Car dies after driving about 1/2 hour

[Danno]

This problem just started within the last month or so. The car starts normal and runs and drives great for about a half hour, then just quits like its running  out of gas. The charging system is good and I have a quarter tank of good gas indicated. After sitting for a while it starts right back up and drives normally again. I thought maybe vapor lock because it's been hot here and I also changed the fuel filter as cheap insurance. This just happened again yesterday at a pretty busy intersection, and if it weren't for my son-in-law, and the nicest young cop I've ever met, it could have been worse. I'm going to have the battery load tested, but I don't think it's an electrical problem. I am leaning towards the fuel pump. What do you guys think?

 

[Carolina_Mountain_Mustangs]

When it happens go to the gas cap and remove it. If you hear a sucking sound the vent in the cap is plugged and as the gas is pumped out of the tank no air is getting in. When the vacuum gets to a point the fuel pump can no longer pull gas to the engine. Just one idea.

 

[Danno]

When it happens go to the gas cap and remove it. If you hear a sucking sound the vent in the cap is plugged and as the gas is pumped out of the tank no air is getting in. When the vacuum gets to a point the fuel pump can no longer pull gas to the engine. Just one idea.

Thanks ,I'll try that today.

 

[Don C]

I agree with David, gas tank venting is most likely the problem. The line up to the charcoal canister or the canister may be plugged, if you're still using them, if not you need a vented gas cap, which may be plugged. I've actually seen gas tanks collapse due to lack of proper venting.

 

[TheRktmn]

When mine did this it was a bad coil.

It would run great, then the coil would overheat, die, cool off, run, overheat, die, repeat....

 

[NOT A T5]

That happened to me too due to a crack in the coil, replaced the coil and all was good!

 

[Bill73Ragtop]

When mine did this it was a bad coil.

It would run great, then the coil would overheat, die, cool off, run, overheat, die, repeat....

Same thing happened to me.  It all depended on ambient air temps and how long it took the coil to get warm enough to quit.

Extremely frustrating since it acted like it running out of fuel......

 

[Heavy Metal]

Ditto on the bad coil. I worked on my carbs for 2 years, before I replaced the coil.

Thick headed I guess....

 

[Danno]

I agree with David, gas tank venting is most likely the problem. The line up to the charcoal canister or the canister may be plugged, if you're still using them, if not you need a vented gas cap, which may be plugged. I've actually seen gas tanks collapse due to lack of proper venting.

Tried that and no help. No sound from the tank when cap removed and no start even after cap was off for a while.

I have had the canister removed and the line plugged for years and this started a month ago....Thanks for the tip anyway...……….

 

[Don C]

Coil or condenser, then. Unless you have an aftermarket electronic ignition, then that may be it, too.

Just for the heck of it I would probably check the fuel pressure and quantity when it's hot and has quit.

 

[Paul of MO]

Had a spongy rubber fuel line cause this same issue.  

Back at the tank there was a 6 to 10 inch rubber hose going from the tank to the metal line.  After some driving it would suck flat and the car would stall.   

The hose would pop back into shape and the car would be good to go for another 30 min - wash rinse repeat.

Took a bit to figure that one out.

- Paul

 

[Danno]

Coil or condenser, then. Unless you have an aftermarket electronic ignition, then that may be it, too.

Just for the heck of it I would probably check the fuel pressure and quantity when it's hot and has quit.

Just did that. Let it idle in the driveway until it died, then made sure it was in the no-start condition.

I cranked the engine and got spark, but when I pulled the fuel line, nothing ran out. It dripped a little and when I cranked the engine I got one weak spurt, then nothing.

Sounds like a bad fuel pump? It feels like it just burns the fuel in the bowl and line, then dies.

Weird! :huh:

 

[Don C]

Did you try it with the gas cap off? You said that you're not using the charcoal canister, how is your tank vented?

 

[Hemikiller]

My MSD did the same thing after it got hit with 18V from a defective voltage regulator. Drive for a half hour, car would die. Let it cool off and it'd start right up. Could always tell when it was about to die, as it would start sputtering and losing power.

If you're not running an electronic ignition, I vote on coil or condensor as well.

 

[Danno]

My MSD did the same thing after it got hit with 18V from a defective voltage regulator. Drive for a half hour, car would die. Let it cool off and it'd start right up. Could always tell when it was about to die, as it would start sputtering and losing power.

If you're not running an electronic ignition, I vote on coil or condensor as well.

Ok, car sat all night, so I knew it would start...….Removed gas cap and started engine, to rule out a gas tank venting problem, engine started after a couple cranks, (empty fuel line between pump and carb?). 

Noted 14.35 volts upon restart with a vom hooked to the battery, after a while this dropped to 14.19 slooowly as the engine started to sound different. Manually moving throttle linkage and watching vom, there was no increase in volts back up to what it started out as, (should there have been?)

Very shortly after that it died, like it was out of gas. Restart attempt, it would sputter then just nothing.

Pretty much ruled out a gas tank vacuum problem.  I am going to borrow a coil from a friend to rule that out, then check the fuel line from the tank to the pump and the small rubber line from the sending unit to the hard line. Then prolly a pump...…...ideas????????   :shootself: :shootself: :shootself:

 

[Don C]

It's normal for the voltage to drop after the battery is back to full charge.

You're going about it the right way, eliminating one possibility at a time.

 

[mjlan]

What type of ignition system are you running?

 

[Danno]

What type of ignition system are you running?

Old school points and condenser. Going to remove the fuel line from the tank to the pump, at the pump, and connect a line hooked to a remote gas can to it to rule out a fuel pump. Kinda fun narrowing it down, but Id rather be driving. :s

 

[73pony]

OK.

I doubt it is fuel pump. I would start with the easier things first. Coil, then points and condenser. Both of these are simple and cheap to change out and I would bet money it is one of the two. If the diaphragm on the fuel pump was bad you would have gas leaking into the crankcase and you could smell it on the dipstick when checking the oil.