• Welcome to ClassicBroncos! - You are currently viewing the forums as a GUEST. To take advantage of all the site features, please take a moment to register. It's fast, simple and absolutely free. So please join our community today!
    If you have problems registering or can't log into your account, please contact Admin.

Unable to start Bronco

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,345
Great pic Slowleak. Visuals are the best. Which is why we love YouTube so much!
Too bad they're not always accurate. But they sure do have the good visuals down!
Thanks.

And by "bowl" Bill, everyone is referring to the "float bowl" by it's short name. It is not visible from the outside of the carb, even with the air cleaner off. In his drawing, Slowleak has the bowl vent with the arrow. The bowl is under that main cover/top.
Only once you take the top off of the carb (this style anyway) will you see the float and it's reservoir/bowl.
In the early days, some of the first carbs had literally a glass bowl held on to the bottom of the carburetor by a wire bail. The name just stuck even as the designs changed.
Lots of that type of carryover with car stuff.

The two holes, or bores, are the actual venturi that make a carburetor work. It's very interesting stuff and shows how much the old guys in the late 1800's early 1900's were figuring out as they went along!
Also called "barrels" this is what makes your stock carburetor a 2-bbl (or two barrel) carb. Versus a 4-bbl or 1-bbl, or other.
Also sometimes indicated as 1v, 2v, or 4v for one, two or four venturi carburetors.

Sorry for going all back-to-school on you, but thought you'd enjoy hearing some of that stuff.

I poured a small amount of gas into the bowl and the engine sounded like it was cranking for just an instant and then went to the sound of the battery turning the starter.

Sounds like you have spark from the ignition then, but not fuel to the carburetor. Back to what the others have said then about ways to check what's going on and where the fuel is stopping.
Not sure if it was mentioned yet but even a pinhole leak in one of the supply hoses can be enough to cause the pump to not be able to pull fuel. The hole is small enough to not leak liquid out (or not much) but enough to allow air into the line to keep an already weak pump from getting a purchase on the liquid.

I did that several times with the same result. I didn't know how much gas I could safely pour in the bowl so I just poured a small amount.

Good call! It's always a good thing to limit what you pour in. At the normal limit you would do what's called flood the engine, which is just having too much fuel in there to ignite. But at the worst you could literally jam up the engine. Called "hydraulicing"(sp?) it's when there is too much liquid in a cylinder to compress. Air and gasses compress, liquid usually does not.
Takes a ton of extra gas to do that, but it can be done. If so, bad things happen.

I appreciate the help of everyone. I am no mechanic but I do have time, basic tools and walking around sense so maybe we can make some progress together. Thanks, Bill R

That's all it takes! You're already on your way.

Oh, and so we'll all stay on the same page, some of your wording might still cause trouble understanding. You (and quite a few others these days) have learned to use "cranking" to describe starting. But that's a slight misunderstanding of the terminology and the word cranking literally means to crank the engine. The process of starting by turning the engine over with the starter. That's what the starter does, so the engine is considered to be cranking ONLY while the starter is spinning it.
It's another holdover from the first cars. When you literally had to hand-crank the engine to start it. The electric starter motors got rid of that need, but it's still called cranking to this day.
I can see where the line can be blurred between cranking and starting, because they're part of the same process. But they are distinctly different steps along the way.

Another one is "turning over" where some people consider that a description of starting. Unfortunately many of us (I believe a majority) consider turning over to be the same as cranking. The starter is cranking the engine, but the engine itself is turning over during that process.
The British use "tick over" to describe starting however, so maybe there is some precedent?

Either way though, cranking is using the starter, firing or starting is when the engine actually starts. Coughing or spitting or sputtering means it's trying to start, but won't quite fire.
Turning over is up in the air perhaps.;D

Don't know how long you've been using that terminology (maybe 40 years!) but hopefully that didn't ruffle any feathers.;)

Paul
 

Skiddy

Bronco Guru
Joined
Oct 8, 2003
Messages
11,557
Not sure if it was mentioned yet but even a pinhole leak in one of the supply hoses can be enough to cause the pump to not be able to pull fuel. The hole is small enough to not leak liquid out (or not much) but enough to allow air into the line to keep an already weak pump from getting a purchase on the liquid.



Paul
Mice like rubber:(
 
OP
OP
B

Bill R

Newbie
Joined
Oct 5, 2017
Messages
41
The information you are providing is exactly what I need - simple explanations, terminology and pictures. Right now, the areas to investigate seem to be carburetor, fuel pump and fuel filter. I will continue to read and re-read what you have sent as well as other information on the forum and try to make some progress on the problem. This is a great source of information and help.
Thanks, Bill R

P.S. As far as how long I have been using some terminology, I'll give you a hint. I have been around three-quarters of a century.
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,345
Hah! Well now we know how long those terms have been running around in circles!

