Technical Problem with Edelbrock 1406 carb.

Hi...

Hope some of you nice folks will help a fellow out.

Motor: SBC 350
Year: Block 78, Heads 80 something.
Carb: Edelbrock 1406, about a year and a half old.
Fuel Pump: Electric.

Problem:
1. Fuel coming out of carb at linkage points on auto choke side.
2. Fuel draining back to tank when key not on.
3. When key is in the on position, fuel pressure reads only 3 PSI,
but I have it set to 4 PSI. On the occasions that the problem does NOT show itself, fuel gage shows the correct 4 PSI.

Other info:
Have high pressure fuel pressure regulator set at 4 PSI.
Exhibits problem, 90% of time now.
Backfired a few times.
Hard starting.
If I take the fuel line off carb and plug it, (have sight glass filter) gas DOES NOT drain back to tank.

Please ask for more info if needed.

Thank you,
John

 

It sounds like its time for a good cleaning and rebuild. Needle and seat are leaking, maybe from debris or deposits from this wonderful gas we HAVE to use.

 

What are you using for a fuel pressure regulator. What are you using for fuel?

The reason you get no drain back to the fuel tank when you block the fuel line is simple physics. You have created a vacuum something that your carb cannot do. same as the trick that you can do with a soda straw and your finger. That probably won't drain your float bowl so no reason to worry about it.

You're fuel pressure gauge is only accurate exactly in the middle of its range, so the 3 or 4 pounds is a nominal number. Your fuel pump may not be keeping up when the car is running or it may be that your regulator is not working as well as we would like, if you are using a cheapo fuel pump or regulator these things happen.

My guess without taking the top off the carb is that you have crap in the float bowl and or the needle valve and seat. if you let the car set for any length of time the alcohol in the gasoline gums things up and corrodes things. That is just agues on my part.

No help? Well I tried.

 

Thought so... what about float adjustment? Any chance of that being an "aside" issue?

Thank you for your help,
John

 

Anytime you got the top off check the float level. That's just a given.

 

Sorry porknbeaner...of course that helped. I just missed the post.
Regular unleaded. Top brand (forgot name) high pressure regulator.
Made expressly for high pressure electric fuel pumps. Never a
problem. Has ran fine for over a year. Nothing cheap about regulator,
paid 150 at high end speed shop. They said it was one of the best you
could get for non-racing applications.

I always kept a close eye on pressure. Once I set it, pressure NEVER
showed less than 4 PSI.

I'm gona pull the top off now and have a look-see.

Thanks porknbeaner,
John

 

others mention possibility of dirt/crap causing part of problem. you do not list fuel filters. if you have any where are they located? where is fuel pump mounted?

 

unless you have a check valve behind the pump if its a non vane type ( aeromotive ) it will back siphon when you turn the pump off ( mechanical pumps the valves in the pump prevent this as they close when the pumping pressure action stops, vane or gearrotor styles the vanes ( holley ) /rotors ( mallory) act as the valve unless the vanes/rotors are worn ) ,also if your running a high pressure pump with a built in relief you could have jammed the relief valve in the open position , for carbs we recommend a 15 psi max pump or lower ( street cars with low pressure the 6 spi pump is perfect , the 15 psi holley blue is too big ) , if your running a EFI 45-65 psi pump you must have a bypass regulator and return line to the tank to keep it from burning the pump up or jamming the internal bypass on it they do not like to be deadheaded .

this is why on race cars we turn the pumps on for a few seconds before we crank the cars to build up pressure and fill the lines so we do not get a dry start , the carb can not siphon the fuel out of the bowls as the drain port is above the fuel level in the bowl and it makes the air break and allows them to siphon back . you can make a prime button for your fuel circuit to prime the system before keying on the ignition circuit .

 

Thanks guys for all the info.

Did not get back to carb yet... wifie had me repair dryer. Took awhile as I live out in the boonies and did not have new parts to replace, so had to improvise. She's happy now.

On to some of the ideas and questions above.

No EFI, off brand 6 PSI pump inside gas tank set at 4 PSI. Edelbrock carb tech told me to set pressure at 4 PSI. I did and have never had a prob until now.

Stock 350 other than the small towing cam I put in it when I rebuilt it about 1.5 years ago.

Stock inline fuel filter about half way back. Recently new.
Way I see it, the pump should have a built in check valve.

Why does gas come out both linkage bolts that go into the carb on the choke side.

Thanks again,
John

 

Bolts too long and broke into fuel in carb?
Put some thread sealer/Teflon tape on the bolts see if that helps.
Adjust the floats to factory specs.

Nick

 

X6 dirt are the fine fuel we have these days.

 

Thanks Nick...

