Carb problem

[jpaz]

Ok I thought I had maybe got some bad gas, not sure now. Yesterday I was driving my car and it started hesitating and then it quit running. Pulled on to a side street and stopped rolling. Then I tried to start the engine and it started back up. Took off and it died again. So after a few minutes it will start again, went through this a few times and I got it home and in my garage. I took air cleaner off to see what is going on. Got it to start right up and when it’s idling it is running like normal. But when I rev the engine up few times and let off the accelerator, fuel comes out of the primary vent tube and it gets sucked into the carb and dies. So it gets basically flooded out and then the engine dies.  
I have the float level in the middle of the site glass, right where it’s supposed to be. So I may have a bad or dirty needle and seat? Carb is a newer Quick Fuel HR 735. I put new non brass floats in last year and I am sure the levels are good. I did put a new fuel pump on this year, old one was leaking. Maybe too much fuel pressure? I don’t have a pressure gauge or a fuel regulator on, never had issues with this before. 
I will remove the front bowl and check out the needle and seat. Then I will reset the fuel level. If I don’t find anything in there then it’s gotta be a fuel pressure issue, right? 

 

[Stanglover]

Ok I thought I had maybe got some bad gas, not sure now. Yesterday I was driving my car and it started hesitating and then it quit running. Pulled on to a side street and stopped rolling. Then I tried to start the engine and it started back up. Took off and it died again. So after a few minutes it will start again, went through this a few times and I got it home and in my garage. I took air cleaner off to see what is going on. Got it to start right up and when it’s idling it is running like normal. But when I rev the engine up few times and let off the accelerator, fuel comes out of the primary vent tube and it gets sucked into the carb and dies. So it gets basically flooded out and then the engine dies.  
I have the float level in the middle of the site glass, right where it’s supposed to be. So I may have a bad or dirty needle and seat? Carb is a newer Quick Fuel HR 735. I put new non brass floats in last year and I am sure the levels are good. I did put a new fuel pump on this year, old one was leaking. Maybe too much fuel pressure? I don’t have a pressure gauge or a fuel regulator on, never had issues with this before. 
I will remove the front bowl and check out the needle and seat. Then I will reset the fuel level. If I don’t find anything in there then it’s gotta be a fuel pressure issue, right? 

 John, on the fuel level, try removing the sight glass (I gave up on those a long time ago) and set the fuel level to the bottom of the threads, i.e. barely visible, then either put you sight glass back in or a brass plug. Also I too would replace the needle and seat. Just where I'd start having had similar problems in the past.

 

[jpaz]

 John, on the fuel level, try removing the sight glass (I gave up on those a long time ago) and set the fuel level to the bottom of the threads, i.e. barely visible, then either put you sight glass back in or a brass plug. Also I too would replace the needle and seat. Just where I'd start having had similar problems in the past.

Why would I remove the site glass? They are not leaking. My carb instructions say to set the float level in the middle of the glass. There’s actually a line cast into the side of the bowl in the middle of the side glass. This is to help with setting the level. I think I have a new needle and seat and that’s the first thing I need to check. 

 

[mjlan]

You can unscrew the needle and seat without removing the bowl if its a Holley-style bowl. Sounds like maybe something wrong with the needle.... 

 

[jpaz]

You can unscrew the needle and seat without removing the bowl if its a Holley-style bowl. Sounds like maybe something wrong with the needle.... 

Good point. Only reason I thought about removing the bowl was to see if I have any crap in there. I think I will just remove the needle and see what it looks like. Thanks mjlan!

 

[c9zx]

+1 on the needle and seat. It could be something in the needle and seat or it could have developed a "stick". I have seen both several times over the years.

Chuck

 

[Stanglover]

Why would I remove the site glass? They are not leaking. My carb instructions say to set the float level in the middle of the glass. There’s actually a line cast into the side of the bowl in the middle of the side glass. This is to help with setting the level. I think I have a new needle and seat and that’s the first thing I need to check. 

