Starting/Running Rough - Input/Suggestions

[jollyjoker]

65 Monaco - tired 383/AFB/727. Bought this back in 1990 from a kid, while I was stationed in San Antonio TX. Am retired military, so I drug this around from base to base, then finally has shipped up here to Ohio when I retired. Drove it fairly regular while I was in Texas, but then less and less. Finally, over the weekend, I unearthed it from its tomb of cardboard boxes (yeah . . . basically so I could clean out the garage).

Started up on about the third twist of the key, but never seemed like it went to fast idle - and wouldn't even idle. Got it onto the driveway, and figured a couple of turns around the block would help - but didn't make much difference. A lot of backfiring, which it had never done before (I figured it was just crappy gas, which had been setting too long). Stopped it, let it set for about an hour - then couldn't get it to start at all.

Seemed like it wanted to start, w/ the starter engaged - let off the start position on the key, and it would just die out. That made me think that maybe the starter relay had gone bad - put a new one in last night, and sure enough, it did start - but still running like crap. Jacked up the idle speed screw, and bumped the distributor a couple of degrees clockwise - and it now will idle. But put it in gear, and it just dies, unless you're there to give it a little gas.

Thoughts? Suggestions? From what I've read online, I'm beginning to think that I've jumped a cog on the timing chain. Especially since I've had to bump the timing a few degrees. Or, am I barking up the wrong tree . . .

 

[Polara_500]

Get some fresh gas in it after you siphon all the old crap you can out of there, let it run for 20 minutes or so and see what that does before you tear into it more.

 

[Ripinator]

65 Monaco - tired 383/AFB/727. Bought this back in 1990 from a kid, while I was stationed in San Antonio TX. Am retired military, so I drug this around from base to base, then finally has shipped up here to Ohio when I retired. Drove it fairly regular while I was in Texas, but then less and less. Finally, over the weekend, I unearthed it from its tomb of cardboard boxes (yeah . . . basically so I could clean out the garage).

Started up on about the third twist of the key, but never seemed like it went to fast idle - and wouldn't even idle. Got it onto the driveway, and figured a couple of turns around the block would help - but didn't make much difference. A lot of backfiring, which it had never done before (I figured it was just crappy gas, which had been setting too long). Stopped it, let it set for about an hour - then couldn't get it to start at all.

Seemed like it wanted to start, w/ the starter engaged - let off the start position on the key, and it would just die out. That made me think that maybe the starter relay had gone bad - put a new one in last night, and sure enough, it did start - but still running like crap. Jacked up the idle speed screw, and bumped the distributor a couple of degrees clockwise - and it now will idle. But put it in gear, and it just dies, unless you're there to give it a little gas.

Thoughts? Suggestions? From what I've read online, I'm beginning to think that I've jumped a cog on the timing chain. Especially since I've had to bump the timing a few degrees. Or, am I barking up the wrong tree . . .

If its been sitting around awhile with ethanol gas in it, I'd bet on the carburetor being messed up. You might also try doing a complete tune up on it too (plugs, wires, points condenser, etc.). After I did all this on my '66 300, it has never run better.

 

[jollyjoker]

A little more info . . . I wired-up a MoPar electronic ignition kit w/ Accel SuperCoil when I got it, back in 1990. So no points/condenser . . . although I think I remember reading that the electronic module can sometimes go bad (I guess some people carry a spare one in the glove box).

Yeah . . . I know this is a problem of my own making. I have another car that I've been using for cruise-ins, shows, etc . . . and since it's not very pretty, this poor 383 car just kind of got used less and less. You're right - I think getting the old gas out of there, and some new plugs might be a pretty good place to start.

 

[CBODY67]

I concur on new gas. Some stations in your area might have ethanol-free gas. You can find an online list of those, nation-wide, but they might be lower octane and such. Either way, new gas is needed. Also look for a possible fuel pump leak, just an advisory.

New spark plugs are probably needed too. No need to spend a lot, just that they are new and gapped correctly.

If you're using the "orange box" that came with the MP ignition kit, it needs 14 volts to work. Normal control units need less voltage to fire the plugs. Keep the original voltage regulator, as the MP regulator is set too high and can cause issues with ANY electrical circuit in the car, and durability of all electrical items, too (as stated in the MP Race Manual). The normal OEM regulator does work fine, as that's what I have on my '67 Newport, with the MP ignition kit.

