so how does a carb work, anyhow?

[Bilito]

Originally Posted by EngineerMike

Carburetors suck. That's really about it. They suck.
Actually the engine sucks, pulling air thru the carb. The air movement causes a decrease in pressure or vacuum (it sucks) that pulls fuel through a jet into the air stream, into the engine's cylinders. The volume of suck determines proportionate volume of fuel sucked. The suck process also attempts to mix fuel & air.
Its a sucky situation, by design. As you can imagine, vs high pressure computer controlled fuel injection, suck technology is not very efficient at either precise metering of fuel or of air, which means both fuel economy and emissions are hard to manage well when the best you have as a control sucks.
Hope this explanation doesn't suck.

If carbruators suck so much why do many of the monster drag race motors use them?

[allegroman]

so much to digest, and thanks for all of it.

yes, it does suck.... every time the can goes down in the cylinder.

there are two giant screws, one on each of the carb tanks. when i take one out, the 'nut' under it is held in place by the screw, and itself is not threaded onto the carb. it just lifts off, but does have a flat spot that keys it into position. it has rubber gasket above and below it. when the screw is out i see a hole. i was hoping to see a removable filter screen, but nope, just a hole down into the carb. is there something more i should know about this hole?

today i ran out there at a crawl, stalled several times too, but always restarts immediately. could not accellerate above an idle.
sat there for many hours, then returned home and it ran perfectly all the way. never skipped a beat.

I know i have a filter at the pump outside the tank. it's a brass thingie that came with the pump, so i put it on when i did the pump job. i see no other filters where ever i can see the fuel lines. my first guess is like yours, crap clogging up the lines. explains intermittantcy. (is that a word?)

I think i'll try to find a clear filter and put it in the line between the 'y' and the pressure regulator, close to the engine. that way i'll see if there's any debris involved, keep it out of the carb, be easy to change as needed.

as for the carb, i would feel more comfortable having an image in mind of what pieces-parts inside it could cause the symptoms described. stuck float, no, road so bumpy it'd be constantly rattled loose. adjustments? if off, would not let engine run 'normally' sometimes. clogged path between where gas comes into carb and where gas travels before the venturi? possibly.

i know slow speeds may not be what this engine was made for, but i bought this old rig for a purpose: i have 64000 acres of preserve just down the street. i go there maybe 2x per month and thoroughly enjoy the solitude, the peace and quiet, the wildlife. i spend the day, then come home somewhat refreshed. some day i'll spend the night, too. it's a washboard, bumpy road half the time, but i'm not in any hurry, so idle speeds are ok. best of all, it's what i can afford. i truely love my camper!

i'll let y'all know how i make out with adding the fuel filter. thanks! am

[CD]

You may have some crap in the gas tank that's plugging the line out of the tank. Have you tried blowing out the line?(be sure to remove cap first). Also, the screw you discribed sounds like an adjustment screw. If so you will need to know how to adjust it to make it run right.

[Bilito]

Originally Posted by CD

You may have some crap in the gas tank that's plugging the line out of the tank. Have you tried blowing out the line?(be sure to remove cap first). Also, the screw you discribed sounds like an adjustment screw. If so you will need to know how to adjust it to make it run right.

Partialy plugged fuel jets and other orifices inside the carb will probably
open up when you add Seafoam. In my Carb, (a Holly) in the bottom of the accelerator pump chamber is a tiny ball no bigger then a B-B held in position by a small spring. When you step on the gas the pump pressure pushes against this ball to seal the opening, when you let off the gas the suction in the chamber sucks gas past this ball and the ball moves against the spring to refill the chamber with gas. I found my chamber gummed up with a brownish gooey varnish like material. The ball did not seal well. The accelerator pump chamber gets it's gas from the bottom of the float chamber, which in my case was also coated with that sticky varnish like material. This stuff is a by product of the crap we call gas today. You cannot let gas sit the way we used to, because it turns to crap and gums up everything. Seafoam is one of the best things around to clean it up other then disassembling the carb.
Seafoam also prevents that from happening and it helps to dissipate water too. No I do not own stock in Seafoam, my fathers father used it, so did my father and I pass this info on to you. They cannot have been around as long as they have unless it works.
my two cents

[CD]

