Glow Plug Resistance

[2HQueues]

Hi All.

Having trouble starting my 2007 95K Patrol GU ZD30 CRD hot or cold. Checked glow plug resistance, all between 1.4 and 1.6 ohms. I know they should be 0.5 ohms.

Questions

A) - Is the range I have acceptable?

B) - Do glow plugs come into play when hot starting?

Thanks in advance :-)

[Rumcajs]

Hi,

Glow plugs resistance should be ~0.8 Ω @ 25°C, temperature is important to consider so:

a) it is acceptable.
b) above 70°C coolant temperature the "glow" is not active. (one can only hope CrD doesn't have the Di type glow period time of 5 mins if it does consider checking/replacing the plugs and fitting aftermarket timer to reduce glow period to 30 secs max.)


I'd quickly guessed you have fuel problems as when engine is hot glow plugs are out of action. I wonder if you have the dreaded low rail pressure due to fuel rail pressure relief valve playing up.

Any DTCs (Diagnostic Trouble Codes)?

Cheers

[2HQueues]

Hi Rumcajs

Thanks for your info, it's very much appreciated.

This has been doing my head in, vehicle's been out of action for about a month now. I've replaced all the hoses that attach to the filter with new clamps, some doubled up. I've swapped out the Coopers filter for a genuine unit, no difference. There were no fault codes last time I checked but will check again tomorrow if I can get it started. I've replaced the battery for a new one. I've replaced the primer bulb with a new double check valve unit. I think I've ruled out glow plugs as it is as difficult to start when the engine is hot.

Tomorrow I will put some clear hose between the filter and IP and see if I can see any bubbles. If I can then I will get some fuel hose and hook it up to primer bulb and put the other end in a fuel container filled with diesel. If bubbles disappear then fuel line prior to primer is at fault. If they don't then it's getting air in somewhere after the primer. Or it's the pressure relief valve. From what I can see underneath, there is only one piece of rubber tubing in the main fuel line and that's where it attached to the tank.

I did have a flat spot for a bit around 2000rpm, which comes and goes. I know air in the line will cause that but I'm not sure if a dicky relief valve will give those symptoms.

[Rumcajs]

Actually lower rail pressure can create a flat spot around the certain RPM.

With the air in the system unless it is sucking huge amounts so the high pressure pump is starving for fuel it should kick in to life and run/misfire for a little bit before it self bleeds....because the gear lift pump is directly attached to high pressure injection pump....

Funny you talk about a new battery.....

Y61s have a common problem with earthing so extra earth strap between the body and chassis is recommended.

Basics first: fuel, air, power and ground.

Cheers

[2HQueues]

Hi Rumcajs

Thanks again :-)

OK, put clear fuel line in. Finally got it started with fresh, newly charged battery.

Some small bubbles at idle, but usually nothing. Some larger bubbles at 3000rpm, but no more than the Nissan documents quote is acceptable.

http://www.nissanpatrol.com.au/Eng-T...iag-Aug-09.pdf

One thing I did notice that at a good cranking speed I'm getting 40KPA fuel rail pressure. If it starts that goes up to 130KPA at idle, and 610-620 at WOT under full load. I'm thinking that my cranking KPA is the problem now. I'm wondering if the relief valve has something to do with it.

[2HQueues]

The solution to my extremely hard to start ZD30DDTi.

FUEL PRESSURE RELIEF VALVE!!!!!

It took about 35 mins to swap over and now it starts like it was brand new.

For Bosch rail 0445214112

Part Number 1110010018

I got mine from United Fuel Injection in Perth ph 1800 199 701. Give them a call, they're very helpful and friendly, and will post anywhere in Aus for a small fee. And you know you're getting GENUINE BOSCH. Much cheaper than buying a whole new rail.

http://www.unitedfuel.com.au/

So if your Nissan Patrol has progressively gotten harder and harder to start then this would be the second thing I'd look at. The first thing to check would be the primer bulb, if the valve in that has gone your diesel will be draining back into the tank. You're Patrol will start easier if you park it up nose down.

Thanks to Rumcajs for all your help.