Engine won't idle

[nymustang]

Let me start by admitting my ignorance.... I swapped in a carbed 5.0 a few years back and other than figuring out how to put everything together, I've never been able to get it to run well. I have had it running and driven it up and down the driveway, but that is it.

As I say it is a carbed 5.0 with a 68 front end setup. Performer RPM intake and Edlebrock 1406 750 CFM carb, points ignition, stock dizzy. There are a few issues;

1. Car has not been run in so long that I need to jump it to start it (minor issue)

2. Fuel drains out of the carb and makes it a pain to start. I have to pour some gas into the carb if I ever want it to start. Carb is getting fuel (I can see it in the filter and smell it as I crank and it doesn't go) but it won't catch if I don't pour some down first.

3. If it does actually start, it will run well for a few seconds, then its starts stumbling, losing rpms and dies unless I bump the gas. If I try and hold steady rpms it wants to die so I can't even disconnect the jumper cables before it quits on me.

I tried adjusting the idle screw to see if raising the rpms would help but it did not. Do I need to start messing with the mixture screws? Is this something different altogether. The timing is close enough to start it, but I'm sure its not right on as I can't keep it running long enough to set the timing.

What do you guys think? Where do I start? This is this first and only weekend I'll have for a while. Hopefully I can make some progress. Thanks everyone.

 

[gotstang]

2) How long does it sit between starts? This is fairly normal if it sits for a long time (weeks?).

3) Is the choke working properly? Adjusted properly? Sounds like classic messed up choke symptoms (or vacuum leak). How high is the idle? Could also be idling too slow.

If the idle screws won't do anything, I'd suspect you have a fair sized vacuum leak. You can try spraying something flammable around all possible spots and see if the idle picks up as it is sucked in. You can also get a vac gauge and see how it behaves at idle; excessive bouncing of the gauge needle = leaks.

BTW, if this is a roller cammed unit, I hope you have a steel gear on that points distributor, otherwise, you're in for some baad stuff (ie. the cam gear eating itself)

 

[nymustang]

Oh yes I have a steel gear distributor. That was an absolute must.

It sits a long time between starts, weeks to months. However After I got the car to run for a few seconds today it was clear the fuel pump was getting gas to the carb and it still doesn't want to kick over without an extra shot down the carb first.

What would I check to see if the choke is working or adjusted properly? It has an electric choke and I know its doing something because if it starts, the idle is high and then you bump the gas and it kicks down. Or at least it used to. It won't run long enough now for me to get to that point. If it isn't working, how would I adjust it?

I didn't touch the idle mixture screws because it won't stay running long enough for me to get out of the car and start fiddling. Should I try adjusting them one way or the other and see if that helps?

I don't have a tach in the car so I think I need to get a portable one. I'll also add a vac gauge to the list.

 

[gotstang]

Sounds like there is some gunk in the carb...my 71 Plymouth needed that extra shot of gas to get started. Cleaned out the needle valve and it ran like a top.

When the choke is activated on a cold engine, you should have a small gap between the choke plate and the carb...probably 1/4" if I had to guess. More or less gap and it won't start that well. Sounds like the choke is working half decent if you're getting high idle and it kicks down when you hit the gas; might just need a little tweaking to improve the way it starts and/or stays running? You can adjust it by loosening the 2 screws holding the little round choke pot to the carb and rotating it until the gap looks good. This should be done on a stone cold engine for best results.

I wouldn't monkey with the mixture screws quite yet...I'd try to look at some of these other possibilites first and see if you can't make a drastic improvement with them first. Seems like people like to just start off by messing with the mixture and it ticks me off. :lol

Sounds like it's either a gooped up carb, vac leak, it's idling too slow, the choke is sorta out of whack, or a combination. Also could be the timing; a lot of timing, and it will be harder to start.

I'd start by cleaning out the carb and setting the choke. Depending on where that leads, I'd set the timing, and then the idle.

 

[nymustang]

Excellent, I will start by cleaning the carb and attempting to adjust the choke tomorrow morning. Thanks for he advice!

 

[johnpro]

As I say it is a carbed 5.0 with a 68 front end setup. Performer RPM intake and Edlebrock 1406 750 CFM carb, points ignition, stock dizzy. There are a few issues;

The 1406 is a good carb, but it's 600 cfm. The 750 cfm Edelbrock is a complete POS. Which do you have? There will be a number stamped on the front of the carb, right at the intake manifold.

