Seff

Evenin'.
I'm stumped as to the problem with my '72 350 Supreme. It has run well in the past, up until four months ago, when it suddenly wouldn't start, but would crank. I took apart and cleaned the Q-jet at this point.

After four months of sitting, it wouldn't crank, and managed to get the starter stuck. A new battery and a hammer solved that problem.

This afternoon I got it going again, but I only ran it for half a minute, since I could hear that my headers weren't properly attached. When I came back this evening and got my headers tightened, it wouldn't start, apart from a few coughs.

I have two jets of spray when I yank the accel. cable, so fuel is flowing.

Is it possible that the distributor has a loose connection of some kind, meaning that the engine will crank but I won't have any spark?



This is what my carb looks like:

881HO.jpg



When holding the accel. as far back (towards firewall) as possible, this is how far the main port opens:

wJAuh.jpg



This is what I'd expect from full throttle:

gocA5.jpg



This thing gets hot quickly when I crank the engine - is it supposed to do that?
EWTTH.jpg

MDchanic

Your choke is staying closed, but that's because the engine is cold and it's not running, so there's no vacuum for the pull-off.

No, your coil is not supposed to get hot.

Have you checked for spark?
If you have no spark or a bad spark, you should check your points - they may have closed up due to rubbing block wear. They may also have corroded.

Readjust your points, and pull a rag soaked with thinner through them a few times, then try again.

Seff

If my coil isn't supposed to get hot, then I've found a problem. Will look at my distributor first thing in the morning.

How do I determine if I have "rubbing block wear"?

Why thinner?

MDchanic

Your coil is not supposed to get hot, but it will if the points aren't opening, and it's got no time to cool down between pulses.

The rubbing block is a little bit of plastic on the points that rides on the distributor cam.
Since it's plastic, and the cam turns at hundreds or thousands of RPMs, over time it wears (much faster if it's not properly lubricated).
As the rubbing block wears, the points get closer together, and the timing becomes more and more retarded, to the point, finally, where the engine won't run.

This is why you are supposed to check and readjust your dwell angle every so-many miles (I don't remember the interval).

Newer, cheaper points have smaller rubbing blocks that wear faster than the older, better ones, so they have to be checked more often.

I'd use some thinner in case the points have become contaminated with oil.
It won't hurt, and it might help.

- Eric

Tony72Cutlass'S'

I had the same symptoms the other week, my timing chain had skipped a tooth.

I had blue spark,

Had good fuel flow,

timing was adjusted the week before,

Low and behold, chain had skipped.

Tony72Cutlass'S'

Come to think of it.

Check your compression if you have a tester, all cylinders should be "around" the same value. Within 5% or something.

Seff

MD: Gotcha. I'll look at points.

Tony: If I have good spark and the points and dist. look good, I'll start looking at the timing chain.

Appreciate the advice, guys. I need this car to run. :P

MDchanic

Seff, your command of vernacular English is just scary .

- Eric

Seff

Mom's a native New Mexican, so I speak the language pretty fluently.

Seff

Alright, I cleaned up my distributor, which made the coil not heat up, as well as awarding me a few coughs. I then grounded #1 spark plug and laid it so I could see it through the window - yellow spark. The business end of the plug was sooty, which I google'd and got this:

Of those symptoms, it could really be most of them. I'll go see if I have another coil from the '72 car, as well as checking the rest of the plugs. Running rich sounds about right, given how much fuel I've been pushing through it with all the carb mischief.

I don't have a compression tester, so I'll blindly assume that it's okay until I've tried to fix everything else


But, I have yellow instead of blue spark, the coil has/does get hot, and my points WERE white with dry gunk buildup, now cleaned. Doesn't sound like bad compression to me.

MDchanic

You've got an ignition problem. The spark should definitely not be yellow.
Sooty plugs would be normal for a car that won't quite start, for nearly any reason.

