Engine - Cranks But Won't Start

Group: 15
Number: 01-02
Date: May 24, 2001

Subject:
Engine Cranks But Will Not Start

Model(s):
A4, A6 with 2.8L 5V 1998-->2000

Supersedes T.B. Group 15 Number 01-01 dated Feb. 13, 2001 due to corrected VIN.

Condition

Engine cranks but will not start.

Service

After vehicle sits for a minimum of several hours (preferably overnight), do the following:

- Be sure battery is fully charged.

- Be sure there is a sufficient amount of fuel in the tank.

- Connect VAS 5051 scan tool.





- Select vehicle system "01 - Engine electronics".

- Select diagnosis function "02-Interrogate fault memory" to check for stored DTC's. Select "Print" and "Save Result". Do not print screens! (Select "Yes" at prompt "Erase old log?", if applicable).

Note:
In most cases no DTC's will be found, and the readiness code will be set.

- Take corrective action for any stored DTC's according to DTC table in the OBD II Fuel Injection & Ignition section of the 2.8 Liter V6 5V Repair Manual; re-set readiness code.

- Select back arrow.





- Select diagnosis function "08-Read data block".

- Read data blocks 04, 06, 32, 55, and 60. Select "Print" and "Save Result" for each data block. Do not print screens!

- With ignition switched ON,

- Check that values in display fields 3 and 4 in data block 04 approximately equal the ambient temperature.

- Select the back arrow on the navigation bar.

- Select "Print", then "Self-diagnosis log".

- Check coolant temperature sensor.





Note:
Manufacturing date of the coolant temperature sensor must be later than week 19 of 1998, i.e. 19/98. This will be stamped into the side of the sensor housing (arrow). For location, see Repair Manual Repair Group 24, "Component locations".

- Check and record fuel pressure.

- Check throttle body for proper mechanical function.

^ Must operate smoothly between closed and wide open throttle.

- Crank engine while observing throttle angle specifications in data block 60.

^ Throttle angle must be greater than 60.

If coolant temperature sensor, throttle body, and fuel pressure are OK:

- Remove all spark plugs and perform a compression test and cylinder leakage test on all cylinders (record results).

Note:
Low compression may indicate carbon particles are present on the intake and/or exhaust valves and the combustion chamber (causing The valves not to seat properly).

If compression and leak check are OK:

- Contact Dealer Technician's Helpline for further assistance.

If compression and leak check are not OK:

- Re-install old spark plugs.

To help prevent any future carbon deposit buildup:





- Install new engine coolant thermostat (arrow), Part No: 078 121 113 G, using new 0-ring Part No: N901 368 02. See Repair Manual Repair Group 19 "Thermostat, removing and installing".

CAUTION!
Part numbers are for reference only. Always check with your Parts Dept. for the latest parts information.

^ Temperature gauge will read slightly higher due to thermostat operating temperature increase from 87°C to 92° C.

The new 92°C thermostat is installed in production as of VIN:

A4: after VIN 8DXA279411

A6: after VIN 4BXN116771

- Depress throttle fully and crank engine until engine starts.

- Road test vehicle for 10 miles /16 km, with engine between 4000 and 4500 RPM (use appropriate lower gear to stay within legal speed limits), or statically at constant RPM between 4000 and 4500 RPM for 5 minutes.

- Switch ignition OFF.

- Following instructions in the kit, use Decarb Tool Kit US 9025 along with Wynn's(R) X-Tend(R) V.I.C. Combustion Chamber Cleaner: Part No: 61510 (U.S.), Part No: 61512 (Can) to remove carbon deposits.

- It will also be necessary to change engine oil after carbon removal (oil filter not required).

Important:
DO NOT use 20W50 engine oil - use ONLY factory-approved oil with proper viscosity. See Owner's Manual.

Wynn's V.I.C. can be obtained through your local Wynn's Oil representative. For your local Wynn's Oil representative call 1-800-98X-TEND.

CAUTION!
Use of any other cleaning fluid could damage emissions components. Use only Audi approved Wynn's V.I.C.

Note:
Customers should be made aware that this type of carbon build-up may be due to fuels that do not contain a sufficient blend of detergents. Customers should be given the brochure "Facts about Carbon and Fuel Quality" (Literature No. W42 552 710 0) and advised to use Autobahn Gasoline Additive (ZVW 239 003), which is very effective in reducing and preventing carbon buildup, even if the fuel used does not contain a sufficient blend of detergents.

- Remove spark plugs.

- Disconnect injector wiring and crank engine for a minimum of 30 seconds.

- Reconnect injector wiring.

To help prevent any future carbon deposit buildup:

- Install new spark plugs, Part No. 101 000 067 AA (NGK BKR6EQUPA).





- Install a set of six 4-hole injectors, Part No. 078 133 551 BA.

These can be identified by their RED color (arrow). See Repair Manual Repair Group 24, "Fuel injectors, checking" or "Fuel injectors, removing and installing."

The 4-hole injector is installed in production as of VIN:

A4: after VIN 8DYA135000

A6: after VIN 4BYN096000

Note:
Perform the following steps only with a fully charged battery.

- Start engine (if necessary, depress throttle fully and crank engine until engine starts). Continue to run engine until warm. With engine fully warmed:

- Road test vehicle under load with engine between 4000 and 6000 RPM for approx. 10 miles /16 km (use appropriate lower gear to stay within legal speed limits).

- Attach copy of VAS 5051 print-out to work order for future verification.





When procedure applies to vehicles within the New Vehicle Limited Warranty, use the following table as shown.

To claim Wynn's V.I.C.: Place $15.96 U.S. (Canadian at current exchange rate) in the Sublet Parts Field of the Warranty Claim.