Jason72Bronco
Jr. Member
- Joined
- Feb 16, 2015
- Messages
- 156
This post is detailed, but I try to address as much as I can in an initial post to take out guesswork:
After lunch today I decided to take the Bronco out for an afternoon ride. It has been starting and running perfectly for months. I started it, let it alone to warm up at idle while I moved another car (3 minutes), came back and was backing down my driveway (slight decline) and it died. It would not restart.
My first thought was I was out of gas...that's how it was acting. I knew the tank was low and I was on a slight decline, so I figured maybe the pickup was not getting gas.
Went and got 5 fresh gallons, put it in, and the truck would start but ran very rough. I could "feather" the throttle and hold the revs, but it would come back down to idle and die. Eventually, after it was warm enough that the choke was open, it would try to run very rough but would just die at idle.
I left for a few hours to work on another project, let it cool down, and think.
Came back later and it started, normal high idle at cold start up (1250 rpm), but still ran rough, and eventually when warm--same issue, it would cough, sputter, would not hold idle and would die. No backfiring or missing.
Specs on my 72 Bronco with 302 V8:
Has been starting and running perfectly for weeks. I drove it yesterday and parked it overnight. Came out today and have these issues, like the Grinch snuck in overnight.
Ignition: All new, 2 months use. Mallory Unilite distributor, Promaster Coil, 8mm wires and Autolite AP 45 plugs. Timed perfectly with my fancy new digital gun last week. All checks out.
Electric: New Optima Red Top (1 month); Duralast Gold Alternator (2 yr.); new electronic voltage regulator and ignition solenoid. All checks out.
Fuel: New gas tanks, lines and fuel pump (2 years old); brand new filter last week; Holley 4160 4bbl carb w/elec choke (3 years old--never adjusted, ran perfect out of box.) Never had any issues with this fuel system.
I drive the Bronco around town maybe 50-100 miles a week, but it is always charged and fresh gas.
Tests (all at 60 degrees outside temperature):
1. After letting it cool down yet again, it started and it would hold a rough idle. While I had the chance I checked spark and timing and voltage. All perfect. After it barely got warm, its back to not running properly and won't hold idle and dies.
2. Filter is clear and clean, fuel pump is pumping. But, the filter is filling up completely now. It used to pump into the filter and exit at a rate that you could see in the clear filter about 1/4 full of fuel while running. Odd, I thought.
3. With truck turned off, pulled fuel line off of carb, and it was under some pressure. Odd. A good amount of gas squirt when I pulled the hose, but no dripping after that. (Is that normal?)
4. Ignition off, I placed pulled fuel line into a container, and using remote starter I cranked it for about 5-8 seconds and fuel pumped out strong--about half a Pint Glass (8 oz.) in 5 seconds. Huh, seems like alot for a mechanical pump.
4. Ignition on, fuel inlet to carb plugged, hose from pump plugged, I remote started and "drizzled" gas directly into carb. I could get it to run/idle, but not exactly a smooth test.
5. Pulled a plug. All normal. I kind of expected to see wet from fuel, but nope.
Clearly a fuel issue, but I'm stumped. "Ran great when I parked it" is absolutely true. It almost seems like it is flooding, or too much gas. Like either the pump took some steroids overnight and it is "overwhelming the carb", or the carb is not functioning properly in restricting flow/pressure. (I am NOT an expert on internal workings of carbs.)
Your comments and thoughts are appreciated.
Jason
After lunch today I decided to take the Bronco out for an afternoon ride. It has been starting and running perfectly for months. I started it, let it alone to warm up at idle while I moved another car (3 minutes), came back and was backing down my driveway (slight decline) and it died. It would not restart.
My first thought was I was out of gas...that's how it was acting. I knew the tank was low and I was on a slight decline, so I figured maybe the pickup was not getting gas.
Went and got 5 fresh gallons, put it in, and the truck would start but ran very rough. I could "feather" the throttle and hold the revs, but it would come back down to idle and die. Eventually, after it was warm enough that the choke was open, it would try to run very rough but would just die at idle.
I left for a few hours to work on another project, let it cool down, and think.
Came back later and it started, normal high idle at cold start up (1250 rpm), but still ran rough, and eventually when warm--same issue, it would cough, sputter, would not hold idle and would die. No backfiring or missing.
Specs on my 72 Bronco with 302 V8:
Has been starting and running perfectly for weeks. I drove it yesterday and parked it overnight. Came out today and have these issues, like the Grinch snuck in overnight.
Ignition: All new, 2 months use. Mallory Unilite distributor, Promaster Coil, 8mm wires and Autolite AP 45 plugs. Timed perfectly with my fancy new digital gun last week. All checks out.
Electric: New Optima Red Top (1 month); Duralast Gold Alternator (2 yr.); new electronic voltage regulator and ignition solenoid. All checks out.
Fuel: New gas tanks, lines and fuel pump (2 years old); brand new filter last week; Holley 4160 4bbl carb w/elec choke (3 years old--never adjusted, ran perfect out of box.) Never had any issues with this fuel system.
I drive the Bronco around town maybe 50-100 miles a week, but it is always charged and fresh gas.
Tests (all at 60 degrees outside temperature):
1. After letting it cool down yet again, it started and it would hold a rough idle. While I had the chance I checked spark and timing and voltage. All perfect. After it barely got warm, its back to not running properly and won't hold idle and dies.
2. Filter is clear and clean, fuel pump is pumping. But, the filter is filling up completely now. It used to pump into the filter and exit at a rate that you could see in the clear filter about 1/4 full of fuel while running. Odd, I thought.
3. With truck turned off, pulled fuel line off of carb, and it was under some pressure. Odd. A good amount of gas squirt when I pulled the hose, but no dripping after that. (Is that normal?)
4. Ignition off, I placed pulled fuel line into a container, and using remote starter I cranked it for about 5-8 seconds and fuel pumped out strong--about half a Pint Glass (8 oz.) in 5 seconds. Huh, seems like alot for a mechanical pump.
4. Ignition on, fuel inlet to carb plugged, hose from pump plugged, I remote started and "drizzled" gas directly into carb. I could get it to run/idle, but not exactly a smooth test.
5. Pulled a plug. All normal. I kind of expected to see wet from fuel, but nope.
Clearly a fuel issue, but I'm stumped. "Ran great when I parked it" is absolutely true. It almost seems like it is flooding, or too much gas. Like either the pump took some steroids overnight and it is "overwhelming the carb", or the carb is not functioning properly in restricting flow/pressure. (I am NOT an expert on internal workings of carbs.)
Your comments and thoughts are appreciated.
Jason
Last edited:
