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Factory Fuel Systems
Pierburg/Solex, or Keihin carburetion
- Years: 1979-1993
- Fuel system controlled by a carburetor
- Locales: outside North America; no Cabriolet was ever sold in North America with
a carburetor due to strict emissions requirements.
Bosch CIS using K-Jetronic Fuel Management
- Years: 1980-1993 (up to 1989 in North America)
- Mechanical fuel injection system. There are two types of CIS K-Jetronic installed
in Cabriolets: CIS-basic and CIS-Lambda. CIS-basic does not use an oxygen sensor
and catalyst (but uses an EGR system in most cases). CIS-Lambda uses an oxygen sensor,
catalytic converter and a Jetronic controller; it is often referred to as Ku-Jetronic
to differentiate the two systems.
- Because CIS is a continuous injection system, fuel is built up at the intake valve
until the valve opens allowing fuel to enter the combustion chamber.
- Additional info: In North America, only 1980 Cabriolets initially sold outside California
received CIS-basic. All other 1980-1989 (up to 1993 outside North America) Cabriolets
- Locales: worldwide
- Years: 1990-1993
- Electronic fuel injection system. Digifant is Volkswagen's in-house variant of the
Bosch L-Jetronic fuel management system. There are two types: Digifant I and Digifant
II. Digifant I uses adaptive controls to comply with California emissions requirements
and has OBD I diagnostics. Digifant I was installed only in Cabriolets initially
sold in California; all other Cabriolets use Digifant II.
- Digifant is a pulsed injection system; therefore, fuel does not enter the combustion
chamber until just before the intake valve opens.
- Additional info: If the 5th digit in the VIN is "B" it's Digifant II, if it's "C"
it's Digifant I and should have a check engine light on the dash.
- Locales: worldwide
Bosch CIS using KE-Jetronic (aka CIS-E, mechanical fuel injection with electronic
- CIS-E was never, ever factory-installed in Cabriolets! Never, never, never... ever!!
- The main difference between CIS-Lambda and CIS-E: CIS-E uses a differential pressure
regulator, a diaphragm pressure regulator, an idle air stabilizer valve and knock
sensor; CIS-Lambda does not have any of that. Both systems utilize Jetronic control
units and oxygen sensor systems, but that's where the similarities end. Do not let
anyone, or any web site, convince you that your factory-original Cabriolet has CIS-E!
Many CIS-basic afficionados are spreading incorrect information regarding CIS-E;
they do not understand the differences between CIS, CIS-Lambda and CIS-E.
Diesel: A small number of diesel Cabriolets were, reportedly, sent to the UK in the
early '80s; these GLD models were the only diesel Cabriolets ever produced (if the
rumors are true) and are extremely rare today.
Which system is better? 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 stock than CIS.
Slight horsepower gains can be achieved with Digifant by simply "chipping it", where
CIS requires mechanical upgrades. Proper maintenance is the key to a nearly problem-free
car, no matter what fuel system it has.
Furthermore, many folks out there proclaim CIS to be "the devil's work" and that
Digifant is the "bee's knees". I read it over and over again and I'm tired of it.
They both have their pitfalls, they both have pluses, and they both are a nightmare
if previous owners have performed some of their own witchcraft on them. Just because
it's CIS (or Digifant, for that matter) should not prevent you from owning the car
of your dreams. Some people will suggest going so far as to do an engine swap. An
engine swap is fine, if that's what you ultimately want to do, but you'll still have
a fuel system to contend with. The bottom line for all fuel injection systems is
to learn how they work!!!
Note: If you participate in online car forums, educate yourself on a) which system
is in your Cabriolet, b) which system is in the other Cabriolets, and c) if need
be, ask the person requesting help what system is in his/her car before answering.
Time and again Digifant people will provide incorrect information to CIS people,
and vice versa. This only adds to the confusion and, more importantly, frustration
to the person trying to solve a problem. Pass this mantra on to the CIS-E people
too if you can, because they often forget that CIS-Lambda exists and the two do not
share the same components.
Original, stock carburetors are Pierburg/Solex (Keihin was optional):
2E2 carburetor troubleshooting and help
Swapping Fuel Injection for 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 Pumps & Fuel Pump Relay
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).
* 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 (from VIN E_11291).
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.
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 (does not apply 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).
Fuel Pump Relay
Jumping the fuel pump relay is a troubleshooting technique to narrow down the cause
of fuel-related starting and/or running issues. To jump the fuel pump relay, pull
the relay out and place a fused jumper wire between the terminals listed below. 1980-1982:
Jump terminals 2 (red wire) and 8 (red/yellow wire) on the remote socket (remove
the fuel pump relay, but leave the harness in place).
- Jump terminals 30 and 87. If the pumps run, the wiring to and from the pumps is
- Jump terminals 15 and 87 and turn the ignition key to "on" (not "start"). If the
pumps run, the ignition wiring is good.
- Connect terminal 31 to ground and check for continuity. If there is continuity,
the ground connections are good.
- If all of the above tests are passed, that leaves the ignition coil feed to check
(consult your repair manual for instructions).
Relay Part Numbers (CIS)
VW ATM/Kräcker/KAE* Rev Limit
321906059F 24.1400.20 Highest
321906059H 3.300.230 Lowest
(see electrical page for additional info)
*ATM = Altrom; KAE = Kaehler
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.
Click here for fuel injector part numbers.
1979-1984 (up to VIN E_11290)
These Cabriolets do use the same fuel tank as the hard-tops Rabbits/Golf I's.
171201075Q: Fuel injection
Capacity: 10.6 gallons
1984½-1993 (from VIN E_11291)
These Cabriolets do not use the same fuel tank as the hard-tops; these cars use Cabriolet-specific
Part number: 155201075B or 155201075C
Capacity: 13.8 gallons
The Spectra Tank replacement (VW5A) is about the only one you'll find in North America
for the 1984.5-1993 Cabriolets. 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.
Replacing the fuel tank
Yes, you'll need to drop the rear axle beam in order to replace the tank.
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 Fuel 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. However, the recall has limitations;
click here for further information. If the tank is leaking, particular at seam welds,
the gas tank will need to be repaired or replaced.
Minimum Required Octane for Countries Using the (R+M)/2 Octane Rating Method
EJ, EN, JH, 2H engines: Unleaded 87
Minimum Required Octane for Countries Using the RON Rating Method
JH, 2H, EW, JB, FA, FN, FV, JB, EM, GG, GH, HK, HN, EW, EX engines: Unleaded 91
EG engine: Unleaded 95
DX, KT, JJ engines: Unleaded 98
Click here for more gasoline information.