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PHL_buggy
Samba Member
Joined: March 20, 2024
Posts: 2
Location: SE Asia
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 Posted: Wed Mar 20, 2024 2:26 am Post subject: weird carburetor problem - 30 pict |
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hello all
I'm posting here because I really need some help/insight with the issue I'm having with my 1973 1300cc beetle, hopefully someone can give any ideas as to what's happening... I've been trying to get the 30pict carb's air/fuel mixture correct so it will run smoothly, but I'm having the following problem:
1. I set the carb's volume control and idle speed according to the rob and dave manual, and the car idles just fine
2. I take the car out for a drive, and after about 5 minutes of uneventful driving (no high-revving whatsoever, keeping it around the 2k rpm range), I let off the gas and pull over to see how the car idles, and the engine can barely idle, it seems like it wants to stall. So I turn the volume control screw out some more (increase fuel) and the idle becomes smooth again.
3. If I decide to go to a mall or something and leave the car alone for a while, let's say for about one or two hours, and I come back and try to start the car, it will start, but now I have to turn the volume control back IN (decrease fuel) because otherwise it will just shut off from too much fuel. I turn the volume control screw back in, and it's fine again, until I do some more driving and have to turn up the fuel volume again (point 2 above).
Can anybody explain what's happening? Does this sound like a jetting issue? To summarize, it just seems like when there is the appropriate amount of fuel to idle, there isn't enough when doing actual driving so I have to increase the fuel volume to avoid stalling out on the road, but then when I do a cold start after leaving the car off for a while, I have to turn the fuel volume back down again. It's just perplexing and I don't really know how to go about this.
Any tips or advice would be greatly appreciated! |
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Dougy Dee
Samba Member
Joined: August 21, 2004
Posts: 1669
Location: Niagara Region, CANADA
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| Posted: Wed Mar 20, 2024 5:00 am Post subject: Re: weird carburetor problem - 30 pict |
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Not your carb.
Your manifold is icing up.
Heat risers must be hooked up and working. |
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baldessariclan
Samba Member
Joined: October 14, 2016
Posts: 1385
Location: Wichita, KS
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| Posted: Wed Mar 20, 2024 7:24 am Post subject: Re: weird carburetor problem - 30 pict |
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| PHL_buggy wrote: |
Can anybody explain what's happening? Does this sound like a jetting issue? To summarize, it just seems like when there is the appropriate amount of fuel to idle, there isn't enough when doing actual driving so I have to increase the fuel volume to avoid stalling out on the road, but then when I do a cold start after leaving the car off for a while, I have to turn the fuel volume back down again. It's just perplexing and I don't really know how to go about this.
Any tips or advice would be greatly appreciated! |
Is your choke working and adjusted correctly? The carburetor's idle settings should normally be made only when the engine is completely warmed up and at full operating temperature. But if the car hasn't been running for a couple hours (or longer/overnight), it's probably not going to be able to idle when first started up, w/out some assistance from the choke.
_________________
1971 Standard Beetle — fairly stock / driver
baldessariclan -- often in error, never in doubt... |
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bsairhead
Samba Member
Joined: October 08, 2008
Posts: 3592
Location: viroqua wi.
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| Posted: Wed Mar 20, 2024 8:43 am Post subject: Re: weird carburetor problem - 30 pict |
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| My guess is float height. |
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PHL_buggy
Samba Member
Joined: March 20, 2024
Posts: 2
Location: SE Asia
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| Posted: Mon Mar 25, 2024 5:56 am Post subject: Re: weird carburetor problem - 30 pict |
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hello all, thanks for your replies
so after some more troubleshooting, I finally found what the problem was so I'll post it here in case anyone else finds themselves having the same issue.
after rechecking the timing and messing with the carb air/fuel mixture to no avail, I did some more reading and came across rob and dave's commentary regarding the carburetor's idle cut-off valve.
| Quote: |
| It provides fuel at low medium revs too, so if it's not working you'll get a rough idle and lean mix at lower revs. |
I hadn't checked whether it was working, so I followed their instructions on how to check it, and I discovered.... it was indeed working, so that wasn't the problem.
as a last resort, I unscrewed the whole idle cut-off valve from the carb and inspected it. It showed no signs of being clogged, but nevertheless I decided to spray it with some carb cleaner. I aimed the red straw at one of the tiny holes, and after a few short blasts from the can of carb cleaner, a sizeable piece of debris flew out of the jet, which I suspect was a miniscule piece of rubber from the fuel hose between the carb and the fuel pump.
After discovering this, I opened up the carb and removed and cleaned the other jets for good measure. There was no other debris in the other jets but there was some very very fine debris sitting on the bottom of the float bowl, which I also removed. Carb was put back together and the car is now idling as it should!
TL,DR: Engine would initally run fine on cold start, but after a few minutes of driving, would idle too slowly and die even after checking timing and setting carb air/fuel mixture. Discovered a tiny piece of debris (presumably from fuel hose) had entered the carb and lodged itself inside the idle cut-off valve, causing the lean idle issue. Used carb cleaner to blast it out. |
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KTPhil 
Samba Member
Joined: April 06, 2006
Posts: 34023
Location: Conejo Valley, CA
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| Posted: Mon Mar 25, 2024 8:44 am Post subject: Re: weird carburetor problem - 30 pict |
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Good troubleshooting.
And thanks for posting the follow-up for others!
_________________
Current Fleet:
'71 Fastback
'69 Westfalia
Retired:
'67 Beetle
'65 Beetle (x2)
'65 Bus
'71 Squareback |
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