1969 Bronco | 302 - Fuel and/or Heat issue?

[atacar]

Hi All,

I'm curious about your thoughts on this. I'm not a mechanic, but I am slowly learning via this forum, YouTube, and some tech friends.

I have a 1969 Bronco with a 302 (carburated) that recently started having engine issues. It's been running fine for a few years, but earlier this summer, it started exhibiting the issues that I listed below.

Through my non-mechnical eye, it "feels" like a fuel problem or possibly overheating? I'm looking forward to hearing back from you all!


The Issues:

• After driving for 10-15 mins, it would stall at stop lights, stop signs, or when I am generally moving slowly (giving it less gas).
  • Sometimes, when it stalls, I can get it to roll back over, but sometimes it acts like I show you in Video 2 (below), and I have to push it off the road and wait until it cools down (waiting 30-45 mins)
• Idling-wise, it starts up from a cold start decently well and can idle forever. No issues at all.
• Put it into gear, that's when it can be very touchy (see both videos below).

What I've done to troubleshoot so far:

• Replaced the radiator thermostat.
  • Note: When I replaced it, I noticed that it was installed backward and installed the replacement correctly (spring facing into the intake manifold). The backward setup has been this way since I bought the truck +5 years ago. Very strange.
  • Note: I'm using a 180-degree thermostat
• Replaced the fuel filter (yesterday - 9/2/2023)
  • Video 2 (below) took place after I replaced this fuel filter

Video 1: When I put the engine into reverse after letting it idle for approx. 20 mins. Note how the engine shakes.

• https://photos.app.goo.gl/jkEZFdWywGwW8ozM8
• Note: I can usually drive it like this for a while (10-15 mins) before it fully stalls. It requires me to give it gas continually, once it is in gear.

Video 2: The truck trying to start after being warmed up (idling for approx 40 mins):

• https://photos.app.goo.gl/2orS9TMNtXsKwkZA7
• Note: I REALLY have to pump the gas for it to turn over... but it stalls pretty quickly after I put it in gear.

 

[don k]

Sounds like a vapor lock. Is the fuel line very close to a heat source like exhaust manifold?

 

[DirtDonk]

Sounds like this has an automatic transmission?

When it’s idling normally have you checked for vacuum leaks by spraying some liquid around the upper engine?
Something like brake cleaner works great, but if it gets too concentrated in one area it can mess up newer paint.
Something like WD-40 or even water in a spray bottle also works. Carb cleaner has always been my go to, but I would never use it on anything that’s been painted in just the last year or two.

Definitely double check for things that might heat up the fuel. Dual exhaust is a notorious culprit.
Since it’s a 69, it would’ve originally come with a points type distributor. Have you checked to see if it still has points or has been converted to electronic?
Do you have any way to check timing? Maybe the local auto parts store has a tool loaner program, if you don’t already on your own timing light.

 

[atacar]

@don k / @DirtDonk - thanks for the suggestions! I'll take a look at everything you suggested this week and report back.

Correct - this is an automatic.

 

[tbratz]

In the first video, the first thing I thought of was a massive vacuum leak. I also noticed that the fuel filter looks to have very little fuel in it. The second video seems like vapor lock, but pretty extreme. Definitely check the fuel system, especially what appears to be lack of fuel in the first vid.