The Stovebolt Site Forums The Shop Area Engine Shop Need help, still cant get it to idle

After figuring out how to clean and rebuild my Carter YF 2100s carb, I proudly placed it on my engine (235) and hooked up the linkage. Everything was working like new, primed the bowl, float set to 9/32. Went to start it up but had the same result as before the rebuild. engine turns over nicely tries to sputter to life fires a couple of times and then dies. Gas is seen spraying out the top of the air horn in a fine mist. I am new to all this but I am dying to get this thing running and idling so I can tune it up right and move on to the brakes and such. I am so close, I am thinking new fuel pump that I bought from Classic car parts might be pumping too much fuel? I open to any all ideas. Thanks in advance for any and all ideas.

Purney,


If a fuel mist is being pushed out the carburetor, then it would seem like one or some of the valves aren't seating properly. Have you taken a compression check on the engine or looked at the top end with the valve cover off. I don't remember if this was covered before.

Stuart

Also, depending on how much is spraying out, you may have the floats too high. If it is a fine mist or vapor it most likely will be like automarc said. If it is more of a stream, then your floats may need readjusting.

It is spraying out in both droplets and a mist. engine makes a sucking sound. I will adjust the float a bit. I that doesnt work then I will pop the valve cover. What am I looking for as far as the valves not seating? I will do the compression check as well.

If fuel is spraying out the TOP of the airhorn, I would agree with Stuart that possibly one or more of the intake valves are not seating. This would cause a pressure in the intake manifold instead of a vacuum, thus blowing the fuel out the top.

A compression test will prove or disprove this diagnosis.

Jon.

In addition to all the good info already given I'd check for a vacuum leak too. Sometimes a wiper motor or vacuum advance canister goes bad, or it could be a cracked or loose hose. Just a thought.

Waldo: Ill check the hoses. Thanks for the suggestions

Stuart/Carb king: What am i looking for in terms of compression? Will a visual inspection tell me anything? How do I fix valves not seating?

Purney,

Your compression check might show one reading that is quite a bit different from the others. This will indicate problems with that cylinder. You could possibly have a blown head gasket, cylinder to cylinder without involving the water jacket.

The strange thing here is that the engine starts and runs for a few seconds. Do a search in this forum on 'compression test'. You will find info on the proper way to do it and what the results might indicate. Have you checked the timing and verified the wire position/firing order.

If a intake valve is hanging open or is burnt to a crisp, when that cylinder tries to fire it usually blows a fireball back through the carburetor. The compression test will be a good starting point to troubleshoot this problem some more.

Stuart

Great info, thanks Stuart. I have checked wire position and firing order, all is well. Timing I have not done yet.

I am not getting a fireball coming up out of the carb its just unburnt fuel spraying up. Ill do the compression test and let you all know. Thanks so much. I am going to get this going if it kills me.

Stuart - If the valve were burned, then you would get the fireball (when that cylinder fired), but if an intake valve were simply sticky, it could be slightly open on compression stroke (thus pressure and the spray), but still close sufficiently by the time of ignition to not have the fireball.

Purney - If the engine has set without running for a number of years, this condition is quite common, and often, will clear itself with use.

Jon.

If gas is running down the throat of the carb. I think your needle & seat arn,t working. Either the float is to high or a foriegn particle got in the needle. How about the float? If a float leaks gas into it, it will be heavy & sink down & cause a high fuel level.

That seems like the most logical wrench bender however the needle and seat are working. I tested it by blowing through the fuel inlet and it shut off when the I moved the float up. I will be checking to see if the float, floats. I should have done that when I was rebuilding the carb.

also I find it strange the fuel could be spewing up out of the air horn. Shouldnt air be sucked down?

Purney,

It is strange it is spewing out...hence the thoughts about non-seating valves and blown head gaskets. If what you are seeing is actually a fuel/air mist being expelled from the carburetor under force, the pump (engine) must be the culprit...maybe!

Stuart

What do you think about the timing being way off? I know you mentioned that Stuart. Ill check it all and let you all know. Thanks for your help

Purney,

That might have been a bum lead on my part. Even if severely advanced, the intake would be closed and the piston would be coming up on compression. Excess advance will show itself by bumping the engine backwards as it fires WAY to early and drives the piston back down..against normal rotation.

A compression test will let you see what is going on inside the engine...this would be the first order of business.

Stuart

I checked the plugs after trying to start and they are wet and smell of gas as well as sooty. Carb still spews gas out the top. she wants to run and fires for about 5 seconds or so then it seems like it is flooded. wires are all in proper order and firing sequence is correct. I checked the #1 cylinder and it is at TDC when the knob is pointed to the correct spot on the distributer. Ill get the compression test done and let you know the results. Am I right in assuming that if the carb was flooding it still wouldnt explain gas spewing up and out?

Purney,

I think your right...a normal flooding situation could fill the manifold and maybe the entire engine, but wouldn't pump out the top of the carburetor. I think something else is going on...something doesn't make sense.

