M4950 Hard Start S2200 engine

[Marley1223]

Worked on a lot of diesels but not many Kubota's
This tractor came to me with cold hard starting complaint

Customer purchased this tractor with only a few hundred hours on it many years ago
Says it has always been a hard starter, requiring glow plugs even on hot summer days
Now it's really bad

At his farm, outside 30 degrees it will crank good and kind of start but then peters out
Keep cycling the glow plugs and retry and after maybe 10 tries it will stay running but is struggling

Mostly black smoke and when it finally starts it clears up quickly

When running fuel lines 1 and 6 made very little change and very little fuel would squirt out
1 and 6 exhaust manifold would take a long time to even begin warming (no smoke)
2 thru 4 are hot quickly

Customer had it at another shop and they claim they installed new rings, rebuilt head, new injectors, and new glow plugs. Checked timing and compression all good
But NO better and maybe worse

When I got it to my shop, I found 1 bad glow plug and low voltage 9.5v at glow plugs
Bypassed the wiring to glow plugs and now 11.5 at glow plugs but still no change in starting

Checked fuel pressure 3psi and installed new filter and still no change
Checked air intake and removed intake hose to be sure and still no change

Pulled injection pump and found signs of water/rust on plungers

Purchased a reman pump

Original Pump had 5 shims and I left one out leaving 4

Still hard starting cold but runs much better and with the exhaust manifold off all ports are hot and even

Found that 1 and 6 had compression leaking around injectors so I pulled them and ran a compression test 250-275 psi. put air pressure on them and found intake and exhaust valves leaking.

Pulled the head found valves did not look like a rebuild and valve recession was .075
Took head to my guy and installed new seats, ground the valve slightly with valve recession now at .048

Installed head and checked piston to head clearance .053 with only the gasket, no shims.

Still hard starting but runs much better
When starting I am cycling the glow plugs and it will try to start rather quickly
Each cylinder will have heavy black smoke while cranking and when it kind of starts it only runs for a few revolutions and peters out
Acts like a gas engine when the choke is left on full after start

Checked timing and looks like it's about 18 and should be 25
Pulled all shims and when bolting the pump back on the rack would bind up so I installed 1 shim and still bound up, installed another shim for a total of 2 and rack is free.
When bound up the rack itself would move just enough to know it must internal problem causing binding
Appears the plungers are being pushed up to far with no shims, is this normal?

Its hard to believe the timing gears are off because customer says the front cover has never been off and I do not see signs of removal

Taking the injectors in tomorrow for testing

Any ideas?

 

[North Idaho Wolfman]

First why would you randomly leave shims out???

Put ALL the shims back under the pump as the only reason the shim count would change would be if they milled the top of the block.

Have the reman pump checked, as it sounds like you either have the wrong pump or it was rebuilt poorly!

Have the injectors tested.

Feeding the glow plugs directly will burn them out in no time at all if you bypassed the glow indicator.

Do a full compression test on all cylinders and post it for us to read.

Did you use a OEM head gasket?

 

[Marley1223]

The reason I left one out is because the hard starting symptoms are common when timing is retarded.
Have cheated the timing ahead many times to help cold starting.

Power is run through the indicator
Voltage drop is between starter and key switch.
I bypassed just to see if any change

Injectors are the only thing that has not be changed or altered.

Hard for me to believe all the injectors are bad but it's possible
I like running with exhaust manifold off so I can see and hear each cylinder
All exhaust is the same color and heat
Cracking each injector line makes the same change in rpm and sound


Compression is running 360-380 which is considerably better than what I started with.
I don't like the hone finish on cylinders
Looks like a hack job

After market head gasket

With all of these changes and improvements there is no real change to cold starting problem but defiantly runs much better

 

[JohnDB]

Thats an impressive list of what you've done and diagnosed. And welcome for the forum.

I didn't get a good understanding of how long you glow the engine for.

My S2600 manual (same block as yours but your engine may be DI so could be different):


I routinely use 15 sec for temps less than +15C anyway, an ex dealer said they always required a lot of glow. If I don't, I get pretty much the starting symptoms you describe.

Lots of discussion (debate, pros and cons) about how long to heat glow plugs for are here too: https://www.orangetractortalks.com/...eep-them-on-before-cranking-the-engine.48244/

 

[Marley1223]

First why would you randomly leave shims out???

Put ALL the shims back under the pump as the only reason the shim count would change would be if they milled the top of the block.

Have the reman pump checked, as it sounds like you either have the wrong pump or it was rebuilt poorly!

Have the injectors tested.

Feeding the glow plugs directly will burn them out in no time at all if you bypassed the glow indicator.

