Hi everyone,

First, I want to say I hope everyone has a Merry Christmas, and thank everyone for the help you have given me so far. I am a novice regarding many aspects of car repair, and bought a mostly restored FB, hoping to have to do little initially to get her running. Now, I have about 5 days I can work on my Bird before I have to park her for about 6 months (if she isn't running). I go to USAF Weapons School starting in January, and the 14-16hr days 6 to 7 days a week does not mix with trying to learn about and then fix my Firebird. To complicate matters, I go out of state for a week beginning Sunday of this week.


The setup-
My FB has an electronic fuel pump on the right rear frame rail area. The fuel pump is the smaller square type that clicks, if that helps. There are two steel fuel lines running from the factory tank. One goes through the fuel pump, the other is smaller and does not, and is a vapor return. They both run up to the firewall, where the primary fuel line juts away from my long headers along the right side of the engine compartment, then over to the Quadrajet carb. Engine and carb are likely from an 82 Chevy. The second fuel line runs to the firewall, and was originally capped with a small steel cap with red paint. The carb has a fuel line running to one of the headers, which may be a second vapor return.
My tank has a very slow (never really drips, but dried fuel often shows up on the driver side front gas tank corner. The gas gauge currently does not work, but has inexplicably moved once to full and then back to empty after a fillup.

The problem-
I went to the gas station for a fillup. The tank was nearly dry, as idiot me wanted to wait until I got back on base to fill up. After filling up, my car began to leak fuel from the vapor return line. The steel red cap had popped off at some point. (Maybe because of the pressure of the fillup?) I put a rubber line cap on the end of it. The next day, when I tried starting the car, it would not start. I popped the hood, and my engine was covered in gas, as the carb overflowed. I think the vapor return cap caused this. The vapor return is a good 18 inches below the fuel tank. I put a 2-foot rubber fuel line on it and anchored it high in the engine compartment, with a filter on the end of it to keep junk out. The leaky carb stopped, and the fuel no longer leaked.

THEN, I drove it about a mile and a half to test it out. When I got home, gas had aspirated out of the air filter, and poured onto the headers. (good grief...no fire though, thankfully)

Question-
How do I stop the fuel leak? What should I do with the vapor return line? Should I connect it to the vapor return on the carb? Should I drain/drop the fuel tank and clean out the vapor return? Should I remove the vapor return line completely? (It appears that there was no vapor return line on the 68 according to the '68 Pontiac Shop Manual.)

you are confusing a vapor line with a fuel return line the gas goes through the pump and the excess goes back through the smaller line if the line is not there, then the pump will put pressure on the float. if the float is weak, the gas will continue to fill the bowl till it over flows. the reason it fills up slowly is the 67 and 68s had no vapor release so the gas will back up through the tank and out on to the body or (burping).
either you have a bad float or the system is incorrectly set up. give h-ll over there!! stay safe.

Thanks. I will do my best.

Why would they have put a second line all the way to the engine? This second line completely bypasses the electric fuel pump. Do you have any idea why capping the second fuel line from the tank would cause the carb to overflow, but not when it was free to vent?

The 68 Pontiac Shop Manual seems to depict a short valve coming out of the gauge on the tank. What is it for, as the manual nor Chiltons describes it, yet they both depict it.

Thanks again,
Dave

The illustration along the top and at the bottom left show the entire fuel and return line routing.

If your electric fuel pump is pushing fuel into your mechanical fuel pump, and the mechanical fuel pump does not have a return line port, then change your mechanical fuel pump to the correct model with the return port. Then connect your return line to the pump and be sure it's connected at the tank.

Venting fuel vapors under the hood is not a good idea. They are highly explosive.

What do you mean when you say: ?

And check your fuel cap, if it does not say "vented" then you need to be certain that your car has a tank vent, a small hook shaped tube at the top of the tank. Even if it does, it may be clogged; switch to a vented gas cap and see if the tank pressure drops. Or, after the car has been running for a while, walk back and loosen the gas cap and see if there is any pressure or suction in the tank. There should not be any.

You will find that the shop manuals do not depict every combination built. Air conditioned cars frequently have the fuel pump return line when none is shown in the auto parts store lists, same with fuel tank sending units.

Most common fuel gauge problems are caused by wiring. Either corrosion on the sending unit terminal, a cut or scraped wire where it passes from the trunk to under the car, or along the wire under the car to the sending unit. Problems at the gauge end are usually in combination with other electrical issues and are often caused by poor grounding of the instrument cluster.

I'll take some pics of the carb to show what I mean about the line running to the valve cover. (I meant valve cover...sorry about that)

There is no mechanical fuel pump in the way the previous owner set up this car. Again with the non-Pontiac stuff ... It's a Chevy 454, and the fuel pump housing on the side of the engine has a plate on it where the pump would have been.

The line going from the carb to the rocker cover should have a PCV valve in the rocker end. That's crankcase ventilation, not directly connected with the fuel system.

