My classic Mustang won't start/run

[440Magnum]

One other thought... you don't still have a load of fuel that was purchased between November and April in there, by any chance? Winter fuel, at least in my area, will practically boil in front of your eyes on a hot day. If you've got a tank of that stuff and are driving in August there's a very good chance it just flat won't stay liquid in the carburetor once the engine is warmed up.

But go back to the basics- Fire, air, fuel. Make sure you have spark. If you have spark, see if it'll fire up (briefly) with a shot of fuel down the carb. If it does that, then its definitely something on the fuel delivery side of the equation. If it won't, then its ignition, or maybe its drowning in fuel from a stuck float valve (pull a plug and see if its wet).

 

[loyd]

Merkava, what do you do for a living?

 

[oldhp]

Have you had the gas tank flushed out? Almost all old hot rods have rusted up gas tanks. The crud will suck up and ruin the sock filter pickup. Get a known good coil and swap it in. These old beast's need some tender loving care, don't give up!!!

 

[Volvohead]

I wouldn't put the tank pick up first on the checklist just yet.

But if you do pull the sender/pickup assembly from the tank, and it's still original, be extra gentle. Some of them had plastic housing plates. By the 1980s, I saw some that had gotten very brittle. At this age, they are only worse. A careless R/R can crack it, and then you have a fuel tank leak.

All this alcohol in today's gas certainly isn't helping the old tanks either. Once you get everything sorted out, be sure to keep up a full tank as often as possible.

 

[dja4260]

Does it have compression, gas, and spark?

Narrow it down.

 

[wag123]

Originally Posted By: Volvohead
I wouldn't put the tank pick up first on the checklist just yet.

Loss of spark will cause the engine to die instantly. Intermittent spark will cause the engine to buck and backfire. Loosing power and gradually dying-out sounds like it is running out of gas.
After this happens, 1st, do what overkill told you to do, check to see if there is fuel in the carburetor's primary float bowl, or, take the air cleaner off and spray some carburetor cleaner spray down into the primary throats and crank the engine. If it attempts to start, you found your problem.
On a limited use car the first things to check are the fuel filter(s), then the fuel pump (probably not the problem), then the gas tank fuel pickup, then, if these all check out, believe it or not the fuel line itself can get plugged with varnish/gum/goo from gas that had gotten old and gone bad after long term storage. The way that I know this can happen is because I had it happen to me on a 65. Right after I purchased the car, this same kind of problem had me tearing my hair out. After throwing a lot of time and money at it, I finally found the plugged fuel line.

 

[drfeelgood]

Thank you all for the responses. I had thought of some of your suggestions and am glad to hear maybe I'm on the right track. To answer some of the questions raised in the thread:
The car is a relatively recent restoration and almost all parts in question are at least "newish". It has a Pertronix III coil and electronic ignition. I'm a bit suspicious of the fuel pump, as it has seemed to at least seep a little recently. These pumps are removable bowl and rebuildable with fresh gaskets, diaphragm, etc. The gas is always stored with fuel preservative and the car ran as usual up until the loss of power both times. After it died, it would continue to crank easily but only rarely sputter or seem to start for a second or two and then die again.

 

[Volvohead]

Originally Posted By: wag123
Loss of spark will cause the engine to die instantly. Intermittent spark will cause the engine to buck and backfire. Loosing power and gradually dying-out sounds like it is running out of gas. . .


No, not so where a coil fades out. A fading coil will exhibit a dying engine mimicking a loss of fuel before its output falls below minimum HV. They don't just cut-out. A points failure is a different story.

Most temperature-related fuel malfunctions will still allow fuel flow, even at a greatly reduced rate. The engine will attempt to restart with most fuel system problems.

Here, you do a restart diagnosis to determine whether the root cause is ignition or fuel related. A fading coil from overheating or other ignition failure will demonstrate a dead cranking condition until the system cools. A fuel system failure will still allow a stumble with accelerator pumping. A can of starting fluid or carb cleaner is useful to determine which system is at fault.

 

[Volvohead]

Originally Posted By: drfeelgood
After it died, it would continue to crank easily but only rarely sputter or seem to start for a second or two and then die again.


Thanks for answering that. Any attempt to start means you have a fuel system problem in this case.

A seeping fuel pump is typically a dead give-away. I'd start there.

 

[Scott_Tucker]

Spray a couple of bursts of carb clean or brake clean into the carburetor and try to start it. If it starts then dies, you know you have no fuel. If it does this, concentrate on the fuel system.

Also, look down the throat of the carb with a flashlight and actuate the throttle linkage. You should see a squirt of fuel from the accelerator pump. It should be pretty obvious. If you see this, then you likely have enough fuel to start the engine so concentrate on spark.

 

[Yah-Tah-Hey]

Can't help but think of Smokey Yunick's admonition about getting the fuel/air mixture close and a spark at the right time,you can't keep em from running.