Choke, cold running misfire question

I fixed my choke when the weather was warmer.  It would work and work well.   But now that the mornings are colder, here is what's happening and what suggestions have you?  

It has always taken about 3 pumps of gas pedal to get started.   Before and after choke.  It's like the accelerator pump isn't giving it enough gas to start and run.    This is worse with the colder weather.   It will fire right up, then run a second and die.   It always starts.  

Once running, it's about 3/4 mile to a 55mph highway.  When I get there and take off, if I go more than approximately half throttle, truck will stutter and miss till good and warm.   It will still run 55 - 60 but probably a gear lower than normal.

Any suggestions?  I assume it to be a fuel delivery issue.  I don't have a duct to front of grille and no vacuum to the air cleaner door in the air cleaner snout, so it's probably getting a good amount of reasonably cool air.  

If your choke is set up correctly, meaning that it has the hot air to it and maybe the electric wire to it then the engine should stay running on the first start.  But there are several "ifs" in all of that.

So show us some pics of your carb and any connections to it?

And, assuming it is a 2150 it'll have several critical adjustments.  One is the set point on the heat stove, the black round thing.  You probably need to dial in at least one if not two more "notches" on it.  That setting determines how much choke you have on initial startup.  And it sounds like you don't have enough choke or it would start easier w/o the three pumps.

Another is the vacuum pull off, which determines how much choke you have when the engine starts.  And it sounds like you have too much pull off or the engine wouldn't die after startup.

The following link is specifically for a 1 barrel Carter, but the idea is the same for others. The need for seasonal adjustments are not uncommon.

https://www.ford-trucks.com/forums/1110073-choke-adjustment-101-a.html

certainly sounds more like choke settings are off and possibly missing some warm air intake to the choke. possibly no choke pull off. accel pump would show up even when warmed up i would expect.  which carb / engine may help.

I don't have a duct to front of grille and no vacuum to the air cleaner door in the air cleaner snout, so it's probably getting a good amount of reasonably cool air.

 
I think you may have too much cool air to the carb.
I would get the door working and add a hose to the bottom pointed to the exh manifold to pull in some heat.

Guys how dose the intake manifold cross over heat work?
Is there a vacuum valve on 1 of the exh manifold outlet to force hot gasses through the intake?
This should also be working right to help heat the manifold and keep the air/fuel in a A/F state.
If the intake and the air is too cold the fuel will drop out and act like the choke is set too rich.

And, assuming it is a 2150 it'll have several critical adjustments.  One is the set point on the heat stove, the black round thing.  You probably need to dial in at least one if not two more "notches" on it.  That setting determines how much choke you have on initial startup.  And it sounds like you don't have enough choke or it would start easier w/o the three pumps.

Another is the vacuum pull off, which determines how much choke you have when the engine starts.  And it sounds like you have too much pull off or the engine wouldn't die after startup.

Go easy if you turn the choke cap as it may not take much to make a change.
If it is not marked mark it before  any adjustments.
My Carter v1 was not marked so I marked it and only turned it a little and it made a change.

On the pull off I thought it only moved the door and not the fast idle cam?
My carb dose not have a pull off and I dont know if I have any that do that I can see how it works and why I asked.

The following link is specifically for a 1 barrel Carter, but the idea is the same for others. The need for seasonal adjustments are not uncommon.

I will have to check out the link as I am messing with my Carter's choke on my 300 six motor.
On cold mornings the choke would not open or pull off.
I have a 2 mile drive to the high way then it's 65 to 70 MPH for 45 min. and even after the 45 min drive the choke still did not open, fast idle was still and and the AFR gauge was way rich!

This setting worked good during the summer but not so much when  it got down to 45* or lower.
I only turned the cap a little and it helped but I am still checking stuff and fixing as needed.
Dave ----

Thanks for all the good suggestions.   I will check those.   I set the fast idle up some already as it just wasn't idling fast enough in my opinion.   I'll check the choke plate at pre start and see if it is closed or open any.   I've got a couple opinions on how much it should be open intially, before start.   I set the vac pull off when I got the choke operational, but may need to be adjusted for the colder weather.  

