I've been running this carb for years and have had it apart many time for cleaning, rebuilds, shaft bushings, etc.
All in all I've got it to where it performs very well, and am quite happy with it.
The problem is that it seems like all of the fuel drains out overnight. It takes many pumps of the pedal to even get it to fire. Most often after it fires the first time it will die right away like it runs out of gas which then requires more pedal pumps and then all is well after that. Idels very well choke works perfectly, can restart it as many times as I want throughout the day . . Life is good, until the next morning.

Adding to the confusion is that with a full tank it only might need one or two pumps of the pedal to fire off, seems that the fuel level in the tank is inversely proportional to the number of pumps required to get her to fire!

Thoughts?

 

Hi Tarheel blue,

After it's sat, have you actually taken the top off of the carb to confirm that there is no fuel in the bowl? If not, I'd suggest doing so, just to see if it is the carb.

Otherwise, I am thinking it might actually be your fuel pump.
I had this issue long, long ago, and the diaphragm in the fuel pump had become weak, which would let fuel drain back out of the line going to the carb. Then, when you start it up, the weak diaphragm take a while to get the fuel back to the carb, but is enough to run it.

A full tank has less air inside of it. The air can create a vacuum, which pulls on the pump as it drops. That might be why it acts up more on a lower tank.

 

Thanks AB,
Both have been my exact thoughts, but there is fuel in the bowl And i have reset float level many times to see effect, none.
Also suspected the pump, replaced it about 6 months ago, no change.

 

I suspect I am not the only one needing clarification - in the OP you say the float bowl is draining, in your second post that there is fuel in the bowl. Can you elaborate? Have you looked whether your accelerator pump is functioning correctly; that it is indeed squirting gas into the carb throat like it should?

 

Thanks Dave,
In my original post I said that it seems like it drains out. I've checked the bowl and it is indeed full. I've been through this before, here's a capture of one of my old threads,

Yesterday morning after my last post I went out to the garage and out of shear frustration thought, OK I'm gonna just mist the hell out out this carb with a ton of gas, so what if it floods. Lo and behold, it tried to fire up! So, OK, I have a fuel delivery problem. Let's remove the carb and tear it down again. In trying to get the top off to look in the bowl, the top was hanging up on something inside. Knowing that there is no physical connection, I wasn't sure what it was, but a bit of wiggling and it came off. First looked at the bowl . . Almost bone dry! Looked over the float real good and it dawned on me. Some IDIOT (that would be yours truly) had installed the float pivot pin in the wrong direction. The shoulder of the pin was on the inside, not thee outside (towards the bowl side). What I'm guessing is that the pin was able to vibrate itself towards the accelerator pump spring and some how restrict its movement.
So back when I claimed to have a squirt, I did, but not knowing what a good squirt vs. a bad squirt looked like, it was obviously not enough to prime the intake. The pin sliding out of position might have also restricted float movement resulting in an empty bowl.
As lond as the carb was disassembled, I took the opportunity to address a vacuum leak and decided to change out the throttle plate with a good one that I had for some time.
Pre-filled the bowl, put everything back together and she fired right up!
I would have posted last night but wanted to let her sit overnight and see what happen this morning. She starts just like my wife's Lexus, barely look at the key and vroom . . . . .

Thanks again to everyone!


So once again, I thought I had everything figured out! But I guess not.

 

Here's where I get confused and need to know if my understandings are correct.

First, the fuel pump sucks fuel from the tank and then pushes it to the carb. The float then shuts off the flow when the right amount is in the bowl.

Second, generally when attempting to start a cold engine you depress the pedal once or twice before turning the key. This does two things, it presets the choke and adds a small squirt of fuel to the venturi to give the cylinders something to ignite.

Now, my bowl has fuel in it when cold and I never have a starvation problem when running, so I would think that my fuel pump is operating properly, right?
The accelerator pump in the carb must be working also as after a number of pedal pumps, the engine will fire. The confusing parts are; I need to pump more times after the truck has set for a long period of time and that the number of pedal pumps increases over time as the amount of fuel in my tank decreases.

My mind does wander to something that AB eluded to, my gas gauge hasn't worked since I've owned it. I diagnosed the problem to the sender but have not replaced yet. I'm wondering if perhaps in addition to the float/ arm/ rheostat assembly being bad, perhaps the pickup tube is also perferated and is causing some suction issues. Just can't get my head around that rabbit hole.

Maybe it's time to bite the bullet and drop the tank to change the sender.

 

On that reasoning if you drop the tank, just ran a hose into tank and bypassed the sending unit, it should fire up like a dream. Between that and doing a simple suction test on the pickup tube to make sure it is airtight, you should have an easy diagnosis. One other thing that occurred - you mention neither an in-line filter nor replacing the hoses in your gas feed. If you have a filter near the carb, does it drain too? Is it full of gas in the morning? How old are your fuel hoses between the tank and the carb? Just throwing out alternatives.

 

It sounds to me that your accelerator pump piston is not sealing in the pump bore, allowing some of the pump shot to leak past the pump piston instead of going out the squirter nozzle. Did you change the pump piston seal? Does the pump bore have any imperfections?

 

Kurt, Along the same line if it is working now after your fix but just trying to under stand what was going on here is my .02

If the pump was not putting out the full amount then you would need to pump many more times to equal say 2 or 3 pumps.
Is you still have the issue then it could be the pump rubber is bad or the bore and it will never deliver the right amount of fuel.

I think you are still running the stock exh manifold that is bolt to the intake right?
I cant remember but I am sure the stock setup has a heat riser valve in the exh manifold. Are you sure this valve is working/moving as it should?

My thinking is if the heat riser valve is stuck closed it is heating up the intake manifold.
You now park the truck overnight and it is boiling the gas out of the carb. This is even more so with the 10%-15% ethanol, just sitting gas evaporates.
Dave----

 

Sorry, I haven't dropped off, just had some other things to deal with.
I'll try to spend some time on it tomorrow as it's supposed to rain all day so good time to be in the garage. Thanks for all of the suggestion. It gives me a long list of things to go back over more closely.
Stay tuned!