Hey guys, I took my car out for a ride today and I was cruising about 60 mph in 4th gear and the motor just started to choke or "stumble" and eventually shut off. The car normally starts right away and it took about 20 turns with the pedal to the floor and barely got it to start. Once it's cranking 2000 rpms it runs; however, when it idles it dies and takes a while to start again. A mechanic told me something is messed up with the carb and it's getting way too much gas. I checked the fuel and the carb is spraying gas into the motor like it should be. I thought it could be something in the ignition at first, but now I'm agreeing with the carburetor issue. Anyone have this happen to them? By the way, this would be my 5th holley carb in 4 years. If it is a problem, I don't think I'll be buying any new holley anytime soon.........thanks guys!

Sounds like you have trash in the needle and seat, pull the needles out and blow them out set your floats , go from there.

Dave

I will have to check it out either tomorrow or Saturday and see if that's the problem. Thanks for the response Dave!

What are you running for a fuel filter? If you are using an inline filter, I would suggest opening it up and looking for rust flakes...5 carbs in 4 years is not normal! Rust flakes play hell with any carb...and I have seen a lot of parts store filters still allow chunks to get thru.

I know 5 carbs in 4 years is not normal. Three holley carbs I bought were not the dual feed design. They both came with factory needle spurs (I believe that's what they're called?) anyway, when the car idled, the 4 barrels would be just pouring in gas due to these "spurs." The first carb I can't even remember what was wrong with. This new street avenger seemed to be such a better carb than the past 4. I never thought of rust in the tank. I'll check the fuel filter. The filter on my car is by the fuel pump itself. Thanks for the idea!

Had the carb checked out and amazingly there are no problems with the carb. The carb's choke, floats, needle and seats are all functioning properly. Had some people say maybe a vacuum leak? any other ideas??????? Thanks!

I would try a new powervalve next. Good luck!

I did not put a new power valve in it, but i sprayed wd 40 around the intake and carb gasket to check for a vacuum leak. One of the bolts was a tad loose on the carb so I tightened it back up to about 10 ft lbs. Anyway, after doing this, the car idled for 15 mins and I thought that probably would be the fix. Anyway, I took it around the block and a few others and nothing happened. When I start to slow down and not press the accelerator, it started to want to choke off again and eventually it did. It then took about 15-20 cranks to start it again with the accelerator pressed to the floor. I got it running and it seemed to run fine again, until I let it idle in my driveway and shut off. What would cause this? Is there anyway it could be the accelerator pump diaphragm? Thanks!

This is a wild guess...fuel pump going out?

So when it quits its obviously flooded correct?
Does it take a while for it to quit?

Dave

I would think if the fuel pump was going out, when i gave it gas, it must be working to pump gas up into the carb. But that's only my guess and I'm not an engine expert. I'm not sure if it is flooded or not when the engine quits. I thought it was at first, but not sure. Now it is off and on when it quits. Like I said above, it was at idle for about 15 minutes, I took it for a short ride, and after about 10 minutes when I was off the gas it started to stumble again. I'm almost thinking that the motor isn't getting gas, and that's why it's quitting.

if you don't see signs of the carb running over it's probably the fuel pump dying or some other problem causing to not get fuel to the carb.

Is the fuel filter between the pump and the carb or on the inlet side of the pump? if it's on the inlet side and plugged up it could be vapor locking.

Ever notice we get a lot of this problem about this time of year?

Hey Tom-

Thanks for your help. This sounds more like the problem I'm having. The fuel filter is on the line before the fuel pump. I'll have to check the filter and fuel pump. The filter and fuel pump are about 5 years old, and I suppose they could have gone bad. And no, I never notice that you get a lot of this problem this time of year. This is the first time it's happened to me.

I'm pretty convinced that it's the accelerator pump diaphragm. If it goes bad, my car has all the symptoms of this happening.

5 year old filter on the suction side of the pump. get it a new one.

