94 Carb

[ABento]

I'm working on a 59 AB with Ford 94 carb on it,its in a 34 Ford 1 1/2 ton truck, cold it starts right now,run to town shut it off it'll start with in afew seconds before the fan make s a complete turn, go in the store and come back out and try to start it'll almost run the battery down when it does start it acts flooded, so on another trip I pop the hood and there is gas dripping out the carb at the throttle shaft,Ah Ha I need to adjust the float, well its at the 1 11/32 as it should be, so I'm thinking about building a shield below the phonolic spacer and see if that'll keep some more heat away from it, I believe it has an airtex fuel pump on it would that have excess pressure to cause this, or am I not seeing something else.


Thanks Aaron

[ford38v8]

Aaron, your heat shield idea can certainly be of help, as the phenolic spacer can also. Anything done to keep heat away from the underhood fuel components will help, but ultimately, it's the fuel itself that is at fault. Modern cars use fuel injection, which has no problem, but with carbureted engines, the modern fuel is an issue due to its lower vaporization point.

The biggest gain to be had in heat shielding will be in bypassing the stock fuel pump arrangement, and installing an electric pump near the gas tank. The stock pump being at the rear top of the engine, it gets all the heat and none of the ventilation required to prevent vaporization.

Vaporization creates pressure, backed by the pumps inlet valve, which pushes right by the carburetors needle valve, as it cannot withstand more than 4 lbs pressure. When you shut down the engine and walk away, the pump will completely vaporize the fuel within, pushing it all to the carb, and flooding the engine. No fuel left to push, locked by vapor, the pump fails to even open or close its valves while you run the battery down.

One other thing you can do, that is to open the hood before you walk away from your car. This will allow the heat to escape your engine compartment before the vaporization occurs.

[Tinker]

Might be a coil or condenser issue also. Skip rebuilt coil is a very nice way to check that off.


If your having carb fuel issues, it may need a rebuild or you might have a pressure issue with the electric pump.


I believe henry or nycharlie is your man to help on 94s.

[ABento]

Thanks Alan, several good points there, I just took an electric fuel pump out of the system as I was blaming that for the flooding issue,I think it may have been a high pressure pump as it looked like one of the older round AC pumps and those can be in the 6 to 8 # range and plumbed both the seat tank and aux side tank neatly thru the tank valve, after i put the shield in I'll run it and take along my heat gun and see what the under hood temps are, water temp runs about 170/175 but I wanted to check ity also.


This has been changed over to a modern coil, and the resistor under the dash has been bypassed, the late model coil is 6 volt and says no external resistor needed.



Thanks

[Charlie ny]

AB,
Your issue is typical of excessive wear between the throttle shaft and the base.
Charlie ny

[ABento]

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Charlie,I've got the carb off while I'm putting the shield on,I've checked for play in the throttle shaft but I'll check again,it is tight,it only leaks when I shut the engine off and I'm guessing the gas heats up and spills over the float bowl onto the throttle plates.


Is there a rebuild kit for an airtex fuel pump the extra for this engine needed a diaphram and check valves and the Dennis Carpenter kit's check valves are a tad too small and there wasn't any gaskets with them, air tex says they don't offer a complete kit.
Thank you

[ABento]

Got the shield built and under the carb, now I can see gas ooze out when the engine gets turned off,doesn't have to be hot, makes me wonder if the fuel pump is too much pressure,or could the needle and seat be poor.

[Charlie ny]

If all else fails remove the t'shaft from the base and 'mike' the shaft where it rotates
in the base both ends. Then mike the bore in the base that the shaft rotates in.......
.005 is too much for a 94. 94's are very sensitive to vac leaks AND vacuum balance.
Charlie ny

[ABento]

Pulled it back off, a little sloppy at the linkage side, idle adjustment screw had to be back out quite a way more to compensate for this and both needles had been tightned in too far and were not pretty.

[Chris_AAFord]

I’m having a very simillar issue right now, I put a fuel pressure gauge on my fuel line and found the stock pump produced 5 PSI which is too much. I put a regulator on it which helped but did not cure my issue.

I did all of the above thoughts , replaced the coil and condensor etc and still have the same issue. My fuel line is not hot to the touch so I don’t think my issue is vapor lock.

I just bought a rebuilt carb hoping that will fix the issue. You might want to consider that your power valve could be bad allowing for a easy initial start and then it could flood when you shut the engine off.

Just some of my experience over the last few weeks.

[kegmon]

Ford38v8 - That was the best explanation of vapor lock I've ever read. Thanks!

[ABento]

I'm thinking its not an electric problem as it leaks gas on my heat shield, I've got a new kit coming for it and have the base being bored and new bushings,should be back together tonight or tomorrow,if the problem persists I'll put a pressure gauge in, C&G Ford has sold a lot of the airtex fuel pumps and have hardly any complaints, I'm hoping it was a worn needle and seat,the power valve doesn't leak,at least with a short vacume test.

[ABento]

One of the bridge tubes above the venturies has a smaller end on it than the other one, my spare 94 the tubes are the same size, this is just on the trumpet end the furthest piece of it hanging down, the rest of it is the same, I would venture a guess that both tubes would be the same, any thoughts on this.

[ford38v8]

Aaron, Sounds like a good place to start would be a known good carburetor. Now that you've found that mismatch, best to break it down and see what else is in there. This may not be causing a problem, but it can't be doing you any good.

[ABento]

My thoughts also, I'll use one of the bridges from the spare and see what happens, the needle had a small bit of wear on it,so that might have been my flooding problem, one of the idle needles was junk but the kit came with new ones and a bushing on the throttle shaft should clean up any of these issues, if I still have a spillage issue I'll check the fuel pump pressure as Chris found his is putting 5#'s pressure, that may be a bit high.

[mfirth]

My 8ba with a 94 runs gr8 @ 2lbs fuel pressure and minimal flooding...terrible gas. m

[ABento]

Problem solved, I left the old bridge in this carb as the other one was a little taller where the hold down touched it, I figured if I had a problem I would do something about it then,it started and ran, the new idle adj needles are within 1/4 turn of each, it starts quickly when hot, not having to grind on it and doesn't leak when hot, the new needle and seat have cured my leakage problem and the base bushings fixed the idle adj.