Sounds to me like whichever carb you have, it's given up the ghost and needs a rebuild. Carb rebuilds are cheap and easy if you do them yourself. If you pay others to do it, it can be expensive and the results will vary wildly. I would start with a carb rebuild, if it's the 1406. I'd start with a new carb if it truly is a 750 cfm, and that would be WAY too much carb for a stock 5.0L. I use a 750 on my 408, which is far from stock.

This time of year, I wouldn't worry much about the choke. They're only needed in cold weather. I don't even have a choke on my 408. It very rarely gets below freezing here, so I just don't need it, and impairs the air flow.

 

[nymustang]

I didn't realize the 1406 wasn't a 750 CFM. I'll check that first thing in the morning to figure out what exactly it is I'm working with.

I do realize the 750 CFM is way too much carb if that is what it is, but I bought it when I was poor and I got a good deal on it. I'll see what cleaning it does for me first then either get the rebuild kit or a new carb.

Now to find a guide on cleaning this thing...

 

[nymustang]

Here is what I have found so far. I was wrong, the carb is a 1411 which if my reading is correct is the crappy 750 CFM model.

I'm pretty sure I had a bad vacuum leak since the cap on the timed port was cracked and fell apart when I took it off:

Also, the area around the plunger (don't know if that is what it is called) on the carb seems to be discolored and after sitting all night looks like there might be trace amounts of fuel leaking around it. Does that make sense? Is it even possible? Here is a bad picture:

 

[nymustang]

Update: It seems that it will run fine if I pour gas into the carb. As soon as it uses that gas up, it dies. The fuel pump is working so I'm guessing that means there is a clog somewhere inside the carburetor.

I sprayed some carb cleaner into it, let it sit then sprayed a little more, but so far nothing. I'm guessing it needs to come apart to clean whatever is clogging it up but I can't find good instructions anywhere on how to do that. I don't want to just start unscrewing stuff without knowing what I'm doing.

If cleaning it doesn't work, I think I'll be taking johnpro's advice and buying a new one. the 1406 sounds like it would be better for my application anyway.

 

[nymustang]

Well I couldn't find any detailed instructions of how to disassemble and clean parts of the 1411, so using the exploded diagram in the owner's manual I dove in. First I took out the metering rods and they both looked a little cruddy to me so I cleaned them up as best I could.
Bad pic:

Then I removed the tiny little clips holding the various rods onto cams (choke and pump) and of course *ping*... there goes one of them, lost in the driveway forever. Gotta find some replacement somewhere. The inside of the carb didn't look to bad to me, but I don't really know what I'm looking for. The gas did seem a little yellow which I think is not a good sign.

I sprayed everything with carb cleaner then attacked the airhorn.The floats looked dirty but the needles looked clean. I shot some carb cleaner in seats anyway just to make sure there was nothing in there.

before cleaning:

Everything got reassembled, jumper cables hooked up and the requisite extra shot of gas down the carb. Turn the key and she fired right up then stumbled a little and seemed on the verge of death. i bumped the gas and it suddenly smoothed out a bit and held an idle. I was able to get out, disconnect the cables and run the car up and down the driveway for a few minutes with no troubles at all. I think the moral of the story is I need to run this thing more often so it doesn't get all nasty inside. The real moral is I need to get this car drivable so I am more motivated to tinker on it. Also I need to look into a smaller carb because I really have no need for 750 CFMs on a 5.0.

Thanks for your help everyone!

 

[johnpro]

That's great news. I agree with everything you said. I smaller carb, 600 - 650 cfm, would do wonders for you.

What you did, is basically all that's required during a rebuild of any carb. The trick is just get everything clean, clean, clean. All rubber and gaskets get replaced (unless they are re-useable and in good shape). Normally, you would also pull the jets and clean them very well, and blast all air passages with compressed air.

Great job in diving in, and getting the job done. My only other suggestion is to ALWAYS pull the carb off the car before working on it. That clip that you lost could have easily been lost into the opened up carb, and gone down the intake, where it could even make it past an open intake valve, forcing you to pull a head.

 

[tarafied1]

how old was the gas in the tank? Maybe you just needed to get fresh stuff? Cleaning sure didn't hurt but if it sits a lot you might want to use "Sta-bil" gas stabilizer.

 

[nymustang]

I realized when the clip went flying that I probably should have removed the carb. Dropping something down there would have been pretty terrible. The gas in the tank is very old. I add a few gallons at a time when I need it but until the car is road worthy its going to continue to sit. Sta-bil is a good idea. Well a new gas tank is a good idea too, but one thing at a time.

Thanks again guys.