Minimec pump Pressure

[Fixersteve]

Right this were I am at the moment with trying to get my NP Super Major starting under her own steam. I've got 300 psi compression on all 4, stripped cleaned and recalibrated all 4 injector using proper sims injector tester. All timings are spot on. She isn't sluggish when she is cranking over but she still needs a bit of brake cleaner to get her going. When she is running she ticks over pretty and pulls like a train, but if I stop her and try to restart her she still won't fire.

So my question is..... Could it be that the pump isn't generating enough pressure to open the injectors when she is cranking??? What i am planning to do tomorrow is take one of the injectors out of the head and conect it to the injector pipe and see if the injector is firing when she is cranking.

Any thoughts.......??

Many thanks
Steve

[JC]

If you're not getting enough pressure, it would be because the pump plungers are worn or scored. If that's the case, there should be a lot of fuel running out of the pigtail pipe. What are the popping pressures on the injectors?

[curtsat15]

I have the same problem occasionally. My problem is leakdown in the fuel line. If you prime it, does it help?

[Fixersteve]

Hi Jc, i dont have any fuel coming out the pigtail pipe, and the injectors have been set to crack of at between 2720 - 2794psi and were atomising the fuel perfectly.

[Fixersteve]

So i have taken the injector out of one cylinder and it is firing fuel in when cranking over. My next thought is perhaps she is turning over fast enough to generate enough heat and compression?? Perhaps lazy starter???

[Pavel]

So close, Steve, but frustratingly not quite there yet -- most of us know the feeling.
With your starting problems I would be inclined to suspect, and check 2 things.
As you will no doubt be aware, unlike a petrol engine, there is no throttle plate air control on a diesel -- it is fully open to ambient air at all times. The fuel supply over the whole rev range is controlled only by the governor -- in your case a mechanical one -- and this could be suspect.
But before having that looked at I suggest you check out the settings of the idle set screw and the stop control lever.
The idle screw should have an exposed length of 21mm, measuring from the pump body, not the lock nut, to the outer head of the screw. It is the screw protruding to the rear of the pump, and behind it.
Next, with the 'throttle' lever closed, remove the the stop control cable and the lever. Then turn the grooved shaft anti-clockwise as far as it will go and refit the stop lever at 30 degrees from the vertical with the cable fitting forward.

Pavel

[Fixersteve]

Thanks Pavel i will have a look at both of those this evening when i finish work. In your opinon would you say that 300psi of compression would be enough for her to start under her own steam??

I know i have got either wear in the engine or stuck piston rings as when i run her hard for abit she is blowing a fair amount of oil out the timing case breather.

thanks
Steve

[Pavel]

Ah, yes, well Steve! Low compressions, as indicated by blowby, are most likely your main problem. Add low air temperatures, plus fair wear and tear to the fuel delivery system, and starting will be a problem.
The SMD has a compression ratio in the middle of the 16s to 1 and needs this to achieve the internal temperature of about 500 C in order for combustion to take place. Once the engine starts and warms up, then its efficiency becomes better than marginal.
In the short term, at least until time and finances become available, whilst not recommended for the long term, I would continue to use an ether product for starting as a tow start would, I imagine, not always be available.
I admit that when I first got my SM I had to resort, for a couple of months, to ether for starting as 700 sheep would not accept hunger as a price to pay for my, and a tractor's, inability to deliver food. As they say; "when needs must; the devil rides."

Pavel

[Fixersteve]

Thanks Pavel for your advise. Would you suggest new liners and rings? or more???? or do i go the whole hog and get an engine overhaul kit from agriline??

[Tubal Cain]

The reccommended injector set pressure should be 160 atmospheres or approx. 2350 psi. I would suggest that you reset the injectors to pop at the lower pressure.

Gerald

[AdrianNPMajor]

Hi Steve

You've done so much work on the rest of the tractor that it would make a lot of sense to do the engine as well, if finances in these hard times will allow.

Full engine rebuild is the way to go - pistons, liners, etc. Not much point in pulling her all apart and not doing everything whilst you're at it. With perhaps one exception - I was advised to check the crank before getting it reground. I've done two engines and in both cases the crank was checked and found to be fine - so just new bearings were required. There's a good chance that yours will be ok too. Worth checking first. Definite case of 'If it ain't broke, don't fix it.'

New oil pump is a must. The auxiliary shaft bearings and seal will also need replacing. And very importantly with regard to your compression and starting issues, getting the head refurbed is a must also - skimmed, valve seats reground, new valves and springs, new guides.

Put her all back together with that lot done and she'll crack into life with just a dab of the starter. Keep her well supplied with fresh oil and you'll have left the planet before she shows any sign of flagging again!

Nice project. I'm envious!

Best

Adrian

[AdrianNPMajor]

Forgot to mention the camshaft. The lobes on mine showed signs of wear as did the cam followers. I replaced both.

