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Mscdman
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Joined: June 12, 2014
Posts: 562
Location: Denver, CO
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 Posted: Mon Aug 18, 2014 10:02 am Post subject: Are dual carb engines more difficult to start? |
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I just had my dual carb mini weber/newly rebuilt engine tuned up for my altitude (Denver). In addition, a valve adjustment was completed
I noticed that once I turn the car off, restarting seems difficult. Is this symptomatic of dual carb engines?
When starting a dual carb ghia are you best to hold the key cranking the engine to start or should you pump the gas when trying to start? |
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Northof49
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Location: Winnipeg, Manitoba, Canada
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| Posted: Mon Aug 18, 2014 10:13 am Post subject: |
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It helps to prime the car by pumping the gas pedal first, and that also resets the choke, if any. I have dual Kadron's on my 1600 motor and find it best to pump the gas once, fully let off the pedal and crank it until it fires (which is nearly instantly), then feather the throttle a bit to warm it up, if cold. Kadron's don't have any choke mechanism. That seems to work better for me than holding the throttle partly open and cranking it. Likely get a stronger signal to the idle circuit if the throttle is closed.
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Bloku
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Location: Tulsa/Jenks Oklahoma
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| Posted: Mon Aug 18, 2014 10:42 am Post subject: |
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I would say just do whatever is best to start the car the fastest. What I do is hold my pedal about half way down and just crank for about 10 seconds. Other than that every car is different so just do what is best.
Also, have you done the timing yet? That was one of my huge problems. Now all I have to do for a cold start is turn the key 
Real quick. If you want to, posting a picture of the engine bay and the carbs would help everyone trying to answer!
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Glenn 
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| Posted: Mon Aug 18, 2014 10:48 am Post subject: |
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No... i've had dual carbs since 1980.
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c21darrel
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Mscdman
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Joined: June 12, 2014
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Location: Denver, CO
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| Posted: Mon Aug 18, 2014 11:09 am Post subject: |
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Hmm I though maybe I flooded it. I'm not very familiar with carbureted engines but I assume the same principle of flooding an engine can occur with a carb system?
It's wierd because when I picked it up from the mechanic who did the tune, it started right up. Went to get gas and it wouldn't start...had to crank for about 10 seconds |
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Danwvw
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Location: Oregon Coast
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| Posted: Mon Aug 18, 2014 11:21 am Post subject: |
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Dual carbs can be difficult to start it the engine is hot or cold but not under Mild outside air temperatures above 50' F, if tuned correctly. Requires not pumping if the engine is hot, Requires pumping if cold especially if they don't have chokes. Mine flood's the engine pretty easy if the engine is real hot!
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Last edited by Danwvw on Mon Aug 18, 2014 11:35 am; edited 1 time in total |
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Mscdman
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Location: Denver, CO
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| Posted: Mon Aug 18, 2014 11:28 am Post subject: |
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| It was a very hot day 90 degrees. I may have pumped too.. |
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vwracerdave
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| Posted: Mon Aug 18, 2014 12:03 pm Post subject: |
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No
If you are having any trouble starting an engine with dual carbs it is because they are not tuned or syncronized correctly.
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squonk
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| Posted: Mon Aug 18, 2014 12:13 pm Post subject: |
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I've also read that when restarting, especially when the engine is still warm, VW recommends holding the gas pedal to the floor while cranking. I've found this to be effective with my dual carb 1600.
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carl4x4
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| Posted: Mon Aug 18, 2014 12:34 pm Post subject: |
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My twin IDF's will fire into life fairly instantly after a initial pump of the pedal before cranking. However keeping them running for the first 10 seconds needs a bit of "tickling" the throttle until it's a bit warmer.
Don't pump the throttle too much or it will flood is my advice
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Mscdman
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Location: Denver, CO
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| Posted: Mon Aug 18, 2014 1:09 pm Post subject: |
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| Is there any harm done in cranking Until it fires up without pumping the gas |
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c21darrel
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Northof49
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Location: Winnipeg, Manitoba, Canada
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| Posted: Mon Aug 18, 2014 1:52 pm Post subject: |
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| Mscdman wrote: |
| Is there any harm done in cranking Until it fires up without pumping the gas |
Well, if it takes 10 seconds every time you start it, you are accelerating the wear on your starter. Do whatever your setup likes. Why make it work harder?
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carl4x4
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ddixon405
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| Posted: Mon Aug 18, 2014 2:30 pm Post subject: |
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what is the advantage to running dual carbs,, if I am just going to use a basic engine not turbo or bore'd out block.
I like the setups I have seen as the 2 carb setup seems like it hides the carbs to the sides and back as opposed to right in front of engine and in the way. |
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rcooled
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| Posted: Mon Aug 18, 2014 2:49 pm Post subject: |
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| c21darrel wrote: |
| I pump pedal as i turn the key....vroom. |
↑↑↑ This ↑↑↑
My 1600 w/dual Kads starts instantly, even after after sitting for two weeks.
| ddixon405 wrote: |
| what is the advantage to running dual carbs |
More power and torque...especially in the higher RPM range. The motor will continue to pull beyond where the stock carb runs out of breath. No problems with clogged manifold heat risers either. Some dual-carb setups will even give better gas mileage than the stock single carb. Porsche used dual carbs on all their air-cooled 4-cyl motors from the late '40s thru the late-'60s.
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carl4x4
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| Posted: Mon Aug 18, 2014 3:02 pm Post subject: |
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| ddixon405 wrote: |
what is the advantage to running dual carbs,, if I am just going to use a basic engine not turbo or bore'd out block.
I like the setups I have seen as the 2 carb setup seems like it hides the carbs to the sides and back as opposed to right in front of engine and in the way. |
They have the potential to feed more air/fuel mixture into your engine, thus letting it run faster, more torque & power. In reality you need to change both the in & out to an engine to allow it breath better, so exhaust, timing, new cam etc. all has a part to play. Dual carbs will help some on a stock engine, but don't expect miracles.
There's a good article here that explains what you can expect with bolt-on items like carbs etc. on a stock engine; http://www.hotvws.com/content.php?contentID=38
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c21darrel
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kingkarmann
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| Posted: Tue Aug 19, 2014 10:03 am Post subject: |
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Dual 36mm dells.
When my Ghia has sat for an extended period, more than 3 days, I pump the pedal 4-5 times then, I crank the engine and feather the throttle until it fires. Progressive carbs stumble until they warm up. It takes about a minute for them to smooth out.
Starting the Ghia after the engine has warmed to operating temp, I just turn the key without throttle. It fires up immediately, as well tuned carbs should.
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