72 C10 fuel leak from carburetor

[thahemp]

I have been reading up on these forums for the past couple months since I got my first C10 project truck. Excellent resource I must say. I'm using the truck this year as a DD during winter as our other 2 cars are grounded on any day with white stuff.

This is the first time I have tried to start the truck (350/TH350) when it was cold outside. It's in the 20s today. The motor has an Edelbrock carb with electric choke. It has been running pretty decent up until now. It started a little slow the first attempt and ran OK for maybe 5 seconds, then started stalling and died. I was able to get it started again by giving it some gas. I was able to keep it running by holding the RPMs up a little with the gas pedal. It smooths out with some RPM, but won't stay running when I get out to watch the motor.

I noticed after the 2nd start that fuel was leaking from the passenger-side rear brass screw assembly on the carb with the motor off. I smelled it first. So I decided not to start it anymore until it clears out and I have a fire extinguisher handy just in case...

This is my first carbureted project car. I'm used to LS engines and EFI. So I have been reading everything I can find to catch up. It looks to me like the first thing I should do is rebuild the carb. Lots of mentions of float problems causing fuel to leak with the motor off. I wouldn't be posting though if I knew what to do! What would you all do?

Here are some obligatory newcomer pics. I love my C10, even in its current form.

[davepl]

Square bore or spread bore? Edelbrock has offered variants of both the Carter AFB and the Rochester Quadrajet under the 'Edelbrock' name.

It likely won't be properly drivable in the cold with an open filter element. You should ideally put the the heat stove, thermac valve, stove pipe and air cleaner back on.

But, it should still idle without that stuff. Generally if it starts cold then your choke is fine, that's all it does. And the return spring on it needs to be strong enough to hold it closed.

Once started, you couldn't keep the choke closed or the engine wouldn't run. So one of two things is likely happening:

- The choke door is opening (more than it should) because the spring is weak, or
- The vacuum system that pulls the choke open by (normally) about 1/4 inch isn't working or is misadjusted

Likely the latter. On a qjet you bend the pulloff rod, but I'd highly recommend a manual before you start bending things.

This all assumes, of course, that everything else is in proper running order.

PS: That's a lot of rubber fuel line. Even if its not the right carb I'd get the pump-to-carb line from an auto parts or repro vendor. If it doesn't thread into the carb then you'll still have rubber hose but only a couple of inches instead of a couple of feet. Otherwise, you and I both know that hose will fail eventually, just neither of us knows when.

[KSWes]

Link This is an episode of Detroit Muscle where they rebuilt an edlebrock carb. Might be worth a look. It came up this season and I remembered it. Good luck! Welcome to the board!

[thahemp]

Originally Posted by davepl

Square bore or spread bore? Edelbrock has offered variants of both the Carter AFB and the Rochester Quadrajet under the 'Edelbrock' name.

It likely won't be properly drivable in the cold with an open filter element. You should ideally put the the heat stove, thermac valve, stove pipe and air cleaner back on.

But, it should still idle without that stuff. Generally if it starts cold then your choke is fine, that's all it does. And the return spring on it needs to be strong enough to hold it closed.

Once started, you couldn't keep the choke closed or the engine wouldn't run. So one of two things is likely happening:

- The choke door is opening (more than it should) because the spring is weak, or
- The vacuum system that pulls the choke open by (normally) about 1/4 inch isn't working or is misadjusted

Likely the latter. On a qjet you bend the pulloff rod, but I'd highly recommend a manual before you start bending things.

This all assumes, of course, that everything else is in proper running order.

PS: That's a lot of rubber fuel line. Even if its not the right carb I'd get the pump-to-carb line from an auto parts or repro vendor. If it doesn't thread into the carb then you'll still have rubber hose but only a couple of inches instead of a couple of feet. Otherwise, you and I both know that hose will fail eventually, just neither of us knows when.

Great info, thanks. To be 100% honest, I don't know exactly what I have for a carb setup. I will look closer tonight when I have more time to play with it. The choke had been working mostly right up until today. I always had to tap the pedal to make it idle down.

What do you make of the fuel leak? I'm onboard with getting rid of the rubber fuel lines. The fuel system is what the previous owner told me he spent the most time messing with. You can see it's more of an "A for effort" sort of job! It also has me wanting to dig into things just to see what all has been done. I don't mind spending money on it. I intend on restoring the truck next year. I thought it might make it through a season and I could catalog all of its issues. Kinda hit the pause button here.

Originally Posted by KSWes

Link This is an episode of Detroit Muscle where they rebuilt an edlebrock carb. Might be worth a look. It came up this season and I remembered it. Good luck! Welcome to the board!

Thanks for that. I think I have seen that one. I wanted to seek some advice on whether a rebuild would be a good first course of action. It looks like I still have some things I can check before I do a rebuild.

[Wrenchbender Ret]

With fuel leaking like that you have a needle & seat problem. It either has dirt in the seat or the float is bad.

[thahemp]

After some more research, I believe I have an Edelbrock 1406. Also, it is leaking from the passenger side throttle shafts. I don't believe it's leaking on the driver's side, but I'm not 100% sure of that. I have found several useful threads on these carbs now that I know what to call the parts I'm having problems with. A stuck needle overfilling the bowl seems to match my symptoms pretty well...

[thahemp]

Originally Posted by Wrenchbender Ret

With fuel leaking like that you have a needle & seat problem. It either has dirt in the seat or the float is bad.

Beat me to it.

[thahemp]

I watched a lot closer this time while I was forcing it to stay running and the whole damn carb fills up with fuel. Something is plugged up! I'm going to go ahead and clean and rebuild it. The carburetor is off the truck, and it is a 1406.

[Augi]

you might just need to tighten the bolts up, It stopped mine from leaking. These old engines like to rattle themselves loose from time to time.

[thahemp]

Originally Posted by Augi

you might just need to tighten the bolts up, It stopped mine from leaking. These old engines like to rattle themselves loose from time to time.

I'll give them all a good once over when I put everything back together.

I took the top end of the carb off tonight. The needles actually looked OK to me. No grooves or gunk on them. One of the floats is full of fuel though. That is likely my culprit. I'm glad I took this thing apart. It is absolutely filthy! It needs cleaned BAD. So my interpretation of what's going on here is that the float filled with fuel. That bowl overfilled and overflowed into the barrels and that's how it was getting into the passageways for the throttle shafts where I saw it leaking out after the motor was off.

[thahemp]

Replacing the floats and rebuilding did the trick. It's so cold here right now that I didn't spend much time readjusting the carb when I put it back on.
It seems to go rich and bog on tip in if I give it too much pedal. That's not surprising after all the crap I cleaned out.
She was back on the road doing work in the snow this weekend.

[KSWes]

Nice work! Looked like it was due for a little scrub-a-dub.

[thahemp]

Thanks! I need to start thinking about a tranny rebuild now. The cold weather has shown me how bad of shape it's really in. It can be hard to get in gear and it howls a lot. It only howled while coasting when it was warmer outside. After seeing the shape that carb was in, I'm inclined to take everything else apart too. This truck is filthy everywhere. Maybe new fluids in everything this weekend will help limp me along for a while.

[KSWes]

That's where it all starts next thing you know you'll have it stripped down to the frame.