cold start/choke issues? What to look at?

[rcarlisle]

Ok, I'm trying to determine what's happening on cold starts. Truck has started from mid March to now (end of May) just fine. Cold weather or hot. Mash the gas 3 times (like all old carbed cars), turn the key and it fires really quickly. However, it is cold natured for a while. And no apparent fast idle. I can live with it, but also think it could be better. What do I need to be looking at on the choke side? Linkage side? I have looked in the reference section but that confuses me a bit and usually you guys explain it better in real terms. Search "choke" didn't turn up what I thought I need.

I don't have photos but can get. It is a replacement engine, so I'm not sure if they put everything back. Carb is not pretty - if I were replacing things that were working, I'd probably replace with a newer one. But it seems to be working well other than cold starts.

I know it is missing the metal heat thing on the exhaust manifold that would attach to the riser and the heat tube that goes to choke if mine is supposed to have it. 81 F 150, 302.

And in most cases, I'm not averse to not having all the emissions and extraneous stuff. So it's ok if it's missing if it's not necessary. Just would like to get cold starts a little better and not have to sit and futz with the throttle for 3- 5 minutes so it will take gas and go. Starts fine, just won't take gas when cold or a few minutes ("Aw she's just cold natured").

Is it cold enough for the choke to really operate? 60s in the mornings, 80s in the afternoons.

 

[Gary Lewis]

If your engine is “cold blooded” then you need some choke. And you probably don’t have enough at the moment.

However, without the heat tube there’s no way for the choke to know how warm the engine is getting - unless you have the electric-assist choke that has a wire to it. Do you have a wire?

But even if you have a wire it doesn’t mean the choke will work correctly. In fact, it probably won’t as most of those only worked in a narrow band of temperature.

So to have it work correctly you will need to replace the hot air tube. Dorman has a kit for that which most part stores sell. Or you could replace the choke cap with an all-electric one. That’s not as good as the hot air tube but it is workable.

[LARIAT 85]

I know it is missing the metal heat thing on the exhaust manifold that would attach to the riser and the heat tube that goes to choke if mine is supposed to have it. 81 F 150, 302.

If you still have your stock carburetor (Motorcraft 2150) then YES, it is supposed to have that heat tube. In fact, you should have two tubes and a wire running from the choke to the alternator. Without those tubes in place, your choke is not going to work correctly.

It would help if you could post a picture of your carburetor - particularity on the choke side - so we can see what you have.

Is it cold enough for the choke to really operate? 60s in the mornings, 80s in the afternoons.

Yes, you better believe it! The air/fuel mixture should be set when the engine is at normal operating temperature, and that would be about 200 degrees. If you did that, there is no way your cold engine is going to run smooth without a choke.

[rcarlisle]

I know it is missing the metal heat thing on the exhaust manifold that would attach to the riser and the heat tube that goes to choke if mine is supposed to have it. 81 F 150, 302.

If you still have your stock carburetor (Motorcraft 2150) then YES, it is supposed to have that heat tube. In fact, you should have two tubes and a wire running from the choke to the alternator. Without those tubes in place, your choke is not going to work correctly.

It would help if you could post a picture of your carburetor - particularity on the choke side - so we can see what you have.

Is it cold enough for the choke to really operate? 60s in the mornings, 80s in the afternoons.

Yes, you better believe it! The air/fuel mixture should be set when the engine is at normal operating temperature, and that would be about 200 degrees. If you did that, there is no way your cold engine is going to run smooth without a choke.

Thanks for the quick replies. I'll try to get some photos this evening when I get home so you guys can guide me. And see what is really there. The carb looks a lot like what's for sale on the internet. But that heat tube part worries me a bit. I'll look up that Dorman kit and see what all is in it. I'd like it to work better, but it does work now. So I can't complain too much, I guess. Just want betterer.

 

[rcarlisle]

If your engine is “cold blooded” then you need some choke. And you probably don’t have enough at the moment.

However, without the heat tube there’s no way for the choke to know how warm the engine is getting - unless you have the electric-assist choke that has a wire to it. Do you have a wire?

But even if you have a wire it doesn’t mean the choke will work correctly. In fact, it probably won’t as most of those only worked in a narrow band of temperature.

So to have it work correctly you will need to replace the hot air tube. Dorman has a kit for that which most part stores sell. Or you could replace the choke cap with an all-electric one. That’s not as good as the hot air tube but it is workable.

