Indicator Glows, Engine Hard to Start

Checking pencil-type glow plugs and their lines.

Problem:
Preglow indicator lamp fails to light up, engine is hard to start; an open circuit in one or more pencil-type glow plugs or in the lines leading to the pencil-type glow plugs is possible.

Problem:
Preglow indicator lamp lights up, engine is hard to start after reaching start readiness; an open circuit of a pencil-type glow plug or a line to the pencil-type glow plugs of cylinders no.2 to 5 is possible or incorrect power may be consumed by the pencil-type glow plugs in cylinders 1 through 6.

- Measuring power consumption of the pencil-type glow plugs with the DC current probe.





- For this purpose place the current probe over the individual lines on the preglow time relay.

Cylinder 1 = 2.5 black/blue
Cylinder 2 = 2.5 black/purple
Cylinder 3 = 2.5 black/red
Cylinder 4 = 2.5 black/yellow
Cylinder 5 = 2.5 black/green
Cylinder 6 = 2.5 black/white

- Turn key in steering lock to position "2", the power consumption of each glow plug should be 8-15 A after 10-20 seconds.

- If the value is above 15 A, replace glow plug.

- At a value below 8 A, check electric lines or glow plug with multimeter ohm measuring range for open circuit.





- In order to test for an open circuit pull 6-pin coupling off preglow time relay.

- Using the multimeter ohm measuring range measure the resistance to ground (engine block) of one after the other as follows:

Jack 1 of coupling = Pencil-type glow plug cylinder 1
Jack 2 of coupling = Pencil-type glow plug cylinder 2
Jack 3 of coupling = Pencil-type glow plug cylinder 3
Jack 4 of coupling = Pencil-type glow plug cylinder 4
Jack 5 of coupling = Pencil-type glow plug cylinder 5
Jack 6 of coupling = Pencil-type glow plug cylinder 6

- If infinite resistance is measured, an open circuit in the respective pencil-type glow plug or the feed line or the connection is the problem.

- Eliminate open circuit in the feed line or replace glow plug.

Note: It may be possible that the indicator lamp (due to unfavorable tolerances) indicates a fault only upon failure of 2 pencil-type glow plugs in the cylinders 2-5.

- In order to ensure that the fault indication in the preglow time relay is accurate, 2 pencil-type glow plugs of the cylinders 2 to 5 have to be disconnected in this case and the preglow process repeated.