Well I don't disagree that its worn out but would this issue manifest itself so abruptly? I would think that kind of problem would creep up on you over time. My uncle had a restored 66 mustang with the original 289 and 2 bl carb. He continually had trouble with the carb and rebuilt it several times before finally buying a new replacement. Problem solved instantly so I guess sometimes they finally give up.

 

Similar carb, with minor changes...the same Motorcraft carb kit fits both the Mustang and 1963/74 Ford truck 2V's.

Same kit...I kid you not.

D4AZ9A586A .. Carb Kit (Motorcraft CT499D) D4AZ-9A586-A replaced: D2AZ-9A586-A & B / C2AZ-9A586-D)

Your truck only has the in-cab fuel tank, correct?

IF your truck has the mid-ship and/or the aft axle fuel tanks...be advised...there are fuel filters inside those tanks...on the pickup tubes of the sending units.

The in-cab tank does not have a filter on its pickup tube.

 

I thought it was likely a very similar carb. His problem was rough idle, hesitation on hard acceleration and difficulty "warming up". You had to fast idle it yourself. I wish my issue was that straitforward. Mine won't stay running if you hold the pedal in one spot, you actually have to pump it to keep the engine running.

 

That's for sure...a fuel delivery problem.

I added additional info (I edit a lot!) about fuel tanks above.

The accelerator pump diaphragm...did you possibly install it backwards? I assume you replaced it...and the check valve.

When you removed the metal cover on the front of the carb behind which those two parts are located...there's a COIL SPRING inside. You re-installed that, too...correct?

The accelerator pump diaphragm has a flat metal plate in the middle of it. The coil spring fits between that and the cover.

 

No, my truck has the gas tank located at the rear of the truck. So there may be a filter there as well huh? I may need to lift the bed (still unbolted) and check the pickup tube filter?

Yes, I was sure to replace the new piece exactly the way the old one came out. The spring rests on a flat round plate with a slightly raised lip to prevent slippage, the opposite side had a raised metal disc for the lever to rest against. The original had a smaller diameter disc but was otherwise identical. Also, the original did not appear damaged. Actually, none of the gaskets or other parts I replaced appeared damaged or worn, or really all that dirty. The bowl had a very fine layer of sediment, but thats all.

 

did you take your fuel pump out yet...Maybe the arm on the pump is broke....

 

No, I thought I would try to replace the filters again and perform the wet float adjustment first. From there, check the filter on the pickup tube in the tank and add more gas to dilute the pita contaminants. I'll grab some more filters on the way home in a few minutes and try them, post back my results this evening.

 

On the sending units for the aft and midship tanks, is a plastic meshed filter screen. It's 3/8" I.D. and slides over the end of the pickup tube. It's prolly plugged up.

While you are replacing that screen, look at the float on the sending unit...it's made from two pieces of copper soldered together.

Solder breaks down, gas seeps in, float settles to the bottom of the tank. The incab sender takes the same float.

All these parts are still available from Ford.

D1AZ9A011A .. Plastic Meshed Filter Screen-3/8" I.D.

MSRP: $21.73 / FTEpartsguy.com price: $15.65

COAF9276A .. Fuel Sending Unit Gasket-Use w/Mid-Ship or Aft Axle Tank Only.

MSRP: $0.77 / FTEpartsguy.com price: $0.60

COAZ9202B .. Float

MSRP: $7.41 / FTEpartsguy.com price: $5.34

C1TF9276A.. In-Cab Sending Unit Gasket

MSRP: $5.37 / FTEpartsguy.com price: $4.19

 

Ok, I've made some progress. After trying all else I decided to adjust the float level. I adjusted the tab down, thereby lowering the bowl fuel level. This allowed the truck to idle on its own with the choke mostly closed. Then the problems started. After 20-30 seconds, the choke begins to open and the more the choke opened the lower the rpms went until it dies. With the choke open it will not idle. My guess now is that I have a choke setting wrong. The choke on my truck is the electric assisted version. The carb is also equipped with a dashpot, however I'm not sure that it works now, or ever did.

