Nothing Special's '71 Bronco

[Nothing Special]

If the idle speed doesn't change when you spray carb cleaner on the throttle shaft then you don't have enough leak there to be an issue. I think all carbs leak there to some extent.

On setting the float level, have you looked at our documentation at Documentation/Fuel Systems/Carbs, Chokes, & EFI/Motorcraft 2150? We have the section from the FSM there.

It does drop a bit now, but no where near as much as it used to. I think I'll quit worrying about that.

I had not seen that. It does make a wet check seem a little more doable than what I found before (running the engine with the top off the carb didn't see like something I wanted to do ).

I still think I'll pull the carb, set the float level dry and blow more carb cleaner through next. But thanks, there's a lot there to help if that doesn't get me where I need to be.

[Gary Lewis]

It does drop a bit now, but no where near as much as it used to. I think I'll quit worrying about that.

I had not seen that. It does make a wet check seem a little more doable than what I found before (running the engine with the top off the carb didn't see like something I wanted to do ).

I still think I'll pull the carb, set the float level dry and blow more carb cleaner through next. But thanks, there's a lot there to help if that doesn't get me where I need to be.

I’ve rarely run one with the top off, but it works.

If your float level is too high you could be getting spill-over on starts or stops. Too low and it could be sloshing away from the idle circuit. So I’d concentrate on the float level.

And blowing out the passages is a good idea. If you have gunk in there it can cause all sorts of issues.

[Nothing Special]

.... On setting the float level, have you looked at our documentation at Documentation/Fuel Systems/Carbs, Chokes, & EFI/Motorcraft 2150? We have the section from the FSM there.

I found the "Instructions" section under Motorcraft 2150. And in that I found instructions for how to set the float level, both dry and wet, on page 24-25-11. But in the otherwise pretty detailed instructions all it says is to set it within the specified limits. However I can't find anywhere that it specifies those limits.

Am I missing something?

 

[Nothing Special]

.... On setting the float level, have you looked at our documentation at Documentation/Fuel Systems/Carbs, Chokes, & EFI/Motorcraft 2150? We have the section from the FSM there.

I found the "Instructions" section under Motorcraft 2150. And in that I found instructions for how to set the float level, both dry and wet, on page 24-25-11. But in the otherwise pretty detailed instructions all it says is to set it within the specified limits. However I can't find anywhere that it specifies those limits.

Am I missing something?

I did find an instruction sheet that I kept the first time I put a carb kit in this carb (I got the carb from a junk yard). It had float level specs, and gave 7/16" dry for my application (and most others). I was at about 3/8". Having the float too high doesn't seem like it would make it run lean. I'm thinking it would go more the other way.

But I dropped it back to 7/16" anyway. I also sprayed a bunch of carb cleaner again while I had the opportunity. The test drive really didn't go any different from yesterday. It's running pretty good, but it needs some choke to make power at mid- to higher speed, and the engine speed drops a little too far sometimes when going back to idle.

Unfortunately I think the next step is going to be to take it to a carb shop. I just don't have the time to keep poking at it right now.

[Gary Lewis]

I did find an instruction sheet that I kept the first time I put a carb kit in this carb (I got the carb from a junk yard). It had float level specs, and gave 7/16" dry for my application (and most others). I was at about 3/8". Having the float too high doesn't seem like it would make it run lean. I'm thinking it would go more the other way.

But I dropped it back to 7/16" anyway. I also sprayed a bunch of carb cleaner again while I had the opportunity. The test drive really didn't go any different from yesterday. It's running pretty good, but it needs some choke to make power at mid- to higher speed, and the engine speed drops a little too far sometimes when going back to idle.

Unfortunately I think the next step is going to be to take it to a carb shop. I just don't have the time to keep poking at it right now.

Bob - There's not all that much to go wrong with a 2150, especially to cause those symptoms. It sounds to me like you still have a vacuum leak that is causing it to be quite lean at cruise.

I expect you are running out of time before the trip, so I'm going to tag Bill in this discussion. Perhaps he will have some suggestions on what would cause these symptoms?

[ArdWrknTrk]

Bob - There's not all that much to go wrong with a 2150, especially to cause those symptoms. It sounds to me like you still have a vacuum leak that is causing it to be quite lean at cruise.

I expect you are running out of time before the trip, so I'm going to tag Bill in this discussion. Perhaps he will have some suggestions on what would cause these symptoms?

I would have said massive vacuum leak, given the need for choke.

[Gary Lewis]

I would have said massive vacuum leak, given the need for choke.

Yes, massive. But seemingly only at speed since the idle screws don't have to be out a long way?

[Nothing Special]

Yes, massive. But seemingly only at speed since the idle screws don't have to be out a long way?

The idle screws are out 2.5 turns, which seems a little far to me. But not as far as they were last year before I bushed the throttle shaft.

I can't think of where to look for a vacuum leak that happens only at speed. It's a pretty simple system. The only vacuum hoses are going to the PCV valve and to the distributor.

And for what it's worth, I have an Autolite 2100, not a Motorcraft 2150. I don't think there's a lot of difference, so I don't think any of the advice has been off-track. But in case anyone's keeping track...

[Gary Lewis]

The idle screws are out 2.5 turns, which seems a little far to me. But not as far as they were last year before I bushed the throttle shaft.

I can't think of where to look for a vacuum leak that happens only at speed. It's a pretty simple system. The only vacuum hoses are going to the PCV valve and to the distributor.

And for what it's worth, I have an Autolite 2100, not a Motorcraft 2150. I don't think there's a lot of difference, so I don't think any of the advice has been off-track. But in case anyone's keeping track...

2 1/2 turns is a bit farther out than I usually find on them, but not bad. Which is why I'm confused with why you are so lean at cruise. And, like you, I can't think of anything that would do that.

Have you checked to make sure the orifices in the boosters are clear? I'd run a strand of copper wire through them. Seems to me like something is blocked.

[Nothing Special]

2 1/2 turns is a bit farther out than I usually find on them, but not bad. Which is why I'm confused with why you are so lean at cruise. And, like you, I can't think of anything that would do that.

Have you checked to make sure the orifices in the boosters are clear? I'd run a strand of copper wire through them. Seems to me like something is blocked.

I haven't tried running a wire through them, but I've sprayed carb cleaner about everywhere I can think of and nothing seems to be blocked.