Stuart

I had a Niagra Falls of gas coming out the top of my old carb until I got the fuel pressure down to 3 lbs or less. Just a thought

Most carbs have a vent tube from inside the bowl/float area. I have seen carbs spew streams of gas out that vent tube when the float got heavy, or the needle and seat got trash under it.

If the plugs are wet with gas, my bet is the floats are either too high, or there is a piece of trash that worked it's way up under the seat causing the bowl to overflow. It can't push it all through the small nooks and craniies, so it hunts the least path of resistance, right out the top. Then a lot will fall back into the throat of the carb.

A lot of times the old brass floats have lost their floatyness over time- they get pinhole leaks in the solder joints. I ended up replacing the float in my "B" and it made a huge difference.

Also, I've found that the needle and seat in a lot of carb kits don't seal very well. The reason is that the originals had a chamfer in the seat where the needle rides, and the new ones have a shoulder. I take the old "BB" check ball found in the "B" and a nail-set style punch and use it to stamp a chamfer into the new seat and it makes a huge difference. It gives the needle tip more surface area to seal against and seems to keep it from hanging up.

Mine won't idle on it's own either... 1958GMCNut is hoping a carb rebuild will help and feels the float may be the culprit too...

I'll be watching this topic with interest until next week when hopefully he comes over to try to solve the problem...

~Trev

Great feedback, thanks all. I will take the air horn off the Carb and recheck the float for "floatyness". I just rebuilt the carb but didnt check that as I am just a newbie to all of this. Compression check is also on the docket. I did install a new fuel pump from classic car parts. How do I check the pressure it is putting out?

When you rev it up does it return to idle RPMs quickly?.....or does it hang at a higher RPM for a bit before slowing down to idle RPM?

That could indicate a intake leak.

I cant get it to idle for more than about 5 seconds beofre dying. I cant wait till I am able to hear it at high RPM's!!

Most vacuum gauges have a pressure side that you can check fuel pump pressure with. Disconnect the gas line going to the carb & hook it to the gauge. Crank the engine a few times & the gauge will show the pressure. If gas is running over like that it has to be getting by the needle & seat. It is either not seating or too much pressure which I dought. Try this. Pinch the flex line shut with a clamp or vise grip. Start the engine & run it till it uses all the gas in the carb & dies or almost dies. Then take the clamp off & start it again. This will drop the float to the bottom & if their is a particle of dirt it will flush it out.

Well I found the problem. Thanks for all the advice here, you guys are the best. I had my 6 year old crank the engine while I put my hand over the airhorn on the carb...suck...suck...suck...suck...blow...blow. That didnt seem right and there is the answer to the gas blowing back up through the carb. I popped the valve cover and turned the engine over again. didnt really see anything until I looked at the push rods. #5 and #6 push rods are bent and out of place and obviously not allowing the valves to open and shut properly. Whats my best way to deal with this issue now?????

Purney,

Great news. I think you can loosen the rocker arm adjusters all the way and slide the pushrod out. If they aren't too gunked up, the rockers can slide sideways on the shaft for a little extra working room.

You will have to get two new pushrods...I don't think you want to straighten them. The most important thing will be to see if the valves are free to move and not frozen shut with varnish. This could be why the pushrods bent.

Stuart

Thanks Stuart,

What is the best way to work the valves and get them working freely? Should I do anything with the others? You were right from the beginning with stuck intake valves, that must have caused the bending. Which valve is intake and which is exhaust?

Purney,

I have never experienced varnished valves and wasn't a 'believer' until I joined this forum. Maybe someone will jump in with a tried and true method to make sure the valves are 100% clean and free.

If this is indeed a varnish deal, I have heard nothing short of pulling the valves and cleaning stems and guides will cure the problem...it's tenacious.

With the valve cover off, you can look at the valve spring groupings and compare their location with the runners on the intake and exhaust manifolds. It will be obvious which are intake and which are exhaust. Good luck and hopefully someone will show up with a secret formula for 'in situ' varnish removal.

Stuart

Purney
I used a rubber hammer to tap the top of the valve, with the rocker removed while spraying WD-40 on it and after a while the WD-40 washed the varnish and the minor surface rust away. You can tell when the valve is opening and closing properly by the popping noise it will make. It might stick open for the first couple ( or more ) taps. If it sticks
just get a small block of wood and a screw driver and pry it back up. this is a bit of a non proffesional way to loosen up sticky valves but it has worked for me in the past on a couple of old tractors that sat for a long time, just make sure you tap it square on the top and not to hard, you will be able to tell how hard to hit it after a couple of lite taps.
good luck
DS

Purney, try this little ditty;
exh, intake, intake, exh, exh, intake intake, exh, exh, intake, intake, exh -- "I got rythem, you got rythem, who could ask for anything more"!!!
Denny Graham
Sandwich, IL

D sinclair, et all: Both valves are soaking currently in PB blaster, I do see minor rust on the rocker arms as well, should that be a concern? I will give your routine a whirl tonight. Hopefully I can report back to all you fine folks that she runs like a sewing machine after replacing the push rods, thanks to your support. Thanks to Denny's little ditty I have a intake stuck open on #5 and an exhaust stuck closed on #6. Its a great little song, good rythem, but a little hard to dance to!