Difficulty "cold" starting
 

When I first go to start my car, it tends to take a bit of coaxing to get it to turn over. I'd say probably a good 3-5 seconds and a bit of pumping the gas pedal before I can get it to turn over. Even then, it idles really low and will cut out if I don't keep giving it a little bit of gas and lightly rev it. Once it's been running for a bit, it will idle without needing me to give it any gas, and I can even shut it off and it will fire right up the next time I start it, but probably the first few minutes or so it's a bit finicky.

I say it has difficulty with "cold" starts because it did the exact same thing yesterday afternoon in 81 degree weather on a sunny day. The engine should have been plenty warm between the ambient temperature and the added warmth under the hood from the direct sunlight, but I still had to coax it a little, and it nearly cut out on me when I took my foot off the gas.

I'm wondering if this is maybe a sign of the choke not working properly? Maybe the carb needs a tune-up or rebuild? Those seem to be the most likely possibilities in my mind, but there may be something else I might not have considered. Does anyone have any ideas on what the cause could be, and how to best fix it?

Re: Difficulty "cold" starting
 

If it's a Q-jet, it's leaking primary metering well plugs.

When the car sits for awhile, all the fuel leaks out of the bowl; then when you go to restart it, it's empty. The fuel pump has to refill it before it will start.

Those cause other problems too. You'll be AMAZED at the difference in how the car runs, and especially the gas mileage, when you fix them.

https://www.thirdgen.org/forums/atta...-jet-fuel-bowl

#3-6; not 1 & 2.

Re: Difficulty "cold" starting
 

Thanks for the reply, that makes sense based on the behavior of the car since it is running a quadrajet. I guess since I'd be replacing those, I might as well go ahead and do a full rebuild while I'm at it. Aside from the starting issues, it runs pretty strong, so the potential for added performance is certainly exciting as well. 😉

Re: Difficulty "cold" starting
 

You can't really "replace" them. All you can do is repair them.

The plugs are aluminum, but the carb body is chinesium. What happens over time is, the 2 dissimilar metals in contact make a little battery, which erodes one of them; specifically, the chinesium. Eventually it turns to a white powder, and where the plug used to fit tight to metal, it doesn't any more. Then since those are at the bottom of the fuel bowl, and exposed to vacuum, the engine constantly sucks extra fuel past them while it's running, especially at high vacuum conditions (idle and cruise), which drastically degrades the gas mileage; and of course, drains the fuel bowl over a period of hours, leading to the starting problem.

Disassemble the carb carefully, making careful notes as you go of how many turns the rich stop, lean stop, and idle air bleed are from bottoming, by gently and carefully screwing each of them all the way to the bottom FIRST before removing them. Clean the whole carb up, except for the electronic parts, in lacquer thinner or similar NON-RESIDUE solvent such as MEK or acetone. NOT brake cleaner, paint thinner, mineral spirits, turpentine. Sand or wire-brush the plugs down to bright metal and clean them again. Cover them with a nice thick void-free layer of epoxy such as JB Weld with the steel filler, making sure that the outer circumference of each plug is particularly well-coated. Put it in your oven on "warm" and let it bake for acoupla hours. Reassemble the carb, with all-new paper & rubber of course, paying careful attention to put the adjustable parts back in at the same # of turns out from bottoming that you counted before you took it apart, and otherwise following the instructions that will come in the kit. Might be wise to replace the float and the TPS as well so that you don't have to worry about those again for a good while.

Re: Difficulty "cold" starting
 

Ah, okay. I thought since it was a 'troublesome' part, a new one would be part of a rebuild kit.

Thanks for the very detailed rundown, I've only rebuilt a carb on a lawnmower before, and well... Let's just say that as of this year, that rebuilt carburetor is now technically old enough to vote, lol. I'm fairly mechanically inclined (I managed to rebuild the timing system on the infamous 5.4L Triton on my F-150... Great way to kill an entire Memorial Day weekend, lemme tell ya), but the rundown you posted will undoubtedly save me a boatload of time and trouble, to say the least, plus gave me a few things to do that I probably wouldn't have thought of.

Thanks again for all your help! Hopefully I can get a rebuild kit locally and knock that whole thing out this weekend. :)

Re: Difficulty "cold" starting
 

No unfortunately, not part of a kit; they're considered part of the casting for that purpose.

Shouldn't be any problem sourcing a kit and the other parts. Might not be in stock at yer corner parts store but they should be able to get everything within a day or so.

I'd recommend against the Tomco kit; not a big fan of their needle & seat. Standard Ignition, Borg-Warner, or of course AC/Delco (Delphi) would be better.

