Tractor bogging/missing

[heymack]

I have a New Holland TT60 that only has 154 hours on the meter. First, a bit of history. Back in 2007 when the tractor only had a few hours, it would randomly die in the field, but would always re-start, sometimes minutes later and sometimes hours later. The selling dealership sent a guy out with a trailer and ran it back to the shop. He brought it back a few days later telling me that the solenoid on the injector pump was the culprit. Since that time the tractor hasn't missed a beat.

Now, fast forward to last Thursday. A buddy was disking a few acres when the tractor just died on him. We let it cool down and added about 5 gals of fresh diesel thinking it may have run out of fuel (gauge showed about 1/2 tank and we could see some in the tank, but tried new fuel anyway). After adding fuel, the tractor fired right up but while driving back to the barn, it sputtered and ran like crud. I let it sit till Saturday afternoon without doing a thing. When we tried firing it up, we couldn't get a thing other than cranking. I put a new fuel filter on and drained all the diesel (around 15 gallons). Thinking back to the fuel solenoid, I contemplated replacing it, but it is a $130 part and upon further inspection, realize that the part on my tractor is the original piece, inasmuch as I can tell it has never been removed (covered and sealed in original paint, same as rest of engine). Nonetheless, I took it off the injection pump, made sure the plunger was moving freely inside and put it back on. Tractor still cranked, but didn't run. Thinking to myself, "what could keep it from running?" I decided that the sensor under the seat might be the problem so I jiggled the wires at the connector, set the seat back down and tried firing up again to which it started right up without hesitation.

Now to the problem at hand. The tractor runs great at idle, up to 1600 RPM and above 1800 RPM, BUT at around 1700-1800 RPM the thing misses, sputters, bogs, etc. making no power whatever....What the heck? It does it sitting still as well as while driving.

Any thoughts? Remember it has fresh fuel and a new fuel filter. I also bled the fuel lines, checked the oil level, radiator fluid, air filter, etc.

 

[woodlandfarms]

Did you clean out your fuel tank? Especially where the tank meets the hose, that connector can get randomly clogged...

 

[heymack]

Did you clean out your fuel tank? Especially where the tank meets the hose, that connector can get randomly clogged...

No, I didn't clean the tank because plenty of fuel is getting to the pump. It only cuts out at certain RPM's, right at 1700, but runs very strong at 2000 RPM. The problem is extremely consistent in that it only/always misses at the exact same point in the RPM range.

 

[LoneCowboy]

Is it timed correctly?
i.e. did the injector pump skip a gear?

Sounds like it. (my first thought would have been woodlandfarm's too, but if it only dies at 1 specific rpm, that can't be it.)

 

[Hooked_on_HP]

Could it still be the seat switch. Is it easy to bypass, just for test purposes.
Bill

 

[Soundguy]

Yeah.. maybee the machine vibrates at the correct frequency at that rpm range to make that flaky switch cut out a lil???


soundguy

 

[heymack]

Thanks for the help so far.

If it were a timing issue, wouldn't it run poorly throughout the rpm range?

How do I bypass the seat switch?

Some more details. Really needing to shred some areas yesterday, I decided to give it a shot despite the problems. In the light stuff, the tractor ran fine and maintained around 2000 rpm (540 rpm pto) but when I got into the heavier/thicker stuff it would lose rpm's and begin to bog. It did this around 10 times and each time I'd feather the throttle lever and power would restore in the 2000 rpm range. Well it did it every time except the last time when the tractor died completely and never restarted. Hence, it's sitting out in the field as I type, dead as a doornail.

Whether it turns out to be a $5 fix or $500 fix, this is ridiculous for a nearly new, meticulously maintained tractor with so few hours.

 

[RWolf]

Still could be fuel related and that is what I'd suspect. You could have plenty of fuel at idle or slightly above but as the demand for more fuel is created you could have a partially clogged fuel line. IMO take off all lines from the tank to the injector (including filter) and blow compressed air through all hoses. You might find a piece of crud that's only letting a bit of fuel through.

Good luck.

 

[kthompson]

I agree with RWolf, but one more out of the normal, check your air intake and filter. Look for such as wasp nest or mice nest. You are sure your fresh fuel is fresh and has NO water in it? Guess all places sell a far share of water in their fuels.

 

[heymack]

Good news, the caper is solved.

After banging my head against a wall for 15-20 minutes this evening, a little light finally lit up. If you've never taken a fuel shut off solenoid apart they're pretty simple inside. There's a spring that looks like it came out of a retractable ballpoint pen and a little plunger that moves up and down depending on current or no current. Anyway, I though that maybe the plunger was stuck downward thus blocking the flow of diesel into the injection pump. I also though that if I took the plunger and spring out of the assembly maybe it would solve my problem. Low and behold it did. The tractor fired right up and ran like new all up and down the rpm range. Problem is now I cannot stop the tractor unless I stall it with the clutch....off to New Holland for a $130 part tomorrow.....yipeee!!!

Thanks again for all the help.

 

[Soundguy]

Thanks fro posting back.

So.. does that fuel solenoid trigger from the seat switch?

IE.. if you get up out of the seat does it use the fuel solenoid to kil the tractor? If so.. you may repalce a 130$ part and figure out the seat switch is still bad!

check it!

soundguy

 

[RWolf]

Glad you found it.

 

[heymack]

Thanks fro posting back.

So.. does that fuel solenoid trigger from the seat switch?

IE.. if you get up out of the seat does it use the fuel solenoid to kil the tractor? If so.. you may repalce a 130$ part and figure out the seat switch is still bad!

check it!

soundguy

Good catch.

I went by and talked with the NH service manager the other day and he basically said the same thing. Said the solenoids don't go bad, rather it's a sign of an electrical problem (short) somewhere else that's triggering the solenoid. I checked power at solenoid plug, 0 volts......uuugh!

The good news is the tractor runs fantastically without the solenoid plunger inside. The bad news is I have to "pop" the clutch to kill the machine. I'd love to put some sort of mechanical switch in, similar to my 555A's, to fix the problem once and for all.

 

[Soundguy]

Your method of killing the machine isn't real friendly..

I'd fix that seat switch and / or jimmy it with a toggle switch to diagnose it.. and go from there.

soundguy

 

[radioman]

I am a little confused. Since I am not familiar with your tractor, I observed the solenoid on mine. I see the plunger is out in normal position and in for cutoff then it pops back out after vacuum or something lets the plunger back out after tractor is off. It looks pretty simple to do it mechanically with a cable or open the hood and push in by hand to shutoff. Can you do the same with yours ? The way I understand it thanks to TBN, is that diesel engine is shutoff but cutting the fuel. I wonder if the simple gas shutoff valve that we see on the little Briggs and stratton engines would work in a pinch as well ? If this little valve works, then shouldn't this be a safety feature be installed on all diesel engines in case of emergency a engine needs to be turned off if the solenoid fails ?

On a side note, I'll be pulling for you to find that phantom electrical short.

 

[Soundguy]

? If this little valve works, then shouldn't this be a safety feature be installed on all diesel engines in case of emergency a engine needs to be turned off if the solenoid fails ?

.

Look under yer fuel tank.. got a shutoff valve on it.. most tractors do.

soundguy