Fuel System: More Trouble With Carburetor .............

[reichsrundfunk]

Hi again, all,

I'm starting to run into more problems with my 63 Lark in the carb. It is a Stromberg WW 2Bbl and the engine is the 259 V8.

The other day, after driving about an hour in unseasonably cold weather (low 40's for this time of year) I shut the car off for about 3 hours. When I went back out and restarted it, the inlet valve once again acted up (failed to completely close) and the carb loaded up. I quickly stopped that by tapping the carb, inserting a screwdriver in the throat to keep the choke open and floored it and it quickly restarted and ran fine the rest of the day.

Today, I drove the car around 35 miles and it ran perfectly. Let it sit for about 30 minutes, hopped back in and took off. After a few minutes I noticed the engine seemed to be bogging when mildly accelerating during run (it idles fines and takes right off from a dead stop) but once began to feel like it was starving for fuel momentarily while leveling off from acceleration. Since then when I ease onto the throttle lightly while running, it stumbles, and bogs a bit. If it tramp down harder on the throttle it accelerates just fine, but as I level off, I feel it running unevenly as though the car is borderline starving. If I gently ease down on the gas it will stumble and bog even more, but if I throttle up more firmly, it responds beautifully. All the time it is idling just fine.

I have done a bit of reading, and there are suggestions that I rich up the idle screws a bit, and some comments seem to indicate it is not an accelerator pump issue. One person who is a carb tech indicated that normally fuel is run thru the idle jets even when cruising up to 2000RPM and if the idle mixture is too lean it will cause bogging like this on gentle accelerations.

I'm at a loss. The inlet valve is brand new - less than a month old. It should be seating and opening just fine. The float is adjusted correctly and is not hanging up. I am running about 8oz of Marvel Mystery Oil in the gas to keep everything lubed and smooth, and since using that have noted a nice little increase in power.

What do you guys think is going on? Should I richen up the idle screws a bit? Why would they suddenly go "out of adjustment" if that were the cause? This is getting very, very frustrating. I've rebuilt this carb once but have not completely eliminated the fuel problems - all of which began when we switched over to winter formulated gas! Should I just replace the carb with a rebuilt at this point?????????? Grrrrrrrrr!!!!!!!!!!!!!!!! :-(

Thanks,
-George-

[doofus]

Hey George check the power valve system. sounds like it is losing the vacuum signal,warped bowl cover can cause this or bad gaskets. Doofus

[StudeRich]

The way it goes well with a lot of throttle, and stumbles at cruise when little fuel is being used, sounds to me like excessive Fuel Pressure. A Vacuum Gauge can be used to test the pressure.

The Carb. flooding is also a sign of this.
A warped fuel pump diaphragm, wrong Pump, bad one way valves etc. can cause this.

[reichsrundfunk]

Ok. The fuel pump is an AirTec from Kanters in New Jersey. It is listed as correct for the Studebaker V8. It is about 6 weeks old. After installing it the car ran flawlessly for around 900 miles then (perhaps coincidentally) the minute we switched to winter formulated gas the troubles developed.

Anyhow, if the pressure is excessive, what is the method to reduce pressure to normal (which is about 4 pounds, correct)?

George

[reichsrundfunk]

Hey George check the power valve system. sounds like it is losing the vacuum signal,warped bowl cover can cause this or bad gaskets. Doofus

You mean the accelerator pump? The carb has all new gaskets which I installed a few weeks back.

George

[reichsrundfunk]

The way it goes well with a lot of throttle, and stumbles at cruise when little fuel is being used, sounds to me like excessive Fuel Pressure. A Vacuum Gauge can be used to test the pressure.

The Carb. flooding is also a sign of this.
A warped fuel pump diaphragm, wrong Pump, bad one way valves etc. can cause this.

By the way: is this vacuum gauge one which is designed to read fuel pressure in the fuel line running to the carb? Can I get one of these at an AutoZone or NAPA store?
George

[pinehurstbob]

I am not sure your trouble is in the carb. I run the same combination and tried to resolve the same symptoms except for the flooding and my problem turned out to be the vacuum advance on the distributor. Fuel pressure should be 3 to 5 lbs so 4 should be correct. Be the way I had an electric fuel pump fail after 2 summers and about 6000 miles of driving this past summer on the way home from Dover. The pump still ran, that is the electric portion was OK, it just pumped less and less till it quit all together. So just because a part is new don't rule out the effects of ethanol & today's manufacturing standards. I now carry a spare pump to go along with ignition parts. Good luck.

Bob

[doofus]

Hey george, if its a fuel pressure problem as in to much pressure wouldnt the tailpipe be sooty black? Luck Doofus

[Son O Lark]

I would try raising the float just a tad. Even if it is already to spec. IIRC our carbs do better on modern gas with the float just a bit higher. It can't hurt to try.