Don't be too surprised to see the electrolysis at other points in the carb as well... that, plus wear at the throttle shafts, is what turns them to carburetor-shaped scrap "metal". (I use the word loosely since it's just chinesium) Pay particular attention to screw hole threads in the castings: when those erode, the threads obviously are what goes away, and then of course you can't really reassemble the carb. A Heli-Coil fixes em right back up. Can't recall the sizes for sure; it's been awhile since I had to deal with em. I think the air horn ones are 10-32 and the TB are 12-24 but don't quote me on that.

Re: Difficulty "cold" starting
 

Turns out my local Autozone has a kit in stock and is holding it for me to pick up this evening. Just a couple of quick questions:

Is this the JB Weld epoxy you were talking about? https://m.autozone.com/sealants-glues-adhesives-and-tape/epoxy-compound/j-b-weld-original-cold-weld-epoxy/522961_0_0?aqs=

When you say to cover the plug with a thick coating, do you mean the entire plug, threads and all, or just a specific area of the plug? I'm just not sure how well putting epoxy over the threads would work out, given that it will make it harder to put back in place, plus the threads on the carb will probably remove all the epoxy as the pieces are threaded together. Just want to make sure I do things right the first time, the only thing I hate more than redoing a bad job is redoing a good one. ;)

Re: Difficulty "cold" starting
 

There are no threads. There's no "remove" or "put back in place". It's just a blob of aluminum, maybe a short piece of rod, spun into the chinesium casting; supposedly permanently.

So yeah; just slather the epoxy all over all 4 plugs real good, making sure there's no bubbles in it. Pretty low-tech I'm ashamed to admit.

Yes that looks like the right stuff to use.

Did the store have the other parts as well? (TPS & float) If not, get them on order so you'll have them on hand by the time you're ready to put it back together.

Re: Difficulty "cold" starting
 

Ah, okay. I saw your comment about corrosion on threads and thought that was what you were referring to.

They did not have the TPS on hand, but my local NAPA apparently does according to their website. I'll have to call them tomorrow to confirm, but otherwise I should be all set. The weather this weekend is supposed to be pretty bad, so I have the perfect excuse to stay in and work on it. ;)

Thanks again for all your advice, this car has seen some neglect and everything you've shared will definitely go a long way toward getting it back to its former glory. Greatly appreciated!

Re: Difficulty "cold" starting
 

Right: when I said "threads", I was referring to the ones that hold the carb together. Kinda hard to do without those. ;) Can't just epoxy those up.

If you see ANY white powder looking stuff (no, not THAT KIND of white powder) on the screws or anything else when you take it apart, I'd recommend having the Heli-Coil kit for that size on hand before trying to reassemble it.

Re: Difficulty "cold" starting
 

Well this car is from the 80's, so I don't know if I can rule that possibility out 100% ;)

I'll put any parts that have any signs of corrosion under close scrutiny, for sure. I've got 2 hardware stores and a NAPA all within 5-10 minutes of me, so I should hopefully be able to get what I need from one of them if I encounter any corroded threads.

Re: Difficulty "cold" starting
 

Well, I finished the rebuild and put it back on the car. The good news is it started up, but it doesn't idle very smoothly and it's a bit smoky when idling. Idle RPM's remain about the same, though. Acceleration is weak compared to before, and the exhaust seems to smell faintly like gasoline.

I made no adjustments to the rich/lean stops, but I'm thinking it may have been tuned rich previously to maybe compensate for the leaking plugs? Either that or I managed to bugger up something when I was putting it back together, although everything seemed to move and work properly when I checked it prior to installing it. But I figured I'd be best to get a second opinion before I start making adjustments and potentially make things worse.

Re: Difficulty "cold" starting
 

Sounds related to the idle air bleed valve.

Try backing that out while it's idling.

Re: Difficulty "cold" starting
 

and ensure that the MCS within the carb is clicking

you can confirm the travel on the MCS, which should be 1/8", by inserting a small rod into one of the vents next to the IAB. should feel it click up and down and can measure how far it moves. relatively easy to have it get hung up when re-installing the air horn. ensuring you have 1/8" of travel is also confirmation that your rich and lean stops were re-set correctly.

Re: Difficulty "cold" starting
 

I started it up again today to try and get everything running properly. The good news is that the fix on the fuel bowl worked perfectly, it fired up without any of the coaxing I had to do previously, so one problem down!

I went to adjust the idle air bleed valve. I first bottomed it out, 3 full turns to the bottom. However as I backed it out, I noticed absolutely no change whatsoever in the engine's idle rate. I reset it back to where it was before and fiddled around with it slightly, opening the vents, pulling the throttle cable gently, just trying to see if there was any hangups anywhere that were maybe affecting the performance of the carburetor.

On a whim, I lifted the secondary metering rods. I'd had to slightly bend the holder as it was getting stuck during the rebuild and the U-shaped part wouldn't seat all the way down into its channels without getting stuck. As I did this, the idling changed and sounded a bit smoother, but when I lowered it back down into its previous position, the idle speed increased to just under 2k RPM's according to the car's tach. If I raised them up again, the idle speed lowered, however nothing I did would get it to idle back at around it's previous usual range of around 1k-1200 RPM's.

