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mcdonaldneal Samba Member
Joined: June 13, 2013 Posts: 2639 Location: Gullane, Scotland
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Posted: Sat Aug 30, 2014 2:11 am Post subject: Frustrated over tuning. There must be something obvious? |
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Last things first, I'm probably going to take the bus to a local garage after the weekend, but I'm interested in suggestions from the Samba.
First things next, we're over 1000 miles from home in Croatia, in our Kombi camper, thread here:
http://www.thesamba.com/vw/forum/viewtopic.php?t=6...p;start=80
She is 1978, 2.0 litre, dual 34 PDSIT 2/3 carb, vacuum advance only, Euro/ Australian stock setup.
Everything was going pretty well, running great all the way here.
I'm NOT a mechanic at all, but slowly learning! Have Bentley and Muir, and patchy internet.
I adjusted the valve clearances after the journey here, couple had tightened a little, a couple loosened.
Reset dwell, 50 deg.
Compression test, No 4 low at 90Psi, as it had been when we set off, comes up with a squirt of oil. Presume worn rings.
Spark plugs on left side oily/ carbonised, right side ok.
Set timing statically initially, 7.5 deg BTdC. That is the figure on the engine sticker, although I know that should be at idle.
Because of plug appearance, decided to run through carb setup procedure, to hopefully balance mixtures.
I have an old strobe light which flashes ok, but when I put the spring in the No 1 distributor connector, the engine runs rougher/ slower (I presume this isn't normal).
Ran through the Final factory dual carb adjustment procedure here:
http://www.thesamba.com/vw/forum/viewtopic.php?t=3...fab773dfcb
Think I got the mixture set (a tad lean) and the carbs balanced for air and fuel, but all is not well.
The idle slows when I pull the vacuum retard off the distributor, the procedure says it should speed up (there is a vac signal from the carb)
Idle is slow and rough on a test drive, and adjusting the idle speed and mixture screws on the top of the left carb has no effect during the procedure.
The distributor position for timing is totally different for the three conditions, static timing, 7.5 BTDC at idle, and 24-28 deg at 3200 rpm, as per the procedure.
Timing effects:
Set 7.5 deg btdc static: runs ok, strobe says 24 deg BTDC at idle 40 deg at 3000
Set 7.5 btdc strobe at idle, vac hose on at dist: 24-28 at 3000. Idles very poorly, if at all.
Set 7.5 strobe at idle, vac hose off at dist: 24-28 at 3000. When vac hose goes back on, reads 20 deg btdc at idle w strobe and 40 deg at 3000 rpm. Idles poorly, if at all, but test run feels great on the move.
Comments welcome, but questions are:
Why does pulling off the vac advance do the opposite to the idle as the procedure says (is it because the timing is wrong?)
When balancing the fuel mixture, pulling off the cut offs on either side drops the idle from say 800 to 500/ stall. Is it normal to have this big a drop on both sides?
Where should I set the timing?
Could the fact that the timing strobe light doesn't connect cleanly affect the timing values it gives me (ie I can't trust them?)
Even if the timing is off, does the fact that the mixture reference hose test (finger ON, finger OFF, no change in idle speed) is ok mean that my mixture is more or less ok?
I would spend time browsing for inspiration, but the connection here is not great.
Sorry for the rambling post, but I am fed up that I can't get it anywhere near right! _________________ 1978 marino yellow Bay Dormobile camper
1969 signal orange Karmann Ghia convertible
1976 martini olive Bay Dormobile camper
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mcdonaldneal Samba Member
Joined: June 13, 2013 Posts: 2639 Location: Gullane, Scotland
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mcdonaldneal Samba Member
Joined: June 13, 2013 Posts: 2639 Location: Gullane, Scotland
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Posted: Sat Aug 30, 2014 4:46 am Post subject: |
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Ok found this, from a different thread, when I was able to search! It does describe what happens with one of my timing options (24-28 with vac hose off), so I think I should try that and then try and improve the idle with the CiS
Amskeptic wrote: |
ianthurlbeck wrote: |
when I checked the vacuum port on the outside of the LH carb. it seems to have been sealed with a brass insert:
Should I just drill it out ?
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I do not believe that is sealed. I would not "just drill it out". I would first test it with a timing light, rev engine to 3,500 rpm with vacuum hose on, see that the timing hits 36-40* btdc at throttle tip-off. Take hose off. Now timing should not exceed 28* when you rev it to 3,500 rpm. If you do not get the 36-40, suck on the hose at idle to make sure the advance unit itself is holding vacuum and advancing the timing, you can hear the engine rev up and your mouth can tell if there is a vacuum leak in the advance unit. If it works correctly and you still don't get vacuum advance, get a properly functioning vacuum gauge with air-tight hose, and read the vacuum as you rev the engine and let it drop down. If no reading . . . then! I might think about drilling that thing out.
Colin |
_________________ 1978 marino yellow Bay Dormobile camper
1969 signal orange Karmann Ghia convertible
1976 martini olive Bay Dormobile camper
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Wildthings Samba Member
Joined: March 13, 2005 Posts: 50257
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Posted: Sat Aug 30, 2014 7:32 am Post subject: |
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In order to set the timing accurately with a light, you have to be at base idle. That is below the engine speed that the centrifugal advance will begin to operate. This may be a lower speed than given in the manual for setting the timing. Also if the throttles need to be opened a bit to get a good idle the vacuum advance may start kicking in at idle.
If either of these condition exist the timing can not be set with a strobe at idle and must either be timed statically or at full mechanical advance, 3500+ rpm hoses off and plugged. |
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mcdonaldneal Samba Member
Joined: June 13, 2013 Posts: 2639 Location: Gullane, Scotland
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Posted: Sat Aug 30, 2014 8:47 am Post subject: |
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Ok. Progress report. I've now set the strobe timing to 30 deg max with vac hose off. (I tried 25 deg but refused to idle.)
Went for a test drive. Accelerates well and seems to drive fine, but idle speed is verging on a stall.
Set mixture with Amskeptic reference hose technique. Ok. (Engine speed still drops when I remove vac advance from distrib.)
Central idle circuit is mysterious. Engine speed increases when the solenoid is disconnected, idle speed and mixture screws have no effect on idle. I can hear air rushing in the intake, which varies with the speed screw, but no change in the idle speed.
Checked for vacuum leaks, dist vac advance hose is ok, and holds the plate in the dist when sucked and blocked. Elbow pieces and tube on left carb have no leaks. Where else can I look?
Problem now is the dangerously slow idle. Cannot increase it with idle mix screw. I turned the lower throttle mix screws out by 1/4 turn each, prob helped a bit, but don't want to richen that too much. Throttle plate screws are 90 deg + 45deg as per Amskeptic.
Sorry I can't reply immediately, but any help much appreciated! _________________ 1978 marino yellow Bay Dormobile camper
1969 signal orange Karmann Ghia convertible
1976 martini olive Bay Dormobile camper
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51057 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Sat Aug 30, 2014 9:05 am Post subject: |
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mcdonaldneal wrote: |
(Engine speed still drops when I remove vac advance from distrib.) |
Are you sure the advance line isn't on the retard nipple on the carb?
Quote: |
Engine speed increases when the solenoid is disconnected |
CIS way too rich?
Edit:, assuming it's the CIS solenoid wire you are pulling off. _________________ Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
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mcdonaldneal Samba Member
Joined: June 13, 2013 Posts: 2639 Location: Gullane, Scotland
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mcdonaldneal Samba Member
Joined: June 13, 2013 Posts: 2639 Location: Gullane, Scotland
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Posted: Sat Aug 30, 2014 9:47 am Post subject: |
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Wildthings wrote: |
In order to set the timing accurately with a light, you have to be at base idle. That is below the engine speed that the centrifugal advance will begin to operate. This may be a lower speed than given in the manual for setting the timing. Also if the throttles need to be opened a bit to get a good idle the vacuum advance may start kicking in at idle.
If either of these condition exist the timing can not be set with a strobe at idle and must either be timed statically or at full mechanical advance, 3500+ rpm hoses off and plugged. |
I've now set timing at full mechanical advance, as you say.
Still can't get a reliable idle.
Going to sleep on it. _________________ 1978 marino yellow Bay Dormobile camper
1969 signal orange Karmann Ghia convertible
1976 martini olive Bay Dormobile camper
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51057 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Sat Aug 30, 2014 11:04 am Post subject: |
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mcdonaldneal wrote: |
I don't see any other nipple on the carb, but ill look again. The nipple on the carb has a suction signal, would a retard nipple have the same?
Even with the idle screws on the carb screwed all the way in there is no effect on the idle speed. And yes, definitely the CiS solenoid!
Sigh. |
The retard nipple is usually on the opposite side of the carb from the advance, retard has constant strong vacuum at idle, advance has none until you open the throttle. Are you doing this with the linkage disconnected?, did you first remove the carbs and confirm the throttle plates are fully closed except for the tiny specified gap (which I can't recall the dimension of right now)? Any response when you turn the small vertical mixture screw on the CIS in? _________________ Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
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Tcash Samba Member
Joined: July 20, 2011 Posts: 12844 Location: San Jose, California, USA
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Posted: Sat Aug 30, 2014 12:00 pm Post subject: |
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Hi
When you pull the Retard hose are you blocking it off. If not you are creating a vacuum leak and the idle would drop.
If the idle mixture screws have no effect.
Throttle plates opened to far. As BD said.
Float level is too high.
Jetting is too rich.
Good Luck |
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1967250s Samba Member
Joined: May 02, 2007 Posts: 2137
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Posted: Sat Aug 30, 2014 12:28 pm Post subject: |
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Idle mixture tube clogged? Carbs are clean? |
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Stuartzickefoose Samba Post Whore
Joined: February 07, 2008 Posts: 10350 Location: SoCal for now...
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Posted: Sat Aug 30, 2014 6:38 pm Post subject: |
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i vote the distributor is sticky...the weights arnt moving freely and therfore you arnt getting full advance curve. way to verify is when revved up, the timing swings from 8* or so up to 30 and back smoothly from idle-3500 RPM. if you cant get that whole range without the vacuum can plugged in, your weights arnt working properly. but of spray lube will help spray under the points plate area and just soak it. then a little bit on the points plate as well. best way is to remove and disassemble distributor, but thats a bit of a task if you are not into it.
start there, then recheck the rest once the timing is smooth and working at least the mechnical, properly. once the mechanical works, check the vacuum side for the extra 10* or so advance and then check fuel.
dont give up! you can do it! let me know if you need more explanation (anyone) to what i just said... _________________ Stuart Zickefoose
2011 Jetta Sportwagen TDi 6 speed manual
206-841-7324
[email protected] |
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mcdonaldneal Samba Member
Joined: June 13, 2013 Posts: 2639 Location: Gullane, Scotland
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Posted: Sun Aug 31, 2014 3:02 am Post subject: |
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busdaddy wrote: |
mcdonaldneal wrote: |
I don't see any other nipple on the carb, but ill look again. The nipple on the carb has a suction signal, would a retard nipple have the same?
Even with the idle screws on the carb screwed all the way in there is no effect on the idle speed. And yes, definitely the CiS solenoid!
Sigh. |
The retard nipple is usually on the opposite side of the carb from the advance, retard has constant strong vacuum at idle, advance has none until you open the throttle. Are you doing this with the linkage disconnected?, did you first remove the carbs and confirm the throttle plates are fully closed except for the tiny specified gap (which I can't recall the dimension of right now)? Any response when you turn the small vertical mixture screw on the CIS in? |
Thanks to all,
The nipple on my carb is on the left side (same as the pics on Ratwells site) I see no retard nipple. However it does have constant slight suction at idle.
Throttle plates are cracked open 90*+45* turns of the screw past contact with the throttle body, as per Colin Amskeptics procedure. He also says there should be a vac signal from the carb retard nipple.
Lying in bed last night, I thought that the CiS is not right. Today I have taken carb off, partially disassembled, really blew out CiS passages with carb cleaner.
Idle was better after this, but during a test drive, slowed off again.
Idle picked up again, but the vertical mixture screw on the CIS still has no effect.
Idle speed screw still alters the sound of air sucking through, but has no effect in the idle speed.
Common sense says, well its blocked again, but carbs are generally very clean. I have put an extra fuel filter before the left carb anyway.
Trouble was I couldnt properly disassemble the carb. The main top plate is integral with the auto choke body, and connected to the throttle plate 'axle' (?) Even getting these free i couldn't separate the two halves of the carb without force. As things are drivable at the moment, I am not keen to force it all apart.
I gave up, put it all back together, washed the bus and I've come away for a coffee! _________________ 1978 marino yellow Bay Dormobile camper
1969 signal orange Karmann Ghia convertible
1976 martini olive Bay Dormobile camper
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mcdonaldneal Samba Member
Joined: June 13, 2013 Posts: 2639 Location: Gullane, Scotland
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Posted: Sun Aug 31, 2014 3:06 am Post subject: |
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Tcash wrote: |
Hi
When you pull the Retard hose are you blocking it off. If not you are creating a vacuum leak and the idle would drop.
If the idle mixture screws have no effect.
Throttle plates opened to far. As BD said.
Float level is too high.
Jetting is too rich.
Good Luck |
Thanks,
I had not blocked off the hose, as Amskeptic said it wasn't necessary. i can try it though.
I cant see anywhere else to check for a vacuum leak. I dont have brake booster elbows or EGR. Carb inlet area seems ok, slight crack in the exit hose from the CiS, but sealing that off (with a rubber glove) made no difference.