Originally Posted by Bilito

Partialy plugged fuel jets and other orifices inside the carb will probably
open up when you add Seafoam. In my Carb, (a Holly) in the bottom of the accelerator pump chamber is a tiny ball no bigger then a B-B held in position by a small spring. When you step on the gas the pump pressure pushes against this ball to seal the opening, when you let off the gas the suction in the chamber sucks gas past this ball and the ball moves against the spring to refill the chamber with gas. I found my chamber gummed up with a brownish gooey varnish like material. The ball did not seal well. The accelerator pump chamber gets it's gas from the bottom of the float chamber, which in my case was also coated with that sticky varnish like material. This stuff is a by product of the crap we call gas today. You cannot let gas sit the way we used to, because it turns to crap and gums up everything. Seafoam is one of the best things around to clean it up other then disassembling the carb.
Seafoam also prevents that from happening and it helps to dissipate water too. No I do not own stock in Seafoam, my fathers father used it, so did my father and I pass this info on to you. They cannot have been around as long as they have unless it works.
my two cents

Thanks for the info on Seafoam. I hadn't heard of it. Any time I take a gas can(s) I add Stabil before I go. I use this gas for tractors, lawn mower etc. It works good. I got the gen set out after it had set for 2/3 yrs and it started right up. It wasn't good idea to leave it that long but it worked.

[jmerritt]

Sorry about the confusion regarding the adjustment nut and lock screw on each fuel bowl. What you are referring to are the float adjustments. There should also be an additional screw on the side of each fuel bowl which opens up to use when making the float adjustments. Don't remove the lock screw on top of the float bowl, just loosen it enough so that you can turn the adjustment nut. If you loosen the screw too much gas will leak out, since you need to make the float adjustment with the engine running at idle. Remove the side site screw, watch that you don't lose the round gasket on the screw, and fuel should just barely trickle out of the site hole. If it runs out turn the adjustment nut CW until the fuel stops coming out. Then slowly turn the nut CCW until you just see fuel starting to trickle out. Lock the adjustment screw down and replace the site screw. Repeat for the rear secondaries fuel bowl. If adjusting the fuel level you can't get fuel from running out of the site hole then your float needle and seat is leaking or the float is riding too low in the float bowl, indicating a bad float. The needle and seat problem is common when you get varnish built up in the carb from the fuel sitting a long time. Sea Foam should help clean some of that out. Stabil is good for keeping the fuel from going bad but it doesn't do much if anything for cleaning up varnish in the carb.

John

[JimM68]

Just to say.... the majority of "carb problems" an be cured with new plugs, ignition wires, distributor cap, and rotor....

give the beast a good tuneup.

[Dunner]

I wish you ppl would stop telling him how to make float adjustments when he barely knows what a carburetor is. There is no reason at this time to suspect the float level is wrong. It is more than likely a fuel filter(s) or gummed up carb and needs a complete tune-up.

[ga traveler]

Originally Posted by BFlinn181

There is no such thing as suck. Higher pressure air pushes into lower pressure area, thus there is no suck, only push.

Then how do the vacumn lines get vacumn? There is a vacum in the intake manifold. It is caused by the intake valve opening and the piston pulling the fuel air mixture in. If you have ever put your hand over the carb. it fells like it is going to suck your hand into the carb.

[Dunner]

It's a negative atmospheric pressure.

[ga traveler]

Originally Posted by allegroman

Need help figuring out my problem, and thought just knowing how the carb works may help me get to the bottom of things. i see lots of problems like this, too.

I have a 1988 allegro with 31k miles. ford 460 with motorcraft carb e6jl ab a8a5. electric fuel pump replaced few hundred miles ago because it was burned and inop. orig owner had run separate power wire to the pump. the fuel pressure reg just replaced, hoping to fix problem. it didn't. fuel lines have the y-connection near the engine to keep fuel circulating, i guess. basically, has been running fine, except not 100% smooth, and smells like unburnt fuel at the exhaust. been like that for a year. i run at most 20mph for 6 miles each way, 1 or 2x/month, but usually run at 5 or 10 mph speeds because of the bumpy dirt roads. usually keep just under 3/4 full tank, but added 12 gals more today to bring up to nearly full.... don't trust the gas gauge.

