Glow plugs

[Oldtractorfixer]

I have a Kubota 25 hp on an old Jacobsen mower (mid 1980's) It requires the glow plugs be run at least 30 seconds if it's 40-50 degress out. It somtimes will fire a couple times then you have to do it again before it will keep running. The new to me B7510 I just got on requires about 5-10 seconds at the same temp. Is there a hotter glow plug I can put in the older engine or is it just lower compression and takes more. I have checked them and the glow plugs are good.

 

[Shimon]

Can you please explain how you checked them? I ask because there are different methods of checking glow-plugs and not all methods give accurate results. If the plugs are good then you probably have low compression. Does it run fine under load once warm?

I don't know which glow plugs that engine takes but there are constant duty glow plugs for certain applications. Some people call them marine glow plugs. These can be left on continuously without burning out. If you put in 6V glow plugs (like the older Ford 6.9 IDI engines) then your time will be cut in half as they will heat up quicker but they will also burn out quicker if left on too long. Another option is to add some sort of "Hot-Shot" ether injection system.

Any of those solutions must be tried with care. Let us know about how tested the glow plugs and we can take it from there.

 

[Oldtractorfixer]

I disconnected the wires to each of them and checked for continutity with a test light. I guess using an ohm meter would be a more acurate but I have found that usually if they have continuity they are good. The engine runs good when it starts, no smoke once it warms a little. Seems to have plenty of power. Has about 2600 hours on a 4wd 72in mower.

 

[Shimon]

I disconnected the wires to each of them and checked for continutity with a test light.

That's not the best method since it won't tell you if you have too low resistance or a short. Resistance check isn't perfect either because there is no load on the plug and I've seen plugs test ok for resistance but open once a load is applied.

Best method is to pull them out and hook each to a battery and watch 'em get hot. Another method (which I prefer) is to measure amp draw of each plug when hooked to 12V. They should all be about the same. Not sure what the draw should be on your plugs but probably around 5A each (may be higher). You can measure with an amp clamp or a multimeter in series with the flow.

Hope this helps.

 

[rsewill]

I don't know what they're done but glow plugs are better nowadays. You just have old style ones and I suppose you could update them.

 

[Jasper661]

I have a Jinma 284LE, which I bought used, I bought it from a third party not the original owner. The original owner installed a push button switch for the glow plugs. Since apparently the ignition switch failed. It no longer has the spring return function from the "H" position. When I got the tractor it was warm and it started without using the glow plugs, but when it cooled off again, beolw 50 deg. I had trouble starting the tractor. I checked the glow plugs and they were all bad.

I replaced the plugs and the tractor started quite easily, then I experienced difficult starting again, checked the new plugs and they were all bad.

I am thinking that when the original owner installed the push button, he may have left something out of the circuit. There is a single wire going to a buss bar that connects all three glow plugs, the voltage from the push button to the buss bar is battery voltage, 12.6 volts measured with my digital voltmeter.

My suspiscion has some foundation in that with the tractor I also recieved a tool box with a few tools and two sets of burned out glow plugs.

 

[skyhook]

OP, Could also be dirty injectors, if the plugs are doing their job, but there's not enough fuel,
you will have starting issues.
Try the fuel conditioners aimed at cleaning the injectors, Sea Foam comes to mind.

 

[Jasper661]

Speaking of fuel addatives, my fuel all has some bio diesel, I always add cetane booster to my truck fuel, should add it to my tractor fuel as well.

What I was looking for in my original post was; does anyone know what the voltage to the glow plugs should be. Some 12v diesel systems have a resistor or some sort of limiting device that reduces the voltage to the plugs.

And I may have posted in the wrong part of the forum..

 

[skyhook]

I believe there in the area of 9 volts when tested "on".

 

[David Devuono]

My mid eightys Kubota requires as per the dash sticker and real life, min 15 seconds even whe its 80F out. 40-50 will require 30 seconds. I think it may be normal though mines a two cylinder.