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Orsocron
Samba Member
Joined: August 29, 2003
Posts: 307
Location: Huntsville, AL
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 Posted: Tue Sep 18, 2012 5:48 am Post subject: Finding a vacuum leak |
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I am at a total loss as to why my car only idles when I have the carburetor at 30 degrees BTDC. It's a stock 1600 DP, with a 34 PICT 3 Bocar carb, and the stock DVDA distributor (with the retard plugged).
The only thing I can think of is it's got a vacuum leak, but I can't find it. I was spraying starting fluid on all parts of the carb, intake boots, and the areas where the castings meet the cylinder heads...nothing changed with the idle speed. The only time I could get any response was when I sprayed a shot into the air cleaner....at that point, the engine tried to die, not pick up speed.
I can hear a faint hissing when it's at idle, but can't find the leak.
I appreciate any help!
Joe
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1964 1500s Notchback
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Busdriver79
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Joined: July 22, 2011
Posts: 1655
Location: The Peoples' Republic of "No" Jersey
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| Posted: Tue Sep 18, 2012 6:12 am Post subject: |
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| you might try using a propane torch fitted with a piece of 1/4" hose on the end about 18"long.....use the propane to find vacuum leaks instead of spraying that messy stuff onto your engine....when the propane finds the vacuum leak the engine rpms will rise and it will smooth out...but use the propane sparingly and be careful....shut it off when you are done....if those various spray products ignite, they will burn until every drop is consumed by fire...not good...if the propane does flash, it will only burn for a second then go out....this propane is the safest way to locate vacuum leaks....BTW, I had a major vacuum leak on one of my manifold boots under the clamp...It would only leak when the engine warmed up fully...there was a split under one clamp...loosen the clamps and check there...best of luck finding the problem. |
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Cadaver
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Joined: April 24, 2012
Posts: 2338
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| Posted: Tue Sep 18, 2012 6:57 am Post subject: Re: Finding a vacuum leak |
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| Orsocron wrote: |
I am at a total loss as to why my car only idles when I have the carburetor at 30 degrees BTDC. It's a stock 1600 DP, with a 34 PICT 3 Bocar carb, and the stock DVDA distributor (with the retard plugged).
The only thing I can think of is it's got a vacuum leak, but I can't find it. I was spraying starting fluid on all parts of the carb, intake boots, and the areas where the castings meet the cylinder heads...nothing changed with the idle speed. The only time I could get any response was when I sprayed a shot into the air cleaner....at that point, the engine tried to die, not pick up speed.
well its not leaking..... new boots and gaskets solve this better
but a smoke machine will too.) (all DIY checks are weak. so....)
I can hear a faint hissing when it's at idle, but can't find the leak.
use a rubber hose to your ear and hear any leak.....
this is 100% effective too. hisssssssss
I appreciate any help!
Joe |
what pulley are you using to claim 30 (stock or not stock)
is the engine hot or cold
is the strobe on #1 wire.
is it a dumb timing light or dial back, hmmmmmm
is the vacuum hoses pulled and plugged at 30?
is the mech advance free, the weights and springs all free?)
service the dizzy first. clean it and lube it, so it has a fighting chance.
if really at 30, vacuum off/ truely
then the carb is bad or vacuum leaks,
vacuum leaks make the carb useless at idle. so...........
that carb has complex idle circuit.
clean and kit the carb. then wonder why the carb dont work right.
the 3 top fails are.
1: fuel cut soleniod sticking closed
2: PILIOT jet clogged. (G55 , 0.55mm orifice is .021") tiny (inside tip)
3: main idle nozzle (looks like tiny hole) is clogged below throttle butterfly plate.
x2 PROPANE, i use it all time time for leaks and for testing EFI.(rich forcing tests)
it is vastly safer....than any liquid fuel... no fooling.
but as you now that is a tool and many here ,just hate tools.
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Orsocron
Samba Member
Joined: August 29, 2003
Posts: 307
Location: Huntsville, AL
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| Posted: Tue Sep 18, 2012 7:06 am Post subject: |
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It's the stock pulley for a 1972 Bug. It has the one dent for TDC, and the little divot behind for 5 degrees ATDC. I made my own mark for 7.5 BTDC, and 30 BTDC using the template you can find on this site.
I know the distributor isn't the best, but the mechanical advance does work, as I can watch it advance when I get to around 3000 RPMS. It even does a small jump from idle which would be the vacuum advance. It's not the smoothest, or most uniform advance, but it does work.
