Classic Mustangs (Tech) Technical discussions about the Mustangs of yester-year.

Car Sputtering/Stalling When Warm

Old 07-23-2009, 09:30 PM
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Mesomorphman
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Default Car Sputtering/Stalling When Warm

Okay... I just got a 1969 Mustang Coupe with a 351 Cleveland in it (not stock, I know). I am not good with cars. As a matter of fact, I just got the car yesterday, and this is essentially the first car I have worked on. I can do the basics (change oil, etc...) and have a bike that I work on myself, so I am not mechanically challenged, I just have no experience with car engines. That being said...

So here's the deal. This car ran pretty well yesterday. The only problem was, when I would peg the throttle, the car idle speed would increase. It would also surge until I could turn it off and adjust the idle screw on the carb. Then when I cut it back on it would be fine again.

Today... As I was going to Autozone, the car began to sputter and surge, losing and then regaining power (and one backfire) until it just quit. I pulled to the side of the road, sat for a minute, examining the engine like I actually knew what I was looking at, and then started it back up. It ran fine at idle. A little while down the road, though, it did it again. Then, if I left the car running in park for about 20 seconds (all this on the side of the road), it would begin to increase in RPM's until I had to shut it off. Also, smoke began to come out of the tailpipe.

I idled home and began to work on it. I popped off the air filter and looked at the carb as I started the car. But the car ran fine at the house (not driving, just in park). I think the choke (if it is the big flap over the hole) is working correctly. It was open as the ran. I have no idea what is going on, and any help would be appreciated.

Just remember, I'm a rookie. So you may have to have patience with me here and explain terms like check the fuel pressure and so on. I know what it is, but I don't know the procedures to do such things. I know the operations of an engine (worked on my bike and a few years ago helped work on a 442) but I have no idea where most of these things are and how to adjust them. I have a ratchet set and stuff, but no electronic equipment or fancy tools and stuff.

This is my first post, sorry that it's so long. Thanks for all the help in advance.
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Old 07-23-2009, 11:04 PM
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sounds like a carb rebuild and cleaning is in order. Probably a new fuel pump too. Sounds like both of those things need addressing

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Old 07-24-2009, 12:38 AM
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Is there some sort of test that I can perform to determine whether the fuel pump is providing enough fuel to the engine under load?
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Old 07-24-2009, 08:59 AM
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Yes there is....

Remove the fuel line from the carb and place the end in a glass jar. Crank the engine over about 3 seconds or so. Fuel should gush out of the hose and you should have about a cup with in 5 seconds. If after 5 seconds you have a couple of ounces then its probably time for a new pump.

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Old 07-24-2009, 10:52 AM
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You could also have a vacuum leak issue. Check your vacuum hoses and ports for cracks, breaks, disconnects, or missing caps.

Not saying you don't have a problem, but carburated cars can vary in idle speed according to the temperature of the air mixture entering the engine. My car varies by 200 rpm depending on the air and engine temp.
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Old 07-24-2009, 11:09 AM
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You might want to get a new fuel filter too while you are at it.

My car did the same thing a while back. It would idle fine, but when I would put it under load it would start to sputter and loose power and wouldnt run right. The carb needed to be cleaned and rebuilt.

Check the fuel pump first though like stated above..
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Old 07-24-2009, 11:45 AM
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Is it difficult to rebuild a carburetor? Also, could someone help me by labeling the parts on my carburetor? I am familiar with most of the idle mixture screws and such (2 mixture screws, 1 idle speed screw), but the ports and such I have no idea. I will post a picture shortly.
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Old 07-24-2009, 04:07 PM
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Here are the pictures. Can someone help me by labeling the numbers? Also, I have no idea where the fuel filter is, still. I looked everywhere that I knew to look, and I can't find one. Is a fuel filter built into this carb? Is it possible that there is no fuel filter? I'm at a loss, here. Edit: Wait, is that gold thing #6 the fuel filter?





Last edited by Mesomorphman; 07-24-2009 at 04:09 PM.
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Old 07-24-2009, 06:27 PM
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Humm Im not familuar with that carb but they are all pretty much the same ill give it a shot....And no its not too hard to rebuild at all.

1) not real sure on the name or function but I think its a vent.... or it could be pointing to the round thing which is a auto choke deal (see 2)
2) thats the choke plate covering the primary ventuires. You'll want to make sure this is open when you attempt to drive the car. It is closed now. If its closed that that when you try to drive it will cause problems very much like you are experiencing now. Its automatic bimetallic strip style when the car is warm it should automatically fully open the choke check to make sure its working

3) secondary ventures open at wide open throttle to about double air/fuel flow

4) possibly vac hose nipple you'll want to make sure its blocked or connected to something....

5) vac hose probably for vac advance on distributor follow it and see if it goes to the dizzy.

6) a crappy looking fuel filter which could be the problem. this is where you would check for fuel flow. Remove that from the carb and stick in glass jar.

So now you have more things to check into...Happy hunting

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Old 07-24-2009, 06:32 PM
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For what its worth if it comes down to having to rebuild the carb I would personally not bother with that carb. If it were my car I would find out what the CFM of that carb was and match it to something new and not **** around with that one.

That would be my plan of attack....thats all

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