Funny I don't remember my mom's 78 Granada needing this much attention in 1982.  302 2bbl, just like this truck.  But that was 40 years ago.  Car was not old then, like the truck is now.  

My choke spring housing is one of those aftermarkets with no markings, but I can find a silver sharpie to mark it now and adjust from there.  

I need to look around the site and find the hose routing for the air cleaner to at least see if I can reduce the amount of cold air going in when cold.  

You guys backed up what I aready knew - that I need to spend some time tinkering and trying to get it better.   I figured when I got the choke working that it would be better but not perfect.   I wish I knew a good local Ford tuner - I'd have them run over it and check all the settings and get it better than I can.  

Thanks

Before starting your cold engine, step on the gas to set the choke - but do not start the engine yet.  Remove the air cleaner lid and verify that the choke plate is completely closed.  In the cold month of December, it should close with an audible *snap."  In other words, there should be a fair amount of tension holding the choke plate tight against the air horn.  If there isn't - or it is only loosely closed - rotate the choke cap a bit richer by loosening the choke cap screws.  

As soon as the engine fires, the choke plate should immediately crack open just a tiny bit to let a bit of air in.  As the engine builds up heat, that choke plate gradually opens until it has tension holding it completely open.

If your truck was running yesterday and you wanted to drive it this morning, it should only take one single pump and the engine should start right up and continue running.  (When I say "pump", that means push the gas pedal to the floor once and release it fully.  Then, turn the key.)  

But if has been sitting for a few days, the carburetor loses pressure and the intake begins to dry out.  If your truck has been sitting for 3 days, pump the gas 3 times before starting the engine.  If it has been 5 days, pump the gas 5 times before starting.  

My own truck starts right up by following the above starting procedure.


Fast Idle Speed Adjustment
The fast idle will work much better when it is set at full operating temperature.  That is how Ford set them when they were new.  This is how you do it:

Get your truck up to full operating temperature and then turn your engine OFF.  At the carburetor, take one hand and open the throttle a little, and with your other hand pull the fast idle cam down (on the other side of the carburetor) until the "V" mark is lined up with the fast idle screw. While holding it there, release the throttle. This will hold the fast idle cam in position and tricks the carburetor into fast idle mode. Then, start the engine again, but DO NOT TOUCH THE GAS PEDAL. If you do, the fast idle cam will drop down and you will have to repeat the previous steps again. Now you simply turn the fast idle screw to the specified fast idle RPM. It is usually 1600 RPM.

If you set the fast idle speed to 1600 RPM when the engine is fully warmed up, it will never need to be re-adjusted.  You will find that when outside temperatures are coldest - like in December - the fast idle cam will initially hold the throttle at about 1250 RPM. (Just like most modern fuel-injected vehicles start at.) This is normal.  If you sit there and let it idle, you will find that the fast idle speed will slowly start to increase as the engine begins to warm up.  When the fast idle speed climbs to 1600 RPM, that tells you the choke is ready to come down to the next step on the fast idle cam.  Gently blip the throttle and the fast idle speed will drop down to about 1000 RPM in cold conditions.  Do NOT whack the throttle in an attempt to get the carburetor off of fast idle before the engine is ready.

You do not have to sit there and let it "warm up" either.  1000 RPM is enough to keep the engine running smoothly and you can drive away immediately, if you like.  As the engine warms up from driving, the choke will automatically come off gradually.  This practice is actually *better* for the engine.  A cold engine will warm up faster in 1 mile of [conservative] driving than it does sitting at idle for 10 minutes.

When the outside temperatures are warmer - like in July - the fast idle cam will initially hold the throttle a bit closer to 1600 RPM.  That's because a warm engine needs very little choke and for a much shorter time period.  Fast idle speed will rise to 1600 RPM much faster, and the fast idle cam will completely drop off when you blip the throttle.

