From cb4n+@andrew.cmu.edu Mon Jul 08 18:25:15 1996 Date: Mon, 8 Jul 1996 13:31:31 -0400 (EDT) From: Colin John Brodsky <cb4n+@andrew.cmu.edu>
This is a summary of my experience rebuilding a carb - 2 barrel model 2100 Motorcraft on my 1973 Ambassador. All of my motivation to try this came from people on the AMC list who reassured me that I could do it. My overall mechanic experience on a car prior to this was very minimal. Last winter, I posted a question about my choke and referred to "that round thing on the square box" as my air filter and carb :) Needless to say, I would not have imagined doing this 6 months later. I hope this is useful as a realistic assesment of what the job is like for those of us who've never done it before, and might be intimidated by it.
Much of what is in here was suggested to me by others on the AMC list.
From the day I got my car, starting was difficult - usually took about 10 seconds. I suspected that the accelerator pump seal was rotted and leaking gas after I turned the car off. As a result, most of the gas in the fuel filter would drain out through this leak (wasting a good amount of gas) leaving only a trace of gas in the carb, and none in the line or fuel filter. The result was a burst upon startup, but then sustained cranking to get the gas down into the carb. Some people suggested that this was just because it's old and you have to live with it, but the rebuild solved this problem beautifully. One easy way to check is if you have a clear fuel filter - just pop your hood and check it right after stopping to see if it's letting air bubbles in - that's probably due to a leak, and if you take off your air cleaner, you may well see it as I did.
More commonly, choppy acceleration and lack of smoothness is a good reason to do this. Although I thought my car ran well, I didn't realize just how good it could be until after the rebuild. I'm also hoping I'll see much better gas mileage - hoping to break 20 MPG on highway!
$18. I had to special order the parts kit, and it was $15. Also, $3 in carb cleaner spray. I got one large can - I'd recommend at least two because it really works better the more you can use. You'll likely have some serious crud to get out. Also, if you don't have any air source, try to find some compressed air in a can - that might be handy.
8 hours of time. This includes taking it off, being very particular in my labeling of parts, spending time learning how it works, the whole rebuild, reassembly, putting it back on the car, and making adjustments.
$200-$300 were rough estimates I heard to either rebuild it or put a rebuilt unit on. Of course those are prices in the city of Pittsburgh, which is a somewhat inflated market compared to some places.
Recommended by Jane Kleinkramer: I use the dip-type carb cleaner that comes in a gallon can, with a dip basket. This type is more expensive (about $20), but can be reused many times. It also keeps the fumes down considerably, from what you describe. You take the carb apart and put the carb body and all of the parts in the dip basket and then lower them into the cleaner and then put the lid back on to keep in the fumes. Let them soak overnight, then pull up the basket, take everything out, rinse it well and blow out the channels with compressed air. Proceed as usual, but rarely will you need to scrub anything because the cleaner just eats away at gunk, old gaskets, etc.
I couldn't find this in the manual, but it was relatively obvious what parts should be separated in the accelerator linkages, and the rest were just hoses. I suggest writing a list of each thing you disconnect, and note what part of the carb it hooks up to. This way, you can just tick them off the list when you put it back together and you won't forget a connection. I think there were about 10-15 things that had to be disconnected, so it's very possible that you could. Then, the carb is simply held down by 4 bolts at the corners - it all lifts out as an assembly. One concern I had was that things would all start popping loose everywhere and I'd end up with a bucket o' bolts. That won't happen - it'll come out with no hassle.
This is something I should have spent more time doing. When you have it off the car, you can still examine how all the external linkages work, because it's a nice secure intact unit you can play with. This is a great chance to do it without being hunched over the car! The tech service manual does a good job of explaining it. It'll help you avoid the one difficulty I had, and that is understanding the choke linkages. Figure out how the choke plate is closed when you floor the accelerator, and how you knock it back out of fast idle. Learn those mechanisms and it'll help later.
This would really be too much for me to explain. But if you have the service manual, you don't need my explanation. The most important point is take care to note how each part you take off fits together. especially the choke linkages. They're actually trickier than the guts of the carb, in my opinion. Put the parts on paper with a note saying where it goes, and how it fits together. This was actually very straightforward with the guided steps in the service manual - something that wasn't in the carb rebuild kit. As long as you're patient, it's hard to go wrong here. When you take a part out, look in your kit to see if there's a replacement for it. Many parts won't be replaced, and if they're metal, clean them up well with your solvent. Don't use the solvent on non-metal parts of course. Any kit and manual will tell you that when you clean small nozzles/jets do not use wires to poke in them.
Just use the force of carb spray and compressed air to clean them. Might take a bit of carb spray, but the stuff is cheap. You may well notice that your gaskets are like gooey rotted rubber. Mine took some time to get off the carb - they had turned to a gummy nasty substance. Especially that pesky accelerator pump seal!
