Carb/Fuel Filter/Cleaning Tips

[So Cal Mark]

the only original filter in the back is a mesh screen on the pickup tube inside the tank. They do deteriorate over time. Fuel starvation problems always show up under load at higher rpms. If you have idle problems or low speed problems, rule this out except at the carburetor.
Whenever a problem seems difficult, go back and verify all of the basics; compression, cam timing then move on to ignition or fuel issues.
I haven't read this thread completely, so I'll go back and research what your issues are


You stated that you thoroughly cleaned the carb. Did you disassemble it or at least remove the top? Did you blow out the various circuits with compressed air? Have you verified that each circuit in the carb is working? Do the spark plugs show either a rich or lean condition?

[maytag]

MAGICWRENCH:
I laid in bed last night worrying about my post I sent ('cuz I should probably be on prozac ) and whether or not it would be taken in the wink-wink, nudge-nudge spirit it was intended. So I am breathing a little easier right now, seeing that you at least took no offense (or so it appears!), and I am glad for that, as none was intended.
After reading your last post, I think I understand a little better where you were coming from, and I can appreciate it, and the value you bring to these conversations in experience & troubleshooting.

Whenever a problem seems difficult, go back and verify all of the basics; compression, cam timing then move on to ignition or fuel issues.

I think this is excellent advice, and goes back to the methodical approach that Magicwrench suggested. Start eliminating the stuff that's easy to check, and that could cause the particular problem.

You stated that you thoroughly cleaned the carb. Did you disassemble it or at least remove the top? Did you blow out the various circuits with compressed air? Have you verified that each circuit in the carb is working?

Good catch, Mark. Oklandspider: I'm guessing that you haven't disassembled the carb, as I had assumed you had when you cleaned it, or you'd have seen the float bowl! this is reasonably easy to do, and can be educational, as long as you're careful!
Remove the fuel line from the carb (I'll usually stick a bolt in the end, to keep it from spilling, and cap the fumes abit.
There should be 6; button-head, flat-head screws that hold the carb top on. DON'T REMOVE THEM!!! just loosen them up 'til they are free from the threads in the carb body (you don't want to drop these into the carb, and risk bumping the throttle and losing a screw into the motor ).
At this point, you should be able to lift the carb-top off. Be careful with the paper gasket, and you'll need to hold the choke actuating arm (has an adjustment screw sticking out of it) out of the carb, as it'll hook. Once you've got it free, be particularly careful not to bend the float mechanism that'll be hanging from the bottom of the top that you've just removed.
From here, you can inspect and clean the float bowl.
I'd also recommend doing as Mark has said: blow the jets out with some compressed air, and / or some carb cleaner with a "straw" on the can. BE SURE YOU'RE WEARING SAFETY GLASSES!!!
If you decide to remove any of the jets to clean them (which I'd recommend) then stuff a rag down the throats of the carb, to avoid the risk of dropping something down in them.
Turn-over the carb top (Don't lose those screws!) and clean out the seat and 'plunger' that are under the float, to be sure you're getting good fuel supply through there.

Reassemble in reverse order!

Let us know what you found.

[kilrwail]

Peter – I have followed this thread with interest, but hesitate to jump back into it while you’re getting help from people who are more knowledgeable than I. However, I have a few questions and suggestions:

1. Have you checked the timing with a timing light?
2. Why would there be painted marks on the cam gears as well as stock timing marks? This is puzzling, but...if it idles well and the timing light shows a correct setting, why suspect a timing problem?
3. Since it idles smoothly but has no power at higher rpm’s, I wonder whether the distributor advance mechanism is working properly. The timing light will reveal this when you increase rpm’s.
4. What colour are your spark plugs? If they are black, this would indicate that the mixture is too rich (possibly due to a malfunctioning advance mechanism), which could be one reason for the backfiring you mentioned.
5. When you try to increase the rpm’s from idle (while parked), does the engine stumble or hesitate? If so, is this condition worse if you open the throttle quickly? Can you increase engine rpm’s from idle only if you gently open the throttle slowly? If the answer to all of these questions is “yes”, I would still suggest inspecting the accelerator valve diaphragm.
6. I am concerned about the suggestions that you disassemble the carburetor to clean it or change the timing belt in an effort to diagnose your problem. They’re not bad suggestions, but I know that you’re still learning your way around in there and these are not trivial operations.

Good luck and keep us posted.

[majicwrench]

Maytag,
Rest assured no offense taken, I can appreciate people that want to express their opinion, we've all got one, and that what this forum is all about.

Oakland Spider,
Hmmmm, had to think hard about posting again, but here goes....

