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beetleman217 Samba Member
Joined: April 03, 2011 Posts: 515 Location: Canada
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Posted: Mon Jul 11, 2016 11:24 am Post subject: Carb instead of fuel injection |
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I am rebuilding a 2.0L bus engine, and would like to drop the fuel injection system for a single carb setup.
Since the fuel injected engine does not have a mechanical fuel pump like earlier engines, do I need to hook up an electric fuel pump to the carb?
How can I regulate the pumping of fuel to the carb? Old mechanical ones were engine driven so their output was proportional to engine rpm, but an electric pump will provide a fixed volume all the time.
What else do I have to consider when canceling the fuel injection in favor of a carb? _________________ If all else fails, stop using all else
1977 Westfalia
1961 Beetle |
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sjbartnik Samba Member
Joined: September 01, 2011 Posts: 5994 Location: Brooklyn
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Posted: Mon Jul 11, 2016 11:27 am Post subject: Re: Carb instead of fuel injection |
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You are making a huge mistake.
If, however, you must drop the FI, go with dual carbs rather than a single. _________________ 1965 Volkswagen 1500 Variant S
2000 Kawasaki W650 |
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timvw7476 Samba Member
Joined: June 03, 2013 Posts: 2199 Location: seattle
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Posted: Mon Jul 11, 2016 11:40 am Post subject: Re: Carb instead of fuel injection |
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I use an electric fuel pump from an old Honda automobile.
The kind designed to feed a three barrel CVCC Keihin carb, an
external fuel regulator is not required with that style pump.
The return stub at the bottom of the fuel tank needs to be
blocked, either a vacuum nipple, or a section of fuel line
and a bolt with an unthreaded shank, to keep fuel from running
down the threads when clamped.
A single centerfeed carb is a bad idea. Dual setup is 2X better.
But, if you already have the single,.......& hang on to the F.I. pieces. |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Mon Jul 11, 2016 11:58 am Post subject: Re: Carb instead of fuel injection |
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I have recently helped 2 bus owners try to dial out their progressive carb problems on T4 buses. While we have these buses running substantially better than many late buses with a single carb, neither runs quite as well as a FI bus or dual carb bus - although dual aftermarket carbs have their own issues these days. I would think Maryland with its humidity would be a terrible place for carb and manifold icing in the spring and fall. This would be such a mistake in my opinion, especially in light of the loss of Bosch SVDA distributors when the plant in Mexico closed. There are many aftermarket SVDA distributors but every week we hear about this or that bay where one went bad, or someone hooks a wire up wrong, leaves a key on too long and the module cooks itself. Were it me, I'd start by spending $10 on new injector seals and see if that doesn't resolve the issue. Every single box of FI parts off a bus I've bought because the owner gave up on FI had rotted injector seals that were leaking. $10 in seals and 20 minutes in work might have fixed their issue. Instead they put a carb on it then sell the bus for a loss. _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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aeromech Samba Member
Joined: January 24, 2006 Posts: 16958 Location: San Diego, California
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Posted: Mon Jul 11, 2016 12:16 pm Post subject: Re: Carb instead of fuel injection |
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A single center mount carb on a T4 has very long intake runners. As the fuel and air passes through these runners they get very cold, even on a hot engine. When they are cold, the atomized fuel/air mixture changes state more from a gas back to a liquid and this doesn't burn well causing rough running. I know from experience. I took a heat gun and warmed the runners and the engine ran a lot better. I shot hot air into the air cleaner and the engine ran better. The problem is that I only know of one person that has made his single mount center carb run well on his T4 and this is his engine
With dual carbs, the intake manifolds are short and you don't have this problem. On a T1 engine the intake manifold has a warm air tube from the exhaust that helps keep the fuel atomized.
Here's the engine I experimented on. See the warm air hose? That engine is mounted on my run stand in my garage.