Also, one time after it idled for 15-20 seconds I throttled it at the carb. When I did, I must have released the fast idle cam or something because the choke opened nearly all the way and the truck died almost immediately.

Ideas?

 

When the choke opens it's getting starved for fuel at idle. Lowering the fuel level in the bowl-lower then the factory setting is not recommended. What is happening is that when the choke is closed? The engine vacuum is pulling fuel out of just about every port in the carb. When the choke starts to open, it reduces the vacuum on all those ports and "leans" out the mixture when the engine starts to get warmed up. Once the engine is at optimal temp? The choke opens full, and the idle screws at the base of the carb allow a slow 'bleed" of fuel just below the throttle plates.

The cam has several steps or stops. The highest=holding the throttle plates open a bit, allow more vacuum to hit the ports to draw in more raw fuel to keep it from stalling. When you first pump the gas a couple of times when cold? The choke snaps shut, and the cam kicks the throttle open a bit. Result? Very Rich fuel mixture. Normally just used to get the ol' girl started. Tap the gas pedal after it's started, and it will (in most cases..unless it is extremely cold) kick the cam-stop down a notch= reducing the idle speed a tad.

Now the choke opens a bit more as the engine heats up, leaning out the fuel mixture--and the throttle cam normally kicks out to the 'off' position. When the engine is at temp, the mixture can and should be leaned out so as not to waste fuel, and blow black smoke out the tail pipe. With the choke fully open, and the only thing holding the throttle plates open slightly will be the base idle screw (located just to the rear/base of the throttle linkage)

From the sounds of it? Several problems, all related to both the choke "circuit" and the base idle "circuit". I'd correct the float level to exact specs, reset up the choke--and check the spring to ensure it's mounted into the receiver/lever in the choke housing. It's real easy to install the choke cover with the spring--and miss that slot in the actuator arm! Try the mid-line adjust on the choke cover as a base line. Set the line on the cover to the center of the casting mark at the top of the choke housing. There will be several dots...kinda like "L....|....R" (L=leaned, R=Rich)

Also while you're playing with it? I've gotta ask...Did you adjust the idle mixture screw(s) correctly? (long screws with a needle end, with a spring between the screw head and the carb base) When I did ours, I ran both screws (we have a motor craft 2100 2 bbl) until they just seated. (just until they seat--any tighter and it reams out the passageway making it damaged beyond repair) Then I backed both screws out 2 1/2 turns. (before anyone asks? We used a vacuum gauge and tach and fine tuned the base idle mixture). I have seen people rebuild a carb, and just tighten the screws for the idle mixture--and forget to set 'em.

Just a few ramble ideas. When you mentioned hitting the gas, and the choke just flopping open all the way? Makes me wonder if that spring is mounted correctly in the housing actuator arm.

Hope it helps..

S-

 

Keep in mind (as my own side bar note) I know I suggested things already suggested. But if this is not something as simple as an adjustment out of wack? I'd kick it up a notch and do a fuel pressure and fuel volume test.

That would either point towards fuel delivery problem before the carb---or remove it as being a possible problem.

Sorry if if seems like I repeated several things. But the operation of the choke system and idle circuit are pretty much cut&dry. It just sounds like something just out of wack enough to give you a headache.

S-

 

The fast idle cam is (white) plastic and has a nasty habit of snapping in two = make sure yours is still in one piece.

According to the parts catalog, you have the electric solenoid on your carb, not a manually operated dashpot. When this device is working, the plunger is spring loaded and will rebound when pressed in.

 

Throttle Solenoid is correct. I meant to correct myself but forgot. The plunger will depress but it doesn't contact the throttle linkage, even when fully extended. It hasn't since I've owned it as far as I know. The fast idle cam isn't broken but I can see how it could easily get that way.

I know that the spring in the choke housing is in the slot. I had to start over a couple times assembling that piece because it slipped out while trying to get the cap on.

As for the float level. I tried adjusting the float level to raise the fuel level in the bowl first since I suspected a fuel starved engine. That provided too much fuel. Fuel was dripping onto the throttle plates after the engine stopped running. So I decided to go the opposite direction. That adjustment provided the most promising results so far. The truck idled on its own for more than 2 seconds, until the choke started to open.

