1977 Bronco - won't start after driving for awhile

[Brunk77]

Got a problem....after driving for short trips, restarting requires more and more cranking. Ultimately, it won't restart when I park at my destination for 30 minutes and want to hop back in and go home. I've had it towed from parking lots to my local classic car shop and the next morning, it starts and restarts without issue. They say "we can't recreate the problem". I'm thinking engine heat may be at the root but....need help! Battery works great, fuel in the filter.....This is my weekend driver and right now, I'm stuck again wanting to avoid yet another tow. Any help would be great!

 

[bronconut73]

Vapor lock.
Do a search here using that term as a filter.

 

[SHX669]

Assuming you have Duraspark II ignition( electronic) it's more than likey the magnetic pickup inside the distributor. I had the exact same problem a couple of years ago and got the tip to look at that from a guy who had the same problem earlier . Not a hard fix and most parts houses carry the part.

 

[B RON CO]

Hi, both guys could be right. You should have a spark tester with you, then you can check for spark. If you have spark, it is the fuel problem. Good luck

 

[jckkys]

Hot engines when shut off can percolate the gas in the float bowl effectively flooding the engine. Try flooring and holding the accelerator peddle before turning the ignition key. If it's flooded this will clear the the excess fuel and the engine should start. If this doesn't work look for a spark.

 

[blubuckaroo]

Carb boil-over is one of the most common hot weather topics on this forum.
Modern fuel just​ boils at too low a temperature for carbs.
There are a few things that can help, but there really isn't a total cure.
I've used carb spacers that seemed to help, but it still occures on really hot days.
The thing that has helped the most is to block the exhaust riser port under the carb.
I'm even considering switching to an air-gap intake to further avoid engine heat to the carb.

 

[76BroncoPete]

I had a similar issue a few years back. I thought it was vapor lock, boil over, or spark, but it ended up being my old crusty gas tank. I replaced the tank and sending unit and haven't had any problem since. It about drove me crazy trying to figure out what was going on. Just another option to check if the other possibilities don't pan out.

 

[Blue71]

As said above by "jckkys".....push the gas pedal to the floor FIRST and hold it to the floor then try to start it.........mine does this every single day when I drive it and then let it set for 30-45 min. It's aggravating, but works every time.

Blue71

 

[blubuckaroo]

Even though can learn to live with it, carb perk is still pouring gas down the cylinders and contaminating the motor oil.
You should do whatever you can to lessen it. Certainly, more frequent oil changes are needed if it'still happening a lot.

 

[BroncoJimbo]

What carb?
Mine is doing this as well on a 7 yr. + old 470 Truck Avenger. It's been getting worse so my plan is to pull the carb, clean and replace gaskets. Might even add a 1/2 spacer.
Holding the petal down while cranking usually cleared it out but that has stopped working.

 

[SHX669]

I should know by now not to assume anything - but - LOL .
I assume {;D} you know that you start a carbureted engine different than a fuel injected one ; and that you start a mechanical fuel pump carb different than a electric fuel pump one - especially with the afore mentioned : formulated gas ".
Unlike EFI you have to push down on the gas pedal to start a carb - it doesn't have injectors that inject fuel into the plenum when you "hit the starter ". Think Super Soaker versus pouring from a cup.
Before you all try to prove me wrong with - ya but mine - both my carbed EBs sometimes start without giving them gas on startup sometimes not . Both mine are adjusted pretty well . On cold start push down the gas pedal and let it up , hit start , they'll run high idle for a bit and when I hear them sounding a little choked out blip the throttle and they kick to medium idle , let em run a bit more, blip throttle again and they kick down to regular idle speed.
But like others who have posted when I drive it a bit and let it sit for a while they're harder to restart. Then instead of pushing on the gas pedal right away I hit the starter and let my mechanical fuel pump "reprime " the carb then I push down on the gas pedal and they usually start.
Now the only reason I went into all this description was that I assumed Brunk 77 was using a similar technique to start his and then the fuel evaporating from his carb wasn't the issue but rather the next most likely which is the magnetic pickup .
SHX