Engine hesitates - fuel exhaustion?

[cpnbnanamn]

So, when I got this truck, I noticed that it hesitates when I bump the throttle from an idle, it bogs or hesitates. I knew the truck had been sitting, so I rebuilt the carb, ran a hardline from the fuel pump to the carb, and put in a new inline fuel filter (there was one inline, but it was nasty!). I've noticed that the filter is not filling up, and it looks like it struggles to keep up with the demand. BUT.. If I trounce on the gas, it takes RIGHT off. Did I miss something?

'67 C10 w/ Inline-6/ Rochester B 1bbl

[Wrenchbender Ret]

For some reason these filters never seem to fill full up with gas. If it runs good it is doing fine.

[cpnbnanamn]

Thanks for answering, Wrench.. And I know they never completely fill.. it just looks nearly empty.. That's what concerns me. Is the hesitation when bumping the throttle from idle normal behavior, or am I just so used to a fuel-injected car, it's spoiled me?

[70STOVEBOLT]

Check your timing and adjust the idle mixture, could be running lean.

[Jrainman]

nearly Empty does not sound rite to me , my clear fuel filter most times carrys a small air bubble but thats it,,,,,,,,,,

[cpnbnanamn]

Yeah, I'm going to have to draft some help for the timing. That was one thing I've never truly learned to do. Done it on a motorcycle.. that was FAR easier. I could YouTube it...
I did adjust the idle, starting with 1-1/2 turns from seated. Not sure the of the RPM's @ idle. - No tach. Yet. Working on it.

[70STOVEBOLT]

Originally Posted by cpnbnanamn

Yeah, I'm going to have to draft some help for the timing. That was one thing I've never truly learned to do. Done it on a motorcycle.. that was FAR easier. I could YouTube it...
I did adjust the idle, starting with 1-1/2 turns from seated. Not sure the of the RPM's @ idle. - No tach. Yet. Working on it.

If the timing is not correct, you will need to readjust the carb after you get it set correctly.

[cpnbnanamn]

Originally Posted by Jrainman

nearly Empty does not sound rite to me , my clear fuel filter most times carrys a small air bubble but thats it,,,,,,,,,,

That's what I thought, too. It's new lines from right where the hardline from the tank stops all the way to the carb.

[70STOVEBOLT]

Does it start right when it's warm up or do you have to crank it for a while?

[cpnbnanamn]

Originally Posted by 70STOVEBOLT

Does it start right when it's warm up or do you have to crank it for a while?

Usually fires right up.. Especially, now that the carb and everything has been cleaned up. It doesn't lope, idles pretty smoothly. I only see that hesitation when I hit the throttle from idle. I don't recall it doing it under load, though. I'm about to run to the store. I'll have to report back on that.

[cpnbnanamn]

Originally Posted by 70STOVEBOLT

Does it start right when it's warm up or do you have to crank it for a while?

So..... I have to correct my previous statement. Right after I finished the rebuild, it fired right up. Drove it around some tonight, and anytime i ever had to restart it.. it was hard-starting.. even while still warm. I still notice a bit of hesitation at speeds going from idle, but not as obvious as when sitting still. Fuel filter is usually very close to empty. Starting to wonder about a bad fuel pump?

[TheGhost]

Look down in the carb when you bump the throttle. Are you getting a little shot of fuel each time? If not, you might have an accelerator pump / adjustment issue.

[Jrainman]

I am assuming the filter is inline after the fuel pump , it should be at least 80% full or more , also when you let the truck sit a few hours the fuel filter should be close to full ,and not bleed back thrrough fuel pump if its bleeding back leaving the filter almost empty I would say there is fuel pump is weak..

[leftybass209]

What kind of carb, what brand fuel pump and what psi is the pump rated at? Is the fuel filter located between the tank and the pump, or the pump and the carb?