As for the idle mixture screws, I adjusted them out 1.5 turns per the instructions. If you used 2.5, maybe I should try that.

The fuel pump works just fine. I ran a long piece of fuel hose into a bottle and turned the engine over a few times. Plenty of fuel.

Based on these comments, I am going to raise the float level again and adjust the idle mixture screws to 2.5 turns from 1.5. These two things should provide a little more fuel once the choke begins to open. Hopefully that will get me a little closer to the resolution.

I really appreciate all the great input and the time you've taken to respond. It is immensely frustrating when something just stops operating correctly so suddenly and I find myself making all these adjustments when it was working fine 2 minutes ago.

 

The instruction sheet with the rebuild kit should have included a list of settings for the dry float level. Normally that's good enough to get things inline ready for fine tuning. Many people have their own ideal setting for the base idle screws. Sometimes 1 1/2 works great, however ours needed 2 3/4 when we got it dialed in. Many factors come into play with those idle screws. Wear, any missed varnish buildup during the rebuild, any little bit of crud that gets kicked loose and finds its way into the passageways.

I'd try 2-2 1/2 turns out from being seated and see how it goes.

If it seems like things are getting "spotty"? There might still be some dislodged crud built up in the passageway. Quick and dirty fix (while it may/may not work?) Would be a can of B-12 carb/choke cleaner with the long tube attached. Unscrew each idle screw and clean off the needle end, and hose the crap outta the port it screws into. If you hold the throttle plate open while spraying? (and yeah...engine off and totally cold!) You should be able to see a stream of that cleaner getting blasted out of the port it exits. Now if you only get a few drips while pointing the small hose into the port where it screws in? Might have to remove the carb, point the hose right into the port and reverse blast any crud build up out.

S-

 

This is going to be a long one. But I want your problem to be fixed. Read up.

Instead of experimenting trial-and-error with the float level, only set it to the factory specification. If you do that and you still have problems, the problem is elsewhere. You can't mask another problem by compensating with the float level.

Since the carburetor is already on the engine, check the wet height of the float. Start the motor and let it run until it's at operating temp, and remove the air horn from the carburetor to expose the fuel bowl. Measure the distance from the center of the fuel level to the top machined surface of the fuel bowl, and this is the wet height. The rebuild sheet will specify what this height should be. If your measured height does not match the specified height, you must remove the float, bend the tang, and start over. Don't forget to snap the float retainer in place when you replace the float.

Be careful when you remove or bump the float, as fuel will spray out of the needle. Also be careful when doing this check, because you have an open fuel source and a running motor. Do this step correctly, and we can take the float out of the picture. Don't waste your time playing guessing games when working with carburetors. Take the time to do things right and do them once, and you won't have problems.

Here is how you take care of the choke and fast idle issues. Once again, proper procedures dominate shade-tree trial-and-error time and time again. Please read my instructions carefully.

Choke pulloff clearance. When you get in any carbureted vehicle to start it first thing in the morning, you push the gas pedal once to "load the choke." This snaps the choke plate shut all the way. Because it's just a spring, its job is to tighten itself. It can't accurately control "how much" it tightens. If we just let the choke pull the choke plate all the way shut when you first start the motor, there will be no way for air to get into the engine. Therefore there is a "choke pulloff" which serves to slightly open the choke plate against the choke spring tension, just enough for air to pass in. The vacuum created by the starter cranking the motor pulls the pulloff diaphragm and lets that first sip of air through.

To adjust the choke pulloff, the motor must be cold and shut off. Loosen the 3 choke cap retaining screws and rotate the choke 90 degrees toward the back of the truck to completely shut the choke. Then, find the choke pulloff vacuum motor on the rear passenger side of the carb. There is an arm coming out of it which actuates the choke linkage. Press the arm all the way in to simulate vacuum pulling the diaphragm, and the choke plate should open slightly. In your rebuild sheet will be a "pulloff clearance" specification and it will be something like 3/32" and such. You must take a drill bit of this size and insert it between the rear of the choke tower and the back-end of the choke plate, to measure how far it is open. It acts like a feeler gauge. There is a small set-screw in the back of the choke pulloff. If your pulloff clearance is not to specification, you must adjust that screw and start the procedure over.