If you are getting good fuel quantity at the carb, that pretty much means that all the filters, pumps from there back are probably OK, no need to look at the mesh screen on pick up, although it could well be failing, doesn't sound like it is creating a problem. Look elsewhere.
Still not convinced about the cam timing, if belt tight, not likely it jumped. Hard to tell from pics, but looks like it may be way off, in which case it would not run!! If car idles fine, like you say, cam timing probably OK. And again, how did you decide Top Dead Center??
Cleaning passages in carb is a good idea, that is what causes issues on my 72. Sounds like you have removed/ replaced carb in an earlier post, if so, I would REMOVE carb again before ttrying to disassemble, a clean bench is much easier to find those tiny parts that are going to get away from you, esp if you are blowing compressed air thru things.
Keep up the good work,
Keith

[OaklandSpider]

Wow-
thanks (again) for all the advice...
work is keeping me occupied M-F...but I'll report back (on as many issues as I can) this weekend.
Be on the lookout for a truck load of new questions/problems come Saturday.
Thanks fellas,
Peter

[OaklandSpider]

Hello again...
today, the carb was taken off, taken apart, and the float bowl was cleaned. It didn't look too bad actually...pics to come tomorrow. Blew out the jets as well...a good flow of air came through, without too much noctible debris. I was actually surprised how little of a mess was inside-no real gravel, jets seemed clean. I can't imagine the insides of this carb getting any cleaner...
LOTS of fuel in it when I took it off its mounts though...normal?
So- put the carb back on, and she started right back up. Idled fine, but still sputtered as I pressed on the gas (video to be posted soon-You Tube seems to take forever to upload...). Ran up to 3000 RPM pretty smoothly, then begins to sputter/cough/jump all over the place between 3000-4000.
Ran out of light before I got much else done. Didn't even get her out to see if she would perform under load....doubtful, though, considering it would not get passed 3000 RPM smoothly, standing still...
So...who's theory still stands?
More recommendations?
Perhaps the video will shed some more light on the subject (perhaps not)...I'll post it tomorrow.
Good weekend to all...
Peter

[maytag]

Peter:
yes, the carb's float bowl should be full of fuel when you take it off. this is normal.

So we've determined so far that the carb is clean, including the jets, and that you are getting plenty of fuel.

Continuing with Majic's suggestion of the methodical approach, there are only two other directions to go: Ignition being first.
Once you've determined there is fuel and spark, then the only thing left is the timing of the events.

So let's look into your ignition. Have you checked all 4 plugs? Here's what I'd suggest, for starters: fire it up, let it idle a minute or two, and then rev it up. When it gets to where it begins to stumble, let it for a couple of seconds, and then shut the ignition off immediately (while the stumbling persists).
Then go pull each spark plug and examine them. See if they're uniform in color. If any appear to be wet,or different from the others, then we have something to chase. let us know what you find.

[kilrwail]

Peter - While you had the carb apart, did you inspect the accelerator valve diaphragm? Even if the float is full, the carb needs a little shot to begin revving higher - hence the acc valve. I know I'm sounding like a broken record (remember those), but I am curious.

[maytag]

this doesn't sound like an accelerator pump problem. IF you have NO accelerator pump, zero, and you try to rev the motor, you'll go to a lean condition and either the motor will die, or it will draw enough air to get the venturis working properly, and then rev up (a matter of seconds). But here, Peter's motor stumbles around at mid-range and will not rev further.

Not to say that we shouldn't check the diaphragm when we're into the carb, but the symptoms don't fit this conclusion.

[majicwrench]

Did we decide cam timing OK??????
Looking forward to the video.
If engine actually runs bad in shop, hood open when you rev it, this is good. Get your safety glasses on, get it to the spot that it starts crapping, hold it there, and SLOWLY cup your hand over the carb to see if it improves, or degrades further. Restricting the air flow will richen the mixture. If engine is running too lean, as your hand starts over the venturis, engine should smooth out and pick up RPM. Try it, let us know.
Not sure about the plug inspection that Maytag mentions, methinks results are going to be way too vague.
Again, what about the cam timing?? Was that just ghost chasing??
Again, looking forward to video.
Keith

[So Cal Mark]

I'd sure like to see a scope pattern when it starts breaking up. Do you have a timing light? If so, watch the timing mark when you accelerate it and see what happens when it breaks up

[OaklandSpider]

Fellas-
Not going to have much time to put into it today....but here are some videos I took yesterday-
http://www.youtube.com/watch?v=uDvP0iAhcJc
and
http://www.youtube.com/watch?v=ar4juU4ZG2U
Wrench-does run a bit better when hand is over the carb. I posted that in an earlier post, as per your suggestion.
So Cal- No timing light...
I'll check in later if I've got time...
Peter

[maytag]

Just to clarify:
as far as I know, we have determined from the timing marks that the cam timing IS WRONG.

BUT: deferring to those who have dismissed that as a possibility, I am trying to be helpful by backing-up in the methodology, and eliminating EVERYTHING ELSE first.

But as far as I know: Peter was never able to get the timing marks to align, and this still fits the symptoms (as described) better than anything else I've heard suggested.

[maytag]

Hey peter:
The videos make me less convinced it's cam timing... but I still don't know what else would cause this. Let's rule-out fuel issues altogether: do us all a favor? Go to the parts store and pickup a $5 clear in-line fuel filter and put it right there at the carb. When it starts buckin' around, see if it's still full of fuel.

If this is carburetion, then it's clearly related to the high-speed circuit. You blew air through the jets, and it was clean. It's not a jetting issue, as it wasn't doing this before, and you haven't changed the jets.

So tell us about your ignition:
Do you have a vacuum advance distributor? Or is is mechanical? Have you had it open to check that nothing has moved? Checked the gap / dwell on the points? Have you put a timing-light on it, as Mark suggested? How much total advance are you getting? (It should be all in by 3k with most curves, I would think)

[So Cal Mark]

trying to diagnose a problem without any tools i.e. timing light, multimeter etc is a crapshoot. Really fellas, if you want to fix cars you need some basic tools otherwise you're just working on them hoping to get lucky (sort of like trying to pick up ladies without showering first)