If you're sticking with the Chevy, and your tank leaks anyhow, you might want to drop and replace the tank and install a sending unit with a single line.

It does have a valve on the end connecting to the cover.

Would it be easier or cheaper to replace the fuel pump? What are the benefits of the electric verses the mechanical? Could I keep both the electric and install a mechanical pump?

I do plan on replacing the tank. I'll check up on the single line sending unit.

Is there anything I could do temporarily that you know of? What about capping the line at the fuel tank? Would that cause problems?


Thanks!
Dave

I do not know how the return line feeds back into the sending unit, but it should not do any harm to cap the return line at the sending unit. However...these sending units are rather pricey, so try to do without damaging the sending unit.

I do not know what line sizes are available for BB Chevy fuel pumps, you'd need 5/16" x 5/16" x 1/4" to match up with the stock Pontiac lines.

If your fuel pressure is properly regulated to no more than 4.5 psi if you have a Quadrajet, then a mechanical or electric pump will work equally well with a good carb. If your fuel pressure is not regulated to this level, invest in a regulator.

New tank, new mechanical pump, correct fuel lines with no more that a foot of rubber in a stretch. Then you will be good to go. Fuel delivery is nothing to mess around with. You've been lucky so far.....

Thanks for the help. I picked up a mech fuel pump today along with the steel fuel lines to connect to the previously capped off line.

I do have two questions, though:

1- There is no fuel filter on my car. Where does the fuel filter go on a 68, and which one should I get?

2- The mechanical fuel pump for the 454 has a 1/4" fuel return (perfect), and a 3/8 input and output connection. My fuel line is currently 5/16". I got all the connections to convert the 5/16" line coming from the tank to 3/8" to fit the fuel pump, and reduced the size of the output from 3/8" to 5/16". The longest run that will be 3/8" is about 10 inches. Will this be a problem with my setup?

I decided to keep the electrical fuel pump on the back side of the car. I have been told this will not be a problem, and will "boost" the mechanical fuel pump.

Thanks again for the help. I plan to get a new tank and clean the fuel sending unit, so all fuel issues will hopefully be resolved.

Having 3/8" fuel line will not cause any issues. If you do a lot of constant full throttle, the 5/16" lines might. Normal driving, no problem.

The bushings won't cause any issues. If you replace the fuel lines in the future, replace the lines and sending unit with the appropriate 3/8" parts and just pull the bushings.

Having the mechanical and electrical fuel pumps together will not be a problem but be sure to regulate the pressure so as not to push the fuel needle off the seat. Quadrajets are easily flooded this way.

The fuel inlet on a Quadrajet has a separate filter holder. Using a pair of appropriately sized line wrenches, loosen the fuel line from the front of the carb. Pull it aside, then use another pair of wrenches to loosen the fuel filter housing/inlet. Be very careful not to cross-thread or overtighten this part, repairing it is no fun. You can add a fuel filter inline anywhere on the pressure side that is safe from moving parts and road rash.

Thanks, Vikki. No plans to do a lot of full throttle driving. It will be more of a daily driver, and base police frown on anything over 25 mph.

I can't find any info on regulating fuel flow with these fuel pumps. Here are the ones I have:

I am more and more convinced the 454 is from an 82 Chevy C20 pickup. This is the fuel pump that matched that vehicle (and matches my engine):
http://www.car-stuff.com/store/images/prodimage/images/airtex/AF41216.jpg

Here's the electric fuel pump (Purolator PRO#12S):
http://www.midwayautosupply.com/images/PRODUCT/large/PRO-12S.jpg

The Purolator is rated for 4 to 7 psi.

4-7 psi should be just fine.

You should not use the type of electric fuel pump you have now with a return line to the tank. The smaller square pumps that make the clicking sound are low pressure and meant to pump up then shut off when pressure gets to about 6 lbs. With a return line it will run all the time.

If the car is running, it will be constantly drawing down the fuel pressure and keeping the electric pump running anyhow, when starting it would help to ensure the fuel line is full at startup before the mechanical pump engages. The only time I see an issue would be if the ignition was left on and the car not running for an extended time.

Ahhh. Am I missing something here...? He said he bought a mechanical pump.... It will be fine all by itself.

yes, it will.

Vikki, the small low pressure pumps are not meant to be run full power all the time witch it would be with a bypass back to the tank. It is a solenoid vibrating type of pump.(not rotary vane type)
It could be used (with a dash switch ) to prime the system or on a full power blast to keep the fuel bole full.
But I wonder if it would be more of a restriction in the system if turned off.

?Thanks, Vikki. No plans to do a lot of full throttle driving. It will be more of a daily driver?

Mine was a daily driver for 14 years and the other was for 8 years. The only way I drove it was full throttle.

If you aren't going to drive it full throttle, why bother with such a car? I wouldn't!