When it first started, it also smoked like crazy. Whitish smoke from the tail pipes, and it looked like it was also leaking smoke from the coolant line on the driver's side of the engine, right where the line enters the block. However, once I fiddled with the secondary metering rods and refilled my coolant (I lost a fair bit when removing the old temperature sensor) that seemed to have stopped.

Driving power is largely restored, although it still feels a tad weaker on my butt dyno. I feel like it was pushing me harder back into my seat previously, although I won't rule out this just being something I'm imagining. Regardless, it's not lagging like it was the last time I drove it.

This is the first carbureted engine vehicle I've really worked on, so there's definitely a bit of a learning curve. I really appreciate all the advice shared so far, hopefully just a bit more tinkering and I'll have this running perfectly. -Especially because I think if I throw too much more money at this car in the near future, my wife may just make me go live in it, lol. :rolleyes:

Re: Difficulty "cold" starting
 

Spent some time working on the carb again today, trying to see if I can figure out why it's idling so high. Unfortunately, nothing is making much sense as to what is causing such a high idle speed.

I tried adjusting the high idle screw, if I tightened it, RPM's jumped up to 3k. Okay, so I'll just adjust it the opposite direction and that will lower the idle, right? Wrong. I backed the screw out to where I accidentally removed it completely and zero charge to the idle speed. So much for that being an easy fix...

All I can think is that maybe I reassembled that part of the carb wrong? Like I maybe had it open too full somehow when I put it back together and made the current setting the lowest possible idle speed? I'm not terribly excited about the idea of pulling the carb again and disassembling it, so I'd like to get a second opinion before I potentially waste time on something unnecessary. Any advice would be immensely appreciated!

Re: Difficulty "cold" starting
 

Also worth noting: the Check Engine Light would come on after a few minutes of driving ever since I bought the car 3 weeks ago. According to the previous owner, it's been like that as long as he could remember. Since I rebuilt and reinstalled the carburetor, it hasn't come on once. I don't know if that's any help in diagnosing the cause of the high idle, but I suppose it's at least a sign that something is working properly that wasn't before. :huh:

Re: Difficulty "cold" starting
 

Well, I managed to back down my RPM's to a more acceptable rate of around 1200-ish at idle. I spent some time fiddling with various components and seeing what, if anything, was making any difference in overall RPM levels. I noticed that the speed solenoid was keeping my throttle bumped out a bit when it was engaged, so using a crescent wrench, I adjusted the solenoid screw back down, which helped my idle RPM's immensely. I took the old girl out for a spin, and throttle response was good. If I put the pedal down, she responded without a hiccup, sputter or anything.

The idle still seems a little rough. Not bad, just not particularly even. The tach gauge flutters a bit, which I know isn't terribly accurate on these cars, but it does fit in time with what I can also hear from the engine. Still, it runs and my Check Engine Light still has yet to come on since reinstalling the carburetor.

If there are any other adjustments anyone can suggest I make (or if I shouldn't have adjusted what I did, FWIW), please feel free to let me know! It was a frustrating afternoon, but I still enjoy working on the old girl and getting her running at least mostly right felt like a pretty solid win to me.

Re: Difficulty "cold" starting
 

the speed solenoid should not be engaged at idle unless the AC is on. it should be adjusted to maintain a decent idle speed with the AC compressor running.

if it's staying on otherwise you need to find out why.

first thing I would check is the TPS. if you don't have a scan tool you can back probe the top and middle lead and it should read near 0.40 v at idle and around 4.0 v at WOT and progress linearly between the two.

another check is the dwell on the MCS. a scan tool or dwell meter can be used.

When adjusted correctly it should hover around 50% at idle and bounce a little as the ecm responds to changes in O2 sensor voltage. a slight hunt at idle is normal.

the fast idle cam should only be engaged when the choke is on. when the choke goes off (straight up) the cam should drop away when the throttle is opened. you can play with the linkage and see how this works.

Re: Difficulty "cold" starting
 

FWIW, there is no AC in the car currently. The pump is there, but is completely disconnected from the engine. The P.O. said it wasn't working and didn't know if the pump was bad or if it just needed to be recharged. I haven't even messed with it yet because that's why the good folks at GM invented T-tops. ;)

I can say with certainty that adjusting the solenoid did help, though. My biggest question is what could have changed between before I took the carb out and when I rebuilt it and reinstalled it in the car. Based on the tightness of the solenoid screw, I highly doubt I could have inadvertently worked it loose without a tool, and I never even tried to adjust it until last night. My opinion is that the P.O. probably just mostly tweaked stuff however necessary to keep it running. The seals on the carb were shot, so I wonder if some of the current adjustments were made to compensate for that.

