[gotyorgoat]

I'm looking for some advice about a few ongoing issues with my 455. Any advice would be appreciated.

1. Overnight the fuel drains out of the carb and lines so that I have to crank it over forever in order to get fuel into the carb. I installed a check valve in the fuel line which worked great for a day and then stopped working.

2. It hates summer traffic. Even though the temp is within normal range, it stalls out like it is starved for fuel making it hard to take anywhere but the grocery store down the street.

3. If I run it and then shut it off for a short period, it wants to stall and acts like it is starved for fuel. It then runs fine after a few miles of using both pedals. This makes it hard to get home from the grocery store.

It was an AC car which has since been removed, but it still has a fuel return line to the tank. What would happen if I pinched this off?

The fuel tank, lines, pump and filter are new. When it runs, it runs great. Thanks for the help.

[AZ Racer]

I would not pinch it off. It sounds like vapor lock. You want lots of fuel flowing the more the better to reduce heat

[1966geeto]

What is your pressure reading running when you shut it down how fast does it bleed off ?Have you done a volume test? was it doing the same thing prior to replacing everything?

[Sirrotica]

One thing to check among other problems is porous neoprene hose on the suction side of the fuel pump from the pump to the tank connection. If there is any original hose in that side of the system I would replace it. While it may not leak fuel it will suck air and cause many of the problems your describing. A pin hole from corrosion in the steel tubing will cause the same problems.

A weak fuel pump could also be a problem so a pressure test would verify is that was a problem. In a Pontiac with vapor lock the return hose is an advantage, blocking it off will only aggravate your problems. The later model T/As has a thermal wrap on the fuel line from the pump to carb from the factory to help with hot soak and vapor lock. It was foam wrap like pipe insulation for hot water lines in a home. I don't know of any company that makes 3/8 inch foam insulation, however you could find the smallest available from HD etc. and slit it for a smaller application and wrap it with duct tape to keep the heat off of the tubing when running or parked.

There is one other trick for vapor lock that Pontiac,Chrysler, and AMC used on some applications and that was an inline fuel filter with a return line back to tank and it was installed just before the carb. If you use that style of filter it could be teed into the fuel return line to keep fuel circulating and keep it from reaching boiling point.

I notice your in CO and higher elevation with lower barometric pressure makes liquids boil at lower temps than sea level pressures, so your also battling that problem too.

Winter fuel boils at 105 degrees, while summer fuel boils at 140 degrees, even at 140 it's not hard to get the gasoline to that temp under hood, ethanol only makes the problem worse as it boils at even lower temps.

One other thing that will make a fuel starvation problem on a Pontiac is incorrect installation of the fuel pump eccentric. If not installed properly the tang can break off and cause the eccentric to spin and not pump enough fuel volume to run the engine in high demand situations. A fuel volume and pressure test as described in a previous post should be used to check this possibility.

Hope maybe there is some info here to help you solve your problems.......

[fyrffytr1]

What has been done to the carb? I was having the same problem with my car as far as draining down overnight. I had the carb rebuilt and it still gave me problems so I bought another one and now I can let the car sit for a week and it still cranks up after a few seconds.

[AZ Racer]

This would not have anything to do with the fuel draining off but I did have a big problem with the choke pull off and air flaps. That problem will tend to make you think it's starving for fuel,

Pat

[gotyorgoat]

What is your pressure reading running when you shut it down how fast does it bleed off ?Have you done a volume test? was it doing the same thing prior to replacing everything?

I will look for a gauge and give this a try. It is a new fuel pump which runs well when it it running so I am pretty sure that it is installed correctly. I have a clear fuel filter between the pump and the carb which I can see is dry. After cranking for a while it fills up and then fires up. Also all of the rubber lines are new.

The later model T/As has a thermal wrap on the fuel line from the pump to carb from the factory to help with hot soak and vapor lock. It was foam wrap like pipe insulation for hot water lines in a home.

That sounds like a quick fix that I could handle. I will give it a shot. I do think that it is related to the fuel heating up under the hood since it runs great a few minutes down the road when that fuel is burned off. Also sitting in traffic allows the fuel to pass slowly through the line which might allow it to heat up causing the stalling problem.

How much should the rubber line loop up and then back down before connecting to the sending unit? Should it go real high to keep it from siphoning back to the tank?

Is there any float or needle valve in the carb that could be replace to keep fuel from draining out of the bowl?

[Baron Von Zeppelin]

Do you have headers or exhaust manifolds ?

Uncoated/unwrapped headers can increase underhood temps drastically.

Todays fuel blends are a nightmare about boiling and vapor lock conditions.

Are you using a 1967 Qjet Intake ?
They have an exhaust heat cross over port/channel under the front of carburetor.

Most times when fuel starved after sitting , on intial crank up , the fuel has dripped/leaked out of the wells in carb float bowl. And drips out into the intake.

[gotyorgoat]

I have ram air manifolds and an edelbrock carb and intake. Ill look for an option to rebuild or go with new to take care of the startup problem. Maybe the insulation will help with the vaporlock problem.

Is there anything in the carb that would prevent the fuel in the line from draining back?

[gotyorgoat]

This vapor lock problem is killing my cruise night fun. I have no problems making the hour trip across town to get there, but as soon as I hit the congested cruise night traffic, it starts to stall out.

I insulated the fuel line up across manifold and to the carb which looks ugly and didn't seem to make a lot of difference. I also checked and the fuel line doesn't seem to be unreasonably close to the exhaust.

I have an Edelbrock 1407 750cfm carb with a 455 and all new fuel lines, tank and mechanical pump. It runs cool enough considering that I dont have a shroud but that is a different topic.