Paul Dwyer adds the following: One thing I would add is that carburetor bodies tend to be made of fairly soft metal, so care must be taken not to overtorque screws upon reassembly. Tighten them enough to compress lock washers or to a "snug" feel, enough to get a good seal on the gasket but not as much as you would tighten a steel bolt/nut of the same diameter. If you strip the threads in the carb (it will strip there before it strips or breaks the steel machine screw), there likely won't be enough thickness to tap out a larger size or use a Helicoil. And even if there were, you'd be running the risk of getting filings into the carb when you drill and tap. Remember, it usually takes more force to loosen a screw that's been sitting there for years than you should apply when you put it back in. Oh, one more thing -- if there are, e.g., four screws holding an assembly together, seat them all, then snug them all, then tighten them all. Don't torque one down while the others are still quite loose, or you might warp or break a part. This applies to all kinds of things, such as wheels, manifolds and cylinder heads, but carb rebuild instructions usually won't make note of it.
Again, this should be easy. Just hook up the same things you took off, and follow the adjustments in the manual, which are fairly well outlined. However, I ran into trouble, and made a desperate plea to the list. Here are some trouble-shooting tips I got sort of patched together by contributor - they sound choppy because I asked for some clarifications which they sent. One of these things saved me. Hint: the really easy one.
Well, there's always starter fluid, aka ethyl-ether spray. Harsh stuff, but it works. Wear goggles and have a fire extinguisher at hand. Good suggestions from others on the list. As for the spark check, there are inexpensive ($5-$10) inductive spark testers at most auto parts places. You just put the tool up to the wire and it flashes if you have a spark. Or you could use an old (cleaned and gapped) plug on each wire, hold the plug's threads to a ground (such as a manifold) and watch the spark. Wear thick gloves, 'cause you could get a hell of a shock.
Another thing to look at is to crank the car with the air filter off and make sure that the float isn't sticking and flooding the car with gas out the vent tube. I have had that happen with a fresh rebuild. If the float is stuck you will see gas coming out of the float bowl vent tube and running down into the venturis. This will happen pretty much as soon as the fuel pump starts to work. If you see gas here you can bet it is flooding.
One last thing, make sure that you are getting spark. I know, you didn't do anything to the ignition. I have said that before. I have also driven myself crazy by knocking the coil wire off and not noticing it. For spark, make sure that all the plug wires and coil wire are on tight at both ends. You can then pull one of the plug wires off at the plug and place it near a ground. It should jump a spark at least a half inch long. Don't hold the wire, because if you aren't near enough to the chosen ground it will try to ground through you. That hurts. Check the float sticking first though. You don't want a spark if there is gasoline anywhere it isn't really supposed to be.
Take a good look at the linkage for the choke. The slightest rub anywhere will hang the choke plate. A good spraying with WD-40 or equivalent won't hurt anything. Make sure that all the linkage moves freely by hand and it should be OK. Prime it down the carb with gasoline or use some starting fluid. Ether (starting fluid) might make it hit even if it is flooded. Be careful and have some dry rags handy to extinguish the fire if it backfires out the carb.
So what was the problem? I knocked off one of the ignition wires :) Put it on and it started beautifully!
Here's some other old advice I got about choke adjustments:
To check your choke, go out in the morning when the car is completely cold and floor the accelerator. The choke plate should close completely. If it does not, either the choke is not adjusted correctly or the mechanism is sticking. Try moving the mechanism by hand and see if it resists. If so, first try cleaning around the plate with choke cleaner, and trace the linkage, cleaning it as well.
Next you can take off the choke cover plate (attached by three screws) and clean the parts in there. If none of this helps and the plate still does not want to close when the accelerator is floored, the adjustment may be incorrect. Loosen the three screws on the choke cover plate that allow you to adjust the richness/leaness of the fuel mixture. Turn this knob until the plate closes. You shouldn't have to go more than a tick mark or so in either direction. Finally, let the car idle for a few minutes and watch that the choke plate opens
up. This is all quite easy; the only frustrating part is that once you start messing with it, you often have to wait until the next morning when the car is completely cold again to really know if you've alleviated the problem.
If you're comfortable with taking routine things apart and putting them together, a carb rebuild is really just that with only marginally more complexity. The insides were actually rather easy! There are some places you can hit a snag like I did. Although I was frustrated, in the end, I was so glad I did this myself - it's very satisfying. If you follow the guidelines above, you should be in good shape to pull this off yourself and save a couple hundred bucks - not counting the potential gas savings.
Feel free to e-mail me via the list (I'll be moving this summer) if you have more questions that I might be able to answer about the difficulty of the job. I can add more details to this where necessary. Others will tackle technical details way better than I!