The Stovebolt Site Forums The Shop Area Engine Shop Suddenly Running Rough w/ Black Exhaust (Flooded?)

Short story: After a few tanks of gas idling in the driveway, and a about a dozen short spins around the neighborhood, finally decided to take my '53 235 for its maiden voyage into town.

She ran like a champ!

Over two days, I put about 100 miles on her: lots of stops for shopping, started every time. Loving life. Even hit 55mph on the highway on the way back from the dump (with a tailwind).

Feeling bold, I decided it was time to take my lady for ride on day 3 -- rather than have her sit by her phone ready to come meet me with a tow strap.

Eagerly, (perhaps too eagerly?) we jumped in, fired her up (sounded great), didn't let her warm up like usual, and backed out of the driveway. Made it 200 ft down the road. Then she died.

She turns over, but only stays running if I'm almost flooring it, and only then she has a loping along, forcefully belching black exhaust. Forget getting her into gear.

My lady walks back to the house for our other vehicle and tow strap (she's a good woman).

Figuring it was flooded, I let it sit overnight in the driveway. Same symptoms the next day.

Noticing my inline fuel filter just before the carb was full, rather than half-full like usual, I thought maybe there was too much fuel gong in. I tried pinching off the gas line going into the pump to reduce gas intake. Same symptoms.

I had a spare set of plugs on hand, swapped them out. Same symptoms.

(A note on the plugs: after turning over for less than a minute (again almost flooring it to keep her alive) the plugs were surprisingly sooty. Well 3 of them were sooty, 1 looked good and 2 were wet with fuel / maybe oil.)

So, still working on the flooded theory, I left the plugs out last night and am going back to it this afternoon.

Any thoughts on what else I should / could be checking?

What position is your choke in?

Choke works. Closed it won't start. Full open the engine catches -- albeit with the issues above. If I close it after I get it started, it dies.

Timing? Did you hear any funny sounding noise? You might try to check timing...if only statically. If you have a fiber camshaft gear it is possible it sheared off a tooth or two. Also possible your distributor was loose and shifted position. Carburetor? Rochester? Have you worked on it? There is a chance the float has failed or stuck...needle could have also stuck open. Look down the throat with the choke open. Do you see raw gas in there? Is there fuel on the manifold gasket or at the point of the throttle butterfly shaft?

Thanks JonG, I'll track these down. Recent carb rebuild, and timing... but the distributor shifting is not unlikely.

Hey ThreeTree,
I am a rookie here and would not usually have anything to offer - except that a similar pattern just happened with me. 1950 GMC 1/2 ton with 216. Ran the best it ever did - took her for a "big" 50 mi trip smiling all the way. Then a week later very hard to start, ran really rough & needed high RPM just to keep ticking. Compression test on #5 cylinder was zero - ended up being a broken intake valve spring. Plug on that cylinder was really dry sooty.
Hope for your sake it is something better - but worth checking the compression.
G' luck
Jim

Thanks GMJim - I've been avoiding, but expecting a more in-depth rebuild... so wouldn't be surprised. Good lead! Thanks. And funny how that "smiling all the way" suddenly can turn into a :-|

Sounds like the float in the carb is stuck open to me. The wide open to keep it running and the belching black exhaust are the clues.

If its a Rochester, the float may be rubbing on the casing causing it to stick. The needle valve on the float may also be stuck open.

You have a piece of foreign matter in the needle & seat. Try this. Pinch off the fuel line with vise grips. You pinched it before but you evedently didn't get it tight enough or it would stop flooding. Start the engine & run it till it uses up all the gas in the carb. & starts to die. Take the clamp off & try it again. Often that will flush the dirt on through & solve the problem. If not you will need to take the carb apart & check the float & clean thr needle & seat. Often the float leaks & gets full of gas.
George

Are you seeing gas pouring out of the side of the carb? A stuck open float valve will cause the overflow to leak out around the throttle valve shaft
It would help to know which carburetor you have.

Just back from vacation and finally getting brave enough to track this down. Turns out it may be simpler than I feared!

The metering jet had shaken loose and was floating in the bowl.

Quick question: is loctite on the metering jet a bad idea?

I'm still playing around with size of jet so not sure I'm ready to commit to one, but it's running smooth at least when the darn thing stayed in it was...

And it's a Rochester single barrel.

Unless something is really messed up, I don’t see why you’d need the loctite.

And my hunch is that the loctite has a greater chance of doing harm than it does of doing good.

Someone with direct experience can correct me.

I don't think LocTite will survive constant submersion in gasoline. Either the threads of the jet or the metering fixture are worn, or the jet needs to be tightened a bit more firmly. That assembly will stand a pretty firm torque without getting damaged- - - -just be sure your screwdriver is a really good fit in the slot of the jet.
Jerry

Don't settle for "close enough" with the screw driver fit. Make it perfect on the bench grinder.

Thanks! Feel like it's pretty torqued... At least I know how to field repair it if it happens again.

ThreeTree53, I just sent this date a thankyou to JonG, Check out the great info he sent to me . Doc.

Three tree 53 This isn't your trouble but might be a tip to remember. Old mechanic I worked with would have people come to him broke down along the road,he would say did the wipers fly-up on their own ?? If yes-he would say timing gears let go !! Puts pressure in the intake,may bend valves !!