throttle position at start

DmansPadge · Jan 29, 2005

( I have a 1 yr old B7800. I have always started w/throttle at min rpm. Glo-plug for a few sec (5-10 depending on temp) and starts right up. Run at idle for 4 min. and up depending on temp to warm up. After a couple of min I put tranny into low range to let fluid warm up... let idle for 10-15 min before putting engine under load.)

That is very good advise IMO. Cold starts are the hardest thing you can do to an engine. I follow the same routine.

( Not sure which of these has most to do w/it, but I have never had any trouble starting on first try in any weather, hot or cold. )

I'm with you... mine always starts right up, hot or cold.

BrettW · Jan 29, 2005

I think I just need to let the glow plugs heat up longer. I have a Yanmar that starts ASAP every single time so I'm use to that. It is a 3 cyl. Sits under plastic for 3 months, starts 1st second. No glow plug warming. But I like my Kubota as well,
thanks, bw

cisco · Jan 29, 2005

No idea what the manual says - never had an issue. I just walk by the tractor a few minutes before I need to use it, flip the key half way for the glo plug to warm (up to 6-8 secs. at 30 degrees, before the audible "click" tells you its ready to start), and crank the engine over. No throttle - I'm not even on the tractor. L3410 with about 250 hours - always starts on first attempt ==== thought that was the usual. I do not advance the rpm or drive the tractor until the temp gauge registers on the lowest section of the temperature bar (instead of being pegged fully to the left).

BrettW · Jan 29, 2005

the glow plug click thing is a new one for me, any B7800 owners have the click option? To my knowledge, the glow plug light just stays on as long as the key is in the heat position, bw

frank_f15 · Jan 29, 2005

I always set the throttle at about 1200 rpm BEFORE I SHUT IT DOWN, then i know that where it is on next start. 10 to 15 sec. on Glow plugs and she fires right up.

cp1969 · Jan 29, 2005

In a pure mechanical injection system, which I think Kubotas all are, it makes no difference where the throttle lever is when you start the engine--the governor is holding the injection pump rack in the wide open position, so the engine gets a full shot of fuel as long as its rpm is below that commanded by the governor setting (throttle lever).

The only reason to advance the throttle lever would be to have a higher idle rpm after it starts to keep it from possibly dying.

5030 · Jan 29, 2005

That about covers it. The Kubota injection pump is similar to a Bosch unit. The cold start mode is WOT. It does immediately go back to an idle position as soon as the engine fires. That's why you get a black puff when it starts warm or cold.

The position of the throttle lever means nothing at start up. The pump overrides the lever.

BRAVO_WHISKEY · Jan 29, 2005

Good thing to know about the pump. However, I will still set my throttle lever every time I start mine. I certainly don't want the lever set wide open causing the engine to rev while most of the oil is still sitting in the pan.

5030 · Jan 30, 2005

I don't understand these owners pre-setting their throttles at more than an idle upon start up.

All diesels are designed to start at WOT whether they are electronically controlled or mechanically controlled.

A diesel engine isn't like a gasoline engine and you gain nothing other than maybe more wear on liners and bearings from oil starvation by starting a cold diesel at any other setting other than idle. Once a diesel "pops" and starts, nothing is going to shut it down other than fuel cutoff. A diesel by design fires from compression, not a spark. Once the combustion chamber is pre-heated by the glow-plug (in Kubotas case) or by actually compression, the "fire" is lit and thats that. Actually, a diesel prefers really cold intake air (like the winter cold). The cold air is more dense and promotes a better charge in a naturally aspirated engine. Put a "hair dryer" (turbo) on and the charge becomes even more dense, resulting in more power and torque from a given displacement. With a turbo, then the need for an intercooler becomes necessary, actually more necessary as the boost increases but that's another story.

Whether it's my caterpillar or my Kubota, I always start it at the base idle and let it run for a moment before advancing the throttle. That applies to a cold or hot start.

You have to allow a little time for the oil to get from the pan to the upper end of the engine.....I know about oil film thickness and all that, but, it's peace of mind for me.

A good example of rated starts are stationary generator sets. All Caterpillar, Detroit Diesel and Cummins diesel powered gen sets have a pre-lube pump on them. Before the gen set will actually start, a pre lube pump runs for a predetermined time to insure that oil is circulating in the engine. It's hard on an engine to start at any rpm other than base idle. I'd think that the engine manufacturers know what they are doing.

Bird · Jan 30, 2005

I'm with you, Daryl. My B2710 came with the idle set at 1200 rpm, and maybe that's where it belongs, but I lowered it to 800-900. And the manual did say to set the throttle half way to start it, and I never recommend others do something contrary to what the manufacturer's manual says, but for myself, I always started mine at the lowest idle speed, gave it time to build oil pressure, then moved the throttle up to 1200-1500 to warm up a little.