Now, as far as fuel pumps go if you change from FI to a carb you'll need to replace the high pressure electric pump (about 40 psi) to a low pressure pump (about 5 psi). You'll probably also want to use a fuel pressure regulator. Here's some pics
A pump you can get on Amazon
Holley fuel pressure regulator (3 psi)
Your best bet is to try and make the FI work _________________ Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound
Last edited by aeromech on Mon Jul 11, 2016 12:19 pm; edited 1 time in total |
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beetleman217 Samba Member
Joined: April 03, 2011 Posts: 515 Location: Canada
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Posted: Mon Jul 11, 2016 12:17 pm Post subject: Re: Carb instead of fuel injection |
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Thank you for all your comments. Funny, I thought slapping on a carb would make my life easy versus fiddling endlessly with the complex FI system. _________________ If all else fails, stop using all else
1977 Westfalia
1961 Beetle |
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jtauxe Samba Member
Joined: September 30, 2004 Posts: 5780 Location: Los Alamos, New Mexico
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Posted: Mon Jul 11, 2016 12:29 pm Post subject: Re: Carb instead of fuel injection |
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If you do end up going carbureted, this pump will work. I have used it, and will again.
But I agree that FI is the way to go. Fiddling with carbs is no less difficult, really, and will have a poorer outcome. _________________ John
"Travelling in a fried-out Kombi, on a hippie trail, head full of zombie..." - Colin Hay and Ron Strykert
http://vw.tauxe.net
1969 Transporter, 1971 Westfalia, 1976, 1977, 1976, 1977, 1971, 1973, 1977 Westfalias,
1979 Champagne Sunroof, 1974 Westfalia Automatic, 1979 Transporter, 1972 Sportsmobile, 1973 Transporter Wild Westerner, 1974 Westfalia parts bus, 1975 Mexican single cab *FOR SALE*, 1978 Irish 4-door double cab RHD
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aeromech Samba Member
Joined: January 24, 2006 Posts: 16958 Location: San Diego, California
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Posted: Mon Jul 11, 2016 12:35 pm Post subject: Re: Carb instead of fuel injection |
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So one thing I've learned about the fuel injection system on late buses is that vacuum leaks are a killer. Solve the leaks and you've gained a lot of ground. After that, it's taking each component and testing it which isn't too hard to do with our help.
I purchased a smoke machine on eBay and if you have a compressor, works great at finding leaks
http://www.ebay.com/itm/EVAP-Smoke-Machine-Diagnos...mp;vxp=mtr
_________________ Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Mon Jul 11, 2016 12:50 pm Post subject: Re: Carb instead of fuel injection |
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aeromech wrote: |
So one thing I've learned about the fuel injection system on late buses is that vacuum leaks are a killer. Solve the leaks and you've gained a lot of ground. After that, it's taking each component and testing it which isn't too hard to do with our help.
I purchased a smoke machine on eBay and if you have a compressor, works great at finding leaks
http://www.ebay.com/itm/EVAP-Smoke-Machine-Diagnos...mp;vxp=mtr
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Gary - what kind of pressure does the regulator that comes with it provide? Is it simply preset or you do have to set it each time? Robbie mentioned he used your smoke machine and thought it worked well. I was going to ask what you were using but you revealed it Basically can I hook up my air compressor at 100 psi and it drops it, or do I need to fiddle with the air compressor first to lower the pressure.
. _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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aeromech Samba Member
Joined: January 24, 2006 Posts: 16958 Location: San Diego, California
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Posted: Mon Jul 11, 2016 1:02 pm Post subject: Re: Carb instead of fuel injection |
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Well Steve, you'd think that the BBQ regulator would bring the pressure down but I actually had to make up a short air hose with a valve so I can regulate the pressure prior to going into the paint can. It needs to be very low. Less than blowing out birthday candles.
When using the machine, you block off the exhaust pipe as well as the intake. I wrap the paper air filter in cellophane and install it back into the air box. I usually pump the smoke into the plenum through one of the small vacuum ports. Then as I find leaks I plug them and keep testing. Once I'm satisfied that I've found all the leaks I go back fix things permanently. You won't find all the leaks the first time.