At this point, I have to think it's a major Vacuum leak, or the carb is just bad (which is distinctly possible). I had the distributor out yesterday, and it doesn't look like the gears on the distributor drive are misaligned. It points to cylinder 1's line on the distributor body when it's at TDC.
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Cadaver
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Joined: April 24, 2012
Posts: 2338
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| Posted: Tue Sep 18, 2012 8:24 am Post subject: |
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| Orsocron wrote: |
It's the stock pulley for a 1972 Bug. It has the one dent for TDC, and the little divot behind for 5 degrees ATDC. I made my own mark for 7.5 BTDC, and 30 BTDC using the template you can find on this site.
lots of templates, some good some wrong.
how many inches is your 30 mark from 0 and what diameter pulley
most pulleys are .06" per degree. so .06" times 30 is ... 1.8 inches.
my page shows this...
http://ac-vw-remove.com/At_Wits_End/timing-all/pulley-madness/html/image_1.html
im sorry if this seems dumb but i cant see the car, touch it or measure that pulley diameter..... Im a 100% suspicious tech, (40yo cars suck for valid parts... etc...)
I know the distributor isn't the best, but the mechanical advance does work, as I can watch it advance when I get to around 3000 RPMS. It even does a small jump from idle which would be the vacuum advance. It's not the smoothest, or most uniform advance, but it does work.
GOOD ! Very good, perfect input !
At this point, I have to think it's a major Vacuum leak, or the carb is just bad (which is distinctly possible). I had the distributor out yesterday, and it doesn't look like the gears on the distributor drive are misaligned. It points to cylinder 1's line on the distributor body when it's at TDC. |
as you know a rich carb will like late timing. (the reason 009 owners ,use this to hide the bad 009 actions)
a lean carb will hate late timing.
so its not timing....
what you failed to do is trust the engine.
set the timing right and you will discover the carb is way lean, , and stalls.
this is the true , problem and not ever the DIZZY (works perfect dizzy like yours)
there are only x numbers of ways to find vacuum leaks
1: i use a vacuum Gage, 15-19inchs at idle and NEVER BOUNCING, !!!!! if bouncing , you have valve issues. big time...
2: hose to ear trick. hisssssssss
3: liquid fuel test, boom , im on fire. (does work very if it dont ignite) carb cleaner works , WD40 dont , they removed the Propane in 2004
4: propane trick much safer ( a Bunsun or map gas bottle and nozzle with the nozzle off and hose added. OTC sells them by thousands. make one. using an old propane torch.
5: water trick,, safe but near useless (but can find tiny leaks)
6: smoke machine. (balls to the wall , dead perfect tests. gets the leak EVERY TIME ! YOUTUBE IT> !
7: the electronic ultrasound hiss finder... (takes skill and patience to listen to each spot)
8: inspections. ( take it down and look,)
9: ugh frak it, put in all new seals and do a riser leak test to be damn sure the riser did not breach the induction !!!
i can not predict what way works best. or if you have tools , or time or cash to do any tests. i can only offer, ALL TESTS.
if you assume it's all bad, you win, ! Mr NG.
there is order, skip the order and waste big time......
motor good (compression, set lash first to .006" on stock motor)
induction not leaking (makes motor and carb and dizzy , useless)
timing dead on , static, and all vacuum and mech advance all work and do not stick.
fix the carb. (full clean,kit, and service) (wrong jets, dead choke, dead fuel cut solenoid (3 ways)? hacked or missing parts in carb>? common that.
ORDER counts. unless you have lots of free time and cash to burn.
I wont tell you to throw a $200 carb on the car , as a guess.
but it's your cash.
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Orsocron
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Joined: August 29, 2003
Posts: 307
Location: Huntsville, AL
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| Posted: Tue Sep 18, 2012 8:52 am Post subject: |
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Your point about a lean carburetor hating later timing is well taken. I can get it to idle when it's set at 7.5 BTDC, but I have to back out that volume screw and richen it a TON.
I really think the majority of my problems are with the carb as of right now. I have one or two spares I can throw on to see if they work better....if that's the case I will work appropriate solutions. I have a budget that will allow a good SVDA distributor and a nice rebuilt Solex 34 PICT 3.
If I Had my way, I'd just yank out the dual port heads and put a single port 30-pict-1 setup on there....at least that carb is fool-proof to tune.