I have found that chokes can work very well when they are set correctly.  In the end, there should be very little difference between driving a cold carbureted vehicle compared to a cold fuel-injected vehicle.

Capiche?

Nice write-up on the choke, Lariat! Thank you for that contribution. Frankly, this should go into a "How To" section, as the requests for choke adjustment are frequent.

I would agree on the choke adjustments link.  Maybe a link to some of the vids on YT as well.   There are a couple good ones there.  

Then all the FB posters that get referred to here can comment on how crappy we are over here for not doing it for them.   Sorry - that aggravates me when we're called out for being too thorough or too technical.  There is no shortcut to thorough understanding of a system.  

But there are a lot of newer people coming into the hobby and a choke adjustment section will help a lot of people on their next carbureted builds as well.   I know just enough myself to really mess things up.   THat's why I asked here - to get better information.  

Lariat,

I just read that thoroughly and will try those adjustments.  That sounds good.  I saved it and printed it to have beside me when I'm at truck.  

Interesting and logical thought process on the days since last start.  I'll try that.   Because that would seem to bear out what I am experiecning after truck sits a few days.  

Thanks
Randy

Machspeed wrote

Nice write-up on the choke, Lariat! Thank you for that contribution. Frankly, this should go into a "How To" section, as the requests for choke adjustment are frequent.

Completely agree!

I am curious about the "multiple pedal depress" advice.  I suppose it is about a "slow" movement, since the goal is to «clip» the choke flap closed...  If "pumping" vigorously, won't it open de flap immediately after the second shot? If the pedal is depressed multiple times, slowly, is it certain that the choke will remain fully closed after the last shot?

On my side, Big Brother has the following starting behaviour:
1- Depress pedal completely and release;
2- Start the engine;
3- Motor starts immediately...  but after 2-3 seconds running, RPM drops and it stalls.
4- Redo step 1.
5- This time, motor starts and continue as expected.  But sometimes, it doesn't run smoothly and seems to have a "slightly" opened choke flap.
6- Choke often omit to disengage when the motor builds its heat, so I have to give a fast shot to the pedal, to slow down the RPM.  Sometimes a second time after couple of minutes, to drop to the "normal" idle speed.

The bad idea I tried was, at step 3, to slightly pump the pedal in order to "help" the motor stay fuelled and avoid a stall:  Yep, it doesn't stall, but I have to stay in the vehicle to keep it running, since the choke seems now to be slightly opened.

I would be very happy to find a starting sequence (and/or an adjustment) that enables Big Brother to start as... well let's admit... a fuel injected one.

The choke is only controlled by temperature and, on some carbs, vacuum.  So pumping the pedal several times while the engine is off will have no effect on the choke since the temp won't change and there is no vacuum.

But once the engine is running several carbs have a vacuum pulloff, and that includes most 2150's and the Holley 4180C you have on your truck.  And that does just what it's name implies - pulls the choke off a bit.  Basically it is a feedback or closed-loop system - if it pulls the choke off too much the engine will slow and the vacuum will drop, which will add some choke back in.  The trick is to have it pulled off just enough, and it sounds like yours is coming off too much.

As for the fast idle, as long as you don't depress the throttle the fast idle cam will be captured by the throttle linkage and can't change.  But if you open the throttle the fast idle screw will release the fast idle cam.  So when you say you have to "give a fast shot to the pedal to slow down the RPM" that is exactly to be expected.

You can see the adjustment procedures below on those two systems from Ford's document on our page at Documentation/Fuel & Air Systems/Carburetors, Chokes, & EFI/Holley 4180C and then the Ford's Service Manuals tab followed by the 4180C-4V tab.  And from your description I'd say you need to do the pulldown if not the fast idle adjustment.

Thanks!

Next weekend, I'll read with great care and pay attention to my carb/choke adjustments and behaviours.  There is no reason I cannot adjust and fine-tune it, since it runs very smoothly when hot.

Yes, you can do it.  But I'd suggest making one change at a time so you know what to back out if it doesn't work.

And don't miss the other tab with the other Ford document on the carb.  They are slightly different so it would be good to have your head around both of them.

