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| Stock/factory
fuel
systems
installed in Cabriolets |
|
Year |
Fuel System |
Notes |
|
1980-1989 |
Bosch CIS, K-Jetronic
fuel injection |
-
If the 5th digit in the VIN is "B" it's Digifant II, if it's "C" it's Digifant I. All 1990 Cabriolets
initially sold in California are Digifant II with unique features; all
1991-1993 Cabriolets initially sold in California are Digifant I. All
other 1990-1993 Cabriolets sold in the USA & Canada are Digifant II.
-
Carburetors were
installed in Cabriolets worldwide except for North America.
-
Cabriolets did
not
ever come from the factory with CIS-E engines!
|
|
1990-1993 |
Digifant
fuel injection |
|
1979-1993 |
Pierburg/Solex, or Keihin
carburetion |
|
One system is not necessarily "better"
than the other, but each has its dis/advantages and quirks.
Carburetors are known to be a pain in the ass, especially the stock
units, but those who know how to work with them can fine-tune them,
upgrade them and receive many years of enjoyment from them. As
for fuel injection, CIS is said to be easier to work on and
troubleshoot and contains less expensive parts than the Digifant
because Digifant is computerized and relies on electronic sensors
and other devices to work properly. CIS, however, because it's a
mechanical fuel injection system, is said to be more finicky than
Digifant and requires fine-tuning to run perfectly. Digifant
engines produce a bit more horsepower than CIS and slight horsepower
gains can be achieved with Digifant by simply "chipping it". Proper
maintenance is the key to a nearly problem-free car, no matter what
fuel system it has.
|
|
| Differences between CIS, CIS-E and Digifant |
|
CIS |
Mechanical fuel
injection on 8V engines utilizing the
Bosch K-Jetronic system |
 |
|
CIS-E |
Mechanical fuel injection with electronic
controls on 16V engines |
|
|
Digifant II |
Electronic fuel injection on 8V engines |
 |
|
Digifant I |
Electronic fuel injection on 8V engines
with OBD I diagnostics |
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| Swapping
from fuel injection to carburetion |
|
Why would you want to??! Many folks who
want to do this "backwards" swap have CIS fuel injection that they can't get
running right. Being fed up, they think it'd just be simpler to switch
out to carbs. The truth is, with a properly tuned fuel injection
system, you will get better fuel economy, actually have less
headaches (carburetors are more finicky than CIS!), and will have a
better-running car. If your Cabriolet is your daily-driver, it's
advised that you simply get your fuel injection properly tuned. If
your car is not a daily-driver and/or you are committed to the carb
conversion, click
here for items you'll need.
|
| Fuel filters |
|
CIS
To VIN: E_11290 |
CIS
From VIN: E_11291 |
Digifant
1990-1993 |
|
Volkswagen part #431 133 511 D
Bosch (part #0 450 905 401) -- OEM
Mann (part #WK 618)
Beck Arnley (part #043-0660)
Deutsch (part #FF600)
Purolater (part #F50155) |
Volkswagen part #893 133 511
Bosch (part #0 450 905 133) -- OEM
Mann (part #WK 834/1)
Beck Arnley (part #043-0798)
Fram (part #G3746)
AC/Delco (part #GF527) |
Volkswagen part #1H0 201 511 A
Bosch (part #0 450 905 030) -- OEM
Mann (part# 830/7)
Fram (part #G3829)
Purolater (part #F60146)
AC/Delco (part #GF358) |
|
CIS fuel filter is in
the engine compartment, mounted to the driver's side fender between
the battery and coolant tank. |
Digifant fuel filter is
located under the car, near the main fuel pump. |
|
Volkswagen part #533
201 511 A -- rectangular filter near the fuel pump for those with
"fuel expansion tanks" |
|
| Fuel
pumps
|
| Fuel injected Cabriolets from
1984* to 1993 have 2 electric fuel pumps. The main fuel pump is located
beneath the car, passenger side, in front of the gas tank. The second pump,
called a transfer pump, is located inside the gas tank; access to this pump
is on the passenger side under the rear seat. Both of these pumps are wired
to the fuse/relay panel. If a pump fails to operate, check the fuse and
relay first (i.e. check the voltage at the pumps).
Fuel pump issues:
- Whining sound: When you hear the
infamous fuel pump whine, one or both fuel pumps are on their
death-beds. In most instances, and especially on 1984.5+ CIS cars,
both fuel pumps should be replaced at the same time
(unless one pump was recently replaced and proves to be good). If
the whine is being heard outside the car, this is an indication that the
internal pump is dead/faulty and, as a result, the main pump is working
harder to supply fuel to the engine. Nine times out of ten, when
only one whiny pump is replaced, 1) problems will still exist and the
second pump then needs to be replaced; or 2) you'll simply be buying
time and will need to replace the other pump sometime within the next
year. If you continue to drive the car with the whine, you will
most definitely need to replace both fuel pumps. When replacing
the pumps, make sure that the electrical connections are clean
(including the wiring).