Do a full compression test on all cylinders and post it for us to read.

Did you use a OEM head gasket?

This is the test procedure for the glow plugs
The related picture shows voltage test from top of glow plug/harness to ground
No mention of built in resistance or voltage drop

Can you please elaborate on how feeding glow plugs directly would cause damage?

Thanks

 

[North Idaho Wolfman]

I said "Feeding the glow plugs directly will burn them out in no time at all if you bypassed the glow indicator."

You didn't do that, so you didn't change the circuit, so no issue.
If you notice it's says voltage not amperage, the delivered amps would change if you eliminate the indicator.

 

[Marley1223]

I said "Feeding the glow plugs directly will burn them out in no time at all if you bypassed the glow indicator."

You didn't do that, so you didn't change the circuit, so no issue.
If you notice it's says voltage not amperage, the delivered amps would change if you eliminate the indicator.

Just trying to learn about these systems.

I was unaware the indicator was not working when I started looking at this tractor the owner was performing the starting.
I wanted to see how he was doing it and watch the engine for any clues.
He would cycle the glow plugs like he always did and then try to start
I was testing the glow plug circuit with a 12v test light at all glow plugs

When the tractor was at my shop is when I saw the indicator was not working while cycling the glow plugs.
I figured the indicator was probably bad and had been bypassed

At this point I had tested the voltage at the plugs, and it was around 9.5v.
When you look up the plugs online it says they are 10v?
With out having much experience or a manual at this moment for this Kubota, I assumed they probably had a resistor?


Talked to the local dealer and they said the glow plug indicator is no longer available and just bypass.
I ask them how do you know when they are hot? "Just give it a 20-30 count"

When I opened the dash, I found it was bypassed so I hooked it back up and it works.

I performed a voltage drop test on each segment of the harness and found the power wire from starter to key switch had a 3v drop when cycling plugs, so I bypassed that section for testing

Just testing one glow plug with and without the bypass makes a huge difference.

"JohnDB" posted instructions showing 40 to 60 second cycle time when cold, so now with the plugs at full power as they should be and a 60 second cycle that should make a huge difference

So, at 60 degrees ambient temp what should be the normal procedure for starting one these tractors?
No glow plugs should be required? Glow plugs required? if so, how long?
What is considered cold?

Maybe this tractor is acting normal, and it requires more glow plug time?

Thanks

 

[North Idaho Wolfman]

Just trying to learn about these systems.

I was unaware the indicator was not working when I started looking at this tractor the owner was performing the starting.
I wanted to see how he was doing it and watch the engine for any clues.
He would cycle the glow plugs like he always did and then try to start
I was testing the glow plug circuit with a 12v test light at all glow plugs

When the tractor was at my shop is when I saw the indicator was not working while cycling the glow plugs.
I figured the indicator was probably bad and had been bypassed

At this point I had tested the voltage at the plugs, and it was around 9.5v.
When you look up the plugs online it says they are 10v?
With out having much experience or a manual at this moment for this Kubota, I assumed they probably had a resistor?


Talked to the local dealer and they said the glow plug indicator is no longer available and just bypass.
I ask them how do you know when they are hot? "Just give it a 20-30 count"

When I opened the dash, I found it was bypassed so I hooked it back up and it works.

I performed a voltage drop test on each segment of the harness and found the power wire from starter to key switch had a 3v drop when cycling plugs, so I bypassed that section for testing

Just testing one glow plug with and without the bypass makes a huge difference.

"JohnDB" posted instructions showing 40 to 60 second cycle time when cold, so now with the plugs at full power as they should be and a 60 second cycle that should make a huge difference

So, at 60 degrees ambient temp what should be the normal procedure for starting one these tractors?
No glow plugs should be required? Glow plugs required? if so, how long?
What is considered cold?

Maybe this tractor is acting normal, and it requires more glow plug time?

Thanks

Yes that engine is a cold blooded ( and cools fast) hard starting monster.
Minimum is 30 seconds more up to a 60 seconds when cold.
A good block heater in the water jacket make a huge difference in the winter.
Also quality of battery plays a huge role in the starting.

 

[Russell King]

I am not sure you need a new glow plug indicator or not but you may be able to get one from NGK?

The OEM part on my L185 was in a NGK box when I bought a new one. The indicator part of it only indicates when it is pretty dim light. It simply is a glowing resistor wire that gets a coating on it from the heat so stops glowing after a couple of uses.

I use mine every time I start my tractor even if the engine is warm and the temperature is hot. Just makes engine start right away and saves on starter.

Interestingly the wiring bypasses the indicator during the starter operation position of the switches. They don’t want the voltage too low from both the starter and resistor voltage drops!