lost

Stang67

Stang67

Well-known member
I have a stock engine and am running a Weber 2 barrel carburetor. Everything was fine until like 4 days ago my car broke down in the middle of the road. I got the car back running now but am having some problems with the carburetor. If I give it gas it’s to shakes like crap and is back firing. I was thinking of selling my Weber carburetor and just get a 1 barrel carburetor so I can be stock all around. I think the carburetor is to powerful for this stock engine.
 
Hi Stang 67,

The old saying is if you think its the carb its probably the timing and if you think its the timing its probably the carb.

Backfiring sounds more like a timing issue and maybe a vacuum issue.

First replace the PCV Valve, it always seems to be the culprit when mine suddenly runs rough.

If you have a timing light, check the setting, but be mindful that if you have an old harmonic balancer, the timing marks might be migrating around - best to disconnect and plug the vacuum advance line (I use a golf tee) and adjust for highest RPM/vacuum.

Then check the vacuum advance line from the carb or manifold to the distributer canister. if its split or cracked its both a vacuum leak and will wack out your timing. get some extra line while youre getting the PCV.

If you are using a stock Dizzy its expecting the spark control signal from the stock carburator, not manifold vacuum, but you said it was running fine, so I doubt thats the issue.

Then it might be another vacuum leak - do you have an automatic transmission or power brakes? Mine had the vacuum lines so cobbled up after 40 years of ham handed mechanics, I built a new vacuum manifold.

I'm afraid if you jump into changing the carb with out checking the vacuum & timing, you'll compound your problems..

mark
 
JackFish":271xjdrs said:
Perhaps it's nothing more than the fuel pump failing.
Click to expand...
+1

Maybe even fuel filter...from running fine to not running :unsure:

from BIGREDRASA's sig...
Okham's Razor: "The simplest answer is usually the correct answer." Sir William of Ockham
Click to expand...
 
DupleDreux":iq5q6ak2 said:
Hi Stang 67,

The old saying is if you think its the carb its probably the timing and if you think its the timing its probably the carb.

Backfiring sounds more like a timing issue and maybe a vacuum issue.

First replace the PCV Valve, it always seems to be the culprit when mine suddenly runs rough.

If you have a timing light, check the setting, but be mindful that if you have an old harmonic balancer, the timing marks might be migrating around - best to disconnect and plug the vacuum advance line (I use a golf tee) and adjust for highest RPM/vacuum.

Then check the vacuum advance line from the carb or manifold to the distributer canister. if its split or cracked its both a vacuum leak and will wack out your timing. get some extra line while youre getting the PCV.

If you are using a stock Dizzy its expecting the spark control signal from the stock carburator, not manifold vacuum, but you said it was running fine, so I doubt thats the issue.

Then it might be another vacuum leak - do you have an automatic transmission or power brakes? Mine had the vacuum lines so cobbled up after 40 years of ham handed mechanics, I built a new vacuum manifold.

I'm afraid if you jump into changing the carb with out checking the vacuum & timing, you'll compound your problems..

mark
Click to expand...
Its a manual transmission and I dont have power brakes. I change the fuel filter and the fuel pump is only a year old.
 
You still have vacuum lines, places on the carb that vacuum can leak from, a plug in the tapped part of the manifold for where the modulator's vacuum line would be. And your distributor could have slipped. CHECK TIMING AND VACUUM BEFORE YOU MESS WITH FUEL!!!
 
Mercury Mike":3fphdeke said:
You still have vacuum lines, places on the carb that vacuum can leak from, a plug in the tapped part of the manifold for where the modulator's vacuum line would be. And your distributor could have slipped. CHECK TIMING AND VACUUM BEFORE YOU MESS WITH FUEL!!!
Click to expand...
Well I think I have the timing on point but dont hold me to it because everytime I move the dist the carb will start to back fire
 
Start all over. Pull #1 spark plug, crank the engine over by hand until you feel air push out of the cylinder, compression stroke. Then move the harmonic balancer forward to TDC. Make sure that the rotor is pointing at #1 spark plug on the cap now. If not, that's gonna be your starting point now, and move the distributor so that the #1 is right there. Hook up your timing light, set it to 10* or 12*, and then check all your vacuum lines. Get back to me. =)
 
Mercury Mike":22ub1f8s said:
Start all over. Pull #1 spark plug, crank the engine over by hand until you feel air push out of the cylinder, compression stroke. Then move the harmonic balancer forward to TDC. Make sure that the rotor is pointing at #1 spark plug on the cap now. If not, that's gonna be your starting point now, and move the distributor so that the #1 is right there. Hook up your timing light, set it to 10* or 12*, and then check all your vacuum lines. Get back to me. =)
Click to expand...
Guess am going to try that tomorrow then and tell u the out come.
 
If youre sure the fuel pump and filter are fine and the timing is on, I'm pretty sure its a vacuum issue. backfiring through the carb isn't usually a carb issue, its the plug firing at the wrong time in the cycle.