What I found, and it may be on earlier Holley sight plugs, they got clouded from the gas and I could no longer see the gas level. Perhaps the QF one's are better quality now and no longer do that. Nothing wrong with sight glass if that's the case and the level is set correctly. 

My Holley manual say to set the fuel level to the bottom of the sight window. If it's higher than the bottom of the sight window,  it is too high. 

 

[TommyK]

I know on the early street avenger carbs the instructions indicated the see through sight plugs will cloud and discolor and are for temporary use and should be replaced.

 

[Hemikiller]

The QF and many newer Holleys have actual clear glass sight windows that are not "removable" in the classic sense, and the fuel level is set to the center of the window. 

The sight window plugs for the classic Holley sight plug that many aftermarket companies offer are for temporary use only. 

 

[Big Red Mach 1]

I run my QF 735 with the fuel level in both bowls right at the bottom of the sight plugs. I used to run them middle and then lowered them during the sorting of various other issues that you all have helped me through. I can't say it's made an ounce of difference either way honestly. I'm another +1 on the needle and seat though. Seems very common for the issue John is describing. I replaced my fuel pump a while back and I think without the FP regulator I was reading way too high at 12psi. Double the 6 we need. That would be my next move if the needle and seat doesn't fix it. 

 

[Stanglover]

I know on the early street avenger carbs the instructions indicated the see through sight plugs will cloud and discolor and are for temporary use and should be replaced.

 Yes, I remember that too. Mine are brass.

 

[Stanglover]

The QF and many newer Holleys have actual clear glass sight windows that are not "removable" in the classic sense, and the fuel level is set to the center of the window. 

The sight window plugs for the classic Holley sight plug that many aftermarket companies offer are for temporary use only. 

As I don't have a QF, I'm wondering if the position of the sight window has actually been lowered slightly in the casting because it would definitely be easier to read the level in the middle of the window, rather than "guess" trying to see if it is at the bottom. 

Good point.

 

[jpaz]

So I happened to have a brand new needle and seat. Changed it and set the bowl levels. It starts and runs good. I reved it up a few times and no fuel coming out of the vent tube. But it’s raining here today so I couldn’t drive it to see how it is under load and at full temp. Got it warm enough for it to come off the choke and idle down though. Anyway here’s a pic of the old needle and I think I had fuel going around the seal. Lot of white junk on that seal.

 

[Big Red Mach 1]

Run any fuel treatment through it lately? Maybe break some gunk loose? Do you have any teflon tape on any of your fittings? Maybe broken down teflon tape? I have heard that can definitely cause issues like this. 

 

[jpaz]

Run any fuel treatment through it lately? Maybe break some gunk loose? Do you have any teflon tape on any of your fittings? Maybe broken down teflon tape? I have heard that can definitely cause issues like this. 

All good ideas, I recently put some dry gas in but no fuel treatment. That probably wouldn’t hurt. No on the Teflon tape for any fuel connections. I did clean my fuel filter screen and made a new 3/8 steel fuel line. I checked everything there too, no kinks or anything like that.

 

[Stanglover]

Little things cause BIG problems!

Glad you found the issue and you'll know for sure once you get to run it under load. Weather here is not good for the next week either.

 

[c9zx]

The chemical soup we now call gasoline is problematic. I'm seeing all sorts of fuel related problems, needle and seat stuck shut, air bleeds clogged with unknown whiteish gunk, Inside of carb covered with grey gunk. They also change the formulation of the "gas" several times a year which causes the carb to need to be adjusted. Where I live, a Phillips Petroleum engineer told me the minimum number of formulation change a year are seven and can be up to twelve changes a year. It is almost worth buying race gas just to get the same formulation every time.  Chuck

 

[jpaz]

Wow, I didn’t realize that they changed it so much. I just thought there was a winter blend and a summer blend. Learn something new every day! Thanks Chuck 

 

[c9zx]

I was chasing my tail trying to get the perfect carb calibration. I'd get it right and a month later it is off just enough for me to notice. Initially I assumed it was changes in weather conditions, and part of it is. But I contact Phillips on a whim not ever expecting to get a response let alone a truthful answer. Chuck