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elansmith70
Samba Member
Joined: May 21, 2020
Posts: 18
Location: Leeds, Yorkshire UK
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 Posted: Mon May 03, 2021 8:59 am Post subject: Deceleration idle fail. |
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Back again. Still having a few issues with shake down running of the buggy.
European 1600 single port, 30pict-3 carb rebuilt and with new spindle bushes, 55 idle jet, 127.5 (was 117.5) main, rocker valve lash set at 0.10mm on F engine, SVDA dizzy, engine set at 7.5deg advance with out vacuum (about 20deg with on tick over).
I am having the problem of stalling on deceleration but only when it comes to a complete stop. I can glide to an almost stop (clutch dipped) but when I press the brake to dead stop, it stalls. (I forgot to put it in neutral to check clutch drag but I doubt it's that).
Only starts again if you give it a squirt from the accelerator pump but will then ticks over while you are stopped fine. Drives off okay until the next stop and repeat.
None of the stalling occurs when the choke is still on, only when it is warmed and the choke is off. Don't know whether that is because the RPM is lifted or because of the choking.
Extra info. When setting the idle with the engine warmed i can screw the mixture (small) screw all the way in and it will still run and adjusting it out makes no difference to idle speed. Only the (large) air screw makes any difference and it needs to be out along way out to get a high idle. You can hear the carb sucking away like made.
That's my puzzle for you.
Thanks.
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Q-Dog
Samba Member
Joined: April 05, 2010
Posts: 8700
Location: Sunset, Louisiana
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| Posted: Mon May 03, 2021 3:30 pm Post subject: Re: Deceleration idle fail. |
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Check fuel pressure and fuel level in the float bowl. Too much of either can flood the carb when transitioning from open throttle to idle.
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Brian
'69 Dune Buggy
'69 Beetle Convertible
'70 Beetle |
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elansmith70
Samba Member
Joined: May 21, 2020
Posts: 18
Location: Leeds, Yorkshire UK
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| Posted: Mon May 03, 2021 3:48 pm Post subject: Re: Deceleration idle fail. |
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| Thanks. Have fitted a new pump but unfortunately don't have a pressure guage. If/when I take the carb off again where would I expect the float to be, sitting level in the float bowl? It was the last time I took it off. I'm also going to double check for air leaks. |
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Q-Dog
Samba Member
Joined: April 05, 2010
Posts: 8700
Location: Sunset, Louisiana
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| Posted: Tue May 04, 2021 3:53 am Post subject: Re: Deceleration idle fail. |
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Most FLAPS fuel pumps put out too much pressure, so start there. I use a cheap pressure gauge with a hose and a T.
I think fuel level is around 3/4" from the top of the carb. Don't remember off hand the exact metric number. The rebuild kits I have used have the spec. I suppose the specification should be in the VW service manual.
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Brian
'69 Dune Buggy
'69 Beetle Convertible
'70 Beetle |
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12735
Location: Western Canada
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| Posted: Tue May 04, 2021 4:16 am Post subject: Re: Deceleration idle fail. |
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First off, I love the clean uncluttered look of your Buggy!
This stalling problem in my mind is perhaps due to 3 things. Idle speed too low. You should be in the 900 - 1000rpm range with the engine warm especially with the dual cannon exhaust you have. That exhaust tends to produce a 2 cylinder idle anyway because of how the timing order is and the fact that each side of the engine now has a leading and lagging cylinder. This causes a draw imbalance on the intake side and a tendency for the front 2 cylinders to run lean and drop off. The cure may be as simple as bumping that idle up.
The second is that it sounds lean on the idle to me. This again is due to the exhaust system you have not giving you proper flow through the heat riser on the intake manifold. At low idle the petrol is dropping out of suspension and pooling in the intake causing the engine to go lean. Search this site for solutions to that.
The third issue is the engine not running hot enough around town. Put a thermostat, flaps and all the stock bottom tins back on the engine.
I too had difficulty getting the carb to adjust just like you are describing and spent a lot of time trying to clean and adjust it but nothing worked, I could never get a dependable idle. Then I bought a new carb but it was no different.
Than I bought a different Buggy, 1600 DP with dual single barrel carbs and cannon exhaust. Back to idle and part throttle around town problems no matter what I did to the carbs. To make a long story short, two things fixed it. A 4 into one exhaust and putting the thermostat and flaps back on the engine to get a more consistent running temperature.
I am back to the first Buggy now with thermostat and flaps installed and a different exhaust. Will see how it goes when I start it up.
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We had the stone age, the bronze age, the industrial age and now we are in the age of mass deception and mind control for corporate profit. (The mass media age) |
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elansmith70
Samba Member
Joined: May 21, 2020
Posts: 18
Location: Leeds, Yorkshire UK
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| Posted: Tue May 04, 2021 11:24 am Post subject: Re: Deceleration idle fail. |
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| Q-Dog wrote: |
Most FLAPS fuel pumps put out too much pressure, so start there. I use a cheap pressure gauge with a hose and a T.
I think fuel level is around 3/4" from the top of the carb. Don't remember off hand the exact metric number. The rebuild kits I have used have the spec. I suppose the specification should be in the VW service manual. |
Thanks again. I may put the original VW pump back on as I only took it of as I suspected too little fuel supply. The fuel filter looked a bit empty but to be fair still does. I still had the stalling at junctions with that also, however. I'm going to try a thicker washer on the needle valve. |
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elansmith70
Samba Member
Joined: May 21, 2020
Posts: 18
Location: Leeds, Yorkshire UK
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| Posted: Tue May 04, 2021 11:43 am Post subject: Re: Deceleration idle fail. |
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| oprn wrote: |
First off, I love the clean uncluttered look of your Buggy!
This stalling problem in my mind is perhaps due to 3 things. Idle speed too low. You should be in the 900 - 1000rpm range with the engine warm especially with the dual cannon exhaust you have. That exhaust tends to produce a 2 cylinder idle anyway because of how the timing order is and the fact that each side of the engine now has a leading and lagging cylinder. This causes a draw imbalance on the intake side and a tendency for the front 2 cylinders to run lean and drop off. The cure may be as simple as bumping that idle up.
The second is that it sounds lean on the idle to me. This again is due to the exhaust system you have not giving you proper flow through the heat riser on the intake manifold. At low idle the petrol is dropping out of suspension and pooling in the intake causing the engine to go lean. Search this site for solutions to that.
The third issue is the engine not running hot enough around town. Put a thermostat, flaps and all the stock bottom tins back on the engine.
I too had difficulty getting the carb to adjust just like you are describing and spent a lot of time trying to clean and adjust it but nothing worked, I could never get a dependable idle. Then I bought a new carb but it was no different.
Than I bought a different Buggy, 1600 DP with dual single barrel carbs and cannon exhaust. Back to idle and part throttle around town problems no matter what I did to the carbs. To make a long story short, two things fixed it. A 4 into one exhaust and putting the thermostat and flaps back on the engine to get a more consistent running temperature.
I am back to the first Buggy now with thermostat and flaps installed and a different exhaust. Will see how it goes when I start it up. |
I'm so glad you like simple/clean look it was what I was going for (it will be getting back seats though). 60's/70's retro.
The engine does idle reasonably (considering your comments) when hot, when it isn't moving. Also drives around town fine. Just stalls when coming from a higher speed to a stop. After stall, pump the peddle twice turn the key it fires up and idles fine, stood. If I can cure that It'll be good. |
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Q-Dog
Samba Member
Joined: April 05, 2010
Posts: 8700
Location: Sunset, Louisiana
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| Posted: Tue May 04, 2021 12:03 pm Post subject: Re: Deceleration idle fail. |
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If I lived where it got cold I would run thermostat and flaps. I don't because the engine didn't have them when I picked it up. And, since I never drive it in weather under 50ºF, I feel hunting down all the pieces when I rebuilt the engine was not a very good use of my time.