 

Fuel can not siphon back out of the carb.
I bet you have the carb directly on an aluminum intake manifold and are suffering boiling in the bowls. Fuel will boil at about 145deg and it is forced out of the carb thru the vents - look into the secondaries on either side of the boosters there are wells that the rear airgate rotates in, look into the bottm of the wells and see if fuel is lying there or it is discolored. That is a sure sign.
Heres the sequence, you shut the engine off, the fuel is trapped between the needle & seat and the check valve in the pump, the pressure will read 4psi at that moment in time, the fuel in the bowls will boil and push fuel out and into the engine which lets the float drop opening the needle & seat, pressureized fuel trapped in the line will flow into the bowl raising the needle & seat. The line pressure drops to 3 1/2 and the process repeats itself until the fuel is gone and that is why it is hard to start. And that is why you see different fuel pressures.
Just get a 1/2" phonelic spacer and put it under the carb, it'll insulate it. An aluminum spacer won't help, got to be wood or phonelic.
The fuel dribbling out the shafts happen when the engine shuts off the throttleblades are closed and that last little dribble lands on top of the closed blades and it has to go somewhere. If the carb is new, then no big deal; if old then the shafts might have a ;little slop.
Kinda windy, I know but its the best I can do.

 

the check valve in the tank could have gotten crap in it and is sticking open or the internal bypass on its stuck open this is the reason why you have to run a sock on the pump inlet , as for fuel stains on the linkage it means the bushings are worn or the carb dribbled on the shafts and are leaking out . happens on Oem carbs too . unless there is alot of play in the shaft or its dripping nothing to worry about , holleys started to do this when they went to the teflon strips for bushings in there carbs . on Q-jets we rebush them to stop this . I do not know what the bearing surface is on the E broke Afb clone but more than likely its the base material not brass

 

While there is the occasional boile, it does not happen often. Actually I have a 1" plastic spacer from Summit between carb and aluminum Edelbrock intake.

Thanks for the idea though.
John

 

on some of the GTos and early pontiacs they used a sheetmetal tin between the insulator and the carb to wick off heat , I know on the later O/t ford trucks ( big bronco and f series with v-8s ) they had to do this to prevent fuel boil , its funny how a little peice of metal can prevent the boiling .

 

This also happens when the engine is cold. Start engine and fuel starts leaking out of linkage shafts within 10 seconds. And sometimes when there is quite a bit of fuel leaking out, it will not even start and fuel pressure has dropped down to about 3 PSI..

 

Time for dinner, be back later,
John

 

If it is leaking while at idle the fuel can only come from above the throttle blades. When at idle the secondary blades are closed, the primary blades very slightly cracked open and the idle circuit is supplying fuel from below the throttle blades, right? Then it is obvious that if you have fuel dribbling out the throttle shafts then that fuel is coming from above the throttle blades, that would suggest the float is a tad high and fuel is coming from the boosters. Can you look into the carb while this is going on? You should be able to see fuel dribbling from the boosters when you shouldn't see any fuel whatever, at idle it is all happening below the throttle blades.
Is it overly rich at idle? Like raw fuel running into the engine?

 

Yes... strong fuel smell.
What do the "boosters" look like?
How could the float adjustment have just changed? Never done this before.

If I need to readjust, where should it be, up a bit, down a bit or level with the carb body?

Thanks,
John

 

Needle and seat valve is malfunctioning.
Since they are controlled by the float, the float itself is a suspect until you open it up and see. It could be mechanically stuck, it could have lost its buoyancy and sunk.

Needle valve is either stuck open or not sealing. There's 101 variations and causes of this problem but all 101 have the same fix.

The float level adjustment can change after a needle valve failure. The uncontrolled fuel forces the float up and that bends the tang.

Either way or anyway you look at this, the top comes off first. Once off, if there's ANY dirt in the bowl, clean the entire carb. If there's no dirt in there, change the needle and seat, reset the float and put it back together - Less than 1 hr if youve never done it. less than 10 mins if you have. Cleaning the entire carb will take longer but still just a few hrs.

 

OK guys... I think I may have found the problem, you tell me for sure?

The 1406 has two floats and two bowls, one float and bowl on each side. The one on the side where it is leaking out the linkage shafts, (auto choke side) has about 20 to 25% fluid in it. Gas I guess.

(Brass Floats)

Needles and seats look good. Bowles did have some debri in them but I will clean it out before replacement.

Thanks,
John

 

OK guys... I think I may have found the problem, you tell me for sure?

The 1406 has two floats and two bowls, one float and bowl on each side. The float on the side where it is leaking out the linkage shaft ports, (auto choke side) has about 20 to 25% fluid in it. Gas I guess.

(Brass Floats)

Needles and seats look good. Bowls did have some debris in them but I will clean it out before replacement.

Thanks,
John

 

Aha! There you go, replace the float and problem solved. Good work.

 

Thank you oj...

 

25% fluid inside the brass float,
Yep, that's going to ruin your day.
The float lost its buoyancy and sunk.

When a float sinks, it's telling the needle valve to pass more fuel no matter how full the bowl is.

 

Yep... I know how the float and needle valve works, I just did not not know if that small amount of fluid would make so much of a difference...

Thank you,
John

 

Oh, ok
Sorry to bother you then

 

Um... sorry... did not mean it that way. you are awesome for sharing your wisdom with me

Thanks a ton,
John

 

Common sense should tell you John that a float is designed to be hollow for a very good reason, and that any amount of fluid leaked into it (even 1 % ) would make it useless in a hurry.
But then as we know, common sense is not so common these days.