New Bronco New Problems - 1975 Bronco

[Ike1945]

Hi All, Not really a car guy. I love them, but never had the opportunity to work on my own. Though, I've always wanted to. In order to further this dream, I bought a 1975 bronco. It was restored 6-7 years ago. Anyways, I had this bronco inspected in AR (I'm in TX), and everything checked out. It gets delivered today, and it starts right up. I drive it around and it's fine. It's idling a little low, but I suspect it needs a carburetor cleaning or something. So I pay the guy and he drives off into the sunset. I start driving and come to a stop light, and it dies. I get it started, but need to rev it to keep it alive. I get it parked, come back, and start it up again. I go to put it into reverse, and it dies. Throw it back into park, start it up again, and it again dies when shifting gears. When it's at speed, it sounds and runs fine. It does have a hand throttle, but it looks to have been disconnected as the knob comes straight out.

Any thoughts? Carburetor?

 

[Uncle Butter]

I’m not one to comment on these tech threads because I’m usually the one asking for help but your experience and problem sounds almost identical to mine when I first bought my bronco. I’m sure most on this forum are much more knowledgeable than I am, but my problem was the ignition control module. I went through three of them in a week before my local shop just deleted it and replaced it with a modern performance distributer. Never had a problem since. Apparently those ICMs were the source of many problems just like this and getting rid of it solves it immediately. Try that and see what happens.

 

[DirtDonk]

Possibly, but too early to say. Hey there car guy and welcome! Welcome to Classicbroncos of course, but also welcome to the world of old vehicles and questionable restorations.

But it does seem common for them to give trouble within a few minutes after a new purchase. After a long trip in a trailer or flatbed.
Hopefully this is just a question of circumstances, rather than some question about the previous owner doing a quick flip.

 

[Ike1945]

I’m not one to comment on these tech threads because I’m usually the one asking for help but your experience and problem sounds almost identical to mine when I first bought my bronco. I’m sure most on this forum are much more knowledgeable than I am, but my problem was the ignition control module. I went through three of them in a week before my local shop just deleted it and replaced it with a modern performance distributer. Never had a problem since. Apparently those ICMs were the source of many problems just like this and getting rid of it solves it immediately. Try that and see what happens.

Thanks! I'm useless as tits on a bull with this stuff. Appreciate the idea.

 

[71 CA Bronco]

Knowing if it was sitting for a time before you recieved it would be helpfull? If it has been sitting a while could be bad fuel or accelerator pump. If it was driven often could be ignition related.

Look for easy stuff first. Check all your vacum lines to be sure they are not damaged/cracked or disconnected. A vacuum leak can cause this problem. It will also make your engine run lean which is not good. Next check to be sure you are gettting fuel at start up. If you remove the air cleaner and look down the carb you should be able to see fuel spray out when pushing the accelerator. If not, could be lack of fuel (clogged fuel filter?), accelerator pump, bad fuel, no fuel, ect. If you don't see fuel spraying in the carb try pooring a small amount of gas into the carb. If it starts up immediatley definitely fuel related.

If its not fuel related. Start checking your ignition system. Does the problem go away when the hood is up? I only ask this because a friend of mine was chasing a similar problem only to find out the hood was arcing to the coil when closed. Are all wires tidy and secure including grounds? Broncos are notorious for bad grounds. You can check for spark by pulling a plug, then connect it back to the plug wire and ground it to the block while someone turns the motor over. You can try a new ignition module but it could be an array of other issues.

Were are you located? Might be another Bronco guy close that could lend a hand.

My 2 cents worth....

 

[gnpenning]

Welcome. A good under hood visual is a good place to start. You can have the engine running as long as you are careful around moving parts. Don't try moving or adjusting anything with it running at this point. Listen and watch. Can you see a spare spark or hear a vacuum leak?

You really need to hook up a tach and see what your idle speed is. Sounds like a automatic?? If so check speed in park and drive/reverse.

You mentioned being new to repair work and i gave you information you may not have a clue about. Start a thread looking for experienced guys in your area. Offer to help them if you want them to help you. You can learn a ton helping them work on theirs and if you really want to learn it would be great chance for you.

 

[Ike1945]

UPDATE: Thanks, everyone. I took Bronco Slave's recommendation and just started it up and sat there for a while listening and watching. Sure enough I heard a massive hissing sound. I found the location (see middle of Pic 1). It looks like the hose just crumbled (see photo 2). Like the curious dumbass that I am, I put my finger over the hole and the engine normalized. I kept my finger there and my brother was able to shift into reverse and the engine did exactly what it should do. Now onto the $64k question, where does this vacuum hose go to? I also took a photo of the carb. Not sure if that looks normal or if there is additional things I should fix. Thanks again to everyone.

 

[DirtDonk]

That small, vacuum manifold with the open port would typically be for the brake booster.
Do you have vacuum assist power brakes? If so, there should be a hose running from the booster to that fitting.
The carburetor looks correct for your year but that open port on top is a bowl vent that would normally have gone directly to the charcoal canister mounted down on the passenger side frame rail behind the wheel.
Many people remove those thinking they’re just more “useless smog crap that robs horsepower”. When in fact, they keep the air clean in your garage.
And in the house!

Definitely take some more pictures of the overall engine compartment and some detailed pics of the different areas. We might be able to see other discrepancies left over from the previous owner.