I don't know how anyone can suggest anything for a diagnosis without this information

[cpnbnanamn]

Originally Posted by Jrainman

I am assuming the filter is inline after the fuel pump , it should be at least 80% full or more , also when you let the truck sit a few hours the fuel filter should be close to full ,and not bleed back thrrough fuel pump if its bleeding back leaving the filter almost empty I would say there is fuel pump is weak..

I put the filter before the pump, however, it was previously after the pump before i rebuilt the carb, and I was seeing the same thing. The truck has been sitting for a few hours, and when I shut it off, the filter was empty. It's now half full. I'm thinking you might be right.. weak pump. Someone else had mentioned they had seen the same thing, and had removed the mechanical pump, and placed an electric pump - problem solved. Question is.. finding the appropriate pump. ~4-6 psi, right?

[cpnbnanamn]

Originally Posted by leftybass209

What kind of carb, what brand fuel pump and what psi is the pump rated at? Is the fuel filter located between the tank and the pump, or the pump and the carb?

I don't know how anyone can suggest anything for a diagnosis without this information

It's the original oem Rochester B 1bbl carb, and I habe no idea about the pump. Not sure if it's OEM, or orginal. I just bought this truck 2 weeks ago. And I have no idea what the pressure is.

[TheGhost]

In your first post, you stated that if you "trounce" it, it takes right off. If that's the case, I wouldn't look towards the pump - that doesn't seem like a fuel starvation problem. I would look, timing, idle mixture, or accelerator pump.

[cpnbnanamn]

Originally Posted by TheGhost

In your first post, you stated that if you "trounce" it, it takes right off. If that's the case, I wouldn't look towards the pump - that doesn't seem like a fuel starvation problem. I would look, timing, idle mixture, or accelerator pump.

Right, but later, I did amend it to say that I do still notice a slight hesitation from idle.
These 1 bbl carbs have a 'power pump' which I'm going to guess is likened to an accelerator pump. There is no adjustment to it. I've replaced the plunger, and the springs, and the little steel balls.
I've been messing with the idle mixture - started at 1-1/2 turns from seated (per service manual), and adjusted from there. Had it too low at one point, and it stalled out on me. Gave it about a 1/4 -1/2 turn, and all seems right with the world again.. all but the hesitation.
If it were a timing issue, wouldn't I be hearing pops or backfires, or dieseling? Some other indicators?
Here's part of the reason I am thinking pump: Regardless of where I had the filter, it hesitates from idle. It's been sitting for a few hours, and when I shut it off, the filter was empty. It's now over half full, and it doesn't appear to be coming from the tank's direction. When I was redoing the plumbing, fuel was flowing through the pump just a bit too easily while the engine was off.
I'm more than willing to look at the timing, and take all the advice I can get. I love this truck, and I want her to run right.

[TheGhost]

You wouldn't necessarily have any of those conditions that you described with a timing issue - only if the timing was wildly off. You may have a pump problem that is letting some fuel siphon back when the truck isn't running, but that shouldn't cause a stumble off idle. That may cause you to have to crank for a while if the truck has been sitting for a long period of time. The carburetor has a fuel bowl that holds a reserve of fuel. A good pump will always have head pressure at the carburetor when it is running. Unlike fuel injection, there is no return of unused fuel. If it were a pump problem, I would expect it to die out during heavy acceleration, not off idle - then pick back up after you let off - since the pump wouldn't be providing enough fuel. Look into the carb and work the throttle. You should see a small "squirt" of gas when you operate the throttle. If you see it, then it's probably a mixture problem. If you don't, then it's the accelerator/power pump. There could be some wear in the bore that the pump sits in or maybe the seal rolled up when you installed it - either wouldn't create a good seal for the pump to work properly. Setting the mixture is pretty easy if you have a vacuum gauge handy. Make sure the truck is warmed up and the choke is off. Hook it up to a manifold vac port and adjust evenly until you achieve maximum vacuum.

[saxart]

I'm really curious what you find out with this. My 1970 with the same carb does the exact same thing. It seems to get better as it warms up, but never completely goes away.