407 2.7 Hdi glow plugs and the P1351 pre heating relay

[407]

Having partially fixed my DPF regeneration issue (so far all okay but still blowing a cloud of dark smoke on take off), Diag global test comes up with a permanent fault P1351 pre/post relay heating circuit / glow plugs.

I found the relay 0281003018 under the ECU but can't seem to spot the glow plugs themselves on the engine ?

Any diagrams / pics of where exactly they are on a 2.7 hdi ? Hidden under covers / other pipes etc

I've pulled the relay out and tested the black wires (G1 to G6) which I assume go to each of glow plug themselves - each is around 1 ohm so assume good

The relay date is 2006 so assume original.

Is there a way to test the relay ? I noticed it has 4 wires into a 5 pin connector (as per pic ST is not connected))

[GiveMeABreak]

This fault means the relay is supplied (as you have found) but the plugs are not. So likely time for new plugs.

I'll put something up for you regarding accessing the plugs - check back here in 20 minutes for the link.

[GiveMeABreak]

Ok, here you go:

407 2.7 HDi Pre-Postheating Plug Replacement

[407]

Thanks Marc

I actually pulled the 6 pin connector off and tested each of the black wires to earth so assume if they were open circuit the glow plugs would be kaput - they all read around 1 ohm so assume they are okay ?

Do you have a circuit diagram for the relay to see what the pins do

ps - it seem numbers like 86, 30 etc seem to be common amongst car relays but not French ones

[GiveMeABreak]

1158: pre-postheating control unit

1376: Pre/post-heat unit command
1386: Pre/post heating diagnostic info
1223 : Engine management main relay power supply









1159: glow plugs supply shunt /

Wiring:
1189 : Pre-heat plug 6 command
1188 : Pre-heat plug 5 command
1187 : Pre-heat plug 4 command

1186 : Pre-heat plug 3 command
1185 : Pre-heat plug 2 command
1184 : Pre-heat plug 1 command

[20th Century Pug]

Measuring the resistance only tells you the glow plugs are not open circuit. An internal fault could cause them to glow in the wrong place, so the fuel dosn't spray onto the red hot part, or the tip might be melted and distorted.
Best to take them out to test and check they really do glow brightly at the tip. On the HDi engine they are supposed to continue glowing for a short time after the engine has started, depending on the ambient temperature. This is controlled by the ECU.

Don't connect them directly to the battery. They are rated at less than 12v to allow for voltage drop when they are all switched on. Use the output from the Bosch control relay. Good glow plugs will draw approx. 20 Amps each when first swiched on, rapidly dropping to about 12A as they heat up. There are actually two resistances inside a glow plug. The tip element which gets red hot, and a series current limiting resistor which increases in resistance as it heats up, preventing overheating of the element. Cheap or knock-off glowplugs may omit the current limiting resistor and fail prematurely, or worse, melt and break off inside the engine.