Edelbrock carb overflowing with gas

[JMD]

Hey all,
Today was supposed to be the day when my 4 year project made it's maiden voyage, but the truck had other ideas. I have a reman Edelbrock 1411 sitting on top of a bone stock 454 with a stock mechanical fuel pump in my k10. The carb has worked flawlessly up until this point, and I've driven the truck a few miles around the block with zero issues. The last time I had then truck running was memorial day, and it ran great.

Fast forward to today, and the carb spews gas out of both vents. I figured there might be some varnish or crud where the needles seat, so I tore the carb apart and THOROUGHLY cleaned everything inside. No change, still runs for a second and then starts pouring gas out the top of the carb. Something is obviously allowing the fuel pump to keep dumping gas into the float bowls. I tore apart and cleaned the carb two more times and got the same result each time. Float bowls and needles look brand new at this point.

What else could the problem be? I can't imagine the float height got all out of wack just sitting there for a few weeks, and I never touched the fuel pump so it can't be too much fuel pressure causing the issue. Any help is greatly appreciated, I'm going nuts over here.

[HO455]

Here are a couple of ideas. Check to make sure the float isn't catching on something and not closing the needle. How is your tank vent? Try running it with the gas cap off to see if the problem disappears. Are the floats brass or resin? If brass shake them and listen for gas inside. Resin ones will absorb fuel and sink or float at a lower level. The new ethanol gas is hard on these floats. Are the gaskets under the float valve seat in good condition? Are the needles flawless? No wear marks where they contact the seat? Did you set the float level with the gasket in place on the airhorn?

['63GENIII]

IIRC, the Edelbrocks take a little less pressure than say a Holley. I think it is around 5psi max. Not 100% sure but am positive that it is less than what most people would think to be normal. I ran a 1406 for a while on my 396. Had to dial back the FP to 4 or 5 psi. Then it seemed to boil the fuel when shut off. Used a phenolic spacer to fix that. The last thing was when parked on a incline (my driveway) it would lose fuel out of the vents and onto the manifold.

I ended up running a Holley. Not saying it was better, just what I was used to. They have their own issues too.

I would say that the issue you are seeing is a result of too high of FP. Get a gauge on it, see what EB recommends and maybe get a regulator on it. It sounds like the needles are getting blown off of the seats.

[randy.powell]

Good advice in Post#2 IRT the floats. I had put a brand new Edelbrock last Summer and it ran great - for about 3 weeks. Then I had flooding issues. So bad it wouldn't even start. Pulled my hair out checking everything like in post #2. Final solution was that the drivers side float (brass) had a pinhole leak in it the where seam was soldered! Took about 3 weeks before enough gas to leak into the float for it not to float so good...

Discovered it when disassembling it for the umpteenth time and for whatever reason shook the floats and felt gas sloshing around in it.

Sent it back to Jegs and they sent me a new replacement.

All has been good since.

[drewbert41]

I am having the same issue with my 2bbl carb.

[JMD]

Thanks for the replies,

Each time I disassembled the carb I took the (brass) floats off and didn't notice any gas sloshing around inside of them, but it is something I could have missed. I'll check tonight after work.

Needles and seats all look great with no goofy wear marks or any other visible flaws. I haven't checked float height or fuel pressure yet, but I don't see how those things would change just sitting in the garage for a couple weeks.

My gas tank has no vent, I'm assuming there's one in the cap. What's the reasoning behind removing the gas cap? Would expanding fuel force that much gas through the pump and into the carb?

If only one float was stuck open, would fuel boil out of both vents or just the side that was stuck open?

[AussieinNC]

Apart from the obvious junk in the needle and seats...or non floating floats...
which other highly intelligent users have detailed...

Does you fuel pump have a return line fitting on it , and if yes, it is plumbed back to the tank. I have witnessed overflows due to excess pressure of the pump at idle, usually a capped off return port on the pump.

It will only take one of the seats to leak over and the carb will boil fuel over...put a pressure gauge in the fuel line between pump and carb...it should read no more than 5 PSI...at idle and run...any more, and you will have issues as you describe.

Does the pump look like the two port pic below or the three port pic below?

[JMD]

I have the two port pump, no return line.