I found the diagram again and it's starting to make more sense, as I knew it would. I don't remember it having a wire and did look for that last night as I remembered reading about a wire somewhere. I'll try to get photos this evening so you guys can dissect what's there and what's not. I hope it isn't missing too much.

[Rusty_S85]

Three times? proper setting for a carb is one hit of the throttle to floor to set the choke and it should crank up and stay running.

It might take some tinkering to get it to that point but that is how it should work when proper.

What you need to do is check your choke make sure it is fully closing when cold. Then you need to check the choke pull off. First you need to see how much vacuum your engine makes at idle. Then while engine is cold not running unplugged the choke pulloff vacuum line and attach a hand vacuum pump and pump it to the vacuum that your engine makes. This is where you now adjust your pull off to be slightly open but not too much. Some engines will like more some will like less. This will determine how well your engine stays running or if you have to attempt starting multiple times.

This is actually a fairly easy thing to fix with OE carbs, the thing I could never resolve was the off idle stumble which is an accelerator pump issue. On mine I moved to the largest squirt setting possible and it fixed most of the stumble but its still there. Reason why I will be glad to dump the OE carb on my new engine build.

On high speed cold idle there will be a screw on the passengerside if I remember right that sets your cold idle speed. Mine was set at 2,500 rpm which is way too high I turned mine down to 1,500 rpm which is just right for a cold start.

The heat riser that you are talking about is this the one that goes to the aircleaner? If so you dont need that mine hasnt had one for years after rotting off. If you are talking about the stove that is inside the manifold near the collector then yes you will need that as even the electric chokes were only electric assist to help open quicker in warmer weather but mainly relied on hot air. You can correct this with some tubing and screw clamp it to one of the exhaust manifold tubes. Attach one end to your choke and attach the other end back to the base of the carb air horn in the back for its fresh filtered air source.

[rcarlisle]

Three times? proper setting for a carb is one hit of the throttle to floor to set the choke and it should crank up and stay running.

It might take some tinkering to get it to that point but that is how it should work when proper.

What you need to do is check your choke make sure it is fully closing when cold. Then you need to check the choke pull off. First you need to see how much vacuum your engine makes at idle. Then while engine is cold not running unplugged the choke pulloff vacuum line and attach a hand vacuum pump and pump it to the vacuum that your engine makes. This is where you now adjust your pull off to be slightly open but not too much. Some engines will like more some will like less. This will determine how well your engine stays running or if you have to attempt starting multiple times.

This is actually a fairly easy thing to fix with OE carbs, the thing I could never resolve was the off idle stumble which is an accelerator pump issue. On mine I moved to the largest squirt setting possible and it fixed most of the stumble but its still there. Reason why I will be glad to dump the OE carb on my new engine build.

On high speed cold idle there will be a screw on the passengerside if I remember right that sets your cold idle speed. Mine was set at 2,500 rpm which is way too high I turned mine down to 1,500 rpm which is just right for a cold start.

The heat riser that you are talking about is this the one that goes to the aircleaner? If so you dont need that mine hasnt had one for years after rotting off. If you are talking about the stove that is inside the manifold near the collector then yes you will need that as even the electric chokes were only electric assist to help open quicker in warmer weather but mainly relied on hot air. You can correct this with some tubing and screw clamp it to one of the exhaust manifold tubes. Attach one end to your choke and attach the other end back to the base of the carb air horn in the back for its fresh filtered air source.

Yeah, I know what "proper" is supposed to be. But this one ain't proper for sure.

Thanks for all the information you included. But I can tell you in all honesty, I'm not that inspired to fix this thing. It does start and run. It will start on one pump, just usually sputters out. Probably better than 90% of the trucks on FB?. You guys here are that last 10%. The upper echelon.

If the choke would close up some, it would probably stay running. If I can get the choke plate working somewhat, I'm sure I'll be happier. If not, it's like an old car or motorcycle - just have to let it warm a bit more. Usually I just keep my foot on pedal to give it a fast idle while I get me adjusted and seat belt on, etc.

As for your off idle stumble, when I worked for the state motorcycle program (stay with me), the majority of our Honda 250 cc Nighthawks and Rebels had a stumble off idle. On some investigation, turned out the ones that didn't stumble had a bigger idle jet. My solution for the ones that stumbled was to put a #4 brass washer under the top of the needle to shim the plunger needle up a bit. Made 300 bikes run better in NC. There is probably a similar solution for the truck carb - figure out how to richen it up between idle and that acc pump squirt. The Hondas had an honest-to-God accelerator pump on them.

