L2550 - Hard starting at all temps

[Flintknapper]

The indicator reads 0.78v during preheat, 0v otherwise. It does not ever glow, did preheat for 25 seconds to verify.

One side is wired directly to the key switch to the pin that says Gr or G1 maybe, it's hard to see. It's a black wire with a red stripe. The other side is grounded.

I'd replace that indicator and check the connections. I'll have to get my schematic out...but I'm pretty sure the GP circuit runs through the indicator.

So if it is burned out the glow plugs wouldn't work or if there is too much voltage loss through it (for any reason) the glow plugs would not heat up properly.

 

[Stinger23]

Key switch voltage (off, on, start, preheat):
Center Post Red: 12.67, 12.43, 0.82, 1.12
ST Post Black/Red: 0, 0, 0.72, 8.2
AC Post Red/White: 0, 12.6, 0.5, 1.1
G2 Black/White: 0, 0, 0.67, 0
G1 Post Black/Red to indicator: 0, 0, 0, 0.78

Started at ST post and moved counter clockwise around switch when viewed from the back of the switch.

 

[North Idaho Wolfman]

Your better off just wiring it like this and be done with it:

 

[Stinger23]

Well there's possibly your problem 2 fold!!
#1A That model does not take a glow plug indicator, someone added it.
#1B That model did take a glow plug indicator
#2A Someone has replaced it with the wrong indicator (there is different ones depending on how many glow plugs you have)
#2B Someone has completely wired it wrong, it should not go to ground, if it was right it would be wired in series to the glow plug buss. You sure it's not wired that way?

We need to see if you have the easy checker or not.

View attachment 146334

If it doesn't have an easy checker this is right.



If it does have an easy checker this is wrong.

View attachment 146333

This is the easy checker gauge cluster with the 5 dummy lights, right?

I'm not sure if all of the tractors come with a hole for the indicator, but this one appears to not be a hole somebody drilled at a later date to add an indicator because the hole is factory punched not drilled. There is paint all the way around the hole surface. Not bare metal like you'd get if you drilled it.

I've not located where the ground side of the indicator goes yet. It disappears between the indicator and the fuel tank and I'm still searching for it.

 

[North Idaho Wolfman]

Ok here is the total answer:

These style glow plugs take an indicator:
Like in a L2350

This style of glow plug does not take an indicator:
Like your L2550

 

[North Idaho Wolfman]

This is the easy checker gauge cluster with the 5 dummy lights, right?

I'm not sure if all of the tractors come with a hole for the indicator, but this one appears to not be a hole somebody drilled at a later date to add an indicator because the hole is factory punched not drilled. There is paint all the way around the hole surface. Not bare metal like you'd get if you drilled it.

I've not located where the ground side of the indicator goes yet. It disappears between the indicator and the fuel tank and I'm still searching for it.

The hole is factory, that hole was for a horn switch on UK models.

Your L2550-GST

It's just like my
My L3450-GST

 

[Stinger23]

Ok here is the total answer:

These style glow plugs take an indicator:
Like in a L2350

View attachment 146337

This style of glow plug does not take an indicator:
Like your L2550

View attachment 146338

I can't tell which type of glow plug I have. The injectors are the style in the picture where you highlighted with green, but without removing one of the glow plugs I can't tell which style I have.

On second look, the bus bars on mine are the z shape like it shows in the picture you highlighted with green. But I'm not sure if that is enough to positively identify them.

Here's a pic.

 

[North Idaho Wolfman]

I can't tell which type of glow plug I have. The injectors are the style in the picture where you highlighted with green, but without removing one of the glow plugs I can't tell which style I have.

On second look, the bus bars on mine are the z shape like it shows in the picture you highlighted with green. But I'm not sure if that is enough to positively identify them.

Here's a pic.

They go hand in hand, You have pencil injectors so you have the long glow plugs that are the non indicator glow plugs.

 

[Stinger23]

The ground side of the indicator is connected to the harness connector on the left side of the steering column under the fuel tank as shown in the pic, but I don't have enough panels pulled off of the tractor to trace it any farther through the loom. With that said, the ground wire does not look factory as it has crimped connectors on both ends. But the wire on the positive side of the indicator is a factory wire that is in a condition that indicates it's been there a long time.

If I'm going to end up deleting it then I'm not going to try to trace it any further.

 

[North Idaho Wolfman]

This is all confused because Kubota changed engines from and IDI (indirect Injection) to a DI (direct injection) after the original manuals wiring was made for the IDI.

You need to make sure that wire doesn't go to the glow plugs.

 

[Stinger23]

They go hand in hand, You have pencil injectors so you have the long glow plugs that are the non indicator glow plugs.