 

[Bronco_007]

That small, vacuum manifold with the open port would typically be for the brake booster.
Do you have vacuum assist power brakes? If so, there should be a hose running from the booster to that fitting.
The carburetor looks correct for your year but that open port on top is a bowl vent that would normally have gone directly to the charcoal canister mounted down on the passenger side frame rail behind the wheel.
Many people remove those thinking they’re just more “useless smog crap that robs horsepower”. When in fact, they keep the air clean in your garage.
And in the house!

Definitely take some more pictures of the overall engine compartment and some detailed pics of the different areas. We might be able to see other discrepancies left over from the previous owner.

I’m trying to follow and learn! Is this the “bowl vent” that goes to the charcoal canister?

 

[DirtDonk]

Indeed, it is. You can either connect it with a hose if you want (best case), or for the time being cap it off, so nothing unwanted gets into the carburetor through it.

 

[okie4570]

I would plan on replacing all the vacuum lines, as well as any rubber fuel lines under the hood. You don't want a fuel line doing the same thing your vacuum line did. Nobody wants to try out their fire extinguisher lol.

 

[71 CA Bronco]

I would plan on replacing all the vacuum lines, as well as any rubber fuel lines under the hood. You don't want a fuel line doing the same thing your vacuum line did. Nobody wants to try out their fire extinguisher lol.

Times 2. I would even add checking all rubber brake lines, however requires a bit more knowledge to bleed brakes properly after the fact. All are cheap insurance.

 

[Bronco_007]

Indeed, it is. You can either connect it with a hose if you want (best case), or for the time being cap it off, so nothing unwanted gets into the carburetor through it.

This is the back of my carb as it came from the PO. It’s a Holley; not sure what model. Both ports were capped off with rubber. Which is for the booster and which goes to the charcoal canister? Just finished install on my new brake system so perfect timing…

Also, it looks like both hoses coming off the top of my charcoal canister are aluminum, and certainly too big in diameter for either ports in question. One goes into the back of the factory air intake but the other aluminum tube is just hanging out in the engine bay. Figure that one might oughta connect to one of the ports? Hence the hose diameter pickle…

Thanks all!

 

[Tiko433]

Do you have a vacuum brake booster ? The port under the carb goes it the booster. That’s how I have always hooked it up.
I have never seen a spacer like that. Those 4 holes in it , are they sucking air ?
Pic 1 and 2 that shows the vacuum tree , has the loop and a cap. Looks like you need another cap.

 

[Bronco_007]

Do you have a vacuum brake booster ? The port under the carb goes it the booster. That’s how I have always hooked it up.
I have never seen a spacer like that. Those 4 holes in it , are they sucking air ?
Pic 1 and 2 that shows the vacuum tree , has the loop and a cap. Looks like you need another cap.

Yes, vacuum booster. I don’t think those four holes sucks air but I’ll check. I have another cap for the tree. What is that tree for though?

 

[Tiko433]

The tree could be for things that may have been removed over the years .
Your booster needs vacuum. Just make sure the tree is plugged. Im not sure what all you have on your truck. Do you have a vacuum line going to your distributor? If you have a vacuum advance you need a line going to it also. Just because there is tree with ports on it doesn’t mean they all have to be used or go to something. PO (s) could have plugged the manifold with what he had laying around.

 

[Tiko433]

Where does this hose go ?
It should be going to manifold vacuum
I would put it at the port under the carb and your booster can go on the tree , looks like it’s a big enough

 

[Oldtimer]

Carb spacer plate for EGR valve.
The valve has been removed and it appears plugs have been used to seal two center ports.
Spacer plate also has vacuum port on front edge.
I think I see somthing connected to it in one of your photos.

 

[tirewater]

This is the back of my carb as it came from the PO. It’s a Holley; not sure what model. Both ports were capped off with rubber. Which is for the booster and which goes to the charcoal canister? Just finished install on my new brake system so perfect timing…

Also, it looks like both hoses coming off the top of my charcoal canister are aluminum, and certainly too big in diameter for either ports in question. One goes into the back of the factory air intake but the other aluminum tube is just hanging out in the engine bay. Figure that one might oughta connect to one of the ports? Hence the hose diameter pickle…

Thanks all!

(Oldtimer beat me too it)

That's a lot of vacuum leaks...

You have an EGR spacer, the EGR valve (and a transducer depending on year) bolts onto it. The outside holes are bolt holes, the inner two are in/out. You'll need a block off plate or EGR valve to cover it.

The nipple on the back of the carburetor is for PCV valve. Original carb would not have that nipple as PCV goes into the front, so cap it.

The vacuum tree is for everything else.
1. Larger nipple is for brake booster
2. Others would be EGR, transmission modulator, exhaust valve, port vacuum switches, etc...

Your carburetor is a Motorcraft 2150 (not Holley). It's missing the lever that activates the spring valve on the top late for the EVAP nipple on the top plate.

 

[Tiko433]

(Oldtimer beat me too it)

That's a lot of vacuum leaks...

You have an EGR spacer, the EGR valve (and a transducer depending on year) bolts onto it. The outside holes are bolt holes, the inner two are in/out. You'll need a block off plate or EGR valve to cover it.

The nipple on the back of the carburetor is for PCV valve. Original carb would not have that nipple as PCV goes into the front, so cap it.

The vacuum tree is for everything else.
1. Larger nipple is for brake booster
2. Others would be EGR, transmission modulator, exhaust valve, port vacuum switches, etc...

Your carburetor is a Motorcraft 2150 (not Holley). It's missing the lever that activates the spring valve on the top late for the EVAP nipple on the top plate.

That’s what I was thinking. I put a red arrow on the PVC hose