- Car dies when hot: If the car
dies, or tries to stall (sputters) when the engine is warm/hot, it's
possible that the fuel pumps are overheating (this is especially true if
the fuel tank is low on fuel). This is usually an indication that
the fuel pumps are on their way out. On CIS cars, it's advised
that you replace both pumps at the same time, unless one pump was
recently replaced (or if the car has no transfer pump). Nine times
out of ten, when only one pump is replaced, problems still exist and the
second pump then needs to be replaced. On Digifant cars, replace
the in-tank transfer pump and then test the main pump; if the main pump
proves to be lacking fuel pressure, replace it as well. When
replacing the pumps, make sure that the electrical connections are clean
(including the wiring).
A fuel pump check valve
is connected to the main fuel pump. This device helps in preventing vapor
lock and helps maintain fuel system pressure after the engine stops. On CIS
engines, this part can be replaced independent of the pump; on Digifant
engines, the check valve is part of the fuel pump and cannot be replaced
separately.
NOTE: A CIS external fuel pump can be
used on a Digifant system when need be, but a Digifant external fuel pump
cannot be used on a CIS system. The Digifant fuel pump does not produce
enough fuel pressure required by the CIS system to run efficiently.
* Only about half of the 1984 models have
in-tank fuel pumps. Those cars with a
full-size spare tire in the trunk do not have in-tank fuel pumps; those with
"donut" spare tires have in-tank fuel transfer pumps.
|
| Fuel
injectors
|
|
Fuel
injectors clogged and/or old and dirty? Don't have the cash to buy new
ones? Here's an injector cleaning method courtesy of "Southcross" of
VWvortex.com:
Using a can of carburetor cleaner...
-
"Spray clean the outside of the injectors,
including special attention to the tip.
-
Insert spray tube all the way into the rear of
the injector, spray "through" the injector. As the injector crud
gets cleaned out, you will see the spray pattern change, spray until you
have a normal spray cone.
-
Let dry and insert back into the car."
Click here to see a trick to installing new O-rings onto CIS injectors. |
|
Fuel
tank |
| Need to replace the fuel tank?
The Spectra Tank replacement (VW5A) is about the only one you'll find in
North America. It is manufactured to OEM specifications and is a
direct replacement. The only difference you'll find when shopping
around is price and how it is packaged for delivery.
There has been some talk of making sure that
there are baffles in the fuel tank prior to ordering one. Baffles
prevent fuel starvation during hard cornering when the fuel level is low.
The Spectra Tank replacement does not have baffles, and neither did
the original tanks from the factory. The in-tank transfer pump (low
pressure, high volume), to a
degree, takes the place of tank baffles on the 1984.5-1993 Cabriolets.
If you're driving the car hard into corners all the time when the tank is
low on fuel (i.e. when there is only a gallon or so left), or driving it at
all when the tank is nearly empty, in time you'll burn up the in-tank transfer fuel
pump and will end up with a fuel pressure and/or running problem... hence, the next topic. |
|
Running the fuel tank
dry |
| Nine times out of ten, when
the tank is allowed to run dry, the in-tank fuel pump is
damaged; therefore, replacing the in-tank fuel pump is the only solution.
The longer you drive with a damaged in-tank fuel pump, the harder the
external fuel pump has to work and will ultimately lead to its demise.
When replacing the fuel pumps, replace the fuel filter at the same time as a
precautionary measure. There is also a filter screen attached to
the in-tank pump; make sure this is clean or new when checking or replacing the
in-tank pump. And: Let this be a lesson and warning to never, ever let the
gas tank run dry! |
|
The gas
tank is leaking! |
| Take your Cabriolet to your
local Volkswagen dealer for a gas tank inspection; certain years of
Cabriolets had a recall on the tanks which is still honored by Volkswagen
(by law).
Click here for further information. If your Cabriolet is not
covered by the recall, the gas tank will need to be repaired or replaced.
No, a hard-top Rabbit/Golf gas tank will not
fit. The gas tanks for these cars are Cabriolet-specific.
|
|
Gasoline |
|
Countries using the RON octane rating
 |
Countries using the (R+M)/2 octane rating
 |
|
JH, 2H, EW, JB, FA, FN, FV, JB, EM,
GG,
GH, HK, HN, EW, EX engines:
Unleaded, 91 minimum
EG engines:
Unleaded, 95 minimum
DX, KT, JJ engines:
Unleaded, 98 minimum |
EJ, EN, JH, 2H engines:
Unleaded, 87 minimum
|
|
Click here for more gasoline information. |
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