G1900 Diesel Start/Run Problem

[charliet05]

G1900 D722 engine hard starting and smoke/missing at low rpm and top rpm. Runs fine at 50 % to about 80%. No smoke, runs smooth.

Have removed injection pump and injectors. Took to a certified fuel injector service shop. They cleaned and checked/calibrated pump and injectors. Did "minor repair" to one of the pump pistons. Said they didn't find anything wrong with the pump/injectors that would have caused any "major running problem".

Cleaned (and dried with compressed air) around injectors and pump prior to removing. Had area around pump/injectors covered with paper shop towels and masking tape during service time. Carefully removed just prior to re-installing. Bleed fuel supply line at pump, injectors at fuel line fitting.

Installed using torque specs in the Kubota G1900 manual. Did not install new pump shims. There are two; both shims (.007" ea) were cleaned using WD40 and shop towels (no scraping or sanding).

The engine is still hard to start (getting it fire). Temp was about 45 deg f after overnight low of about 20 deg f. Good battery, engine turned over normally. Would fire after "running" the glow plugs about 20 sec's, run maybe 5 sec's and die. With glow plugs on for about 45 sec's, engine would fire and run after several attempts. Black and very light grey smoke (lots) at about 800 - 1200 rpm. Would smooth out at about 1500 and run without any smoke/missing up to about 2200 to 2500 rpm (estimated). At full throttle, intermittent missing would occur with light grey smoke. Let run at mid throttle for about 15 min's before moving to full throttle. I think long enough to "force out any remaining air bubbles in the fuel injection system. Lift pump puts out a good stream of fuel when disconnected and also at the pump bleed port.

Have new air filter. Have not made any changes other than adjusting the idle speed screw and "taking up some slack" in the throttle cable (cable nuts at the cable mounting "slot".

Have three older diesel farm tractors that are cranked in all kinds of weather. All have a tendency to run rough in cold weather (with the expected diesel smoke at start up) but will smooth out in a few minutes.

This D722 seems to be more of a headache. I am having a real problem understanding why it runs "very good" at mid range but not at the lower range. If it was a compression problem, would it run that good at mid range (and higher) without any smoke/missing? I don't have an operators manual and try to start engine the same way I start the farm tractors (except no ether).

Will greatly appreciate any time/suggestions/help,
Charlie

 

[North Idaho Wolfman]

Being that it misses on both low RPM and High RPM to me suggests a intake or exhaust valve problem, could be as simple as a valve or valves out of adjustment.

 

[charliet05]

Appreciate your response!!

Can probably try that this week end. Snowing now @ 19 deg f. Supposed to be around 50 this weekend.

Charlie

 

[SteveF]

Did the problem gradually develop or come on all of a sudden?

You have covered most of the mechanical bases and should explore valves and timing as Wolfman suggests... have you already ruled out ignition issues?

 

[charliet05]

SteveF, Appreciate your response.

Purchased it in Jul-13. Have had running issues since I've owned it. Just much worse in winter weather.

Have not done a compression test (no test kit) due to how good the engine runs at greater than 50% throttle. Timing is done with the shims, I think(????). If compression or timing issues, would it run good at the mid engine speeds (50% to 80%)?

Charlie

 

[trouble11]

Please keep us posted.

 

[charliet05]

Adjusted the valves to 0.006" this afternoon. Found two valves were pretty close to 0.006" and the other four were greater than 0.007" (.007 gauge was very loose when inserting). None were below 0.006".

Engine started after several attempts (temp around 55 degf). Runs somewhat better now. The "better range" is now wider than before adjusting the valves.

Still have considerable light gray smoke at low speed; some smoke/missing at top rpm. Engine sounds/runs good in the mid range. Decreasing throttle from mid range speed down to the low speed, the engine starts missing/smoking at about 1/3 throttle (estimate about 1000 to 1200 rpm) and gets rougher as the throttle is decreased to minimum. At minimum throttle, engine runs very rough and has considerable light gray smoke. Then as the throttle is slowly increased, engine "acts like" a gas engine when the choke is sticking (engine seems to want to stall on a rich fuel mixture). Smooths out (no smoke) at about 1/3 throttle. Runs/sounds very good from 1/3 all the way to about 90% throttle.

