Ct322 fuel system help

[thepumpguysc]

I guess if it doesn't like the throttle at start-up.. don't give it throttle.. as long as it starts, who gives a crap, right??
& yes, GOOD JOB figuring it out.. you saved yourself A BUNCH of money & down time, sitting in the dealers parking lot..
Seeing this was a "cold start" problem.. it woulda sat there for weeks if not months..
Swap a part, get it started, wait till the next day to see if it starts.. no start.. swap another part, get it started, wait till the next day to see if it starts.. no start.. swap a part.. on & on..
All the while, that clock was ticking -off, adding 100.00 bills onto your invoice.. Congrats..

 

[Kxnate]

A little theory on the cold start advance for that engine:
The cold start advance on the JD Series 250 engine is controlled by oil pressure in the hydraulic roller cam followers, or lifters, for the unit pumps. During cold starting, engine oil is sent by the cold advance thermostat to the cold advance piston in the cam follower via the cold advance oil gallery. The oil pressure lifts the piston 1.5 mm, thus increasing the overall travel length, or stroke, of the unit pump plunger. This advances the pump timing. The increase in stroke of the plunger causes the cam to raise the plunger sooner. This change results in the injection timing to be advanced approximately ten degrees. The oil pressure needed to provide full cold start advance is about 35 psi. A ball check at the base of the piston prevents pumping forces from collapsing the advance.
The cold start advance thermostat begins to block the oil flow when oil temperatures reach approximately 80°C (176°F). When the oil supply port to the roller cam followers is fully blocked, residual oil in the piston cup bleeds out through a drain orifice located in the cup end of the follower. At approximately 15 psi oil pressure, the cold start advance is fully disabled. The follower piston returns to the lower position, returning timing advance to the optimum performance level for an engine at normal operating temperatures.
Normally when there is a cold start issue I check the advance oil pressure to make sure it is funtioning properly (after checking the fuel return check valve first which you did of course). And yes, those engines will smoke and miss at start up when cold. That is quite common.

Good job Kxnate!

Very interesting, thanks for the info. I always wondered why the engine made a very distinct audible change at a certain point when warming up. I always assumed it must have had something to do with injection timing advance, but never knew for sure. I am guessing what you have just described is exactly what I am hearing.

 

[Kxnate]

I guess if it doesn't like the throttle at start-up.. don't give it throttle.. as long as it starts, who gives a crap, right??.

Yep my thoughts exactly, I just read that in the manual and wanted to try it out and see what it did. I imagine JD has a reason for telling you to do that, and I tend to try to do things by the book, especially with expensive pieces of equipment. But yes, I probably won't do it anymore. The check valve wasn't just a cold issue actually, it had been doing it all summer long, it just kept getting worse as it was getting cooler, but I totally understand what you are getting at with the dealer. I was struggling to verify for a while if the check valve cured it because the temperatures plummeted the day I changed it, and I was not accustomed to how hard that thing is cold starting as I just purchased it this spring, so I had to start plugging it in to verify the check valve really was the cure.

I like to try to fix as many things as I can myself before I resort to the stealership, so I appreciate your pointers as well as everyone else's. I auto mechanic'd for a few dealers for a couple years out ofhigh school, so I understand them and try to avoid them like the plague haha.

Thanks again everyone!!

 

[Jmichaelis11]

Should the cold start advance still activate when starting after engine is already warm? they seem to from any of this series engine i've seen but you wouldn't think it should! good information though thanks

 

[mg2361]

Should the cold start advance still activate when starting after engine is already warm? they seem to from any of this series engine i've seen but you wouldn't think it should! good information though thanks

No, the engine will not be advanced unless the oil temperature drops below 176 degrees. Of course sitting through a lunch break could bring the temp down enough for it to activate, but would shut off fairly rapidly since the oil will still be pretty warm at start up. The engine oil thermostat for those engines do fail more frequently than many tech's realize. That is why I test the advance galley oil pressure for cold start complaints.

 

[Jmichaelis11]

Okay good information mine seems to ldle up for just a split second every time I start regardless of temp or run time. I should look into it I guess

 

[mg2361]

The engine "idling up" at start up is from the fuel rack being at full fuel at start up and then when the engine speed is fast enough to throw the governor weights out it comes back to idle. That is normal on all 4024/5030 JD engines. That has nothing to do with the "cold start advance" which advances the timing of the engine only.

 

[mg2361]

Correction: That statement above applies to"pre-electronic" engines.

 

[dan j cassidy]

kxnate: what did u find out?; did u get your machine running? i am having the same issues. thanks