Reluctant start....could it be the harness/leads - help please.

[LeighEnfield]

Hi, Rav4 2.2. diesel 2009, 110,000.   Reluctant starting.  We've changed the glow plugs and wonder if the original leads could do with changing.  What are they called.  I must be missing the obvious.  Are they called ignition leads, harness?  Is it sold as a set from the glow plug end to the other?  Please give me a leg up on this.7

Symptoms:  when cold (e.g. morning) it requires two/three/four turns of the key whilst it warms each time.  Glow plugs and diesel filter changed.  Car Battery is very new and fine and fully charged.

Many thanks, L

[Corolla2004]

On a petrol engine the ignition spark plug leads carry a high voltage and do fail. The glow plug leads carry a 12 volt highish current and are unlikely to fail. But you could have a poor connection somewhere in the circuit. If you have a multi-meter you could check a solid 12volts is reaching the glow plugs & by using the resistance range see if all of your new glow plugs have the same resistance.

[flash22]

If the heaters are cutting out too quickly this points to the Heater relay starting to fail

[Devon Aygo]

Glow plugs on AD engines are fairly rare and are a monitored circuit so a faulty glow plug usually sets a warning light, far more common on AD engines and are nearly always highlighted by cold weather is the SCV this will stick when cold stopping fuel supply and resulting in extended cranking of the engine before it will start. There is even a TSB from Toyota concerning it:

EG-0132T-1110-EN

Subject: 1AD- FTV and 2AD-FTV Engine - Hard to start in cold condition

Models: AURIS, COROLLA, COROLLA VERSO, RAV4, AVENSIS

Model codes: ADE150, AUR10, ALA30, ADT250, ADT251

DESCRIPTION OF PHENOMENON Customer may complain about engine that is difficult (delayed) to start in cold condition but cranking speed is normal. For low cranking speed (< 200rpm) or no cranking, please follow the relevant diagnostic procedure in repair manual.

PRODUCTION CHANGE Improved design of the Suction Control Valve (SCV) to improve sliding performance and newly developed software to increase target fuel pressure in cold condition.