What exactly did you do to clean the points? Modern points have a thin plating that can be removed by excessive abrasion, such as by filing, which will lead to rapid wear, and points always have to be cleaned very squarely, to maintain their relationship.

Based on what you've said, I would try a different coil, then replace the points as soon as you can, and see whether a different condenser helps. Wires are another consideration - if they're old, they could be leaking badly and contributing to your problem. They often do this without any obvious problems at idle, causing problems only under load, so keep this in mind if you get it going, but it just doesn't run right.

New Mexico, eh? Having both EU and US documents must be nice .

- Eric

Seff

I polished them with steel wool. How to clean very squarely eludes me, though, I must admit. :P

Getting a new coil is a big 'if' over here, but I'll see if I can work something out.

Wires look healthy, plugs at the distributor being very fresh. One of the times I got it to run, it ran long enough to let me put it in reverse and drive about five feet, before dying, so I'd call that a form of 'under load.'

Before I focus on one problem: There are three screws on the carb I'm not sure how to adjust - the one on the driver's side, affecting some part of the throttle arm, and the two at the very bottom of the carb, on either side. Would improper adjustment of any of these cause or compound the problem?


Complete dual citizenship, yes - I get ahead in the immigrations line both in the US and here. Perks perks perks. :P

MDchanic

With a points file .





You can temporarily use a coil from another kind of car, as long as it's got a comparable number of firing cycles per minute (like a BMW straight six that revs to 6,500 RPM).
You can also "borrow" a condenser from a different car.

Doesn't count. A classic sign of bad wires is a car that starts, runs, and idles fine, but "flattens out" or "breaks up" whenever you floor it.

That's a whole other question, and one I can't address now.
They have to be adjusted correctly.
The two at the bottom are the idle mixture screws, and should start somewhere around 2½ turns from the bottom before you fine tune them.
The one on the side is the idle speed screw, which adjusts the idle speed.
There should be one on the other side for adjusting the fast idle speed as well.
Instructions for adjusting all of these are in your Chassis Service Manual.

Good luck!

- Eric

Seff

Ah, gotcha on the file. I'll see what I can do.

Finding a similar coil should be doable. I'll start by measuring the resistance in the one I have - the values should be in the chassis manual, yes?

The carb problem sounds like it wouldn't keep me from starting the engine, however roughly it would run before being tuned correctly.

Seff

A'iight, here's the rundown.

I got a new coil, some godawful contraption from an Alfa Romeo... that actually works. Blue spark! After working and working and swearing, setting the choke coil spring for the fourteenth time, and finally pouring a bit of gas down the carb, I got the damned thing running and idling, roughly.

Depressing the throttle completely doesn't open the primary venturi (or whatever it's called) very much, and I can't get the secondaries to open at all, unless I manually lift the damned things, at which point the RPMs slowly pick up. Something's wrong with my carb. The glass fuel filter is completely full of fuel, and yanking the throttle cable still nets me two sprays of fuel in the primary, so I'm stumped.

Putting it into reverse got me another two feet before it died. Gonna take a while to go a mile to the inspector at this rate. :P

Tony72Cutlass'S'

Until the car is fully warmed up, your top choke plates will not open much more than 1/4'' (Unless you slam the gas to WOT).

Looks like we need to perform some basic tune up on your Quadrajet. If you look on the driver's side of the carb, take note of the number stamped in the aluminum. Let us know and we can probably let you know what series of Q-Jet you have. It'll be much easier at that point to do a tune-up.

Tony72Cutlass'S'

Although come to think of it. Your car doesn't look like it has a choke pull off (it's the little vaccum pod on the rear-passenger side that keeps the choke cracked open when your car is in the initial warm up stage.) This could be why the car seems like it wants to die.

Seff

This carb does indeed not have such a thing, but I've had the car running with this carb before, so something else is different as well. One of my spare Q-jets has a vacuum pod where you describe that the choke pull off should be, so I might be able to scrounge one up? Dunno if that'd help or not.