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Orsocron
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Joined: August 29, 2003
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Location: Huntsville, AL
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| Posted: Tue Sep 18, 2012 6:20 pm Post subject: |
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I definitely think there is a major vacuum leak. I tried another carburetor tonight but it still runs like before. Only stays running when it is choked and not very well at that.
I have to get that propane and see if I can find the leak.
I'm going to take the fan shroud off this weekend and replace the intake boots.
Is it possible there is a hole in the manifold?
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HRVW
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Posts: 2531
Location: Rosarito, Mexico
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| Posted: Tue Sep 18, 2012 9:35 pm Post subject: |
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:idea As a former VW mechanic would always use a Flat file on the man/carb flange and also on the DP elbow casting
The Carb/man portion always has a vac leak.
Elbow castings will leak with the old metal gskt.
Even though the metal is thick they will warp from tightening the nuts down. |
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Orsocron
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Joined: August 29, 2003
Posts: 307
Location: Huntsville, AL
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| Posted: Thu Sep 20, 2012 8:35 am Post subject: |
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I can get it to idle just fine now. Even at 7.5 BTDC...it likes 10 better, but that's no biggie. It is noticibly hotter in the exhaust, etc, when I run it at 30 BTDC.
At any setting it won't accelerate. If I keep it at 7.5 BTDC, and quickly push in on the accelerator, I can hear pops in the carburetor and the engine will die if I keep the accelerator pushed in.
If I go slowly, the car runs OK, once I get into the mechanical advance range it really runs well.
I must have used 1/4 of the bottle of propane yesterday and got no leads on a vacuum leak. Nothing I did caused the motor to run faster.
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baja69
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Joined: January 12, 2013
Posts: 29
Location: santa rosa
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| Posted: Mon Jan 14, 2013 9:08 pm Post subject: |
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I'm experiencing the exact same problem with my bug right now and I'm losing sleep (and hair) trying to figure out what the problem is. Did you find a solution?
Thanks,
B. |
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Vwman37
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Joined: February 24, 2013
Posts: 120
Location: Nutwood, Il
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| Posted: Mon Apr 15, 2013 6:22 pm Post subject: |
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| Same here how did you fit it? |
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Vwman37
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Posts: 120
Location: Nutwood, Il
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| Posted: Mon Apr 15, 2013 6:23 pm Post subject: |
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| Fix* |
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hippyvanman
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Joined: June 10, 2011
Posts: 126
Location: Raleigh, NC
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| Posted: Wed Jan 29, 2014 2:18 pm Post subject: |
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Would an unignited butane lighter work the same as an unlighted propane torch? Just trying to think of alternatives without having to buy a new propane torch...
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pwmcguire
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Location: Kennesaw GA
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| Posted: Wed Jan 29, 2014 2:25 pm Post subject: |
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| HRVW wrote: |
:idea As a former VW mechanic would always use a Flat file on the man/carb flange and also on the DP elbow casting
The Carb/man portion always has a vac leak.
Elbow castings will leak with the old metal gskt.
Even though the metal is thick they will warp from tightening the nuts down. |
I was going to suggest to double up on the carb mounting gasket. |
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pwmcguire
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Location: Kennesaw GA
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| Posted: Wed Jan 29, 2014 2:28 pm Post subject: |
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| To detect a leak at idle, sometimes the idle just smooth's out a bit. |
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Thebugkid
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Joined: August 08, 2016
Posts: 40
Location: Oregon
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| Posted: Wed Feb 22, 2017 1:34 pm Post subject: Re: Finding a vacuum leak |
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| Having the same problem, I replaced my intake manifold and carb to 34pict 3 bocar ( dual port 1600cc ) I replaced the metal gaskets to non metal in between the head and intake and cleaned out heat riser tubes with wire, got lots better. But now when I accelerate it takes a second or three to get back down to idle when you drive. I rebuilt and cleaned my carb, but still when you accelerate it doesn't even out in between shifts it just stays up for a couple seconds. Don't know what to do now, just reading around on here looking for a solution, let me know if you have any ideas! |
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joey1320
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Joined: September 12, 2006
Posts: 2325
Location: Cleveland, OH
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| Posted: Wed Feb 22, 2017 1:46 pm Post subject: Re: Finding a vacuum leak |
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You can do as posted above and spray carb cleaner around all the contact/division points in your intake system along with the carburetor.
You can also search on youtube for a homemade smoke tester.
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joey1320
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