I noticed the "missing" at top speed with the deck disengaged last summer. Would "smooth out" when the deck was re-engaged. Seemed to have adequate power for mowing.

Plan to check fuel timing when I "figure out how to do it". Supposed to be cooler and wet again next week. Hope to catch a warm day. Cool out where the mower is.

Again, appreciate any and all suggestions,
Charlie

 

[North Idaho Wolfman]

I don't remember did you dump old fuel and replace it with new and new filter?
If not I would do that!
Does it have blow by out the valve cover hose?

 

[charliet05]

The previous owner indicated the fuel lines (and filter) are new from the injector to the fuel tank along with a new fuel pump. Assumed he cleaned the tank and lines when installing the new parts. Indicated he had all of the work done with the help of a dealer he had connections with (family, close friend??). There are also new electrical parts. He indicated all parts were purchased from Kubota.

I ran several tanks of diesel through the system last summer. I would think the fuel in the tank is mostly new. All fuel bought from a local store that "turns over" diesel rather quickly. I will check fuel/lines ASAP.

Last summer, when the engine was hot (after mowing for two to three hours), did see some vapor "coming from" the cover hose. Did not seem excessive to me at the time. But this is my first experience with a Kubota diesel and first with a small diesel. Did not check that yesterday. Will check, maybe today.

The hour meter now indicates 1357 hrs (think it had about 1313 when I bought it). Changed oil and filter before I started using the mower and level has not "gone down" very much. Check oil before each use.

Appreciate your response and suggestions.

Charlie

 

[charliet05]

North Idaho Wolfman,

Started the Kubota this morning. Yes, it does have vapor coming out of the blow by hose. Volume increases with engine speed. It's there even when in the "engine smooth range". Don't remember this much vapor last summer. About 45 degf here this AM.

Thanks,

Charlie

 

[North Idaho Wolfman]

Sadly if the vapor is heavy to excessive it means one of 2 things, bad rings (compression blow by) or bad valve guides (compression leakage).
2 ways to tell:
Pull the valve cover and run it, if the smoke comes from the bottom end then it's rings and if from the top it's valve guides.
If you can get a hold of a diesel compression tester that will also help narrow it down.

 

[charliet05]

Cold wet weather is forecast here for most of the week. Will pull cover and check the blow by when weather permits.

Don't have access to a compression kit just now. The cheaper ones seem to have pressure gauge issues. Looking for a cheaper kit that would work properly. A good used one seems to be hard to come by.

If I should have to rebuild the engine, would a used one be an acceptable approach? I see that several used D722's are for sale within a day's drive round trip. Will any D722 fit the G1900 or will it have to be from a G1900. There is a 20 hp D722 about 150 miles away that was pulled from a Bob-Cat with less than 400 hrs run time.

Do not have enough room in the shop right now for disassembling the engine. Presently trying to resolve the limited shop space problem.

Really appreciate your responses. Have been a big help.

Will post a reply on the blow by issue. Then will keep the thread posted on progress with the engine.

Charlie

 

[North Idaho Wolfman]

There might be some variations to different D722's, but most if not all should be fixed by pulling off parts on your motor to make it work.
Like changing intake, exhaust manifolds, brackets and such.
If you can get a good used motor for cheap that's great, I did the same thing for my B, it was quicker and cheaper than rebuilding.

 

[charliet05]

North Idaho Wolfman,

Last week, I attempted to perform a compression check. Ordered a compression kit and also ordered an adapter for a D722 glow plug hole. Adapter did not "fit" the compression gauge fitting and leaked when testing. With the glow plug hole area clean, I attempted a check with a 10mm adapter that came with the kit. Holding the flat end of the 10mm firmly against the head (over the hole), I "got" the same reading on the front and the middle cylinders (a little over 300 psi; gauge pressure increased in steps as expected until stabilized). The rear cylinder was about 60 psi lower than the front and middle cylinders. When inserting the Kubota 8mm adapter, I encountered carbon in the rear glow plug hole (resistance encountered about 1/4 " from seating of the adapter) and also removing the rear glow plug required more wrench pressure than the other two. Front and middle cylinders had no resistance and seated without any problem.