Other than the dual exhaust and lack of thermostat, the engine is stock. I run manifold heat and vacuum advance distributor and an original Pierburg fuel pump that I rebuilt. Engine starts quickly and idles rock steady at 850 rpm.
I originally ran a 30-31 pict on this engine with a 009 distributor. It stalled at hard stops until I lowered the fuel level in the carb and installed the rebuilt VW fuel pump.
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Brian
'69 Dune Buggy
'69 Beetle Convertible
'70 Beetle |
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MrGoodtunes
Samba Member
Joined: May 14, 2012
Posts: 852
Location: South Florida
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| Posted: Tue May 04, 2021 1:47 pm Post subject: Re: Deceleration idle fail. |
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| elansmith70 wrote: |
| ... stalls when coming from a higher speed to a stop. After stall, pump the peddle twice turn the key it fires up and idles fine, stood. If I can cure that It'll be good. |
Once had a similar symptom. Mine would sort of sputter and act like it was about to stall. It kept running, while giving off the exhaust stink you get from running too lean. Turn'd out to be a combination of at least 2 issues. The primary issue was not enough gas in float chamber. So, when braking for a red light or whatever, the too little bit of fuel in there was all being thrust away from the main jet. The other contributing factor was excessive wear in throttle butterfly plate axel rod bushings. If you're facing the same low float level, then a thicker washer under your needle valve would actually make things worse! |
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elansmith70
Samba Member
Joined: May 21, 2020
Posts: 18
Location: Leeds, Yorkshire UK
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| Posted: Tue May 04, 2021 3:49 pm Post subject: Re: Deceleration idle fail. |
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| Q-Dog wrote: |
If I lived where it got cold I would run thermostat and flaps. I don't because the engine didn't have them when I picked it up. And, since I never drive it in weather under 50ºF, I feel hunting down all the pieces when I rebuilt the engine was not a very good use of my time.
Other than the dual exhaust and lack of thermostat, the engine is stock. I run manifold heat and vacuum advance distributor and an original Pierburg fuel pump that I rebuilt. Engine starts quickly and idles rock steady at 850 rpm.
I originally ran a 30-31 pict on this engine with a 009 distributor. It stalled at hard stops until I lowered the fuel level in the carb and installed the rebuilt VW fuel pump. |
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It's 50F now was 70F last week. I won't be running it in colder than 50F. No lower tin, thermostat or flaps. Had none before I started the resto.
The old pump I took off (which is probably fine) is an original Pierburg it was just missing the top fuel shut off spring. As mentioned above, SVDA and 30pict-3 50 idle 127.5 main (was 117). I'll try a fuel level lowering washer and probably put the old pump back. |
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elansmith70
Samba Member
Joined: May 21, 2020
Posts: 18
Location: Leeds, Yorkshire UK
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| Posted: Tue May 04, 2021 3:55 pm Post subject: Re: Deceleration idle fail. |
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| MrGoodtunes wrote: |
| elansmith70 wrote: |
| ... stalls when coming from a higher speed to a stop. After stall, pump the peddle twice turn the key it fires up and idles fine, stood. If I can cure that It'll be good. |
Once had a similar symptom. Mine would sort of sputter and act like it was about to stall. It kept running, while giving off the exhaust stink you get from running too lean. Turn'd out to be a combination of at least 2 issues. The primary issue was not enough gas in float chamber. So, when braking for a red light or whatever, the too little bit of fuel in there was all being thrust away from the main jet. The other contributing factor was excessive wear in throttle butterfly plate axel rod bushings. If you're facing the same low float level, then a thicker washer under your needle valve would actually make things worse! |
I get your point and do have to check the spindle for air leaks (but I did put new bushes in). I'll check out over fueling first then move to under if no improvement. |
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12735
Location: Western Canada
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| Posted: Wed May 05, 2021 4:05 am Post subject: Re: Deceleration idle fail. |
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Without all the stock tins and engine temperature control it will have to be run rich to run smooth. Stock jetting will feel and act lean.
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We had the stone age, the bronze age, the industrial age and now we are in the age of mass deception and mind control for corporate profit. (The mass media age) |
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