Installing a fuel pressure gauge would be a huge pain in the butt due to how my fuel line is routed. I'll install one if absolutely necessary, but I don't understand how fuel pressure would be a problem all of the sudden. Can a float's ability to stop fuel flow deminish over time?

[randy500]

does the carb have a screen behind he inlet fitting? If it doesn't then you probably have debris holding the seat open. Did you check the hang height of the floats? They could be hanging too low and catching on something. You should always check float height upside down and hang height right side up.

[AussieinNC]

You havent mentioned any inline fuel filters in the system...

This sounds just like the following scenario:

Clean tank in truck that oxidizes over time during the build...fresh fuel washes oxidation into fuel line...fuel pump pushes "dirty" fuel into carb...might run ok for a couple of days until a bit of crap or even worse, fuel pump diaphragm rubber flakes off and lodges under a needle and seat...

1/ Put a good quality fuel filter in the suction line between the tank and the pump.
2/ Put another fuel filter between pump and carb
3/ Clean out the carb once more, fully removing the needle seats and inline port based filters often found in those Edelbrock carbs...I am attaching the page from Edelbrock carb manual, look the hang setting...usually about an inch and the float setting, usually 7/16"...

I will almost guarantee the fuel pump diaphragm is breaking up due to the ethanol in our fuel nowadays...

I dont run rubber pumps any more...I use electric pusher style, and always two filters...

Hope this helps you out...

[HO455]

Originally Posted by JMD

Thanks for the replies,

My gas tank has no vent, I'm assuming there's one in the cap. What's the reasoning behind removing the gas cap? Would expanding fuel force that much gas through the pump and into the carb?

Yes it does happen. In warmer weather the fuel in the tank expands and vaporizes causing pressure to build in an unvented tank. As sensitive as the Edelbrock carbs are to pressure it only takes 6 or 7 lbs of pressure to lift the needle off the seat. Just an extra 2 psi from the tank added to the pumps normal pressure will make the pressure too high. Pumps without a return line have no way to relieve extra pressure as there is no regulator inside.

I have witnessed these carbs overflowing just parked in the hot sun. Part of the problem on that car was a worn fuel pump that had bad check valves. The other part was a wasp nest in the end of the vent hose. When you remove the gas cap there is no way for pressure to build up in the tank and if that is the problem the flooding should stop.

Another thing to look for is fuel lines that are running to close to the exhaust. This is more of an issue with headers, but it causes boiling in the fuel lines (also known as vapor lock) which will cause flooding.
Both of these things are problems that may not be apparent in cool weather but show up in warmer weather.

If all of the posts above don't help you might try installing a carb heat insulation block between the carb and the intake manifold.
Good luck.

[JMD]

Thanks for all the help guys, I got it figured out. Turns out the problem was a lot more simple than I thought, one of the floats developed a crack and had filled up with fuel. I don't know how I missed it the first time.

$14 and 15 minutes later I was on the road! Went for a 30 mile drive with no major problems, couldn't be happier!

I appreciate all the suggestions, now I have a better idea of what to look for if I have problems in the future.

[leddzepp]

Great to hear

[LockDoc]

Originally Posted by JMD

Thanks for all the help guys, I got it figured out. Turns out the problem was a lot more simple than I thought, one of the floats developed a crack and had filled up with fuel. I don't know how I missed it the first time.

$14 and 15 minutes later I was on the road! Went for a 30 mile drive with no major problems, couldn't be happier!

I appreciate all the suggestions, now I have a better idea of what to look for if I have problems in the future.

Thanks for posting the solution. Too many times people are so excited about getting to drive their truck again they forget to come back and post the solution in the thread...

LockDoc

[HO455]

Originally Posted by LockDoc

Thanks for posting the solution. Too many times people are so excited about getting to drive their truck again they forget to come back and post the solution in the thread...

LockDoc

What he said!

[demian5]

Originally Posted by JMD

Thanks for all the help guys, I got it figured out. Turns out the problem was a lot more simple than I thought, one of the floats developed a crack and had filled up with fuel.

My friends holley did that, and since I don't throw away anything car related, i had other floats. However after years of dealing with carbs, one of the first things I do when rebuilding is sink the floats in water and look for bubbles...

Glad you found it, it's always nice to fix complex issues yourself.

[LostMy65]

Saved for future reference.