Quick Start Pre-Glow System Installation/Testing (15/23)

Publication date: 1984-02-01
Reference number: 15/23

QUICK START PRE-GLOW SYSTEM INSTALLATION/TESTING

TECHNICAL SERVICE BULLETIN

Reference Number(s): 15/23, Date of Issue: February 1984

QUICK START PRE-GLOW SYSTEM

A. TESTING PRE-GLOW SYSTEM WITH INDUCTIVE CLAMP-ON AMMETER

B. INSTALLATION NOTE OR PRE-GLOW TIME RELAY

Model(s): Mercedes 300CD/D/TD/SD, 240D

Group: Electrical

Bulletin No.: 15/23

Date: February 1984

SERVICE INFORMATION

A. TESTING PRE-GLOW SYSTEM WITH INDUCTIVE CLAMP ON AMMETER

Testing of pin-type glow plugs with an ohmmeter can be an effective quick test to determine if a glow plug is inoperative. However, this test is not sufficient to determine glow plug heat output; low output may cause difficult engine starting, especially in cold temperatures.

A simple supplementary test can be performed to measure current draw of each glow plug using an inductive clamp-on type ammeter, such as the SUN DMM-5 digital multimeter.

TEST PROCEDURE

Clamp inductive ammeter pick-up around lead of pin-type glow plug.
Turn ignition key to pre-glow position "2". The ammeter value should be 8-15 amps., measured after a pre-glow time of 10-20 seconds. If the measurement is greater than 15 amps, replace the glow plug. If less than 8 amps, check glow plug lead for continuity: if O.K., replace the glow plug.

B. INSTALLATION NOTE FOR PRE-GLOW TIME RELAY

Extended storage of a pre-glow time relay (check production date) may shorten its specified pre-glow time and prevent the engine from starting. After the installation of a new relay, pre-glow repeatedly (approximately 5 to 10 times) until its condenser energizes sufficiently to reach the specified pre-glow time.