Good luck with achieving gas!;D

Paul
 

66broncoCT

Contributor
Full Member
Joined
Feb 6, 2012
Messages
296
Loc.
Torrington, CT
Sounds like you weren't pouring enough gas down the venturis for it to start. But its a good thing you stopped before dumping too much and hydrolocking the motor like Paul was saying. I would fill the fuel bowl through the vents and try starting again. What I do when I'm unsure about a fuel pump is take a small lawn mower gas can and hook it temporarily up to the carb inlet. Then lift that above your motor (I hang it from the rafters in my garage to free up my hands) and the gravity plus head pressure is usually enough to keep the bowl full. Make sure you put the old fuel line into a bucket or something though because if the fuel pump is working it will spit fuel out as the motor runs.
 
OP
OP
B

Bill R

Newbie
Joined
Oct 5, 2017
Messages
41
PROGRESS (but not complete success)!!! I was not able to work on the Bronco Saturday or Sunday but I got back on it today. I poured gas in both vents and the engine started immediately and ran strong. I revved it up and let it idle and it ran well both ways. While it was running, I got out and made a visual inspection of the engine. There was a constant drip, drip from the carb. It was dripping in the area of the plunger on the front of the carb that is actuated by the throttle. It was not dripping from that plunger but behind it. It continued to drip for a while after I shut the engine off. I don't know if the engine was running on gas that it was pumping from the gas tank or just running on the gas I poured into it (probably 2 to 3 ounces). Whichever it was running on, it sure did sound good. I let it run about 5 to 6 minutes. This carb has a valved bowl vent as shown in the picture in a previous post. By the way, what is the container mounted on the firewall that is connected by a line to the valved bowl vent?

Thanks again for all the help and patience. It is paying off. Bill R
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,345
Hey, congrats!
Sounds like you were running on the pump at that point. What you put in the carb initially would have likely idled for only a couple of minutes at the most. After five or six, I'd say you were pumping gas.

The bowl vent goes to the "charcoal canister" which is the evaporative emmissions stopper for the gas system. One smaller line (likely right next to the one your carb is connected to) runs to the gas tank(s) while the larger one goes to the air cleaner to let the vapors get sucked gently into the engine.
The second large port should have a cap on it (we call them "mushroom caps") to keep debris out, but let air in.

This system might be for smog, but like the PCV system it's a good thing for not only the environment, but your engine and the general health of your family if you park the truck near the house or in the garage.
I'd leave it if you can. Most try to remove everything related to smog, but in most cases that has turned out to be a mistake other than for having less clutter.

Paul
 

sprdv1

Contributor
REBEL
Joined
Mar 8, 2007
Messages
81,734
1 problem at a time Bill.. U got this

PROGRESS (but not complete success)!!! I was not able to work on the Bronco Saturday or Sunday but I got back on it today. I poured gas in both vents and the engine started immediately and ran strong. I revved it up and let it idle and it ran well both ways. While it was running, I got out and made a visual inspection of the engine. There was a constant drip, drip from the carb. It was dripping in the area of the plunger on the front of the carb that is actuated by the throttle. It was not dripping from that plunger but behind it. It continued to drip for a while after I shut the engine off. I don't know if the engine was running on gas that it was pumping from the gas tank or just running on the gas I poured into it (probably 2 to 3 ounces). Whichever it was running on, it sure did sound good. I let it run about 5 to 6 minutes. This carb has a valved bowl vent as shown in the picture in a previous post. By the way, what is the container mounted on the firewall that is connected by a line to the valved bowl vent?

Thanks again for all the help and patience. It is paying off. Bill R
 
OP
OP
B

Bill R

Newbie
Joined
Oct 5, 2017
Messages
41
You need to fix that drip, drip, drip. That is the accelerator pump. You can just buy that part or buy a full rebuild kit. Could just be screws loose their only supposed to be hand tight. I would not drive it until you get it fixed unless you want to roast marsh mellows or something.

https://shop.advanceautoparts.com/p/dorman-help-accelerator-pump-diaphragm-90082/5014301-P

I picked up the part and I am ready to put it in. Is there anything I need to know about how to do this or is it just common sense? Touching a carburetor with a tool is a new experience to me.
Thanks for your help, Bill R
 

Rustytruck

Bronco Guru
Joined
Feb 24, 2002
Messages
10,875
Its not a big deal 4 screws takes it off. Once you get the cover off you peel off the pump. There is a light weight conical spring behind it watch for it and put it back in the same direction. Screws are only tighten snugly not cranked down tight. little screws in aluminium you don't want to be stripping them out. Took me longer to type this than do it.

Put a rag under the carb as there may be some fuel dripping. Catch that in a rag and remove the rag before you go on starting the truck.
 

bronconut73

Bronco Guru
Joined
Aug 7, 2012
Messages
9,916
Not to hi-jack but...
Have y'all seen an accelerator pump diaphragm go bad but not leak?
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,345
Absolutely. If anything is consistent about these old rigs, it's that they're inconsistent!

But in this case, consistency aside, the diaphragm and gasket are sometimes separate pieces anyway. Sometimes the same thing, though and I can't remember what type this is on our carbs.
The diaphragm can fail and stop pumping gas through the squirters without leaking out the cover.
On the flip-side of that you can have a leaking seal/gasket around the cover and have the pumping part of the diaphragm will still be pumping.

Paul
 
Top