Hey Tom-

The reason why the filter is on the suction side of the pump is because there is a metal line being ran to the carb. Don't ask me why, that's how I got it when it's set up. You sure this is the problem??????

Hello Tom and Everyone else-

I replaced the fuel filter with a glass one and reran the lines so the fuel filter is between the carb and the fuel pump, instead of being ran off the main gas line and before the fuel pump. Well guess what, it actually seemed to be running worse than with the old fuel filter on it! It wouldn't idle at all. I know it's not because of the new fuel filter, but the key thing here is that the fuel filter is NOT causing the motor problems. Anyone have any ideas? I still think it's because of the accelerator pump diaphragm....., but not sure?

You need to narrow this down to "too much fuel" or "not enough fuel".

You've got several symptom here that lead to "too much" - fuel pouring out the 'four barrels', won't idle, really hard to restart because it's flooded. All of these things point to too high of a fuel level in the carb bowls, which could be caused by worn needles, incorrect float height or trash in the needle/seat. The idea that it gets better and then gets worse again would point to intermittent trash in the needle/seat. Frankly, so would changing the fuel filter if you got particles of the line into the system if changing the fuel filter made it worse.

The idea that it runs fine but then seems to die all of a sudden would seem to point more towards a weak or failing fuel pump -- as it is going out, it's unable to keep the carb supplied with fuel. The concept that it will idle well in your driveway, but can't keep up while your driving would point to this. So we need you to narrow down to one state or the other.

The accelerator pump diaphragm has nothing to do with idle quality. And it has nothing to do with constant speed driving. It is a transition circuit. A hard start and a stumble on acceleration that clears up would be symptoms. A bad accelerator pump would not cause the car to die when idling or when running constant speed, and is unlikely to cause it to die when you accelerate.

Some basics:
Are your plugs really sooty black? Do you see fuel dripping out the boosters immediately after you shut the car off or even when it's running? Do you get a lot of black smoke out the tailpipes when it's running rough? Is there any fuel puddling on the intake manifold?

What is your fuel pressure? Tap or tee into you system and check it with a pressure/vacuum gauge.

Check your float height. I know you said someone else checked and it was good, but pull the screws and look at it yourself. The fuel level should be right at the bottom of the screw hole and dribble out only slightly if you bounce the car up and down.

With your glass fuel filter, can you see any air in the fuel when it's running, little bubbles? What happens after your shut it down?

Check that accelerator pump. With the car off, look down the carb throat and work the accelerator linkage. Do you see a nice stream of fuel down each barrel?

Zeke-

What a response! I will answer all the questions you ask me to the best of my ability. I checked the fuel in the 2 bowls on the carb. Both were right at the bottom of the screw hole, like they should be. So I don't know if this rules out the needle/seat issue. I am having problems now with it, and it won't idle at all. The only time the car will run is if I manually give it gas by pressing the throttle. You have it backwards- the car sometimes will idle in the driveway, and sometimes will not. Whenever I keep on the accelerator while I'm driving it will run. It's when I let off of the gas it will start to "stumble." So to be honest, I see no fuel overfilling out of the carb or overfill vents onto the intake. The float levels appear fine. I did change the fuel filter and seemed to not better the issue. So myself, I can tell you what is happening but I believe that the car is not getting enough fuel, even though the problems appear to be getting too much fuel. The reason why I believe it could be flooding out is because I have to press the pedal to the floor to get it to start. When I have someone else keeping the RPM's around 2000, I look in the carb and I can't hardly see any gas going in except for the 2 front barrels, they drip gas.

I pulled 3 of the 8 plugs that are easy to get at (due to headers) and they all had a dark browish/ black electrode, and they were not really "sooty" black. I did not see any fuel dripping out of the boosters after I shut the car off or when its running- only when its running at 2,000 rpms. When it does start eventually and I have the pedal pressed to the floor, it does smoke black, and i know, this indicates it's getting flooded. There is no fuel puddling by the intake manifold. I have no way of checking the fuel pressure. The float height appears to be fine. I also could not see any bubbling going on in the glass fuel filter. After I shut it down, gas was in the fuel filter but eventually it drained all the way out (down the line). The accelerator pump works fine, with the car off, i worked the accelerator linkage and there are nice streams of gas going down each barrel. I don't know if this will help at all????

try this: kepp it running with the throttle for a minute or two, then just let it die on it's own. then, without touching anything else pull the front sight plug, see if there's fuel in the bowl or not. If you don't see any crack loose one of the lower bowl screws.