I didn't adjust the fast idle again after I adjusted the solenoid screw, it was late and I didn't want to deal with angry neighbors, as she's a bit throaty even at idle. I'll pull out my voltmeter and test what you suggested tonight, and see if I can narrow down any further causes.

I did also notice that the throttle sticks just a tad. When I'm driving and come to a stop, it idles a bit higher, but if I justllightly tap the gas it lowers back to around 1200. Not sure if that offers any further insight to the idle rate, but I figured I'd at least mention it for posterity.
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Re: Difficulty "cold" starting
 

I ran about a half can of Seafoam through the fuel system at the recommendation of a shade tree mechanic buddy. First off, let me say the old girl did not care too much for it: she immediately became stubborn to turn over and keep running while her engine was cold and she cut out on me a couple of times when I took her out of gear while driving. Nothing a quick pop of the clutch couldn't fix, but a tad annoying. And then there's the white smoke, not a lot, just enough to barely be seen, but I'm told that's apparently normal with Seafoam running through the fuel system.

​​​​However, once she's warmed up enough, she'll quit cutting out and in neutral idles at around the 800 RPM range. So it seems like I'm slowly getting back to normal with it, but I'll know better once I fill up and run a Seafoam-less tank of gas.

Re: Difficulty "cold" starting
 

I'm a little overdue on the update, but I ran into a new problem this morning that's likely an extension of the previous issues.

I'm on a new tank of fuel now and the engine still does not like running after a cold start. I've got to feather the gas a bit at idle to keep it running at a stop light, but once I've driven it for bit, it idles just fine. I'm thinking I probably need to adjust the fast idle a tad, since I did adjust it when I was trying to bring my idle rate back to a more normal level.

Onto this morning's adventure, I was driving with the same behavior in the engine as described above, nothing out of the current ordinary, I'd driven it just fine all last week with the same behavior. As I came to a stop sign the engine cut out, so I did the usual thing and popped the clutch and did made my right hand turn. The car was sputtering I thought maybe I was geared too high, so I dropped it from second into first, but the car just wasn't having it, and it continued to sputter. I put the clutch in and tried to rev it a little, but it just stayed sputtering below 500 RPM. The second I took my foot off the accelerator, the engine died on me completely. I tried to start it back up, turning the key and pumping the gas, but to no avail.

I pushed it to the side of the road and popped the hood and removed the air filter housing to get to the carb. I checked both top throttle plates to make sure nothing was jammed and everything seemed to be moving properly. I hopped back in and went to try and start it while trying to watch the carb. Suddenly she started to sputter again and fired up after 2-3 seconds of cranking. I put the air filter back on and drove the rest of the way, no further problems. Idle rate was up a tad, about 11-1200 RPM's when I came to the next stop ,but otherwise it was driving like it did when it was warmed up.

Hoping someone might have some insight about what the possible root causes could be. I know the carb probably needs a proper tuning after the rebuild, but given this morning's refusal to start back up followed by its inexplicable startup without me really doing anything has me a bit stumped. Thanks!
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Re: Difficulty "cold" starting
 

Did You Make All 3 Idle Adjustments.


https://cimg7.ibsrv.net/gimg/www.thi...b26485fd7a.jpg

Re: Difficulty "cold" starting
 

I'm going to adopt "Chinesium" into my daily vocabulary...

Re: Difficulty "cold" starting
 

ensure your choke is functioning correctly.

the top choke plate should be closed when the engine is cold and should slowly open once the engine is started. it should be completely open when the engine is warm after about 3-5 minutes of running.

all of the above adjustments won't help if the choke is not working properly.

if the motor fails to start hot, it may be flooded. to clear it and restart it, hold the throttle completely to the floor while cranking.

Re: Difficulty "cold" starting
 

I adjusted the fast idle and idle speed solenoid, and I think the old girl (I don't know why I call it that, I've got 3 more years on this planet than she does, lol) and I have come to an understanding. She starts without any issue now and I don't have to feather the gas to keep her running when she's cold. No idea what caused the stallout and subsequent starting issues from the other day, but the incident hasn't repeated itself yet. Initial acceleration out of 1st gear is better as well, there was a bit of hesitation unless I had the RPM's high, now she starts moving a lot more smoothly.

Regarding the post about the RPM levels for the fast idle and the idle speeds, I'm assuming I'll need something like an Auto X-ray or the like to accurately achieve those specific RPM's? All my adjustments were done by listening to the engine then reading the dash tach - not exactly the most accurate methods, but I think I got it fairly close, albeit still a tad high. I'd like to get everything dialed in perfectly, though, so whatever it will take to get those timings where they need to be, I'm all for.

Lol, I know what you mean, I've already used it a few times since reading that post. Perfect word to describe cheap/flimsy garbage metals.