Have a ZD326 diesel engine Kubota with about 750 hours on it it belongs to the airport i work on. The filters are clean, diesel is good, battery is new. Cranking the engine cold or hot the engine turns well. The problem is it appears that the engine is overly "rich" I realize that is a gas engine term one must crank continuously for an extended period of time while smoke belches out and raw fuel as well from the exhaust. Crank long enough the engine will begin to run. It is a dog for a brief time while it clears the fuel smoking heavily eventually clears and runs smoothly. You can sit just above idle no problems pull the throttle all the way back to idle for any period of time the engine will start to run rough. Before I locate a shop to work on this what if anything can I take a look at or check. Thanks.
Kubota ZD326 Starting Problem SUPER RICH
- Thread starter sidehack
- Start date
Leaky injectors is a good possibility with those symptoms. A leaky injector will result in a hard start with a lot of smoke because of constant fuel dribbling from the injector(s) even when it is should be closed. As you raise RPM enough, especially under load, the percentage over-fueled becomes smaller compared to the needed amount so the engine appears to operate closer to normal.
Be very careful with this because a really bad injector can easily hyrdolock the engine given the small combustion chamber volume and then the repair gets really expensive if a connecting rod decides to see what the world looks like outside of the block.
Any chance it got some bad fuel in the recent past? I would pull the injectors and have a shop test them as a starting point of your diagnosis.
Rodger
Be very careful with this because a really bad injector can easily hyrdolock the engine given the small combustion chamber volume and then the repair gets really expensive if a connecting rod decides to see what the world looks like outside of the block.
Any chance it got some bad fuel in the recent past? I would pull the injectors and have a shop test them as a starting point of your diagnosis.
Rodger
Thanks. No the fuel is good we use it on our Kubota 8560 tractor which we mow the property with also. I take care of about 150 acres of airport in hill country! I will find someone who can test them and I am also looking for the glow plug location on the engine. I assume the have to be close to the injector. I work on GA engines, gas, have worked on lots of cars too first time I have messed with a diesel. Thanks for the advice.
You are welcome! If it was just hard to start, I would think glow plugs are it but if it continues to run unusually rough at idle after it warms up then the combination of symptoms make injectors a likely suspect.
Rodger
Rodger
Russell King
Well-known member
Lifetime Member
Equipment
L185F, Modern Ag Competitor 4’ shredder, Rhino tiller, rear dirt scoop
You also need to look into the engine oil and probably change it after the injectors are repaired or replaced.
The excess fuel can leak past the rings and fill the crankcase with diesel fuel.
The dealer should be able to sell you new injectors and sealing washers if you go that route but avoid cheap aftermarket injectors.
The glow plugs are usually near the injectors and they have a fairly heavy weight connection from one to the next. The top looks like a threaded stud with a small nut (which may not look like a normal nut) holding the connector down.
Post five times and then post a picture of the area if you still need help finding the glow plugs, sometimes they are well down in there and difficult to find.
The excess fuel can leak past the rings and fill the crankcase with diesel fuel.
The dealer should be able to sell you new injectors and sealing washers if you go that route but avoid cheap aftermarket injectors.
The glow plugs are usually near the injectors and they have a fairly heavy weight connection from one to the next. The top looks like a threaded stud with a small nut (which may not look like a normal nut) holding the connector down.
Post five times and then post a picture of the area if you still need help finding the glow plugs, sometimes they are well down in there and difficult to find.
North Idaho Wolfman
Moderator
Staff member
Lifetime Member
Equipment
L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
Just because the fuel is good, doesn't eliminate the possibility of there being algae in tank, lines, or fuel filters.
It doesn't sound like fuel delivery to injection pump is an issue.
What your explaing can be compression issue, glow plug issue (if it's only effected at start up and then clears up after warm up), and injector issue.
Pull the injectors and have them tested.
Test the glow plugs
Test the compression.
Is the smoke black or gray?
And read the WSM on how to do all of this.
Last edited: