www.ColoradoClassicBroncos.com

Hi Gang,

Happy to to have found this forum. I just bought my first bronco - a yellow 72'. It's a pretty amazing truck with a stock 302. It's not a show truck but perfect for me. I'm looking forward to enjoying it for a long time with my family. Hopefully I'll have some nice photos soon.

I've had a couple other classic trucks including a 62' and 55' F100. I currently also have a 59' F100 and 69' D100.

Quick question about the bronco - although I have a fair bit of experience with other trucks I'm having a really hard time in cold weather. It fires up great but nothing happens when I hit gas. It's like the pedal isn't hooked up (it is though). I can let the truck idle for 5 minutes or so and then the throttle responds again and the truck drives great. I thought perhaps it was the autochoke but I readjusted it and still the same response. It's the stock motorcraft 2100 two barrel carb. I put in a new fuel filter, fuel pump and all hoses are new. I also put in a new alternator, voltage regulator, and battery and starter. (not because it was related to this problem but because the truck needed them...)

Any thoughts?

Thanks,
Danny

Mine does the same thing but, not as bad as what yours sounds like. its the choke on mine...... going EFI soon. Highly recommend it!
And Welcome! get those pictures posted!

That does sound like a choke issue. Welcome! Pics?

Welcome!! Thanks for stopping by!! Watch the staging section for tech days and breakfasts!

Do you have someone who can help you when starting in the cold? It would be nice to see the beginning choke plate setting, likely too far closed.

Welcome! You'll find lots of good help here. Post us some pics. We are all suckers for Bronco porn!

Thanks for the welcome, guys! I'll try to get some photos this weekend.

I can also get a photo of the choke. I'm wondering too if it could be the choke pull off ?- it appears a past owner put a later model choke pull off on but I'm not 100% certain. If I take a picture of that too would you guys be able to tell?

Thanks again for the warm welcome!
Danny

dcombs wrote:Thanks for the welcome, guys! I'll try to get some photos this weekend.

I can also get a photo of the choke. I'm wondering too if it could be the choke pull off ?- it appears a past owner put a later model choke pull off on but I'm not 100% certain. If I take a picture of that too would you guys be able to tell?

Thanks again for the warm welcome!
Danny

Welcome first off. Take pics and I'm sure someone will be able to help out.

Hi Guys,

Here are two photos of the carb when cold. You'll see how I adjusted the choke plate open just a little bit. I put the yellow dots on the autochoke to set it back the way it was if needed. Also, here's a photo of the choke pull off at the back of the carb - is that the correct one? The serial number on the carb dates it as a 72' to match the truck.





Thoughts?

Also, please forgive the poor photos but here are some garage shots of my Bronco. I'll get some better shots in the sun after the snow we're suppose to get today... Plus one photo of my 59' F100.













Thanks again!
Danny

The heater hose should be sitting inside that clip on the side of the choke spring housing. It helps to heat the spring.

Cool! Thank you! -Good eye. Does the choke setting look OK?

Thanks,
Danny

It looks like it's all there and connected correctly. I think it may be set too lean but it's been a while since I ran a 2100.

You might be right - I made it a bit leaner since it's idling rough and unresponsive to the gas pedal (except when it chokes it out, backfires and dies). It seems to be running very rich. So, I thought it needed more air but that's not helping either. Even with the choke fully open nothing I get the same response. It's really weird. I just put it back to the original setting.

Is it possible for the throttle valves to not close all the way and almost flood the engine while running? When I look into the carb I can see them responding and I can see the accelerator pump working too.

Thanks again for your help,
Danny

You are going to have to start at the beginning I fear, especially if it's an original carb. Most of the pivot points are worn and you most likely have at least some air coming in that isn't metered.

If you have a rebuild kit it should show how all the linkages should be set up from the factory, i.e. which of the three holes should be used on the accelerator pump, etc.

Has it been cleaned out and rebuilt? From the additional remarks you've made I think something is clogged up.

Thanks, Kinder. You may be right. I've cleaned it with carb cleaner but haven't rebuilt it. I might need to.

I'm going to try replacing the fuel pump tonight or tomorrow and see if it's just perhaps that the fuel pump is putting out such weak pressure that it's enough to keep the truck idling but not enough to help it accelerate.

Thanks,
Danny

That sounds more like a fuel filter problem, not completely clogged yet so just enough fuel gets through to idle well but not run well.
Or possibly a partial clog in the fuel line.
Usually when fuel pumps fail they fail all the way.

Thanks, sykanr0ng. That's been my experience too but a friend suggested I try changing the pump. I just changed it and it's doing the same thing. I had just put in a new filter that screws into the carb and all the fuel lines (the previous owner replaced all the hard lines and rubber lines with the braided stainless) have been replaced. Tonight I added a second filter - a clear in-line style before the pump - so I can double check and make sure there's no rust in the tank coming through the lines. I'll replace the carb filter again tomorrow and see if perhaps it's just a bad filter.

Thanks for helping me think through it!
Danny

If it Sat for a long time check the rubber fuel lines.The new gas plays havoc on the rubber.Lines can look new on the outside but the inside may have turned to goo.

JGZ wrote:If it Sat for a long time check the rubber fuel lines.The new gas plays havoc on the rubber.Lines can look new on the outside but the inside may have turned to goo.

There is 10% ethanol in all pump gasoline these days, which causes a lot of problems due to it being corrosive to older vehicle fuel systems.

Also gasoline really only has a "shelf life" of about three months, then it separates into varnish and other things.
So old gas is bad news for a fuel system.

Thanks, guys! I replaced the filter last night and I'm still getting the same response. I pulled the horn off the carb to check the float and needle and seat - there's still full in the bowl and the gas is clean looking. Although, there is a sediment deposit of rust in the bottle of the bowl. The rubber float seams water logged (it's the rubber kind). I'm going to replace the carb and hope for the best. Then I'll rebuild this one for a back up.

More soon...

Thanks,
Danny

Do yourself a favor and blow the fuel lines out .

Update: I blew out the lines, and put the new carb on today. Perfectly clear gas in the inline line fuel filter.

BUT now I can't get the truck to start. Any thoughts? I've even tried starter fluid into the carb but it's just not firing.
There is brand new electrical everything (spark plugs, wires, points, ignition coil, alternator, battery, starter and solenoid, voltage regulator, etc) and that end was good before the new carb.

Any advice would be appreciated.

Thanks,
Danny

Did you adjust your points? Timing? Pull your cap, and make sure you put your rotor back on.

Check the 3 basics; air, fuel & spark.

Hi Guys,

It fires! If I hold the choke all the way open and my wife holds the gas pedal down it'll turn over. I think the new carb will just need a bit of adjusting to run right. I adjusted the idle screw and can keep it idling and it actually reved when she hit the gas! But only once and then it did the exact same thing it was doing before I put the new carb on...

More soon as I try to tune it. Hopefully the new carb will fix the problem.

Thanks,
Danny

Hi Guys,

I got the carb tuned today and the truck ran great. Something in the old carb was clearly causing the problem. Thanks again for everyone's help, I appreciate it!

Thanks,
Danny

Well, I thought I had it. Now I can't even get it to start again. Fuel pressure is good. Vacuum is good, spark is good, everything is new, timing is good, etc.

Can someone please recommend a good local mechanic? I have no idea why this thing won't run... I'm feeling totally defeated by this truck.

Thanks,
Danny

I got it going again today.

Thanks,
Danny

Ran great all week, took it several days to work and then.....



Hope to figure out what went wrong tomorrow,
Danny

What symptoms?