Motorcraft 2150 issues

phyler · Jun 26, 2021

Hey all, recently rebuilt my 2150. This is the first time I've gone through this carb and I've learned a lot. That said, I am dealing with two issues that I'm hoping to get help on.

Back history, I've owned this Bronco since the early 90's. A friend rebuilt this carb last in ~95. It ran well but had some quirks for sure. I had recently noticed a drop in fuel mileage so after doing the normal tune up, timing, etc. thought it would be a good time to go through it. Prior to going through it, I know the choke wasn't working properly. I did go through the various adjustments (thanks to YouTube for this) and it definitely helped.

When I cleaned it, I let all the parts soak in cleaner for about 2 days. Everything is moving freely from what I can tell.

The truck starts way easier now which is nice. Give it two pumps of gas and turn the crank and it fires right up. Prior, I had to crank for ~20 seconds before it would fire.

On to the issues:

1. This was happening prior to rebuilding. I would be going uphill and it would act like it was getting starved for fuel. It was hot so I figured it was a bit of vapor lock. Got home and realized it was the mechanical fuel pump crapping out on me. I replaced it then rebuilt the carb. The other day I was driving and it did it again (also while going uphill) but less severe. Guessing maybe a float issue?

2. When you first start the truck up, it will high-idle til it warms up. Fully expect this. Typically, after a min or so, I can blip the throttle and it will come down. (FYI, I'm running a manual NP435.) It was cool yesterday morning (~55 degrees) and after driving several miles, it was like while driving it would get stuck on high idle. Again, a blip of the throttle would bring it back down. Maybe the choke is closing on me? Or could it be the vacuum pull off? Other ideas on why this might be happening?

Thanks!

jckkys · Jun 26, 2021

The rebuilding kit instructions would have included the set up and adjustment of the choke pull off. That process should tell you if the 2150 pull off diaphragm is cracked. That would be the first thing to look at. Here's the least expensive I can find;https://allcarbs.com/product/motorcraft-choke-pull-off-2/

phyler · Jun 26, 2021

I did the adjustment of that by pushing the outer piece in. I'll grab a vacuum pump and test to see if the diaphragm is cracked.

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jckkys · Jun 26, 2021

The rod from the pull off diaphragm to the choke should start moving as soon as the engine starts. If it doesn't move the diaphragm is no good.

phyler · Jun 26, 2021

jckkys said:
The rod from the pull off diaphragm to the choke should start moving as soon as the engine starts. If it doesn't move the diaphragm is no good.

Good to know. I'll pull the air cleaner and watch for that.

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phyler · Jun 27, 2021

Put a vacuum pump on the pull-off and it moves and holds vacuum. So, good news is that is working correctly. Back to the drawing board.

Also, if this helps, it is a 1975 with an auto-choke.

B RON CO · Jun 27, 2021

Hi, when the engine is cold, in the morning before start up, the choke should snap closed, and be held closed by spring pressure. Right away, vacuum pulls the choke pull off open a little. As the engine warms up the choke slowly opens.

When the engine is fully warmed up the choke should be held open by spring pressure. Make sure the choke is held open. You could think about spraying the choke linkage with WD 40.

Good luck

Rustytruck · Jun 28, 2021

Are you using the heat choke tube from the passengers side up to the electrical choke?

https://www.ebay.com/itm/2645997852...f1oaLK7kYHdlW79UtVl4KzoDNtxoqMk0aAr6REALw_wcB
https://www.ford-trucks.com/forums/1157890-choke-stove-setup.html

phyler · Jun 28, 2021

Rustytruck said:
Are you using the heat choke tube from the passengers side up to the electrical choke?

https://www.ebay.com/itm/2645997852...f1oaLK7kYHdlW79UtVl4KzoDNtxoqMk0aAr6REALw_wcB
https://www.ford-trucks.com/forums/1157890-choke-stove-setup.html

No. That's blocked off due to being an auto choke. I do have the tube from the passenger side to the air horn.

