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996 starting problem

Posted: Wed Sep 26, 2018 5:44 pm
by Patrick98
Hello. My 996 is very hard to start when cold.. I don't think it's a dirty fuel problem.. it's not injectors.. I think it's the pump.. I took her to a well trusted mechanic and he said that if she is running normal it is not the pump.. he said that an engine overall may be needed but he doesn't know yet.. Any thoughts..

Re: 996 starting problem

Posted: Wed Sep 26, 2018 7:53 pm
by rid54
I'm sure there are lots of knowledge about this, but my 5 cents are like this:
Ignition in a diesel depends on heat. Heat in the combustion chamber comes from the compression of the intake air. Pressure (and thus temperature) in the cylinder depends on the tightness of the piston and the valves, and on the cranking speed.

Engines with inline injection pumps normally have a cold-start device that increases fuel delivery beyond normal maximum, which makes starting easier, while distributor-type pumps have a system for fixing the injection timing to the most favourable for cold starting.

First check is the cold-start device - active or not?
Next check is the low-pressure side (after feed/lift pump); all filters OK and lift pump working as it should?
Next check is cranking speed; does it seem normal/good (good battery, starter motor in good shape etc)?
Next possible problem is compression - may be a good idea to check this.

Re: 996 starting problem

Posted: Thu Sep 27, 2018 1:45 am
by cobbadog
Would a pre-heater type glow plug help this situation in the air intake manifold?

Re: 996 starting problem

Posted: Thu Sep 27, 2018 8:00 am
by DB780
Get your 'well trusted mechanic' to test the compressions on each cylinder.

Re: 996 starting problem

Posted: Thu Sep 27, 2018 8:24 am
by Patrick98
With a pre heat it helps a bit but not much. I use the cold start on the fuel pump as well and it doesn't overally help. If the compression is gone in a cylinder.. would that just be rings of the Piston needing replaced??

Re: 996 starting problem

Posted: Thu Sep 27, 2018 8:55 am
by rid54
I have an 880 that has a "thermostart". This works very well imho in really cold weather, but the tractor will start nicely without it, if the temp is not lower than freezing point. The cold-start device on the injection pump is frozen solid in the "run" position, so that I don't use.

Bad compression can be due to worn/stuck piston rings, severe cylinder wear or worn/damaged valves or valve seats. If the problem really is about compression, there are methods to get more detail about the situation without opening the engine (a leak-down test).

Re: 996 starting problem

Posted: Thu Sep 27, 2018 9:51 am
by broadsword
Patrick - is the pre-heat plug working properly ??

I had a 990 that started usually ok with plug pre-heat but then the plug started to fail and she was a pig to start. New plug and she was ok again.

To be honest she had 5000 hours and never stripped so was getting a bit worn anyway but only an occasional use / plaything tractor. Depends what you are using it for, if its occasional use is it worth stripping and fettling.

The plugs are quite cheap anyway, I`d start there first.

Re: 996 starting problem

Posted: Thu Sep 27, 2018 1:02 pm
by Patrick98
With the pre heating plug I hold it for 10 seconds then turn it on around.. it is harder to start the tractor without pre heat but it is alos hard to start with the preheat. A wee tractor like a 996 shouldn't need to be turning over so much to start.. the mechanic was confident that it's something to do with the Pistons as he said that to do it right an engine rebuild will be needed (ie engine boar etc) but he said that new rings and maybe Piston heads will temporary fix the starting problem but no completely fix the problem.. I can't afford £1500 to rebuild her and even at that is it worth doing.. the mechanic said to leave it with him and he'll wait till the next cold morning to see what the story is.. what is your opinions.. ie what would the value of the tractor be if the engine was rebuilt.. the body work is nearly immaculate as I am restoring her for showe.. she will be doing some work like ploughing, lifting round bales and pulling the odd trailer..

Re: 996 starting problem

Posted: Thu Sep 27, 2018 2:54 pm
by ollek
Using the Thermostart for only 10 seconds before cranking the engine is all too short. It will take at leas 10 seconds for the flame to start burning and the heating of the air in the inlet manifold will only start after that. Keep the key in pre hat position for 25 to 35 seconds and look at your watch, most people think that they use the thermostart for long enough, but 25 seconds is in practice a quite long time. You may be able to hear a "puff" when the flame starts to burn and the flame has to burn for at least 15 seconds before it heats up the air in the inlet manifold to a temperature that can help starting the engine.

Re: 996 starting problem

Posted: Thu Sep 27, 2018 5:03 pm
by Patrick98
Ok.. but the fact that she needs the preheat in the warm weather doesn't make sense..

Re: 996 starting problem

Posted: Thu Sep 27, 2018 5:21 pm
by rid54
Patrick98 wrote:
Thu Sep 27, 2018 5:03 pm
Ok.. but the fact that she needs the preheat in the warm weather doesn't make sense..
No, it doesn't. There seems to be some sort of problem. It may be compression that is not up to par, so this needs to be checked. Checking this, however, is not normally done by tearing down the engine, but rather by measuring the pressure and doing a leak-down test with the engine in place, only removal of the injectors are needed. If compression is good, you need to look at the injection pump timing and other relevant settings (max delivery), and also have the injectors checked. If compression is bad and evidence suggests that pistons are leaking, major surgery may be needed, but I suspect that nobody wants to take top and bottom off an engine without a good reason.

Re: 996 starting problem

Posted: Thu Sep 27, 2018 6:27 pm
by Patrick98
rid54 wrote:
Thu Sep 27, 2018 5:21 pm
Patrick98 wrote:
Thu Sep 27, 2018 5:03 pm
Ok.. but the fact that she needs the preheat in the warm weather doesn't make sense..
No, it doesn't. There seems to be some sort of problem. It may be compression that is not up to par, so this needs to be checked. Checking this, however, is not normally done by tearing down the engine, but rather by measuring the pressure and doing a leak-down test with the engine in place, only removal of the injectors are needed. If compression is good, you need to look at the injection pump timing and other relevant settings (max delivery), and also have the injectors checked. If compression is bad and evidence suggests that pistons are leaking, major surgery may be needed, but I suspect that nobody wants to take top and bottom off an engine without a good reason.
If there was a compression problem, are there other symptoms other than starting problems?? The tractor for is going 100%, and I have four other people saying that the tractor is going the best!

Re: 996 starting problem

Posted: Thu Sep 27, 2018 8:32 pm
by rid54
Bad compression may cause smoky exhaust under load, lack of power at low engine speed, high oil consumption, among other things. It is not certain that your problems are caused by bad compression, that is why there are suggestions here, that proper compression tests should be carried out. Before the engine is taken apart...

Re: 996 starting problem

Posted: Thu Sep 27, 2018 9:14 pm
by Patrick98
Thanks.. it's just very strange case.. I'll post on this page when I know what's wrong.. with the symptoms that you have said I don't think it's compression... Hopefully not..

Re: 996 starting problem

Posted: Thu Sep 27, 2018 10:10 pm
by philedge
Is the engine spinning over quickly when you try to start? My battery has seen better days and doesnt turn the engine over quickly enough to reliably start quickly. If I leave the battery on charge over night it starts much better as its spinning over noticeably quicker.