Also, in addition to buying the smoke machine you'll need to purchase some mineral oil and lantern wicks. The wicks don't last very long so get a bag of them. i use ones that are 1/2" wide. I put the mineral oil in a squirter bottle for soaking the wick. A rock works well for weighing down the gallon can so it doesn't tip. A lead divers weight would be better as long as it's not the shot filled bags. _________________ Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Mon Jul 11, 2016 1:07 pm Post subject: Re: Carb instead of fuel injection |
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do you know what purpose that regulator is if it doesn't drop pressure? _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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secretsubmariner Champagne Wrangler
Joined: January 08, 2011 Posts: 3104 Location: Tulsa, OK
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Posted: Mon Jul 11, 2016 1:16 pm Post subject: Re: Carb instead of fuel injection |
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beetleman217 wrote: |
Thank you for all your comments. Funny, I thought slapping on a carb would make my life easy versus fiddling endlessly with the complex FI system. |
The VW Air Flow Controlled Fuel Injection Manual (check ebay!), an ohmmeter, a testing light, and a timing gun can help tremendously with the fiddling part. The complexity is solved by your own ability to understand how to test each component. It's not that hard
That book really makes it easy^ _________________ -Tony
ᏣᎳᎩᎯ ᎠᏰᎵ
1978 Champagne Edition Bus FI
1970 Auto Fastback FI |
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sjbartnik Samba Member
Joined: September 01, 2011 Posts: 5994 Location: Brooklyn
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Posted: Mon Jul 11, 2016 1:18 pm Post subject: Re: Carb instead of fuel injection |
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beetleman217 wrote: |
Thank you for all your comments. Funny, I thought slapping on a carb would make my life easy versus fiddling endlessly with the complex FI system. |
There is nothing complex about that FI system. _________________ 1965 Volkswagen 1500 Variant S
2000 Kawasaki W650 |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Mon Jul 11, 2016 1:28 pm Post subject: Re: Carb instead of fuel injection |
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sjbartnik wrote: |
beetleman217 wrote: |
Thank you for all your comments. Funny, I thought slapping on a carb would make my life easy versus fiddling endlessly with the complex FI system. |
There is nothing complex about that FI system. |
it seems intimidating at first but it is a very simple system and easy to troubleshoot. It gets blamed for many other issues - tight valves, dropped valve seats, loose vacuum hoses, bad injector seals, dirty fuel filters, bad ignition wires, corroded connections etc., on a 35 -40 year old car. _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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Randy in Maine Samba Member
Joined: August 03, 2003 Posts: 34890 Location: The Beach
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Posted: Mon Jul 11, 2016 1:29 pm Post subject: Re: Carb instead of fuel injection |
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What is the FI system doing or not doing that is the problem? |
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mechanicjay Samba Member
Joined: November 26, 2014 Posts: 63 Location: Seattle
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Posted: Mon Jul 11, 2016 2:15 pm Post subject: Re: Carb instead of fuel injection |
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Feel free to send me your entire FI system. I'll put it to good use in my bus _________________ 1973 VW Riviera Camper - "Sunshine Daydream"
1981 Ford F100 - In family since new!
1983 Rx-7 - The Sports car.
2006 Jeep Wrangler LJ - The wife and kid mobile. |
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aeromech Samba Member
Joined: January 24, 2006 Posts: 16958 Location: San Diego, California
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Posted: Mon Jul 11, 2016 2:59 pm Post subject: Re: Carb instead of fuel injection |
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SGKent wrote: |
do you know what purpose that regulator is if it doesn't drop pressure? |
I thought that's what it's for. How much pressure is a propane bottle? Pressure the burners want to see just a few psi. Maybe my compressor at 130psi is too high. I just use the valve in the hose pigtail I made and it works fine. _________________ Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Mon Jul 11, 2016 3:09 pm Post subject: Re: Carb instead of fuel injection |
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aeromech wrote: |
SGKent wrote: |
do you know what purpose that regulator is if it doesn't drop pressure? |
I thought that's what it's for. How much pressure is a propane bottle? Pressure the burners want to see just a few psi. Maybe my compressor at 130psi is too high. I just use the valve in the hose pigtail I made and it works fine. |
is this one something like it? If so what do you set it to?
_________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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aeromech Samba Member
Joined: January 24, 2006 Posts: 16958 Location: San Diego, California
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Posted: Mon Jul 11, 2016 3:13 pm Post subject: Re: Carb instead of fuel injection |
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My valve doesn't have a gauge. I just set the flow very low. If it's too high it will blow the lid right off the can. All you want is enough to move the smoke into the engine. I'd say more than just 2-3 psi would be too much and you'd start making new leaks by blowing off hoses. _________________ Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Mon Jul 11, 2016 3:45 pm Post subject: Re: Carb instead of fuel injection |
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looks like a propane regulator so I looked up specs. Requires 2 stages or a dual stage regulator. 1st stage reduces 127 psi (at 70 F) to 10 psi. Then the 2nd stage reduces it from 10 psi to 2 psi. I wonder why the guy isn't including a dual stage regulator, have to ask him. _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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