I'm not getting 1/4" (6mm), more like 0.040-0.080" (1mm), no matter how hard I stomp the gas. So yeah, SOMETHING's definitely wrong. :P

I'll look for a stamped number after dinner.

Seff

Stamping on the carb on the car: (1) 7041250 NC 0291

Spare carbs:
17057253 APW 0277
17057253 APW 3446

Carter carb: O - 1609 3904S AD5

Oldsmaniac

You can see he does have a choke pulloff in one of the carb pictures. In the video it seems the carb is running low on fuel. Too low a float level is not good either. Maybe try to fill the carb with a squirt bottle thru the top vent to be sure there is enough fuel in the carb now...

Seff

Which video are you referring to?

Last time I got it running was indeed by virtue of some fuel poured into the carb.


ID'd them myself:
Car carb is made on the 29th of January 1971, and it's a Federal Standards 4bbl Quadrajet. Olds division, auto trans. Seems spot-on for an engine out of a '71.

The two others are 1976 and 1977, Fed standard, manual transmission, Olds div. Would also work, I guess. Would these have more emissions(smog?) stuff than the '71 one?

Oldsmaniac

OOPs I watched the guy with the Toronado video with a similar problem here...got it mixed up with your thread.

Seff

Fair - I read his thread as well. If you want and/or think it could help, I'll make a video for you guys.

Oldsmaniac

In one of the pictures the coil is circled. I see a pink wire that looks partially chewed thru and a black square pack along side the coil.... I do not know what that is or how bad that wire is.

Seff

The wire-part of the wire is intact, and the little black box is a resistance of some kind, if I recall correctly. That, or a fuse. Hard to tell, it doesn't have very much text on it. There are more of them scattered around the engine compartment.

Octania

According to your 1st photos you do have a choke pulloff- that vacuum canister at the carb's right front. It's even hooked to the secondary air valve, and appears that it might unload the choke properly.

If you are opening the throttle all the way, and the CHOKE PLATE - that plate at the top of the front half- is not getting cracked open a little- say 7mm or so- the manual and rebuild kit have the exact spec, then your unloader is not adjusted correctly, and thus probably a LOT of adjustments are out of whack...

You need "QJets 101"... try a few youtube QJet videos, and a google search for rebuild articles. Get a kit for a 7041250 carb [epay perhaps], and a Chassis Service Manual [free at WildAboutCars.com]. While the carb kit is on the way, read over all the carb info. It seems scary and intimidating, but really there are a finite number of mechanisms and systems, and folks dumber than you rebuild carbs every day. The unloader is a very simple tang bend adjustment. You have to start with the basics- are the throttle blades opening all the way, to exactly 90 degrees, and stopping there. I am in he midst of a rebuild and modification of a 1977 Toronado carb for my hot cammed 403 fresh motor. Becoming quite the carb expert. Ruggles' book is a wealth of info, and lots of info can be had on the interweb, don't ya know... some of it is even good info.

PS I can get a nice rebuilt carb, probably the same number even. They are $300 delivered in the USA- Europe will be somewhat higher shipping.

MDchanic

I'm back. Work, you know...

Just a quick note of agreement that you DO have a choke pull-off diaphragm, and your carb looks correct from the outside.

The black box on the coil appears to be a replacement radio suppression condenser.
They normally don't go bad, but you could try disconnecting it to see if the car runs better without it.


From the above, I'm assuming that you are looking in the right places, at the right things, but I am not completely certain.

From the top of the carburetor, you cannot see the primary or the secondary butterflies.
What you CAN see is the choke butterfly (above the primary venturis, in front) and the secondary air valves (above the secondary venturis, in back).
When the throttle is floored with the engine cold, the choke butterfly, as Octania points out, should open ¼" or less, depending on the exact setup required for that carb and car.

The secondary air valves should never open while you are looking at them, unless you are driving with no hood or air cleaner. They are pulled open by the vacuum of the engine when the secondary throttle butterflies are open and the engine is sucking in large amounts of air, and lift the secondary metering rods to adjust the mixture for the amount of air needed.