[reichsrundfunk]

OK, the story so far:

Today I connected a fuel pressure gauge, warmed up the engine and checked the pressure. The needle was flickering between 4 and 5 pounds, meaning 5 pounds during the pumping action and down to 4 pounds between pumps. I installed an inline fuel pressure regulator, in which you can dial in the pressure desired. Setting it to 3.5 pounds made the engine run anemic when throttled up over about 2000 rpm or so. Dialing it up to 4 pounds the engine idles nice and throttles up to any rpm, no issue with starvation, bogging during light acceleration, all very smooth.

So I took it out onto I78 between Easton and Bethlehem, all good nice, smooth good responsive power. Then came back using localroads, about 35 - 45 MPH. Again, all smooth and nice. As I got back home and up to the garage I noticed the engine was idling slower and rougher a bit, so I pulled it into the garage and got out. The exhaust was popping very slightly and when I opened the hood and pulled off the air filter - - -found the top of the car was wet again. So with the engine running I took my trusty little light hammer and tapped the top of the carb and like magic, the idle went to normal and engine was perfect again.

So obviously, the inlet valve is still periodically allowing gas to get by when it should be fully closed off and the carb bowl is loading up again. Now, the inlet valve is about three weeks old, is brand new, not a used one. The float is set at the correct specified height - and not higher which would raise the fuel level even higher in the bowl. No problem with fuel starvation at run, but the inlet valve seems to be not fully closing 100% of the time. And the float seems to be floating just fine, not sinking to the bottom of the bowl (I've seen that before and it's very obvious!)

Now, what are the thoughts amongst us all? I personally think the issue is the carburetor and it's time for a rebuilt from Dave T, etc. I think I have effectively eliminated fuel pressure as a problem, and by tapping the carb top with the hammer when it was fully warmed up and idling rough after a drive to see the idle return to perfectly normal tells me the basic issue is in the inlet valve, or valve control (float).

Thoughts?????????????

-George-

[doofus]

Hey George, about now if you havent driven the car again i'd pull off the carb top and look in the float bowl for loose bits or possibly the float pin retainer has come astray. rust on the inside of a good looking fuel line can trip you up also. are you using thread tape on the fittings, this can be a no no also. sure sounds like something is collecting behind the needle and seat holding it open. you might try this, warm up the engine then shut it off and remove carb top and start it up again less top, this is tricky so keep your extinguisher handy. the float bowl will stay full and you can watch the float do its thing. any chance the float hangs on the bowl sides? keep after it and we'll try to help any way we can. oh the accel pump is sseperate from the power circuit. the pump gives you get away gas and the power circuit gives you keep going away fast gas. if you want a book explanation i'll send copies from a repair manual. Keep at it Doofus

[reichsrundfunk]

Actually I got brave and drove it out to Newburg and back (about 12 miles each way). Ran perfectly - smooth as silk but I like the ideas you posted, Doofus. An inline fuel filter would solve the rust issue if it exists and I have one which I'll install over the weekend. As for the float, I can inspect it's travel very closely and if there are any obstructions or anything looks too close for comfort I can fiddle with it and try to get a better center. I had a mechanic who specializes in classic cars swap out the fuel pump for me, as I was just too busy to tend to it and had to drive the car to New England a day later. I seriously doubt he would have been so dumb to use tape, but anything is possible. Hes a guy older than myself, so if he did use tape, it was a senior moment. And it would be easily correctable.

Will keep you all posted, and thanks!
-George-

[Son O Lark]

OK, the story so far:

So I took it out onto I78 between Easton and Bethlehem, all good nice, smooth good responsive power. Then came back using localroads, about 35 - 45 MPH. Again, all smooth and nice. As I got back home and up to the garage I noticed the engine was idling slower and rougher a bit, so I pulled it into the garage and got out. The exhaust was popping very slightly and when I opened the hood and pulled off the air filter - - -found the top of the car was wet again. So with the engine running I took my trusty little light hammer and tapped the top of the carb and like magic, the idle went to normal and engine was perfect again.

George-

This was the first you've said something about having a engine wet from gasoline.

[conrad01]

if the needle and seat need replacing the engine will run good while driving. When parked or idling is when it will start to flood. You are going to have to remove the float and needle and then use compressed air to blow and crap out of the fuel inlet.. Make sure there is a fuel filter on just before the carb.. There is also a possibility the seat wasn't cut properly and the needle wont seal and or the float is too heavy.. Or when the carb was rebuilt the seat wasn't replaced and the needle is not centering its self to seal properly.. Carbs can be a pain..

[reichsrundfunk]

This was the first you've said something about having a engine wet from gasoline.

Only the carb. When this occurs gas comes out from the accelerator pump shaft hole and the top and sides of the carb get wet. Typical flooding scenario. I tap the top of the carb gently with a loght hammer and imediatly it stops and will operate perfectly till the next time it happens, whch could be in a day or a week. It is completely random. Well before going further I am going to install an inline filter and I will carefully check the float and float mechanism. Beyond that if I still cant get it, I will probably rteplace the carb with rebuilt that was done by someone who is good at it.

The needle and seat were replaced last month first thing when this situation began, and it cured the problem for a short while, but its back.