The fuel pump is just a series of check valves, technically fuel shouldn't be able to drain back through it. if one or more of the check valves is toast or has junk in it fuel can drain back to the tank. this is also the cause of most low volume deals.

So say if there isn't any fuel in the bowl after I shut it off, and assume the second thing you said about the fuel running back to the tank is true. Do I just get a new fuel pump and bolt it on then? Is that causing the main problem? I will check it out tomorrow and post back. Thanks for all the great help!

I agree with Tom's next step.

To summarize an answer to the questions in the last post: I would agree that the float height, needle seat are okay and you are not overflowing the carb because: fuel level is at the bottom of screws, no visible fuel dripping from boosters at idle or after shut off, no fuel puddling on manifold, plugs not sooty.

No visible bubbles in the fuel filter would indicate that it is unlikely you have vapor lock of fuel percolation.

Nice streams of fuel from the squirter would eliminate the accel pump, although we kind of knew that anyway because that circuit wouldn't give the symptoms you have.

At this stage, I would agree you're not getting enough fuel. Tom's suggestion is intended to determine if fuel pressure drops off as the cause of your stalling. So do that check to confirm or eliminate.

I am beginning to think by your description of having to keep your foot in it that if it's not low fuel pressure/volume, then it's something in the idle circuit of the carb. Even running down the road at moderate speed and low throttle opening, your running primarily on the idle circuit for most of your fueling. So if that's not delivering fuel, then getting the RPMs up by open the throttle blades delivers more fuel out the main circuit (this kind of fits with with why you are seeing fuel dripping at high idle in your driveway). Do Tom's test first and then we'll try to go down this path.

All of this assumes that the choke is wide open during all these tests. I have seen a choke not fully open give the same symptoms but for a different reason, the partial choke over fuels the primaries so you have to get the throttle opened up to get additional air flow through the secondaries to make it run. That would also cause hard starting and having to hold the pedal to the floor. And it should be tight wide open, not a little bit off wiggle.

So say if there isn't any fuel in the bowl after I shut it off, and assume the second thing you said about the fuel running back to the tank is true. Do I just get a new fuel pump and bolt it on then? Is that causing the main problem? I will check it out tomorrow and post back. Thanks for all the great help!

If this is what you find, then a new fuel pump would be my next step.

Thanks Tom and Zeke for helping me out! I will be reporting back tomorrow with what I find out. The fuel pump I believe is about 5 years old and was about $15 from napa. I wouldn't doubt if this is the problem. I went out and looked at the fuel filter and there is no gas in it. The fuel filter is in the line and it is running up and down, or vertical. So this means that the gas would have had to flow back down the line some distance. I don't know if this means the fuel pump is bad or not. Is the fuel filter always supposed to be full of gas?

Fuel will eventually either bleed down or evaporate off. But it should take a while and occur slowly. I haven't paid enough attention to mine and haven't driven it very often lately to know what is normal. I also don't have a glass filter any more so all I can tell is if I still have pressure, but not whether there is any fuel volume.

BTW, my filter is also vertical: http://web.mac.com/zemke2/iWeb/Site/The%20Shop.html

I see. Mine is a braided rubber hose going to a metal dual feed line to the carburetor. It is running vertical in between there. I'll get back to you tomorrow. Thanks for the help!