Throttle plates 90*+45* past screw contact. Checked for 'tiny' gap when carb was off.
Couldn't get into float chamber as above.
Stock jets, but cant get to them anyway. _________________ 1978 marino yellow Bay Dormobile camper
1969 signal orange Karmann Ghia convertible
1976 martini olive Bay Dormobile camper
Stop dead photo links! Post photos to The Samba Gallery!
Last edited by mcdonaldneal on Sun Aug 31, 2014 3:28 am; edited 1 time in total |
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mcdonaldneal Samba Member
Joined: June 13, 2013 Posts: 2639 Location: Gullane, Scotland
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Posted: Sun Aug 31, 2014 3:15 am Post subject: |
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Stuartzickefoose wrote: |
i vote the distributor is sticky...the weights arnt moving freely and therfore you arnt getting full advance curve. way to verify is when revved up, the timing swings from 8* or so up to 30 and back smoothly from idle-3500 RPM. if you cant get that whole range without the vacuum can plugged in, your weights arnt working properly. but of spray lube will help spray under the points plate area and just soak it. then a little bit on the points plate as well. best way is to remove and disassemble distributor, but thats a bit of a task if you are not into it.
start there, then recheck the rest once the timing is smooth and working at least the mechnical, properly. once the mechanical works, check the vacuum side for the extra 10* or so advance and then check fuel.
dont give up! you can do it! let me know if you need more explanation (anyone) to what i just said... |
Thanks,
Mechanical advance seems to work smoothly. Reattaching vac advance (I hope, see above!) gives the extra 10*
I have been this close (indicates tiny distance with fingers) to giving up several times, especially as the bus is running so-so just now (crappy idle is really the only obvious problem).
Thanks all for help so far, the Samba is amazing, and for all my frustrations, I have learned a lot trying to sort this! _________________ 1978 marino yellow Bay Dormobile camper
1969 signal orange Karmann Ghia convertible
1976 martini olive Bay Dormobile camper
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mcdonaldneal Samba Member
Joined: June 13, 2013 Posts: 2639 Location: Gullane, Scotland
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mcdonaldneal Samba Member
Joined: June 13, 2013 Posts: 2639 Location: Gullane, Scotland
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Posted: Sun Aug 31, 2014 8:17 am Post subject: |
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Ok.
Haven't seen any replies since I last posted, but,
Done all I can, I think.
Got carb apart. Looked pretty clean, but blasted the bejeesus out of it with carb cleaner. Float floating. Needle valve new and slack. Cleaned out whole of CiS. Reassembled with new main gasket.
Suspicious tubing sleeve from CiS on carb to idle circuit metal spider (split in tube). I don't have this size tubing, so I covered it in the finger of a nitrile glove and wrapped the whole in Teflon tape, hose clip on the top.
Started the engine, wouldn't idle BUT left cutoff solenoid had become disconnected. Fixed.
Idles ok.
Haven't tried fiddling with the CiS screws, but engine is cold.
Vac line from dist is connected to the advance nipple. There is no retard nipple. Has gentle suction all the time, as Amskeptic seems to suggest.
Disconnecting vac line from dist slows the engine still, blocking the hose does allow the idle to pick up, and reconnecting speeds things up.
I've had it.
I'll live with what I've got, and maybe get the garage in Austria to take a look (and prob replace the hoses in the CiS spider.)
Back to the beach. _________________ 1978 marino yellow Bay Dormobile camper
1969 signal orange Karmann Ghia convertible
1976 martini olive Bay Dormobile camper
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mcdonaldneal Samba Member
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Tcash Samba Member
Joined: July 20, 2011 Posts: 12844 Location: San Jose, California, USA
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Posted: Sun Aug 31, 2014 10:16 am Post subject: |
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Hi
Another thing to note is.
Does it idle better when it is cold chokes on or when it is hot chokes off? |
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51057 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Sun Aug 31, 2014 10:48 am Post subject: |
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The more I think about it an Australian or Euro delivered bus wouldn't have the retard feature and likely would lack the retard nipple on the carb, that's a North American smog feature.
It's still perplexing how that advance nipple is making vacuum at idle if the plate is indeed fully closed, are you doing the 1/4 turn past contact thing with the linkage disconnected so nothing is pulling on the throttle arm on the carb? Maybe you are 1/4 turning past an existing preload?
The vacuum advance circuit is above the throttle plate, for it to make vacuum the plate has to be open, in your case I suspect it's still open too much which would also render the CIS nearly inoperative as it's dependant on closed plates so it can act as a third little carb to supply most of the idle mixture. Here's a cutaway of a carb (earlier model than yours) that shows the advance circuit (#35)
_________________ Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
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