I fiddled with mine on Saturday and Sunday.  Found a couple things out of adjustment.  Choke plate doesn't always close completely on pedal to floor at cold start.  So it is remaining at the pull down opening when cold if it doesn't close completely. I can lightly touch the choke plate linkage and it will snap shut.  Not sure if it's got a little stickiness in there or what.  Will continue to investigate.  

I removed the cap and cleaned the edges a bit and notched the case to know where the spring is at rest.  the cap was taking two hands to twist.   The gasket was sticking.  

First testing I discovered that the choke plate isn't opening fully as it warms and still at pull off position for too long.  So it would be running pretty darn rich when I was experiencing the missing.   I think I am about to get it all adjusted.  I had the adjuster too slack.  The one that goes into the plastic piece behind the cap that determines how fast it comes off fast idle cam.  

So check, drive, check, drive.  I had it really bad at one point.   Missing at speeds and any measureable throttle opening, but idling at about 2500.   Ugh.   Roadside adjustment.  

Also found that when I open the throttle all the way, it leaks about 3 drops of gas off the throttle linkage.   It's leaking a little somewhere.  One of my dudes at work says I probably need to rebuild the carb.  Wonder if I need to rebuild or just get a new carb.   If it's leaking around the throttle shaft, does a kit have the parts to fix that?

I installed a tach too.  Just to get and idea of engine speeds.  At 55 ish, tach reads 2000 rpm.  Shouldn't I be getting better mpg than 10?  It's a 5 spd, so 2000 is in the realm of possibility.  I don't think the tach is necessarily wrong.

What should idle speed be on a manual trans when warm?  I"m going to go looking for that and a carb kit.   It's got a reman tag so not sure what carb is set for, but surely a kit for 81 302 manual trans?

If you have gas leaking out between the throttle shaft & carb base plate a rebuild kit will not fix this.
There is wear on the shaft and / or base plate and I see this as something beyond the normal person.
Even I would not try to fix as bushings would need to be installed and the shaft turned and if you dont get the blades back in the same place you can have even more issues with the throttle sticking.

Then add a choke not working right I would look into a new carb.
I did not say rebuilt as rebuilds may have the same issues with the throttle shaft.

So a 302 with a stick so you dont have to play with auto kick down linkage and that is good.
Check with local parts stores and Rock Auto for new carbs and prices.

If you dont have smog check you may want to look into Holley 2300 carb.
It comes as a 350 CFM and a 500 CFM and should be a bolt on to your intake.
You will have to deal with the gas line as it may feed differently and hooking up the throttle cable, may need a ball it snaps on to on the carb.
I have a 500 CFM on a AMC 304 to replace a Motorcraft carb and it was the best thing I did to the car.

With a new carb the choke should work,may need a little adjusting, and no more gas leak at the throttle shaft and should run a lot better.
Dave ----

/\  /\  What he said!

To fix a worn carb that way would require pulling the butterflies off the shaft, pulling the shaft out, boring the carb base out, pressing bushings in, reaming the bushings to the right diameter and alignment, and reinstalling & aligning the throttle shaft and butterflies.  Not something just everybody should attempt.

THanks gentlemen.  That's kinda what I was thinking as well, from what I do know.   That is not a place that can be fixed easily.  

I'll start looking.  The reman tag on mine says 2015, so it's probably done its time and is ready to be a shelf piece.  

Take a close look at base of carb - there is an extra piece in there.   It has some sort of thing on rear of extra piece.   What is this plate?  Do I need to keep it if I replace carb?  I'm going in search of docs on this.



Also below the vac pulloff in this photo.



Under carb here.



Feel free to comment if you see something that needs to be addressed.  I didn't install this old reman carb on the new reman engine.   I haven't touched anything except dist cap and rotor because cap was cracked at tower 3.  

That is the EGR valve/plate. I don’t remember what you need to do to eliminate that on that engine/carb setup. But if you do the ignition timing should be changed as it will be advanced a long ways at part throttle.