Date: Tue, 26 Jun 2001 22:29:33 -0800
Reply-To: Mark Keller <kelphoto@ISLANDNET.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mark Keller <kelphoto@ISLANDNET.COM>
Subject: Vanagon Power loss Misfiring or Hesitation testing
Content-Type: text/plain; charset=iso-8859-1
I'm reposting this to the list, as several people of late have asked
about trouble shooting the fuel injection system. I might add I saw on
GENE BERGS website that Radio Interference generated by the use of
metallic spark plug wires was a problem when HE installed a Haltech
System on HIS own 84 Vanagon. He converted to spiral wires, The fix
below is to install a ground strap from the AFM to the cylinder head.
This test sequence is for DIGIFANT only.
Sincerely,
Mark Keller
91 Carat.
The following information is condensed from a service communiqué. It
was intended for dealership personnel and some of the details must be
obtained from other repair publications. I do not have access to the
Digifant I & II ProTraining manual referred to many times in this
document. Maybe someone with access to that information may be able to
help out. VW must, by law, make all repair information available to
the public. They may charge for this service. I don't remember the
details of this. I quit working at the dealership before this repair
information became available so I cannot verify its content. Obviously
there are more economic means to make some of the repairs.
Sporadic reports of intermittent misfire or stalling on Vanagons with
Digifant fuel injection. A "Test Sheet" has been developed to aid in
the diagnosis of such drivability problems.
DO NOT ATTEMPT TO "SHORTCUT" THE REPAIR/TEST.
Basic Engine Set-up
This information can be found on the microfiche or on pages 35-39 of
the Digifant I and Digifant II ProTraining Manual. There can be no
deviation from the basic checks.
PB Campaign
Campaign Circular PB: Assure that the campaign was performed as outlined,
including the relocation of the vent hose and removal of the restrictor,
if applicable. If this campaign is done wrong you will have a
drivability problem.
Carbon Build up
It is very important to check for carbon buildup on the intake valves.
To check this you must remove the intake runners and visually inspect
the intake ports. Remove carbon deposit before continuing. Refer to
Technical Information Circular, Group 24, Number 89-04,
dated April 24,1989.
Fuel Quality
Check that the fuel is a quality grade and octane rating, devoid of
water, alcohol, and other impurities. See TechTalk tape and card #203.
Ignition Cables
Check for corrosion and fit. This primarily concerns the terminal of
the coil. In addition if you have Beru spark plug connectors, replace
them. Check the resistance of all wires. Coil wire value is 2000 Ohms
resistance and plug wire value is 6500 Ohms resistance.
Ignition System
Check to see if the ignition coil is leaking. Use green labeled coil
Part #211 905 115D.
Ground Studs
If the vehicle cuts out around corners it is most likely an interruption
in the circuit for the ground being provided for the fuel pump by the
ECU, check the wiring between the two components.
Move the ECU ground connection to the seat belt retaining bolt as a
check. If this solves the problem install a new body ground. Protect
for corrosion when installing the new ground.
Check the ground connection near the coil, on the left side of the
engine compartment. This is also the ground for the oxygen sensor and
the fuel pump relay. In some cases the fuel pump relay has been the
problem and using part #443 951 253K has been used with some success.
Refer to the Vanagon Wiring Diagram for details.
Electric Harness
Check the connectors in the ECU plug and at all the other fuel system
components connections.
Are the connectors in good shape, with a solid crimp on the wires?
Are they the union power timer connectors?
Power timer terminal can be recognized in the following way:
These terminals are basically the same as the original except that a
stainless steel spring is crimped over the original terminals contact
fingers. This keeps tension along the contact surface during movement,
vibration and high current draw.
Fuel injection wire harness internal connections (injector power and
ground terminal #94, G1 and G2) butt type connector inside the harness
cover can also be a problem. Intermittent missing in lower gears and
some at highway speeds. These three connections are to be soldered.
(I have no other information on the exact location of these butt
connectors other than a photo copy that is too dark to point out
anything and the communique states see your District Service Manager
for approximate locations.)
Refer to harness checks in the microfiche or the Digifant I & II
ProTraining manual, pages 40-43.
Oxygen Sensor Wiring
High resistance or a short in the wire for the oxygen sensor (the
green wire that would be disconnected during C.O. adjustment) that runs
inside the fuel injection harness. Symptoms are missing and cutting out
with thick black smoke coming from the tailpipe. The green wire is
replaceable without replacing the complete harness, part #443 971 108A.
Temperature Switches
Be sure that the temperature switches are within specifications. Refer
to microfiche or Digifant I & II ProTraining manual pages 17 & 18.
Throttle Body and Switches
Throttle plate stop screw adjusted properly and check the throttle
switches with a multimeter, refer to microfiche or Digifant I &II
ProTraining manual page 13.
Replace if shaft is worn.
Air Flow Sensor
Air flap binding and potentiometer within specifications, refer to
microfiche or Digifant I & II ProTraining manual page 18.
Added note: Even if the air flow sensor checks O.K. it may still be a
problem. After making a complete check of the system replace the air
flow sensor. Make sure a ground wire is added between the air flow
sensor and the right cylinder head.
Fuel Injectors
Spray pattern and delivery quantity (too much and too little can be a
problem) and leakage. Refer to microfiche or Digifant I & II ProTraining
manual pages 19-21.
Deceleration fuel Cut-off
Refer to microfiche or Digifant I & II ProTraining manual page 22.
Carbon Canister
Be sure the evaporative system is working properly, refer to microfiche
or Digifant I & II ProTraining manual page 34.
Fuel Pump Circuit
Check connections at relays and grounds. Check the P1 connection in the wire
distribution box on the firewall. In the distribution box there is a
stud with several power wires attached. Two of these wires are for the
fuel pump relay and the ECU relay.
Check for corrosion and poor crimping of connectors.
ECU Versions
After checking the complete system and the problem persists replace
with the latest ECU s. Part #025 906 022D for fuel control and
part #251 907 393D for idle control.
Air flow Sensor Modification
The addition of a capacitor to the air flow sensor wiring may help with
intermittent miss. (The mechanic at the dealership says this will also
cause stalling after being driven awhile and will not restart for
about 30 minutes. Runs fine when restarted.)
A 10uF/25 Volt capacitor can be installed.
1) Remove the connector from the air flow sensor.
2) Pull back the boot on the connector for the air flow sensor.
3) Remove connectors 2 and 4 from the hardshell connector for the air
flow sensor.
4) Cut the connectors of the ends of the wires,
strip the ends of the wire and connect the '+' side of the capacitor
to the #2 wire and the '-' side of the capacitor to the #4 wire.
Crimp on new power timer connectors on the #2 and #4 wires
and reinsert them back into the hardshell connector.
5) Reconnect the airflow sensor connector.
6) Connect a ground from the metal part of the air box to the
empty 6mm ground connection point on the right cylinder head.
