Corvette Consternation Part 3 Fuel Foley

Let’s recap for a minute: 

1.  Rack and pinion failure 

2.  Power steering leak 

3. Electrical system failure 

As you know the electrical system failure was the alternator and it was replaced. 

A now the story continues…… 

I picked the car up and it started fine, even had power to flip the lights up (it could do that when I dropped it off) and I drive two miles home.  It ran just horrible. No power at all.  That was worrisome. 

Now the ’84 Vette has  a very simplistic computer that controls the fuel injectors and it does take a bit after a “power outage” for it to get the mixture correct.  This should happen after a couple of miles.  Well by the time I got home there was no change in the how utterly horrible it ran.  So I took it for another spin and still no change. 

So I disconnect the battery for a few minutes and then tried it again…still the Vette could barely keep idle and giving it gas made it shake and the idle dropped to 400, 500 rpm.  So I thought ..ok..I’ll drive it to work in the morning and see if the 10 + miles will straighten it. 

Next morning, a Volkswagen bus filled with 40 people could have passed me like I was up on blocks!!!! 

Ok…at this point I’m getting a little bit…P.O.’ed…(that’s short for…oh..you know what it’s short for!!)  I call up my guys and I explain my displeasure.  My take was that they should have test driven the car and that they have had the damn (that’s short for @#$@#%%!!!!!) thing enough to know that it wasn’t running right.  I expanded on my thoughts in person when I limped the car back there after work..which was not a great day…which might have contributed to my disposition.  Sorry Sean, but you ya know noting but love…its all good dude….Sean later told me I hurt the only “feeling” he had…I told him to get over it.  They had a new guy there and he was the one that test drove it after the electrical work. 

This was the start of a 3 day, all hands on deck, WTH…(that’s short for “What The Heck” >wink?<…I didn’t want to push the envelope with the “bad words”, because I would have had to add “put the kids to bed ..I’m about to use some adult verbiage”) is wrong with this car!!! 

I’m thinking it’s still electrical, computer was F ‘ed (short for “fried”) or there was a short somewhere.  I ended up at the garage a couple of nights after work poking around a bit – Tim Sisk the guy that runs the places is good about that.  

So here is what was happened. 

 It appears that the evap system that is supposed to take the fumes from the gas tank for emissions was filling up with fuel every now and then.  This system is supposed to push the fumes through a canister filled with charcoal and remove some of the harmful particles.  Of course it doesn’t stop there the “cleaner” fumes then are pass back into the intake manifold to be “re-burned” and sent out in the world through the Vettes exhaust system.  This simple hose highway runs along the entire length of the car and isn’t designed to handle fuel.  

The end result was fuel running through the hose design for only fumes, traveled the hose highway all the way to the front of  the car,  filling the charcoal canister – which wasn’t designed to hold gasoline.  Once full the gas has not where to go but across the engine, just following Avenue Hose, and dumping fuel directly in to the intake.  That’s the cause of the poor (understatement) idling and running. The car was drowning in fuel. 

 

How does this happen? Well it occurs when too much pressure builds up in the fuel tank.  The venting of the fumes is supposed to prevent that. Once the pressure builds, which doesn’t take long with a full fuel tank, the gas has to go somewhere, so it takes a trip up the evap hose. 

Now, here is where a guy starts to wonder  WTH (short for….) am I doing with a one off car???!!!  Really the 84 Vette is a one off production year.  There were not ’83 Corvettes sold and although it has the same basic engine as the ’82 Covertte crossfires, nothing else was the same, and the ’85 Vette was an entirely different animal.  This leads to a fairly significant lack of printed knowledge on the system..this many years out.  Why do I mention this?  Because it’s tough to find the knowledge after this long and the newer repair books treat the ’84 systems as ..”oh yeah..it’s not the same as the ’85 or the “L83 (my engine) is similar.”  Gee..thanks for that.  But it is different and it’s not similar in many ways. 

Here is one.  

The fuel tank on ’85 Vette has what is called a check valve with allows vapor to travel through it, but if fluid enters it, a small ball is pushed by the denser liquid to a point where it will block the hole.  There is a diagram of that in many of the new  repair books.  But there are none for the ’84, and no, upon actually view the parts, you aren’t going to see anything that looks like the ’85 check valve. 

Ok..armed with is knowledge, I showed up at the garage and share the info.  This left us all scratching our heads.  There seemed not logical reason for pressure to build up. There is only the fuel pump down there (that we tested in a bucket of fuel and worked as it should)  there was only one other fuel delivery system was the “limp home” system which use the oil sending unit to push just enough, when the tank was low or fuel pump failed, to get you home or a repair shop. 

This lead into the third day, at which point the fuel module was removed from the tank again and it was discovered that there was indeed a check valve. 

There is a check valve built-in to the fuel module, it had a piece something (appeared to be plastic or maybe rubber) lodged in it large enough to keep the ball in a position where the it increased the pressure so much that sent it shooting fuel out up the vacuum line.  It was incorporated into the system in a way that was not conducive to separate replacement.  It was cleaned and that solved the problem..well most of it. 

The canister should be replaced find one it not easy. Right now we replaced the PVC valve with a right-angled and the canister is no longer in the flow. 

For my 84 that’s not a problem since there is no sensor that checks that and the car is running great. I’m not sure but I think she’d even pass emission, unless they were to visually see that it wasn’t connected. 

Of course I’m a big tree hugger and (you can tell because the Mustang gets 4 gallons to the mile ..hey that’s what dead dinosaurs are for!!!!) so I’ll eventual get it replaced. If I can find one.  In the mean time I’ve re-routed the  hose to protrude under neigth the engine so the fumes don’t fill the engine bay. 

Some pics: 

 

 

So there you have.  Good thing there wasn’t a car crusher in towing distance….nah…I love that car. 

Thanks for reading. 

TIm