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If your Kubota ZD28 is starting at wide open throttle with black smoke coming out of the exhaust and the throttle is not working, it could indicate a problem with the fuel system or throttle linkage.
Here are a few potential causes to consider:
Incorrect injector pump timing: If the injector pump was not installed correctly or the timing is off, it can cause the engine to start at full throttle with black smoke. You may need to re-time the pump to resolve this issue.
Clogged fuel injectors: If the fuel injectors are clogged, they may be supplying too much fuel to the engine, causing it to run at full throttle with black smoke. You can have the injectors cleaned or replaced to fix this problem.
Faulty throttle linkage: If the throttle linkage is not properly adjusted or is broken, it can prevent the throttle from working properly. Check the linkage to ensure it is properly connected and adjusted.
Air intake system: Check the air intake system for any blockages or leaks. If the engine is not getting enough air, it can cause it to run at full throttle with black smoke.
It's important to address this issue promptly, as running the engine at full throttle can cause damage to the engine and other components. If you're not comfortable diagnosing and fixing the issue yourself, it's best to take your Kubota ZD28 to a qualified technician who can diagnose and fix t
You will need to have the THROTTLE RETURN DASH-POT
on your (unspecified) carburetor tested and adjusted... and the IDLE SPEED correctly set.
Idle Speed and a slow rate of RPM reduction is
critical to the proper function...
Some LESSOR "mechanics" will attempt to raise the
IDLE SPEED to compensate for a malfunctioning
DASHPOT... This will PROFOUNDLY exacerbate
the problem.
Hi Thomas:
I'd guess that the throttle linkage and Carb (if not fuel injection) need some maintenance.
Try removing the air filter so you can see the linkage and with the engine OFF, spray cleaner on all pivot points, then work back and forth until they move freely. Spray carb cleaner into carb to get everything moving easily.
Make sure throttle return spring is attached correctly.
Reply as a COMMENT to this post if more info needed.
Cheers
Follow The Hose From The Air Filter Housing It Goes To The Throttle Body Assembly.... Then Follow The TV Cabe From The Transmission To The Throttle Body Linkage The Grommet Usually Brakes Causing The Transmission Not To Shift Correctly Or Not At All.... The Grommet is Pressed Into The Throttle Body Linkage Pretty Simple Fix!!!!
Real good chance the throttle valve cable and linkage from throttle to top of linkage is seized, or seizing and needs lubrication. You'll have to remove battery to see it good under battery tray, and look for the piece of linkage on top where shifter linkage attaches.It needs to move freely. It also regulates your shift points as well, when passing etc. If you push gas pedal hard, it will begin to stick in lower gear longer (revving) before it shifts up, and will downshift hard as well when slowing to stop. Gas pedal will feel stiff, until you get it freed up. Try penetrating lube like WD-40 first to get it freed up, then spray white lithium grease or similar on it after. Do not try to remove nut holding it on, and remove linkage, just leave it on there and keep working it until it will move a full sweep back and forth freely. If you remove that piece of linkage, shaft will drop down and need to remove pan etc to fix it. If you need a picture, let me know, I have one from past experience with same.
That carburator most likely has vacuum secondaries, meaning that the secondaries won't open until there is enough vacuum for them to operate, usually mid or full throttle. You can try to operate them by hand to confirm that the shaft isn't stuck.
There is a technical service bulletin that may apply to your problem the no. is 09-8-9
ISSUE:
Some 2005-2009 Escape Hybrid and 2006-2009 Mariner Hybrid vehicles may exhibit an intermittent Red Triangle On and Stop Safely Now message displayed on the message center accompanied by a sudden RPM loss/no start symptom with a diagnostic trouble code (DTC) P1A0C. Vehicles may exhibit this symptom on the first start of the morning or after an extended idle. The symptom will clear on the next key cycle. ACTION:
Follow the Service Procedure steps to correct the condition. SERVICE PROCEDURE
For vehicles outside the new vehicle limited warranty, if diagnostics lead to replacing the throttle body you may use this procedure to clean the throttle body as an alternative to replacing it.
This procedure is not covered by the new vehicle limited warranty.
NOTE:
THIS CLEANING PROCEDURE CAN ONLY BE USED ON NON-COATED THROTTLE BODIES.
Refer to Workshop Manual, Section 303-04C Removal and Installation - Throttle Body.
Remove the throttle body.
With the throttle body positioned to the side, open the throttle plate.
Using Motorcraft® Choke and Linkage Cleaner or equivalent, spray the throttle body plate and bore.
Using a suitable (nylon) brush, clean the edges of the throttle plate and the mating surface of the throttle bore to remove all carbon build up.
Reapply Motorcraft® Choke and Linkage Cleaner or equivalent and wipe clean with a lint-free cloth.
Remove old throttle body gasket and discard. Install a new throttle body gasket.
Install the throttle body.
PART NUMBER
PART NAME
PM-14
Motorcraft® Choke and Linkage Cleaner
There is a linkage on the Loadflight A-500 transmission that travels from the throttle linkage to a lever on the transmission. Proper adjustment of this linkage controls the shift schedule of the transmission with respect to engine throttle position. This would be the most likely place to start after ensuring that your fluid level is correct.
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