Ok, then it's weird that someone added this indicator for some reason and killed GP function. Hopefully removing it will get more voltage to my glow plugs, as 6.7 volts isn't going to cut it I don't think.

I'll take a closer look at the diagrams later to see what's the easiest path to fixing whatever they did. It's 12:30 now and I've got to be up early so I can't put too much more time in it tonight.

 

[North Idaho Wolfman]

All you need to do is make sure G1 and G2 both go to the wire that goes to the glow plugs, then it will work properly.

 

[Stinger23]

You need to make sure that wire doesn't go to the glow plugs.

I just took a look before I walked out the door of my shop and there is only one wire going to the glow plugs and it is the power wire that is connected to the front glow plug. From there the only thing connected to the other two is the bus bars connecting them all together.

 

[North Idaho Wolfman]

I just took a look before I walked out the door of my shop and there is only one wire going to the glow plugs and it is the power wire that is connected to the front glow plug. From there the only thing connected to the other two is the bus bars connecting them all together.

Disconnect that wire and the wire off the added glow plug indicator and use a meter to see if they are the same wire.

 

[Stinger23]

Disconnect that wire and the wire off the added glow plug indicator and use a meter to see if they are the same wire.

I will do that hopefully tomorrow. I know the wire going to the glow plugs is black with an orange stripe which does not match G1, G2, or the mystery wire coming off of the indicator.

So neither G1 or G2 provide any real voltage (<1v) according to my tests. So I assume that must mean that the voltage that's going to the glow plugs is coming from a relay that's triggered by G1 or G2? If it's a normally open relay, then an ohms test will not indicate that they are connected end to end on those wires, correct?

G2 Black/White: 0, 0, 0.67v, 0
G1 Post Black/Red to indicator: 0, 0, 0, 0.78v

 

[North Idaho Wolfman]

I will do that hopefully tomorrow. I know the wire going to the glow plugs is black with an orange stripe which does not match G1, G2, or the mystery wire coming off of the indicator.

So neither G1 or G2 provide any real voltage (<1v) according to my tests. So I assume that must mean that the voltage that's going to the glow plugs is coming from a relay that's triggered by G1 or G2? If it's a normally open relay, then an ohms test will not indicate that they are connected end to end on those wires, correct?

G2 Black/White: 0, 0, 0.67v, 0
G1 Post Black/Red to indicator: 0, 0, 0, 0.78v

You should get 12V on both G1 and G2 with nothing connected to the other end of the wire.
There should not be a relay for the glow plugs on that model

 

[ruger1980]

If your measurements below are accurate I would be surprised the engine even turns over.

The measurements in yellow show an incredible voltage drop in the circuit feeding the switch. If wired as per the schematic with the indicator you should see somewhat less than 12v at the buss bar during preheat and close to 12v when cranking.

Regardless the glow plugs are not you starting issue. A direct injected engine should start at well below 40F without any starting aid. This is even stated in the WSM.

Most DI engines do not have glow plugs.

If I were to guess I would say you either have an issue with cranking speed or compression with a lesser possibility that the injectors are not atomizing fuel properly.

 

[Stinger23]

If your measurements below are accurate I would be surprised the engine even turns over.
View attachment 146359

The measurements in yellow show an incredible voltage drop in the circuit feeding the switch. If wired as per the schematic with the indicator you should see somewhat less than 12v at the buss bar during preheat and close to 12v when cranking.

Regardless the glow plugs are not you starting issue. A direct injected engine should start at well below 40F without any starting aid. This is even stated in the WSM. View attachment 146360
Most DI engines do not have glow plugs.

If I were to guess I would say you either have an issue with cranking speed or compression with a lesser possibility that the injectors are not atomizing fuel properly.

It seems to crank at a decent speed by ear. Tach doesn't work so I can't say exactly what RPM it is. I can take a video of a cracking attempt and upload it to YouTube if necessary if you want to hear it.

I would agree that some old the readings are low, though I don't know what each one should be. You'll now I questioned this low voltage during cranking last night when I was asking how the GP's get 12v if the switch is somehow under 1v.

I may double check these readings for sanity.

 

[ruger1980]

Yes double check your readings.
As a general rule diesel engine need to turn about 150rpm to reliably start. If it cranks wickedly fast compression is likely lacking.

 

[Stinger23]

New readings with better ground (direct to battery):
Center Post Red: 12.67, 12.43, 8.7, 9.8
ST Post Black/Red: 0, 0, 8.6, 0.3
AC Post Red/White: 0, 12.6, 8.3, 9.7
G2 Black/White: 0, 0, 8.4, 7.7
G1 Post Black/Red to indicator: 0, 0, 7.9, 9.7

Added video of it cranking, let me know if this sounds abnormal.