Theres a very remote chance your timing chain jumped a tooth, but I'd first make sure the vacuum, and especially the vacuum advance, systems are all fine.

Are you running the stock Dizzy? a load a matic usually needs a modulated vacuum signal from a stock 1100. Then you'd be right to go back, but again, its not because of the carb, its the timing and specifically the vacuum advance that's your issue.

Mark
 
DupleDreux":1i8tnmzx said:
If youre sure the fuel pump and filter are fine and the timing is on, I'm pretty sure its a vacuum issue. backfiring through the carb isn't usually a carb issue, its the plug firing at the wrong time in the cycle.

Theres a very remote chance your timing chain jumped a tooth, but I'd first make sure the vacuum, and especially the vacuum advance, systems are all fine.

Are you running the stock Dizzy? a load a matic usually needs a modulated vacuum signal from a stock 1100. Then you'd be right to go back, but again, its not because of the carb, its the timing and specifically the vacuum advance that's your issue.
Mark
Click to expand...
Am running a 68 dist with dual vacuum. How can I even tell if my fuel pimp is bad its only a year old. If my timing chain did jump a tooth how can I fix that.
 
[/quote] because everytime I move the dist the carb will start to back fire[/quote]

That pretty much tells you its a timing/vacuum advance issue. I bet your canister was stuck, the timing was set with it stuck, you were running fine without vacuum advance, and then it became unstuck. Your timing went haywire. If you were running a stock dizzy, now you have all the problems of folks who change the carb without also going to DSII or DUI!

a search on Load o Matic will turn up only a hundred or so posts on the topic.

let us know!

mark
 
because everytime I move the dist the carb will start to back fire[/quote]

That pretty much tells you its a timing/vacuum advance issue. I bet your canister was stuck, the timing was set with it stuck, you were running fine without vacuum advance, and then it became unstuck. Your timing went haywire. If you were running a stock dizzy, now you have all the problems of folks who change the carb without also going to DSII or DUI!

a search on Load o Matic will turn up only a hundred or so posts on the topic.

let us know!

mark[/quote] I thought 68 dist were not load o matic
 
Again, the timing chain is very very last, you have to pull the timing chain cover (after waterpump and harmonic dampener) and make sure the marks line up. so its definatly last. The cover is aluminum, easily stripped with the oil pan bolts, fneeds the seals replaced. and the dampener needs to be retorqued to like 90 ftlbs. Overall it takes time and patience.

With the fuel pump, you need a helper. Get a glass jar and long length of fuel hose, and crank the engine a few times, gas should come out (into the glass jar) in even pumps or streams. Rebuilt pumps generally are not as trouble free as the orginal ones were, they are not remanufactured as the original equipment was manufactured.

Finaly, for the 68 Dizzy, I don't have any experience with them, but I know they need a ported vacuum source on the carb. Is that how yours is attached?

Other wiser members need to step in here.

mark
 
Sorry Stang 67 I thought you had a 67, I was writing at the same time you were, and not responding to your last post.

mark
 
DupleDreux":218300x0 said:
Sorry Stang 67 I thought you had a 67, I was writing at the same time you were, and not responding to your last post.

mark
Click to expand...
I do have 67 stang
 
It will fix you up just fine. Just like a DSII. Either way, you're going to have to follow the procedure that I wrote for you above for setting proper timing before you go anywhere else. Don't even TOUCH fuel until you're 110% positive that your timing is perfect or as close as you can get it. =)
 
Stang67":1trbut8i said:
.....Am running a 68 dist with dual vacuum. How can I even tell if my fuel pimp is bad its only a year old. If my timing chain did jump a tooth how can I fix that.
Click to expand...

One thing at a time :D

First off, I do not wish to insult anyone but as it is impossible to know what a person's skill level is I will make an obvious statement or two. With a "dual vacuum" distributor it is possible to have the vacuum advance connected to the side that actually retards the spark rather than advances it. Are you absolutely certain you have the correct side connected? Next, as mentioned above, you need to have the vacuum advance connected to the proper vacuum source at the carburetor.

It has been my experience (having been born on the "other" side of the tracks) and having driven numerous old junker vehicles and farm implements that a plugged fuel filter first manifests itself at HIGH SPEED FULL POWER. The only exception I have seen to this is when a tractor would sit unused for a long period of time and sediment would settle in the bottom of the tank causing a "no start" situation.

Thus far in my life every time I have had a situation that turned out to be "no fuel" the engine just wouldn't run when more fuel was demanded. Think about what happens when you run out of gas.

You may have vacuum leak problems but I'm thinking that a spark is happening at the wrong time/place. Double check the firing order for proper placement of the wires, make absolutely certain that the points are good and properly adjusted, etc.
Joe
 
You must log in or register to reply here.
Back
Top