Diesel starts rough when cold?????

Submitted: Saturday, Feb 07, 2004 at 10:46
ThreadID: 10344 Views:12512 Replies:7 FollowUps:1
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I have a MQ SD33 diesel engine, when i start it up in the morning it sounds like it's only running on a couple of cylinders at first then starts to smooth out, it is very rough and blows out clouds of smoke grey/white to light blue.
I have put in new glow plugs, air filter and injectors. Does anyone have any idea on what i could try next, or has had any experience with a similar problem?

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Reply By: ross - Saturday, Feb 07, 2004 at 11:20

Saturday, Feb 07, 2004 at 11:20
Could be low compression on one or 2 cylinders.I had a 4 cyl diesel that had identical symptoms.The low compression makes it difficult to compress the air enough to be able to burn the fuel. As the engine warms up the valves or piston rings expand and eventually are able to compress the air.Another sign of engine wear is the blue smoke.
Before you do anything drastic check the new glow plugs are actually getting power and working as they should.
AnswerID: 45790

Follow Up By: steve - Saturday, Feb 07, 2004 at 11:41

Saturday, Feb 07, 2004 at 11:41
Thanks for the reply, sorry i should have mentioned that i have just finished rebuilding the engine mainly new rings and bearings, it started fine before i rebuilt it. Yes i will have a look to see if there is power at the glow plugs, possible that i didn't put the main wire back on properly.
FollowupID: 307801

Reply By: Member - Gordon- Saturday, Feb 07, 2004 at 13:39

Saturday, Feb 07, 2004 at 13:39
If the diesel starts I would'nt worry about the glow plugs.
I had the same problem in my GQ,rough as bags when cold then after it warms up a bit the engine evens out. Problem is the oil is old/dirty or too thick when the temp. is low. I was using 20w60 (for very hot weather). first noticed this condition one cold morning , last year when pulling out of Narrabri.Changed oil when I got back home (15w40) no problems since,but then it does not get as cold in CQ. May help before you spend more money.
AnswerID: 45798

Reply By: ianmc - Sunday, Feb 08, 2004 at 12:33

Sunday, Feb 08, 2004 at 12:33
I have a Triton 2.5td and it was the same for a while. Blue/white smokey on starting too. It does not use oil but still puffs a bit. Ifeel that the turbo probably leaks a little lubricant into the intake and maybe the oil soaked foam air filter may after standing a while. Certainly sounds like glo plugs may not be getting hot enough.
Triton seems to have corrected itself, dunno why, maybe a few long runs fixed it!
AnswerID: 45855

Reply By: sensei - Sunday, Feb 08, 2004 at 23:33

Sunday, Feb 08, 2004 at 23:33
There is one more thing too check, if memory serves me correctly there is a glow plug timer under the driver side kick board. If this fails or starts to fail the length of time the glow plugs stay on will alter. This also changes with engine temp.
The box contains some electronics, if you do buy dont grab a Nissan one as it is so very costly. It only contains a 555 timer and can be repaired.
Another thing that may help is if when you start your car in the morn try turning the key a little forward (going to the cranking position) until the glow plug lights come back on. You will hear the engine smooth out in a very short time.
You said that the engine had just been rebuilt, did you use copper valve guides in the head, if so they can retain a lot of oil in them and will drain down into the chambers when the engine is shut down giving you a very rough and blue smoke inthe morning. The grade of oil will make a big difference to tthe amount that drains back but they will still drain.
Had an MQ SD33 with the same problem, never did like the 24v system as I had one flat battery and the car wont start..haha
Hope it hopes
AnswerID: 45933

Reply By: David N. - Monday, Feb 09, 2004 at 11:14

Monday, Feb 09, 2004 at 11:14
All of the above advice is good, BUT
don't try to start your diesel when cold as soon as the glow plug light goes out.
They actually stay on a fair bit longer, and when cold it's a good idea to delay your start atleast a few more seconds, in any indirect injection diesel- you'll get a much better start. (You will hear the relay cut out quite some seconds AFTER the glow plug light goes out- on some diesels as much as ten to fifteen seconds. I only start mine as soon as the light goes out in warm conditions....)
Also put a multimeter on your glow plugs and check the voltage they're getting when you turn the ignition on.

Hope this helps, Cheers
AnswerID: 45966

Reply By: Mick - Monday, Feb 09, 2004 at 21:40

Monday, Feb 09, 2004 at 21:40
Sounds like the timing is slightly out, it wont take much to blow white smoke, only a degree or two.
The only way to check it is to do the spill timing again and make sure its correct.
AnswerID: 46064

Reply By: Allan - Tuesday, Feb 10, 2004 at 00:23

Tuesday, Feb 10, 2004 at 00:23
All of the above, try bypassing the glowplug timer by bridging from the battery positive to the glowplug rail for 10-20secs.

I had a problem with my vehicle in winter which I assumed was a glowplug problem but it turned out to be a fuel hose on the fuel filter had a slight leak which allowed air into the system overnight and in the morning gave symptoms of a glowplug problem when it idled rough until the air had been bled out.

Let us all know how you go??

AnswerID: 46097

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