IF the timing chain has jumped, rather than just a "few degrees" of movement of the distributor, you'll need to turn it basically one spark plug terminal's worth of movement. On my '66 Newport, moving the distributor vacuum advance just a smidge will take it from 12.5 degrees BTDC to 15 degrees BTDC base timing, which also ups the idle speed about 40rpm or so. Also make sure the vacuum advance unit still holds vacuum.

The OEM AFB is a relatively simple carburetor, but the aluminum can get corroded from moisture in the fuel. But soaking it as a part of a rebuild will probably not remove any related gunk in the passageways of the venture cluster.

But, new gas in the system, then some new spark plugs (OR pull the old ones out, dress the electrodes with an ignition point file, regap, a drop of motor oil on the threads, reinstall). Plus wires are not expensive, but there are various ones for 383 engines . . . year model specific, with different plug boots on them for how they were routed. I like the BWD Mag-core wires as they are magnetic suppression, rather than carbon core, but either one will work, with the correct plug boots.

Keep us posted on how it goes!

CBODY67

 

[jollyjoker]

Well, I found out what the problem was. Falls into the category of: "even a blind pig finds a acorn, once in a while"!

Seems that somebody, at some point, had rebuilt the AFB. Apparently they lost one of the brass (?) plugs under one of the idle mixture adjustment screws (on the front of the carb), and had replaced it w/ a little rubber plug. This had fallen out . . . found it laying on top of the manifold. Stick it back in, and instantly the rpm picks up maybe 200 or so, and it runs perfectly. Was sucking air through this opening, and leaning-out the mixture to the point where it darn near wouldn't run at all.

Many thanks to all who provided input. BTW . . . can anybody tell me what those little brass block-out plugs are for? I searched the FSM and a bunch of other AFB reference material, and I couldn't find any mention of them.

 

[CBODY67]

Well, I found out what the problem was. Falls into the category of: "even a blind pig finds a acorn, once in a while"!

Seems that somebody, at some point, had rebuilt the AFB. Apparently they lost one of the brass (?) plugs under one of the idle mixture adjustment screws (on the front of the carb), and had replaced it w/ a little rubber plug. This had fallen out . . . found it laying on top of the manifold. Stick it back in, and instantly the rpm picks up maybe 200 or so, and it runs perfectly. Was sucking air through this opening, and leaning-out the mixture to the point where it darn near wouldn't run at all.

Many thanks to all who provided input. BTW . . . can anybody tell me what those little brass block-out plugs are for? I searched the FSM and a bunch of other AFB reference material, and I couldn't find any mention of them.

That sort of thing is "non-user-serviceable", so it's not in any normal service literature.

In the S-A Designs book on Rochester carburetors, there's something similar to cover an "adjustable part throttle" "sealed adjustment" that affects part-throttle mixture strength. In the case of Rochesters, it offers a different fuel path, but when you removed those plugs and turn the hidden screw, part-throttle metering becomes more consistent and drivability improves.

Check with Jon at The Carburetor Shop in Eldon, Missouri. He has much knowledge on the orig AFBs and such.

It's somewhat common for soldered-in round plugs to become "moveable" as ethanol-blend fuels deteriorate the solder and the related plugs fall out. NO matter what brand of carb. On the Rochester 4GC 4bbls, the particular passageway leads to the bottom of the float bowl! When that plug falls out, the float bowl empties onto the intake manifold. These plugs are usually very visible, but little attention usually paid to them.

CBODY67

 

[Big_John]

can anybody tell me what those little brass block-out plugs are for? I searched the FSM and a bunch of other AFB reference material, and I couldn't find any mention of them.

If you mean these, they are to cover holes that were put in the side to facilitate machining of the carb. The passages are drilled/machined from the side and then the access hole is plugged. Usually they are just an aluminum expansion plug.

Some guys pull them out during rebuilds and sometimes they just fall out. As Cbody67 says, the ethanol gas might even bring it about.

I think these are the ones you want... You might even be able to find a similar generic expansion plug.

Aluminum Expansion Plug 5/16