If I could get to the carb to study it better, this choke thing would be a lot easier. When I get photos tonight, I will be able to study it all a llittle closer. But there are still a lot of moving parts behind the choke pot thing. Thought about buying a new carb, but till I figure out if all the stuff is there, it might not fix it.

[rcarlisle]

Yeah, I know what "proper" is supposed to be. But this one ain't proper for sure. http://www.garysgaragemahal.com/uploads/6/5/8/7/65879365/laughing-25-x-25_orig.gif

Thanks for all the information you included. But I can tell you in all honesty, I'm not that inspired to fix this thing. It does start and run. It will start on one pump, just usually sputters out. Probably better than 90% of the trucks on FB?. You guys here are that last 10%. The upper echelon.

If the choke would close up some, it would probably stay running. If I can get the choke plate working somewhat, I'm sure I'll be happier. If not, it's like an old car or motorcycle - just have to let it warm a bit more. Usually I just keep my foot on pedal to give it a fast idle while I get me adjusted and seat belt on, etc.

As for your off idle stumble, when I worked for the state motorcycle program (stay with me), the majority of our Honda 250 cc Nighthawks and Rebels had a stumble off idle. On some investigation, turned out the ones that didn't stumble had a bigger idle jet. My solution for the ones that stumbled was to put a #4 brass washer under the top of the needle to shim the plunger needle up a bit. Made 300 bikes run better in NC. There is probably a similar solution for the truck carb - figure out how to richen it up between idle and that acc pump squirt. The Hondas had an honest-to-God accelerator pump on them.

If I could get to the carb to study it better, this choke thing would be a lot easier. When I get photos tonight, I will be able to study it all a llittle closer. But there are still a lot of moving parts behind the choke pot thing. Thought about buying a new carb, but till I figure out if all the stuff is there, it might not fix it.

Here's photos - I took 21 in all, but won't post them all - only as needed. Let's take a look to get started on figuring out what is here and what isn't.

What is the capped red thing in this photo? It rotates down to this position when throttle is fully opened.

Any insight you guys can provise will be helpful.

 

[Gary Lewis]

Here's photos - I took 21 in all, but won't post them all - only as needed. Let's take a look to get started on figuring out what is here and what isn't.

What is the capped red thing in this photo? It rotates down to this position when throttle is fully opened.

Any insight you guys can provise will be helpful.

Houston, we have a problem. Your choke doesn't have a connection on it for a wire, so doesn't have a provision for heating electrically. Given that, w/o the hot air tube it will never work correctly. If you give it enough choke to make it start well it'll take forever to come off and the engine will run very rich, if at all.

I can see several options:

• Fix the hot air tube and the cold air supply. This would be best.

• Get an electric choke cap. I think the Holley ones fit the Motorcraft. This isn't as good as hot air, but it'll work. I have an electric choke on Big Blue.

• Convert to a manual choke. There are kits for that which replace the choke cap and have a cable, like a throttle cable for a lawnmower, that runs into the cab where you can control it.

[rcarlisle]

Houston, we have a problem. Your choke doesn't have a connection on it for a wire, so doesn't have a provision for heating electrically. Given that, w/o the hot air tube it will never work correctly. If you give it enough choke to make it start well it'll take forever to come off and the engine will run very rich, if at all.

I can see several options:

• Fix the hot air tube and the cold air supply. This would be best.

• Get an electric choke cap. I think the Holley ones fit the Motorcraft. This isn't as good as hot air, but it'll work. I have an electric choke on Big Blue.

• Convert to a manual choke. There are kits for that which replace the choke cap and have a cable, like a throttle cable for a lawnmower, that runs into the cab where you can control it.

Yep after our posts yesterday and when I looked at photos, I saw it was a mess of things missing.

And ya know, the the truck will start quickly like it sits. Just have to be easy on giving it gas to start with. And that's from March til now. What will happen in January may be a whole other story.

I grew up with cars of suspect nature and that sound of mashing the gas a few times is almost as much of the starting process as turning the key.

The manual choke idea has crossed my mind.

I guess for now, I'll have to let it ride and deal with it later. Maybe the Dorman kit.

Thanks for the input.