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Old 07-27-2010, 03:55 PM   #1 (permalink)
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72 Mustang 302 dies when hot.

[SIZE=3]Hey everyone,

I'm new to the forum, and have recently purchased a 72 Convertible with the Mach 1 Package. Fun car, but we're still getting to know each other. What I know now is that she doesn't like the desert! Originally thought I had an electrical issue, but now I'm really stumped! This is driving me nuts!

[/SIZE]
[SIZE=3]Runs like a champ when cool to warm. After it's hot/heat soaked, it will rev, and idle (ok, but not great), but when you put a load on it, it just dies. Here’s what I’ve done since the problem began, and what I am observing:

Parts
• New carb (already had, so put it on
• Hard metal fuel supply lines (at carb)
• New coil (Mallory resistor coil)
• New electronic distributor internals (Mallory)

Observations
• The fuel bowls are full
• Timing at 12 btdc
• The fuel filter is nice and full when cold, but as temps rise, fuel filter drains to near empty, and I can see random (not steady) spurts of fuel every few seconds into the near empty filter. However, carb bowls are full, so fuel starvation should not be a problem, correct? Or, could pump cavitation cause an issue, even with full fuel bowls?
• Once engine reaches max temps, at idle, if I try to hit the accelerator, it just dies.[/SIZE]
[SIZE=3]

I have a Carter fuel pump with about 2k miles from another project, which I could try. I also have recently rebuilt the old Holley 1850/600, which I could swap, but somehow I don't think that's the issue. I was having this problem with the old carb before rebuilding it. It almost seems like a rich condition after it heats up, but again, I really have no idea!

Thanks to all for looking!
-Sean[/SIZE]
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Old 07-27-2010, 05:07 PM   #2 (permalink)
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Re: 72 Mustang 302 dies when hot.

Are you saying that just idling and you give it gas it dies or when you have it in gear and trying to move? The fuel filter running empty is suspect. You need to check the tank pick up to make sure it is clean and any hoses on the fuel lines for cracks or loose clamps to make sure it isnt sucking air. Since it doesnt idle good you could have a vacuum leak.
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Old 07-27-2010, 05:52 PM   #3 (permalink)
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Re: 72 Mustang 302 dies when hot.

I let it good and hot again, and shut it down. I could hear a faint hissing, and upon closer inspection, the fuel in the carb is boiling. I could see down the carb that fuel was spurting out of the squirters with the engine off. Looked through the site plugs (temp clear ones) and could see fuel jumping around a bit.

Car is cooling properly, and there's no detonation, so I don't think I'm overheating the engine. What can I do about this fuel boiling issue?

Thanks again!
-Sean
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Old 07-27-2010, 06:56 PM   #4 (permalink)
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Re: 72 Mustang 302 dies when hot.

You could try a phenolic carb spacer.
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Old 07-27-2010, 07:17 PM   #5 (permalink)
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Re: 72 Mustang 302 dies when hot.

Going to try that, and a whole lot of other heat shielding material for the fuel lines, headers, and a heat shield for the carb. This desert is hot. Hopefully this stuff helps! Will let you know.
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Old 07-28-2010, 06:44 AM   #6 (permalink)
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Re: 72 Mustang 302 dies when hot.

Sounds like the timing is retarded and to compensate you turned the idle screw way open and now it is dripping out of the carb. when you give it gas nothing happens, sounds like a vacuum leak somewhere... after the engine got so hot it may have melted or deformed the vacuum line leading to the vacuum modulator (close to header).... disconnect the vacuum line going to the modulator and plug that port on the carb to eliminate that possibility. try running again, with a vacuum leak you cannot properly set the timing. with a can of wd-40 or carb cleaner, carefully spray under the carb and intake manifold gaskets to see if the engine picks up speed, if it does you have a vacuum leak in that area... with the vacuum line disconnected from the modulator try resetting the timing.. also, the new carb may not be tuned correctly yet, so it could be running lean. you have many variables to check...I just went through this and it sounds very similar to the conditions I had and those were my problems, so check that out...
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Old 07-28-2010, 08:34 AM   #7 (permalink)
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Re: 72 Mustang 302 dies when hot.

what carb? What Choke?
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Old 08-01-2010, 09:16 PM   #8 (permalink)
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Re: 72 Mustang 302 dies when hot.

Hey everyone,

Thanks for all of your helpful advice. Here's the outcome of some work this weekend:

1. Fuel WAS boiling, and causing some undesirable issues as you would expect. Put on a 1" phenolic spacer, along with heat shield under carb, and a reflective thermo/insulating sleeve around the hard fuel line from the fuel pump to the soft line at the carb. Made a huge difference. Also went ahead and put a heat shield between the exhaust pipe and the exit line from the tank, since that line was about 2 inches from the exhaust pipe.

2. Although it ran much better without the vaporization problem, after a few cycles of running the engine around with the A/C on in stop and go traffic, and then turning the ignition off/back on, I started getting some stumbling. It wasn't as bad, so I kept on doing it for another 20 minutes to see if I could make the problem worse—got to the point it would not even restart after sitting a couple of minutes with the key off. No spark.

3. Was running 12 volts to the NEW Mallory resistor coil, as recommended by Mallory. Instead, went back through the resistor wire, to a standard Accel coil, and have been running strong all weekend long, through SUPER hot air temps. I don't think the resistor coil was letting enough voltage through after it heated up.

SO, the problems were multiple fuel and electrical issues.

Thanks for all the replies and suggestions. I'm sure I'll be back!

-Sean
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Old 08-01-2010, 09:21 PM   #9 (permalink)
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Re: 72 Mustang 302 dies when hot.

You mentioned your fuel bowls are full........seems to me they should be around 25% ish not full.
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