[Pavel]

Steve, I support TCs suggestion that you re-calibrate the injectors to the lower PSI. Whilst higher pressures give better atomisation, and therefore a cleaner and more efficient 'burn', there is the strong probability that a beyond it's best injector pump may not be able to overcome the higher injector pressures so as to give the required volume of fuel because they will be opened later and close earlier. Your report of white smoke would tend to bare this out.

As to whether or not a full monty overhaul is required; that rather depends on the wear found on examination -- and that can only be ascertained after removing the head. Certainly, with blow-by piston rings, they will require replacing. Whilst I must admit I am not a fan of this modern 'throw away society' thinking -- if one part is broken, then throw the whole lot away and replace the complete assembly -- it does mean that checking all wearable parts is important so as not to have to rip the whole thing apart again in the immediate future to attend to something that should have been done in the first place. For instance, I remember a bloke who replaced all the main and big-end shell bearings, only to be noisily reminded later that the thrust washers should have been replaced as well.
To help in making a decision check out the Agriline prices. You will find that a complete engine overhaul kit is cheaper than just buying individual parts -- with the added bonus that it includes valves and guides for the head. Of course, shell bearings and thrusts are not part of the kit because of the different oversizes.
The adage of my mentor was 'measure twice; and cut [or replace] once' -- I've found it's a good policy.

Pavel

[JC]

Hi Gerald and Pavel,
My repair manual says that the injectors should pop at 175 to 185 ats. Where did you find the 160 spec.?

[Tubal Cain]

I have just realised that I qouted the set pressure for the Dexta!

Gerald

[Fixersteve]

Hi Chaps, Thanks for all your replies to my post and apologies for my lack of responce, Have had a busy couple of days doing some work with our latest All Weather lifeboat and Launch and Recovery equipment.

I have managed to order a complete engine overhaul kit from Agriline though, After deciding if im going to do it i may aswell do it properly. And have peice of mind that its not going to let me down in the middle of summer. So im going to start stripping the engine this evening i think.

[Pavel]

Whilst I do not have access to all the FMD technical specifications, but rely on gleaning those from these pages, TC still had a point. Re-setting the injectors to the lower, 175 atmos. [2572psi] may have made the difference to your starting difficulties.

Pavel

[Tubal Cain]

An extract from Wikepedia just for info:-
Advancing the start of injection (injecting before the piston reaches to its SOI-TDC) results in higher in-cylinder pressure and temperature, and higher efficiency. Delaying start of injection causes incomplete combustion, reduced fuel efficiency and an increase in exhaust smoke, containing a considerable amount of particulate matter and unburned hydrocarbons.

Lowering or raising the injector set pressure results in earlier or later injection.



Gerald

[JC]

I'm of the opinion that your Major will run and start best when everything is set to Fordson specifications. If you have concerns about your injector pump, take it to a fuel injection shop and have it tested. It probably wont cost much to do that.

[AdrianNPMajor]

Hi Steve

I'm good at stating the bl**ding obvious, so forgive me if I'm doing it now.

If the liners are tight - the ones on my NP Super were extremely tight - apply pressure with your drawer then deliver a sharp tap with a lump hammer to the crossbar at the base of the liner, then apply more pressure and repeat.

Before you disassemble the big ends and main bearing caps, not a bad idea to dot punch them and the cylinder block in the corresponding places so you know what came from where. Dot punching the con rods so they go back in the same order is also not a bad idea.

When it comes to removing the oil gallery bungs, I found making a pull-through as if for cleaning the barrel of a rifle worked really well. All galleries need to be spotless, as you will know. I think you've got compressed air available in your workshop, which is ideal.

Wire brush on the end of an electric drill is magic for cleaning up the block, especially the apertures top and bottom where the new liners will sit.

Petroleum jelly smeared in the grooves will hold the new O ring seals in place when you slide the new liners into place.

Wash and lay out all parts, bolts and nuts methodically. Time consuming but also time saving when you get to the good bit - reassembly.

Hope some of this is helpful. You probably knew such basic stuff anyway, but no harm in making sure.

Best

Adrian

ps Any chance of photos before during and after rebuild?

[Fixersteve]

Thanks Adrian for your helpfull points! I will deffinatly be calling on you for some more advice during the rebuild. And will defo take lots of pictures. Will try and post a picture of what ive been playing with for the last couple of days. also had a txt msg today from agriline to say my rebuild kit will be here tomorrow


Untitled by fixersteve, on Flickr

Untitled by fixersteve, on Flickr

[henk]

Does it have a Fordson engine in it?

Seems like a serious tug.

[JC]

Thanks for the pictures. I'm happy to see that someone is using something besides a Major to launch a boat!
Good luck with your rebuild. I'll be curious to see what you find when you tear it down.