Full throttle to start

[Will S]

OP,
I have pretty much the same mower, but mine is a Woods Mow'n Machine. Bought new around 1998, same Kubota engine. It always starts with the throttle at idle, although I'd say idle is somewhere over 1000-1200 rpm, IDK. I turn my K.S. CCW for 10 sec. to light the glow plugs (all still original), then start. Always starts, but if very cold, I bump the throttle up a bit.

I just replaced the fuel shut-off solenoid last week. It was weak and wouldn't pull all the way, but if I manually pulled it open, it would usually stay once the engine started. (I used a bungy cord to keep the fuel shut-off valve open, so I could mow, while I was waiting for a new solenoid).

The engine has had only synthetic 15W-40 HD diesel engine oil, and Amsoil injector cleaner, pretty much since new. Never any smoke, even when cold, and doesn't use any oil.

Your engine uses a simple mechanical throttle cable. Check to see that the mounting clamp screw isn't loose, and out of adjustment. As someone already posted, check that the glow plugs are all working. You machine is 5 years newer, so I don't know if it uses a glow-plug timer, or if it is like mine, putting 12v to the gp's only while the k.s. is held over to pre-heat position.

 

[90cummins]

You lead a sheltered life then. Mechanically injected diesels all start at 100% fuel then immediately revert back the the previously set throttle position. Always been that way on Bosch style pumps. Don't know about others. Read the previous post. Pump Guy knows his chit. You don't. No clue on the new ECM controlled common rail diesels. Don't have any, don't want any.

We are talking about two different things. Most injection pumps as mentioned automatically add additional fuel for starting.
And (2) manually moving the throttle to add fuel to start.
I’ve owned a first gen Dodge diesel since 1990 bought new & still have it. The first gens from 1989 to 1993 have a Bosch VE style injection pump which automatically starts at full fuel so no added throttle input is needed to start. The second gen dodge Cummins 1994 to 1998-1/2 uses an inline p-pump, it does NOT add additional fuel for starting, it requires manual throttle input to start.
I worked in an engineering lab designing, building and testing transmissions for the Bradley Fighting Vehicle. We had 5 test cells with VTA-903 Cummins v8’s rated at 600 hp. Theses were the engines used in the Bradley vehicle. Throttle input was not needed to start.
We also had 1 test cell with a Cummins KTA 1200 V12 1200hp diesel again no throttle input was required to start.
The 903 & KTA 1200 had a PT (pressure timed) system.
My Kubota ZD1211 has a D1105 it starts fine in the idle position as does my Ford 1720 and my L100 Yanmar.
JBob’s post was about his mower needing more & more throttle input as time progressed indicating a progressive problem.
A statement was made that all mechanical diesels start or should should be started at 1/2 to full throttle POSITION. This statement is not 100% true.

Not a sheltered life!!
90cummins

 

[5030]

Never said it was. I'm very familiar with the Cummis PT system as well as Cat and Detroit Diesel. I worked on them for 29 years.

 

[JBob]

OP,
I have pretty much the same mower, but mine is a Woods Mow'n Machine. Bought new around 1998, same Kubota engine. It always starts with the throttle at idle, although I'd say idle is somewhere over 1000-1200 rpm, IDK. I turn my K.S. CCW for 10 sec. to light the glow plugs (all still original), then start. Always starts, but if very cold, I bump the throttle up a bit.

I just replaced the fuel shut-off solenoid last week. It was weak and wouldn't pull all the way, but if I manually pulled it open, it would usually stay once the engine started. (I used a bungy cord to keep the fuel shut-off valve open, so I could mow, while I was waiting for a new solenoid).

The engine has had only synthetic 15W-40 HD diesel engine oil, and Amsoil injector cleaner, pretty much since new. Never any smoke, even when cold, and doesn't use any oil.

Your engine uses a simple mechanical throttle cable. Check to see that the mounting clamp screw isn't loose, and out of adjustment. As someone already posted, check that the glow plugs are all working. You machine is 5 years newer, so I don't know if it uses a glow-plug timer, or if it is like mine, putting 12v to the gp's only while the k.s. is held over to pre-heat position.

Mine is like yours, puts 12v to the gp's while switch is held in preheat position. I have replaced the throttle cable in the last few years. There is potential it has one of these issues. Thanks for the recommendations!

 

[Mike1955]

I said it once and I’ll say it again..
All mechanical injected Diesel engines, SHOULD BE started at OVER 1/2 to FULL THROTTLE..

The pump guy. May I ask why you say that. I always thought it was good to start slow. Thank you

 

[5030]

Lol.. I was biting my fingers trying not to respond.. I’ll leave it at that..lol

Why not. You comment may hold true with CAV pumps but it don't with Bosch style pumps. They always advance to 100% fueling upon cranking and the instantly revert back to the initial throttle setting once the pump senses rotation.

In 35 years, I've never advance the throttle on any of my Kubota's (I've owned at least 12) now and same holds true for my Class 8 diesel tractor with it's 3406 Caterpillar engine.

Winter and summer, I always start them at base idle and let the pump decide the fueling rate.

 

[thepumpguysc]

Why is it that YOUR experience with certain types of pumps make it THAT WAY for the rest of the internet.??
And your comment about Bosch style pumps is complete horse ****.!!!
I understand that u think u know what your talking about..but..

 

[5030]

Why is it that YOUR experience with certain types of pumps make it THAT WAY for the rest of the internet.??
And your comment about Bosch style pumps is complete horse ****.!!!
I understand that u think u know what your talking about..but..

I never said that, I said my pumps which are all Bosch style fuel rail pumps. I know exactly what I'm talking about with them. Candidly, I don't care one way or another.. Have a nice day.

 

[Hay Dude]

Why is it that YOUR experience with certain types of pumps make it THAT WAY for the rest of the internet.??
And your comment about Bosch style pumps is complete horse ****.!!!
I understand that u think u know what your talking about..but..

thepumpguysc,

Thanks for all the help & suggestions with pump issues.
Your observations are pretty much spot on.