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jckkys · Jun 28, 2021

A little info is needed here regarding this thread. What year is the 2150 and the year of the Bronco? What is included in your fuel system? What kind and where is the fuel filter? What kind of fuel pump? FYI the the automatic choke needs a heat source to work. Ford used 2 heat sources on all 2150s from '75-'77. There was the electrically heated thermostatic choke cap AND hot air off the exhaust manifold. They are not mutually exclusive. Also there is no reason to buy a vacuum pump. Any engine IS a vacuum pump. Plus I've been able to suck well enough with my mouth to do anything automotive.

phyler · Jun 28, 2021

Bronco and the carb are 1975. In the time I've owned this bronco (since 93), it's never had a connection from the choke to the exhaust manifold. Not saying it's right, just it isn't there. I've watched a few videos and they have called out that spot being plugged due to being auto chokes. I'll have to try and find a better diagram then what's in the rebuild kit or the Chilton's.

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phyler · Jun 28, 2021

Apologies, watched another video from Mike's Carburator and I think I'm using the wrong term. The choke is an electric choke. That said, he did comment in his that if you have an electric choke that you cap off the heat tube. So, I'm still confused and am pretty sure things are close but something is just a hair off.

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Rustytruck · Jun 29, 2021

My 1974 had both the heat tubes and electric choke. there is a vacuum leak if the tubes are disconnected and not plugged at the carb. the choke can get stuck up if the heat stove parts are not cleaned properly despite using an electric choke. Vacuum in the choke pulls heated air through the tubes coming from the exhaust manifold air coming in to the exhaust manifold comes from the top back of the carburetor air horn base.

jckkys · Jun 29, 2021

The heat tubes from the exhaust manifold that are still there and functional are a rarity now. Most EB owners over the years have been too lazy to maintain the choke system. So in most cases the tubes simply aren't there. That doesn't mean they're not needed. Between the heat from the exhaust manifold and water splashed by the front tires, the tubes rusted away in about 10 yrs. All auto choke EBs had tubes as built. Replacement heat tube sets aren't expensive but usually require the manifold to be pulled out to install new tubes. EB automatic chokes, had both heat sources from about 1974 to open the choke sooner. Calling these electric chokes is misleading. The choke is the same as any automatic choke. They simply have an additional heat source in the cap. On carbs that only use electricity to heat the choke, clean air is still needed in the choke, to avoid over heating the puck in the choke cap. Don't cap or plug it. There's always a small vacuum leak with automatic chokes.
The symptoms may also indicate a plugged fuel filter. We still don't know what and where filter/filters are on the OP's Bronco. The fuel pump may also have been part of the problem and we don't know what kind of fuel pump is in this EB.

phyler · Jun 29, 2021

Missed the question about the pump and filter. Stock mechanical pump. Just replaced it after the last one died after a year or so of use. Just the inline filter at the front of the carb. I should replace that.

I do have the heat tube from the exhaust to the air horn.

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jckkys · Jun 30, 2021

There are simple tests for mechanical fuel pumps and an in line filter can just be blown through. If you can it's OK, if not, it needs replacement. Most any part needs to be tested before it's replaced. Throwing new parts at a problem is only a good diagnostic technique occasionally. New parts are hit and miss themselves with all the ChiCom junk on the market. The tube from the air horn to the exhaust manifold is 1/2 the system.

1970 Palmer · Jun 30, 2021

jckkys said:
There are simple tests for mechanical fuel pumps and an in line filter can just be blown through. If you can it's OK, if not, it needs replacement. Most any part needs to be tested before it's replaced. Throwing new parts at a problem is only a good diagnostic technique occasionally. New parts are hit and miss themselves with all the ChiCom junk on the market. The tube from the air horn to the exhaust manifold is 1/2 the system.

Exactly correct.

The choke tube running from the airhorn to the exhaust manifold is arguably the most important of the two tubes. Since it's purpose is to supply clean filtered air to the choke assembly. With that tube broken or missing, your just sucking dirt into the choke.

John

phyler · Jun 30, 2021

Thanks all. I'll check that air tube. Good chance it's damaged and I just don't know it yet. I'll have to report back in a few weeks as we are headed out on a two week road trip across the west.

I did check the fuel filter and I can blow through it fine. I still need to recheck the float level.

Thanks for the info. I've learned a lot about the air tubes and choke.

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phyler · Jul 20, 2021

Just an update now that I'm back home. I started back at the beginning and found that the choke coil was not in the notch properly. Fixed that and can confirm the choke opens properly now.

I still think I need to adjust the fast idle cam a bit so it comes off it a bit better when the choke is fully open but it feels like progress.

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Motorcraft 2150 issues

phyler

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