Pulled the head this morning. Have not dis-assembled head or block. Most of the head gasket came off with the head. A few small (1/2" - 1") pieces of the gasket remained on the block. Was expecting the head gasket to remain in one piece upon reading the G1900 service manual compression check section.

No visible scratches/cracks on the block. All cylinders looked pretty much the same. Something that "looks like" radial wear marks in the top 1" - 1.5" area of each cylinder (no ring "lip" at the top). The lower part of the cylinders appeared to be free of these "marks". My fingers and finger nails are somewhat old and their ability to "feel" small scratches are "not what they were a few years ago". I could not feel the scratches on any of the cylinders and nails could not "grab" on the marks.

Looked at the "bottom" area of the head. Areas around all valves were surprisingly clean. No sign of carbon deposits on the rear valves either. Have not checked for irregular head face yet.

Would like to keep cost "down as much as possible".

We are now experiencing heavy snow in our area (maybe a foot). As soon as this clears out and we can get snow plowed/moved, may be able to get a local experienced diesel mechanic to "take a look" at what I have.

If you have any suggestions, they would be greatly appreciated.

Charlie

 

[North Idaho Wolfman]

Did you do the blow by check? That would help you pin point Valves or Rings.
Sounds like it's not cleanly firing on the rear piston, could be bad Injector, Valves or Rings.

 

[charliet05]

A lot of snow here Tue and Wed. Just getting back to the engine this afternoon.

Just completed a more thorough "check" on the engine block. Two of the three cylinders (#2 & #3) definitely have issues that would cause compression loss. Engine seems to have recently been "overhauled" and it was done badly. Probably why I was sold the G1900 "in the first place".

Now in the process of deciding between taking the block to a machine shop (hard to find one these days) to be "re-bored" or trying to get a used engine.

Found 20 hp D722 that, as I was told, "had low run time hours" (less than 1000 hours) out of a piece of farm equipment. Seller said it would "work" in the G1900 without any problems. I'm feeling a little "gun-shy at the moment".

Appreciate all suggestions/comments (especially "Idaho"). Good forum!! Will post as soon as I get this thing "going" again.

Charlie

 

[charliet05]

Picked up the used D722 engine today. Somewhat different "setup" than the G1900 engine. In the process of changing mounting brackets, flywheel, front pulley, etc.

This engine has a hydraulic pump that appears to be connected to the injector cam. Pump is mounted to the end of the injection pump. Plan to remove this pump. Can it be removed without causing damage or engine problems?

There appears to be a small (3/4" ???) coolant type hose connected (with hose clamp) at the bottom of the injector pump housing and "points down" toward the oil pan. All hoses and wiring were cut when the engine was removed. Anyone know what this hose could be?

The flywheel on this engine is thicker than the one on the G1900 engine. Seems like I will have to use the G1900 flywheel in order to keep the PTO belts aligned. See any problem with changing the flywheel?

Charlie

 

[North Idaho Wolfman]

No problem removing the hydraulic pump, just make a 1/4" to 3/8" thick plate and gasket or silicone to block off the hole.

The 3/4" hose connection was a heater bypass hose or radiator bypass, you can either pull the fitting and plug or just put a cap on the fitting.

If the flywheel holes line up (Note: there is one hole that is in a slightly different spot than all the rest for flywheel alignment) and the spacing on the back side is the same then it should be no problem.

 

[charliet05]

Appreciate your response! Great help! Hope to install/crank engine this coming week.

 

[charliet05]

North Idaho Wolfman,

I really appreciate your help/time. I have "run into" another concern with the recently purchased D722.

I am in the process of changing manifolds between the two D722's this afternoon. The intake manifold seems to have had moisture in it sometime back (is not recent). The ports to the head have surface rust (even back into the ports). The seller said the compression was 400+ pounds on each cylinder. Also indicated the engine had been "run a number times without any problems".

How much of a problem is this?

Should I remove the head?

Have a 14 day return period. Don't know if "pulling the head" will affect the return or warranty.

Thought I had better ask about this before I proceed. Was hoping to start the engine today.

Again appreciate your help/time,

Charlie