Hello Tom and Zeke-

I put a new fuel pump on the car and guess what, didn't solve the problem. It was a pain putting that thing in with only one person doing it. Anyway, I started the car up and the thing was smoking black like crazy. I know for sure it is being fouled and the carb was dumping gas in. I pulled the rear bowl plug and no gas came out, it was at the right level. I pulled the front bowl plug and gas came pouring out, indicating a clogged needle/seat in the front bowl. Also, I just put in a new fuel filter yesterday and it's already full of some dirt debris. I think I will be changing out my tank and lines for new ones soon. Am I right on this one, or could there be another problem? Thanks for the help!

So a day ago the bowl level was fine, but now it's high in the primary side and fuel is pouring out the top. And now you have a known good fuel pump. I think you've narrowed this down to intermittent trash in the needle/seat. So the question is how do you intermittently get trash? And the answer is to start looking at the condition of the lines and fuel tank itself.

This sucks, but if it's any consolation, the the inside of the tank on my 64 is starting to shed.

Becareful with those glass filters, if it breaks there will be gas spraying everywhere.

It sounds like there is crud in the system - gotta fix that of course. Now that this is identified, I think a good quality filter is the next step as it is hard to get rid of 100% of the crud at first. A carb cleaning will be next on your list after that I'd think. Good luck.

Hello Zeke and Ron-

The tank on the car is the original tank. In a month or two, I will be putting a new gas tank in the car with brand new lines, and with the proper emissions system (charcoal canister, etc). Just by running the car a little bit tonight, I can see a few dirt particles in the gas filter already. And yes, I believe the tank is the main source of the problem. I hope that the glass gas filter will last at least until July when I replace all of the stuff. I will take the needle and seat out, spray it and clean it with carb cleaner and hopefully that will help. By the way, the gas wasn't pouring out over the carb, I took the fuel bowl plug out and it came out just like a stream. So, I'm pretty sure that there is junk in the needle/seat, especially seeing how much dirt is already in the new fuel filter. I appreciate all of the help guys! Any more advice is appreciated!

I ran a glass fltler for a number years without issue, but when I redid my carb there was sediment in the bottom of the fuel bowls - I think there are better filters out there and it would be a worth while investment to get one, I think they call them a sintered bronze or brass type, that will trap smaller particles. Up to you of course. The glass one I had did not have a flow direction arrow on it, so keep that in mind so you can re-install it the same way each time.

I see. I will have to look- I just bought this $12 glass filter, and it does have a fuel direction flow arrow on it. It's actually a filter and it has different size "nozzles" on it that you can screw in to fit your specific fuel line. I was worried at first thinking that these obviously would leak, and so far, they do not. I did put some sealant on them so maybe that is what is helping. Hopefully I can get the trash out of the needle/seat and everything will be fine.

Possibly you have a better filter than I had, it was a few years ago now. Hope oit works out for you, post back if you find any new issues.

I hope so too! haha. I will post back probably Wednesday afternoon/ evening the outcome. Thanks!

If that is the "pro-form" glass fuel filter (and it sounds like it is), I would take it off and heave it as far as possible. The standard Wix inline fuel filters are vastly superior. I know this from experience...my old '78 1/2 ton's fuel tank was rusting badly, and I went thru a bunch of filters!

Problem solved guys! I cleaned out the needles/seats today and the car runs great. I was surprised by how much junk was in there. Anyway, I will have to buy a new tank and lines if I don't want to deal with this issue in the future. I have a glass Mr. Gasket filter. It was about $12. The stuff that is plugging my carb up are pretty big pieces. It was from the filter before, because it was so old. That's what I believe the problem was. Gas tank and a really old filter. Thanks for all of your help!!!

With your glass fuel filter, can you see any air in the fuel when it's running, little bubbles? What happens after your shut it down?



what does it mean when you see bubbles in a glass filter?i was seeing them in mine.

mine gets trash in there once in a blue moon, I try to get it running and then just nail the throttle as much as possible to rush gas though and it usually cleans out without having to take it a apart

also, I now change my fuel filter every oil change (7-8k intervals) because after Katrina I noticed just how nasty a lot of the gas we get is...especially Valero brand

even changing it at 7k, I had 2 oil changes where the filter was so clogged I could barely blow through it