Lately, i drive for a bit, sometimes 5 minutes, sometimes 1/2 hour, then 'lose power'.... that is, engine rpms down to idle speed, and if i keep trying to gas it, it'll stall dead. restarts immediately. drives at idle speed ok for the most part, but won't run any faster. while still rolling, put it in n and try to rev it. sometimes it revs, but runs up and down the rpm scale without me doing it, sometimes just won't rev up, and dies if i keep pushing it.

today i went around the block at about 25mph to test it, about 2 miles. 1st time ok, 2nd, 3rd, 4th times it acted up and couldn't get back up to speed. it didn't recover until i backed it 80 ft into the driveway to the house. then it revved to maybe 1500-2000rpms for a couple mins with no problems.

so, if i understood what was going on inside the carb, i might better understand how this problem might be something inside the carb rather than pump, filter, fuel lines or press reg. being intermittant makes it hard for me to analyze it.

looks like this is a common problem for these engines. any ideas out there?
thanks! am

This sounds just like a problem I once had with a 78 Argosy MH. The gasket between the carb. base and the intake manifold had crumbled and would let air in. This would cause the carb to lose vacumn and not pull the fuel in. The next time it happens, while it is acting up, spray around the base of the carb. with WD40. If the engine speeds up, replace the gasket

[HotMech]

+ 1 on the float adjustments, not only does he not know much about carbs in general, floats don't just get out of adjustment. on their own, they have to be tinkered with.
Now, with that said, I don't feel like it has anything to do with a plugging of anything. Plugged fuel filters take some time to do that, and when they do, they don't become intermittent. My guess is, that this is not a stock, factory Ford system, I will take a guess here and say that this electric pump is aftermarket, and it is installed somewhere along the Frame rail with rubber hoses and worm gear clamps.
Most likely, save for the fact that the fuel pump itself might be to blame, (not condeming just yet, just speculating) My best and most educated guess, (since I cannot actually be there) is that the rubber has dried out and thus has loosend the clamps at the pump inlet, alowing air to enter. Air of course, is easier to move than fuel, so there can be some starvation. As for vapor lock, as some call it, that can only happen before the pump, not after it. The term Vapor Lock, refers to a condition, where the fuel in the line, going to the pump evaporates faster than the pump can move it forward, thus, moving only vapor, not liquid fuel. One downside to that is, there needs to be some heat involved, like road heat or cooling air from the radiator, heating up the underside of the vehicle, then there has to be a higher demand for the fuel, ie. heavy throttle. 20mph and near idle is not a heavy demand. Most likely, there is a loose connection, probably at a hose that is clamped on to the pump, or the tank fitting, or maybe one of the pre pump filters, if any are installed.
It's easy to check for loose hoses, just give them a little twist. if they move easily, they are loose enough to pass air. Lastly, there is no vacuum, only reduced pressure. Atmospheric pressure is what makes all this magic work. It falls under the heading of Physics, with a little help from Fluid Dyanamics.
K.

[HotMech]

Originally Posted by Bilito

If carbruators suck so much why do many of the monster drag race motors use them?

1. They dont have to idle with any quality.

2. They don't have to do any kind of part throttle transitions.

3. It's way easier than Fuel injection.

4. It's cheaper by far, than fuel injection.

With carbs on a drag car, it's like flushing the toilet.
K.

[allegroman]

yes, i maybe put the float adjs at risk by removing the big screws and nuts, but i think from what y'all have said, to adj anything, the nut has to be turned, and i dint turn it at all. just removed the screw and the nut just lifts off. besides, if the float were misadjusted, ie too little fuel in the bowl, it would not ever be able to run fast. today it layed a hundred feet of 2nd gear rubber... oh wait... that was the lawnmower. sorry. still, it ran home 15 mph with no issues, while trip out sucked.

pump is def aftermarket, mr gasket, 4-7 psi, 35gph. bought same as what was there before. replaced all the rubber from tank to pump, from pump to steel fuel line. i sometimes wonder if 4-7 psi is enough. it worked for 6 months before problems started, but maybe needs more oomph to blast thru any crap in the lines? is this good thinking or not?

interesting note... leads to believe fuel bowls are empty at time of failure... when it acts up, pumping gas pedal would squirt gas via accellerator pump into intake and engine ought to perk right up... but it doesn't, maybe saying no gas in bowl for pump to squirt. hows this sound? maybe not carb problem, but as many of you have said, crap in the fuel lines somewhere between tank and carb not letting bowls fill.... sometimes. also, the pump squirts fine when i look into the carb before i start it.

oh yes, this rig is also built on a deere chassis. one question i have about it, this is an 88 allegro with a carbed 460 ford.... internet keeps saying no fords used carbed 460 in 1988 or later...

also, what is meant by efi engine? is that what i have? plumbing pipes everwhich way and place? if there was an empty space they stuck a pipe in it?

also, thanks for dumming it down for me. i'm not a mechanic, and i have to admit to being slightly intimidated by gas... too many horror movies where the monster gets burned alive, i guess.

am