Compression Test & Stop Lever/Knob

[tak1313]

Good Morning All,

My name is Wayne, and I live in NH. I've lurked for a few years, since I got my old B9200HST to do stuff around the property, but never posted before, as I usually find any solution I need from searching.

I'm currently having a problem for which I will be pulling the injectors to test and possibly rebuild/replace and since they will be out, I will also be doing a compression test. The last time I started it in the summer, everything was fine, but when I started it for the first time this winter, it ran really rough and blew white smoke. I'm suspecting a leaky injector, as it started and ran absolutely fine the last time I ran it in the summer.

Anyway, looking at the service manual, the procedure states to pull the stop lever when doing the compression test to stop the fuel.

This is my first tractor ever, let alone my first diesel anything, but my understanding of the stop valve is that it also decompresses the cylinders. Am I wrong - does it just stop the fuel delivery? If it also decompresses the cylinders, how can you do a compression test with it pulled?

Thanks for any help, this is a GREAT resource board!

 

[D2Cat]

tak1313, welcome! Now you'll feel free to ask questions, but lurking is OK to.

You mention pulling the injectors to have them tested. You also mention your tractor ran fine last summer.

Before removing parts I would suggest to drain all your fuel, install new fuel filter, bleed air out and try starting the engine. You may simply have bad fuel with an addition of condensate moisture from setting so long.

The decompression knob is a mechanical lever that doesn't allow the valves to close. This allows the engine to turn over faster. This feature can be used to warm a cold engine some to help it start with less stress on the starter. Once the engine starts, just push in the decompression knob and you're "off to the races".

The fuel shut off lever does just that, shuts off the fuel. Use this lever to stop the engine, not the decompression knob .

Might re read your manual. I do not think the decompression knob will in any way stop fuel from flowing. The fuel shut off lever does this.

Wayne, go slow in your "getting it going process" or you could be working on the wrong problem.

 

[Daren Todd]

Using the decompression lever doesn't stop fuel from flowing. It just releases the compression to the motor. I have a 30 plus year old starter on my tractor. It will spin the motor over fine in 50° plus weather. But below that, the bearings like to drag

I usually glow plug mine for around 1 minute when its below 40°. Then pull the decompression lever and get the tractor spinning up to speed. Then throw the lever in, and it will usually fire off within 1 or 2 revolutions. If it's really cold, I may have to do this twice to get it to start.

If you do it in a garage, you'll really notice an unburned diesel smell on initial start up. That is normal since your pumping diesel into the exhaust

 

[North Idaho Wolfman]

The fuel stop lever is on the right below the steering wheel, it will be a red if not painted over. most are spring loaded and return to a run state when released.

I would also do as D2Cat suggested, and dump the fuel and replace it!

 

[tak1313]

Thanks Daren and D2Cat.

I should probably give more info, but first it sounds like the decompression lever and the stop lever are two different levers?

The "stop lever" I'm thinking of is the knob below the right side of the main "dash." It is pulled to stop the engine. I thought that it did two things - stop fuel delivery and decompress the cylinders.

The Service Manual section regarding compression testing says (after attaching the tester):

5. Cut the fuel (pull the stop lever), and run the engine for 5 to 10 seconds (at 200 to 300 rpm) and read the maximum pressure." (italics mine)

I assume this is what is referred to as the "engine stop knob" in the owner's manual (the one used to stop the engine).

As far as doing 'so much,' it's cascading events. When the rough running/white smoke was happening, I cleared the tank, filter, etc. and in 'partial testing,' was cracking each fuel line in sequence at the injectors to see if any one injector made a diff.

When doing that, one line was tight enough that it also SLIGHTLY unscrewed one of the injector. I tried retightening it, but noticed that the little diesel that spilled from the line was bubbling slightly from the cylinder pressure escaping around the injector. Tried tightening it within reason (to make sure nothing strips), but there is still a tiny leak - I think because it's all original, the copper injector gasket must be heat and pressure hardened after all these years so now can't seal properly.

So OK, I have to pull that injector to replace the gasket at minimum. So OK, since I have to pull that injector, I might as well pull them all and have them tested, since there's a local injector shop that tests mechanical injectors for free. So, OK, since I'm pulling all the injectors, I might as well do a compression test to make sure, seeing as how old this tractor is and everything is original.

The white smoke isn't just at startup - it's while running, even after warm up as well. It seems to be one cylinder, based on how it sounds/when it spits the smoke (kind of erratic and not 100% consistent when it happens, though consistent enough to run like crap) - that's why I was doing the 'crack the line' thing to see if any one made a diff.

I might try re-cleaning the tank/lines again, though, as it did make a bit of difference the first time.

 

[tak1313]

NIW - yes, that's the lever/knob I'm thinking about when I read "stop lever." I mistakenly(?) thought pulling that also decompresses the cylinders. Mine doesn't have a 'return' spring though - pull out to stop, if you want your engine to run, push it back in.

As a side question, then, does the B9200 (V1200 engine) have a decompression lever? I understand some tractor diesels do not.

 

[D2Cat]

On your B9200, I am not positive it has a decompression knob, but I think it does. If it does it will be on the left side of the dash, down to the lower part, and probably have a RED knob to pull. It should have a spring on the front of the valve cover to help close the valves, but you have to manually push or pull the knob to activate the compression release.

 

[North Idaho Wolfman]

No, the B9200 did not come with a decompression lever/ knob.

 

[tak1313]

Ok, thanks for the info NIW. So I should be all set pulling the knob for the compression test.

 

[North Idaho Wolfman]

Yep pull the stop knob/lever and it cuts the fuel.
If you pull all the injectors it will spin much easier.