Should I install a secondary electric fuel pump in front of the tank? Maybe I could switch it to turn it on only when I anticipate that I would need it?

[Scarebird]

I would rethink the Edelbrock carb. I had nothing but issues with mine.

[1966geeto]

My Edlebrock has performed very well had o rejet it but after that no issues vapor lock is caused by heat do you have access to a digital thermometer HF sells them cheap where is your filter located read your temp as soon as it starts giving you issues pull the fuel line and read the temp of the fuel do a volume test hot also do you have an inline fuel pressure gauge what are the readings hot and cold read the temp at the carb are you sure its a fuel issue post your findings someone here should be able to figure this out.

[rohrt]

A pusher pump would remedy the fuel drain back. I don't use them I just crank forever and pump the hell out of it.

With my cars I make sure to insulate the fuel line. I run a metal line from the pump to carb regardless if its Q-jet or Edelbrock. I make sure the metal line is not touching anything. I then use 1/2 pipe insulation from the hardware store and do some trimming to fit the 3/8 line. I run it from the pump to carb and secure it with zip ties.

On my FB I put in the exhaust crossover block off plates and that helped me a lot on that car. I also used the 1/4 gasket under the carb to optimize the insulation from the heat.

One last thing is I use a factory HD clutch fan and 180 thermostat.

I installed a return line on mine sounds like you already have one. I assume your using it.

I have had really good luck with the Edelbrock on my tempest. It always very easy to start. The one thing I hate about them is the slight stumble from off idle. Can't ever seem to get ride of that.

[GT182]

I'm running the Weber built Carter AFB Competition Series carb with a manual choke on my 400, and have had no problems like that at all. I do have a spare with an electric choke if you need one. The fuel inlet on the carb is on the driver's side like the Edelbrocks.

Weber took over from Carter, and then Edelbrock took over from Weber. To me the Weber built "Competition Series" is way better than any Edelbrock carb I've seen to this day. Just my .

[Greg Reid]

Doesn't seem to me that you have determined yet that the problem IS vaporlock. Just like electrical problems, almost all fuel delivery problems will be aggravated by heat. Identify the problem first, then you can repair it.
I may have missed it but...have you checked the fuel pressure to the carb? Check it cold and then again when the problem is evident.
I had a truck that gave me fits for two months. First I had to determine if it was fuel of ignition related. I drove it until it started skipping and jumped out, removed the breather and pumped the carb. I was just getting a weak splatter of fuel.
It would run fine in the morning and would starve for fuel in the hotter evenings. As soon as I thought it was going to die and pulled off the road, it would idle fine. Turned out to be a worn fuel pump eccentric. I only found it when it finally got bad enough to stop delivering fuel altogether.
Bypassed it with a Purolator electric pump.

[lust4speed]

An electric pusher pump is a band-aid approach -- but a really great band-aid fix.

1. It will pre-prime the carb after the car has been sitting for awhile. Much less strain on the starter and electrical system with the engine firing within a second or two.

2. If the problem is with a suction line sucking air, the pusher pump will pressurize the bad line with fuel and you will see where the mystery leak is. Even if you don't, the engine is going to run fine.

3. If the problem is with a weak mechanical pump or eccentric, the pusher pump will supply enough additional fuel to keep the carb full.

4. If it is truly a vapor lock situation, then the pressure pump will keep the fuel line under pressure and the fuel in a liquid state (compared to vacuum which easily allows fuel to boil into vapor).

I've come across the desert through New Mexico and Arizona with temps hovering at 107° in the shade with my A/C blasting, and the Edelbrock Thunder Series 800cfm carb never burped once even on hot starts after refueling or after lunch. It did fine crossing the Rockies also...

[Greg Reid]

Boy, that's a great photo Mick.

[gotyorgoat]

Sounds good. I plan to check the pressure with the mech pump in the next few days and then maybe install the electric pump. The question is do I leave the mech pump in place or bypass it all together to eliminate the heat that is passed from the block to the mech pump.

If I bypass the mech pump, the return line wouldnt work anymore since it is only connected to the body of the mech pump. Maybe I could get the fuel filter with the outlet to connect return line.

[1967Tempest]

Here is a less than $20.00 option that might help. This has helped some friends in the past.

Its my $0.02

Dave

http://www.summitracing.com/parts/edl-9265

[lust4speed]

Originally Posted by gotyorgoat

...If I bypass the mech pump, the return line wouldnt work anymore since it is only connected to the body of the mech pump. Maybe I could get the fuel filter with the outlet to connect return line.

You can get by with a small pulsator pump if you maintain the mechanical pump, and only run the small pump to prime the engine after a week of sitting, or if you are worrying about a vapor lock situation. When you go to only an electric pump, then you have to step up to a larger and more expensive pump. This Mr. Gasket pump from Summit would make a good booster pump: Mr. Gasket Pump. The vane and gerotor pumps won't allow fuel flow through them when they are off, so they shouldn't be used unless you plan on leaving them on all the time. we have plumbed a bypass with check-valve around them so we could use a bigger pump, but the additional plumbing was expensive.

My current setup on my cruiser is an off the shelf AirTex mechanical pump, stock fuel lines, and a little pump back at the tank. So far I haven't had to use the pump except for priming. What I did have was the standard racing setup of -8AN aluminum line, Mallory 140 pump into a dead head regulator. Had a minor problem with the pump over heating running it dead headed, so changed out the regulator to a bypass and installed a 5/8" hose return line. That worked fine for awhile, then the Mallory gave up (probably from previous dead head running). At this point I threw in the towel and went back to basically a stock setup adding the pusher pump. Absolutely no problems so far, and am really happy with the simplicity. The cruiser has the 400ci engine with a small HR cam - so really no big fuel demand to worry about.