When the choke is off, the choke butterfly should be completely open, and you should be able to see the primary air valves open as you pull the throttle cable, then, by pushing the secondary air valves held open, you should be able to see the secondary throttle valves open as you continue to pull the cable (all this with the engine off, of course).

I suppose if you've got a good spark now, I would confirm timing is about right, then try starting the car and holding the choke open, and see whether it runs better that way.
Your symptoms could reflect too much choke, too.

- Eric

Seff

I have blue spark now. My timing isn't totally off, judging by rotor position during TDC. I don't see a screw or device for adjusting dwell, so I haven't worked on that.

We had the car running, it sounded almost normal and idled roughly when we manually opened the choke valve a bit. Stomping the gas only opens it about 0.04", and I'm gonna go see if it opens the primary throttles valves as well - I assume full throttle should set have these standing clearly vertical, yes? Or is that vacuum controlled as well?

As for the vacuum canister at the front of the carb, I'll have to check whether or not it can affect the choke as it should. If I forgot some oddball little part during assembly, then that'd explain some things, at least.



So, I'm taking off the carb again and running it through a few tests and adjustments.

MDchanic

Not a bad idea to (carefully, slowly) go through the carb again, with the manual open, so as to be sure you've got it right, especially since it's the thing you've had apart between when the engine ran and when it didn't.

I think this has come up before, but you may drive yourself nuts until you get a dwell meter and timing light to completely nail down your timing. I am certain that someone you know must have them for you to borrow - everyone's got one hiding in a toolbox somewhere. You can use the "Duty Cycle" range of a modern muti-meter to check dwell - should read 66.6% if my calculation is correct.

- Eric

Seff

I'll ask around for a timing light and dwell meter. My distributor doesn't have a breaker like the one in the chassis manual, though, so I'll have to figure out how it works.

As for the carb, I'm working on it now. So far, I've noticed that the rod between the vacuum actuator and the secondary venturies was on back to front, meaning that it didn't touch the fast idle cam at any point. I fixed that, of course, but it still didn't run, so I went ahead and start on the overhaul adjustments as per the Chassis Manual.

At this point I'm glad that I identified a problem, because that decreases the chances of more serious problems. :P

MDchanic

If you get the right points, they will be a hundred times easier to adjust.

The same points were used for all GM V8s from about 1959 to 1974, so you should even be able to find a set "over there."

- Eric

Seff

It's easier to find HEI for cars of this type than good ol' points. 99% of what we get is aftermarket.

Octania

"My distributor doesn't have a breaker like the one in the chassis manual, though, so I'll have to figure out how it works." - Clarify? The photo shows what appears to be a standard issue points distributor. There is a little metal window in the side of the cap- under that window is a 1/8 hex bit adjustment for the points. Dwell should be at 30 degrees. Another way to set dwell is to turn clockwise until engine stumbles, then back CCW exactly 1/2 turn. Every time I have ever done this and then checked with a dwell meter, it results in a dwell of 29-31 degrees- perfect. Easy.

Flexible shaft hex tool makes pts adjustment easier.

http://www.ebay.com/itm/CTA-DISTRIBU...item2ebac39e07

Seff

I don't have my firewire for the camera at the workshop with me, of course, but I can easily take a picture of it. Perhaps I'll go home for lunch and do it immediately.

Tony72Cutlass'S'

Doesnt rockauto ship worldwide? They've got really decent prices.

Tony72Cutlass'S'

Nevermind, i digress.

Seff

This is a nice place to live, most of the time. This isn't one of them. :P

Anyway, carb is now overhauled per the chassis manual. Found something like four errors on it, so we'll see if this makes a difference.

Seff

Ladies and gentlemen, we have a a working car.

Tony72Cutlass'S'

Congrats,

Let her warm up a bit, and make sure the choke operates correctly before you hit the highway and bury the gas pedal.

MDchanic

Fantastic!

Congratulations!