Carb instead of fuel injection

[beetleman217]

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

[sjbartnik]

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

[timvw7476]

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.

[SGKent]

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

[aeromech]

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

[beetleman217]

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

[jtauxe]

[aeromech]

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

[SGKent]

[aeromech]

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

[SGKent]

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

[secretsubmariner]

[sjbartnik]

[SGKent]

[Randy in Maine]

What is the FI system doing or not doing that is the problem?

[mechanicjay]

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.

[aeromech]

[SGKent]

[aeromech]

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

[SGKent]

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