Fast idle index. While the choke is engaged, there is a mechanism to raise the idle above curb idle because the enriched fuel mixture requires the engine to run at a higher RPM. There are two settings for this - fast idle speed, which controls engine RPM during this time, and fast idle index - which controls how much of the choke engagement time that the linkage actually contributes.

When things are functioning properly on a Motorcraft 2V carburetor, there are 3 stages to startup - start, fast idle and curb idle. A small cam on the passenger side of the carburetor has 3 steps and controls this. When you first start the truck and you load the choke in the morning, the engine starts at its highest possible RPM and the throttle linkage is on the first step of the cam. When you bump the gas pedal again, the fast idle linkage is released and allowed to drop, at which point the throttle linkage is on the second step of the cam. The throttle linkage remains on this step of the cam for the entire length of time the choke is opening. Once the choke is completely open, the cam drops out of the linkage completely and the carburetor returns to curb idle. This is where the engine remains for the rest of the driving until the engine cools down again the next morning, and the process starts over.

To properly idle during warmup, it is imperative that you sync your choke with the fast idle cam. Again, there is a factory procedure for this. If you're with me so far, your choke cap is still rotated 90 degrees from when you were setting the choke pulloff clearance. Here is where to go from there:

1. If the choke isn't rotated toward the back of the truck already, do so now.
2. Open the throttle, and hold it there with one hand.
3. With your other hand, push the choke pulloff rod in all the way, the same way you did in the pulloff clearance procedure. The choke should now be open in the pulloff position.
4. Your other hand is still holding on to the throttle. Let go of the throttle, so that it rests again.
5. Now the important part. Look down at the fast idle linkage, underneath the choke cap on the passenger side of the carb. There is a small cam above the throttle shaft. You will see a small V notched onto the second step of the cam, and you will see a long screw with its tip touching the surface of the cam. The tip of this screw must be aligned perfectly with this V. This is the measurement Ford uses to tell you that you've set the fast idle index properly. If it is not aligned with the V, there is a small hex screw on the plastic fast idle arm in the linkage. You turn this to adjust the index. Each time you adjust this screw, you must start this procedure over and check for alignment.
6. Note that anytime you adjust pulloff clearance, you must adjust fast idle index. This is why I had you check the clearance first, before doing this procedure. Make sure one thing is right before you move on to the next.

This configuration gives the following results: when you first start the engine, the idle is high. Once you get out of your driveway and start driving while the engine is still warming up, the idle is still high, but not as high as when you first started it. Once the truck is warmed up completely, the choke is open and the idle returns to normal.

Fast idle speed. Once your fast idle cam is properly aligned, you must adjust the speed at which the engine idles when the fast idle is engaged. You will notice that under fast idle, the throttle plates are open further. I usually adjust this to allow the engine to run at a 200-300 RPM higher than curb idle. Contrary to most of my statements in this post, this adjustment can be trial-and-error provided the linkage is working in the first place.

Choke cap index. If you're still with me, the choke cap is rotated toward the back of the truck. Now you must align it properly. On the rim of the black choke cap is a small notch. On the metal choke housing to which it attaches are seven notches. The goal here is to align the notch on the cap to one of the seven notches on the housing. Going from the back of the truck toward the front, the notches are represented as 3 Rich, 2 Rich, 1 Rich, Index, 1 Lean, 2 Lean, 3 Lean. On the emissions label attached to your hood or valve cover, it will say which notch to align the choke to. If your label is long gone, 1 Rich is usually a safe ball-park figure. This adjustment is often changed during winter and summer season changes. While you're doing this, this is a good time to make sure the choke spring is properly engaging the choke linkage tang inside the housing, as this is often overlooked during a carb rebuild. Once you have the choke cap aligned, tighten the three retaining screws back down.

If you follow the procedures above, your choke and fast idle will be set properly. Like I said before, proper carburetor performance comes from closely following proper procedures, not making guestimates. Ford engineers marked these carbs with all sorts of notches and numbers for a reason - so that they may be tuned properly.