Rough idle, can't find vacuum leak?

[ray_]

That carb rebuild page sez you can smack the venturi for a snugger fit.

 

Cheers,

[flagoworld]

1 hour ago, John76 said:

Take the air cleaner off the carb and look down the primary when the engine is idling.

If you see an occasional drop of fuel, and then milliseconds later a stumble in the idle, it could be a "heavy" plastic float.

My theory is the Ethanol added to our fuel degrades the plastic float gradually, causing it to become heavy, and therefore over-flowing the float bowl.

This only shows up noticeably at idle....as a "skip".

I solved this problem by changing the float from plastic to brass.  Result: No more random fuel "drips" and a smoother idle!

 

PS: I tried to measure the weight of the plastic float with a digital letter scale....didn't work. I've heard there is a weight spec for the Weber float, but I haven't  found it.

 

 

Good. Call. I compensated for its heaviness by increasing the float level (mm) by 2. It now runs MUCH MUCH better. Awesome! I'll replace that thing at some point soon.

 

[flagoworld]

I replaced my float with a brass one, which definitely helped a little bit.

 

Then I found the *real* problem... As I ran the car longer, it got worse and worse. So I checked the voltage at the battery while running and noted 12.3 volts, 12.8 while off. Whoa! No charge!

 

Did the bypass test on the regulator and the battery read 18v and no more misfire!! Well there's yer prablem.

 

Note to self: Next time to spend the 5 minutes to rule out the easy-to-diagnose systems before going off on obscure tangents.

 

Edited February 3, 2018 by flagoworld

[flagoworld]

OK, I picked up a new voltage regulator. It's keeping the voltage at about 13.1v. That should be sufficient. The idle is improved further, but not as good as it was when the regulator was removed and it was pushing 18v... Hmm, this is becoming a head scratcher.

 

I checked the resistances of the coil... it's a black/orange coil (OEM KW black) with the resistor wire. The resistance across the low voltage winding is 2.3ohms, and between low and high is 13.3kohms. Which I think is OK.

 

I checked the voltage between the poles of the coil. While running it's 5.01v, when the ignition is on but motor is off it's 7.6v. That seems rather low to me...

 

I checked the voltage before the resistor wire and it's 11.7v with the car off and the battery at 12.6v. There's something else causing some resistance there, but I'm, not sure how relevant that is.

 

The resistor wire measures in at 3.3ohms. According to below post, it should be 0.6-1.0ohms. Also, see the attached image I found online... the sticker (no-longer on mine) says 0.9omhs.

 

With the ignition on and the car off, the resistor wire gets quite warm. That concerns me a bit as I would not expect a properly rated resistor to get too warm...

 

So, I'm running the KW Black coil. At this point I believe my resistor wire to be incorrect and causing the voltage to drop far too much. This is in line with the 18v running better than 13v I think.

 

What say ye?

Edited February 4, 2018 by flagoworld

[ray_]

Yeah.

[jimk]

2 hours ago, flagoworld said:

With the ignition on and the car off, the resistor wire gets quite warm

When the car is running current flows only when the coil is fluxing (charging in street talk), i.e. when the points are closed.  When the engine is not running, and points are closed there is constant current in the line.  Go figure.

Edited February 4, 2018 by jimk

[flagoworld]

So... this morning I started it up and it was running on 2 cylinders(sounded like). Hot rod lope! I eased off the choke a little bit and it idled low but wasn't missing as much. When accelerating it would miss and buck. So I just unchoked completely and it returned to normal power/running conditions, except for nearly stalling at idle because it was still cold.

 

To me this sounds like it's running much too rich while choked and drowning out the cyls. Plenty of gas smell. I am not sure what changed... nothing since the last choked start that was perfect. The only adjustment I see for the manual choke is the fast idle bar.

 

One thing to note is that it also started at much lower rpms while choked than it has in the past.

 

Any ideas what could be causing this all the sudden? Not sure where to look here, as I haven't experienced this before.

Edited February 11, 2018 by flagoworld

[Simeon]

When you rev the engine with the choke applied are the choke flaps opening up?

 

The choke has a pull off diaphragm that starts with the choke fully closed while cranking but then opens the flaps slightly when the engine fires. The flaps should swing open when the engine speed rises as well. This stops the engine from fighting the choke. 

[flagoworld]

Its all actuated by springs and a cam last I checked. But the issue is there even at idle... I dont rememeber those springs ever giving when not under load. They are pretty stiff...

 

I will be able to check more spcifically later though.

[flagoworld]

Ok, checked a couple things...

 

When fully choked and the fast idle cam is engaged, it fully compresses the choke spring and prevents it from opening any extra with vacuum. When the fast idle cam is disengaged(half choke) it allows the spring to flex and let in more air under load.

 

This has always been like this as far as I know on this carb, and at cold idle it's always run "properly" while fully choked.

[flagoworld]

Well.. Pretty much Ray called it in the chat. My carb was flooded because I had no pressure regulator on it. There was a nice pool of gas down in the intake manifold.

 

Installed a jeep regulator and all seems well again.

[ray_]

11 minutes ago, flagoworld said:

Well.. Pretty much Ray called it in the chat. My carb was flooded because I had no pressure regulator on it. There was a nice pool of gas down in the intake manifold.

 

Installed a jeep regulator and all seems well again.

 

It's Tom's fault

[flagoworld]

I would like to resurrect this because I am not happy with my idle. It just doesn't seem right compared to what I am seeing with other people.

 

• Spark seems great: I can even disconnect a spark plug and hear it jumping the gap to the spark plug. From half an inch away from the plug it still ignites and makes no difference to how the engine feels. Of course, I pull it any farther and it clearly stops running on that cylinder.

• I've done timing a million times

• I have played a lot with the float level at spec and with some adjustments up and down

• Idle and mixture screw are nearly right where the book says they should be as far as number of turns, not that that means a lot

• I have pertronix and an electric pump and it is running better than it ever has, but still not what I would like to see

• See attached photo of plugs. I'm guessing they are a little wet mainly because I only started and ran it for a few minutes this morning so it was running rich while choked... The ceramic is still pretty white, but the rest is pretty black. That means I'm rich, right? (These plugs have very few miles on them)

• See video of idle

• Edit: Added color adjusted photo of plugs because original was too dark

 

 

 

Edited March 25, 2019 by flagoworld

[ray_]

What's your Idle AFR? And plug gap?

[flagoworld]

AFR is in the works. Plug gap is uh... "factory spec". And I've seen the conversation that factory spec isn't best these days. I can definitely give a different gap a try.

 

I do kind of suspect this is rich related. I need to try some other jets, probably. Currently it's CD prescription which has been mentioned runs a bit rich.