A learning opportunity, and an opportunity to get more comfortable working on cars, and a working vehicle at the end of the day, so I think I'll call it a victory.

As a follow-up to my earlier post: http://blog.compumike.com/new-tires-now-including-a-free-broken-lug-stu

Thursday 3/25: I got new tires. They broke a lug stud and the broken part is stuck inside the wheel nut. The tire place sent me to a nearby mechanic and said they'd take care of it (paid for by the tire place). I'm informed that they'll get the parts and will call me either Friday or Saturday to do the repair.

Friday 3/26: Hearing nothing, I call the mechanic in the afternoon. They have the lug stud, but haven't been able to get the wheel nut yet. I make sure they have my number, and they assure me that they'll call as soon as they get it.

Saturday 3/27: Heard nothing -- and they're open on Saturdays.

Monday 3/29: Heard nothing. Should have called them, but got busy with work and didn't get to it in time.

Tuesday 3/30: Still hearing nothing, I called the mechanic in the afternoon, and was informed that they got the wheel nut from the dealer, but it was the wrong one, so they're sending it back and trying to get the right one. I'm assured that they'll have it on Wednesday, and they even ask me whether the morning or afternoon is better for me. I say morning, and am told that they'll likely call me around 10am, and confirm that I could bring my car in around that time.

Wednesday 3/31: It's now 2pm. So much for that 10am call. Haven't heard anything, and am about to call them. Any bets?

All for < $10 in parts, and a job that I could probably do myself in about an hour -- but really shouldn't have to.

My car had Goodyear Eagle RS-A tires that were down to a sad 2 to 3/32" of tread after roughly 36K miles. I've only been the vehicle owner for less than a tenth of those miles, so I can't say much about how well they hold up, but in any case it was time for new tires.

Just picked up four new tires: "Bridgestone Potenza RE960 AS Pole Position", which were moderately priced and had excellent customer reviews on tirerack.com and discounttire.com.

Unfortunately, while they were doing the work, the shop broke one of the lug studs on the front right side. They only do tires and wheels, so they referred me to a nearby mechanic and said they'd cover it, but it was late in the afternoon and they didn't have the part on hand, so I've got to head back tomorrow. (The mechanic tosses in a "we'll also give you 10% off on an alignment" up-sell.)

Ultimately, we're talking about a $5 lug stud and nut, plus perhaps 20-30 minutes to actually get to it and do the work. Still, it's a reminder of how simple things like a 30-minute new tire installation can turn into a complicated multi-hour / multi-day affair.

Hopefully tomorrow I'll be able to report that the situation was resolved swiftly and painlessly, as an example of humble and competent customer service responding to an unfortunate incident. Of course, until then, I'm torturing myself by dreaming of all the ways that this can go wrong from here...

First, we successfully changed my brake pads on my front disc brakes.
Back when I did the oil change, it ended up taking much longer than I
expected, however the brake pad replacement took much less time than I
expected! Perhaps more importantly, the amount of money saved versus paying a
mechanic to do it is tremendous in the brake case, and not so much (or
even negative if time is included) for the oil change. I was further pleasantly surprised by the AutoZone lifetime warranty for
the brake pads, where they'll replace them free for life as long as you
don't wear them down to the bare metal. In any case, it's one thing to take a bunch of mechanical engineering
classes, and another thing entirely to get your hands dirty and figure
out how various car systems are really put together.

Pair of jack stands at Harbor Freight:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=38846
$20 (were on sale), but have provided hours of entertainment, education,
and lots of savings already just by doing the oil change and front brake
pads myself!

Second, NerdKits did end up buying the Smithy CB-1220XL lathe/mill combo
machine I took pictures of in this earlier post:
http://blog.compumike.com/lathemilldrill-combo-what-do-you-think
We've got a lot of work to do to dig in, clean it up, and get some
tooling so that we can be useful, but this opens up an exciting new.
Quite an adventure in Fred's new (old) pickup truck to move the thing!

Being my first manual car...

My car makes a sound when I push the clutch pedal in. I think it's new
-- never noticed it before. I'd describe it as a sad trombone. It
makes almost no noise as it's released. Recorded it being pushed in and
released three times -- see attached MP3. Audible from both inside and
outside the car. Might be coming from near the clutch slave cylinder.

Clutch fluid level is within normal range -- didn't bother to uncap /
examine the fluid itself though.

Clutch was replaced about ~3000 miles ago. I'm not sure but I don't
think that includes the slave cylinder...

Should I worry about this? Does this simply mean that some joint needs
lubrication (like the pivot point attached to the clutch slave
cylinder), or something worse (like something internally wrong in the
slave cylinder itself)?

Really, I just wanted to test out posterous's ability to handle audio
uploads. In any case, maybe it's just in my head, but the sounds have
stopped.

I have to replace the brake pads pretty soon, and I pulled off the left
front tire just to check and have probably ~2mm left. If I buy the pads
and do it myself, that means that the rotors won't get resurfaced. Can
anyone tell by these photos whether the rotor "needs" to be machined? All I can do at the moment is assume that the inner face looks about the
same.

If only I had a lathe...

After a successful oil change, I'm now looking to do my own brake
replacement on my '03 Hyundai Elantra. Getting to the front disc brakes
is easy, but I'm currently stumped about the right way to get at the
rear drum brakes. The drum cover won't come off! Do I have to remove
the bearing cover first, and if so, with what tool?