Engine cutting out

THis is a really interesting case. The 2nd gear-only effect and no backfiring are real puzzlers. I guess the absence of backfiring supports the fuel starvation theory--no raw fuel to be passed on to the exhaust. But it would have to be nearly complete shutoff, not just leaning out. So, I'm thinking something like MassAMan or Benson suggest must be going on--but why only in 2nd gear; if it's a WOT effect sucking lots of gas, there's never a higher flow rate than wide open throttle in 1st gear. Must be some really subtle intermittant blockage that requires a high but not-too-high flow rate, I guess.
 
Benson said:
A couple of things to check:

1. Sometimes the plug on the bottom of carb for the main jet will have an indentation inside the plug where a small piece of Gasoline saturated cork or rust will be "floating" around on the bottom the plug.

Under high flow conditions (WOT) the gas flow will suck the cork up and block the main jet temporarily. Then at idle or lower speeds the cork drops back down and all is fine until the next WOT.

The same thing can happen inside the port for the cap jet/ secondary well also. Either one will limit gas flow.

2. Remember the flat thin piece of solder that forms when you flick some hot solder off of your solder iron onto the floor?

If the gas tank has been soldered in the past I have seen a flat thin piece of solder "floating" around in the bottom of the gas tank. Occasionally the solder piece will cover the outlet, stopping or limiting gas flow to the carb.

NOTE if the shutoff valve has a "finger" filter installed then this will not be a problem.
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The carb was recently rebuilt by Jim Adams and when I had the problem last week, I opened the carb and blew everything out with carb cleaner and compressed air. Nothing was found and the carb was as clean as a pin. The problem persists.

The tank has a pinhole in it but, it has been there for years and no other fixes have done. The inside of the tank is clean as a pin and there is no rust dust in the sediment bowl or the carb bowl so there is none in the tank. Opening the valve, the fuel drains into a glass jar clean and doesn't slow down in a half quart. I don't think I would use a half quart in a mile or two even at full throttle no matter what gear.
 
1928Pickuppain said:
If I'm not mistaking when you floor a car and open up the carb the vacuum drops that's why when going high speeds our vacuum whipers slow down if you already have a slight vacuum leek in eaither the carb to Maifold or manifold to block when you floor it open you will loose vacuum and run to lean for and start feeling like your out of gas. Same sinaro happened to me about two yeas ago had a crack in my manifold ran ok (yet on the leen side) till I tryed to goose it. Then bla bla bla bog bog uhg thppp.
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I had just resurfaced the manifolds and replaced the paper gaskets with copper sandwich type with copper coat sealer. The intake and exhaust do not have any cracks. At idle the vacuum gauge sits steady at 17hg.
 
steve s said:
THis is a really interesting case. The 2nd gear-only effect and no backfiring are real puzzlers. I guess the absence of backfiring supports the fuel starvation theory--no raw fuel to be passed on to the exhaust. But it would have to be nearly complete shutoff, not just leaning out. So, I'm thinking something like MassAMan or Benson suggest must be going on--but why only in 2nd gear; if it's a WOT effect sucking lots of gas, there's never a higher flow rate than wide open throttle in 1st gear. Must be some really subtle intermittant blockage that requires a high but not-too-high flow rate, I guess.
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I'm with you. I don't notice the problem in first because I usually shift pretty soon out of first so, even at WOT I only run a short way before I shift. In second I sometimes run up to 35 before shifting and I don't shift so quickly. In third I would have to run probably 60 for a good distance before it would cut out. I may try to run it at WOT in the other gears to see where it quits or if it will. This might tell if it is gas or electrical.
 
James Rogers said:
I'm with you. I don't notice the problem in first because I usually shift pretty soon out of first so, even at WOT I only run a short way before I shift. In second I sometimes run up to 35 before shifting and I don't shift so quickly. In third I would have to run probably 60 for a good distance before it would cut out. I may try to run it at WOT in the other gears to see where it quits or if it will. This might tell if it is gas or electrical.
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35 mph in 2nd! I wonder how many of our A's would get a bit squirrely in that range--I'll never know about mine. I'm starting to wonder if we have different understandings of what constitutes having to baby it. Could you hook up a tach and see if there is an rpm threshold for your problem?

Steve
 
I don't baby my car BUT, I build the motors so, I figure I will find out what the limits are and where I make mistakes by running the krap out of it. So far 10,000 miles and this is the only problem. I do remember that the last time I drove it, it topped out at about 55 in third. I am just going to have to do some experimenting to see what is the deal.
 
James Rogers said:
The carb was recently rebuilt by Jim Adams and when I had the problem last week, I opened the carb and blew everything out with carb cleaner and compressed air. Nothing was found and the carb was as clean as a pin. The problem persists.

The tank has a pinhole in it but, it has been there for years and no other fixes have done. The inside of the tank is clean as a pin and there is no rust dust in the sediment bowl or the carb bowl so there is none in the tank. Opening the valve, the fuel drains into a glass jar clean and doesn't slow down in a half quart. I don't think I would use a half quart in a mile or two even at full throttle no matter what gear.
Click to expand...

Is that through the drain plug in the carb? That is the only sure test.
 
steve s said:
35 mph in 2nd! I wonder how many of our A's would get a bit squirrely in that range--I'll never know about mine. I'm starting to wonder if we have different understandings of what constitutes having to baby it. Could you hook up a tach and see if there is an rpm threshold for your problem?

Steve
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I've never babied my cars or broken one except sheering an axle key in 1976. My hill climb run below was in second gear as I lost too much time shifting to third in such a short run. It does have 3.54 gears.


climb-1.jpg


climb-2.jpg
 
James,
There was talk awhile back about some of assembled types of float valves that didn't flow enough fuel?? Have you tried an original type, SIMPLE, needle & seat float valve? Bill W.
 
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