Engine/Transmission (1994 - 1998) Glow plug or not question.

[RVTRKN]

I know that the 12 valve has a grid heater, but where can I find some solid evidence that glow plugs don't exsist. We didn't argue about it but he seemed to stick to his belief that it has glow plugs. He is a very nice guy and I don't want to seem to agressive about it, I just want to set him strait. I'm sorry to be ignorant on the 12 valve, but my first CTD was a 04. 5 24 valve.

 

[surfbeetle]

You are correct, there are no glow plugs in a 12 valve. There is the grid heater in the intake manifold at the entrance from the air tube. If there were glow plugs, like on all of the V-8 diesels out there, you would be able to see the glow plugs and wiring at each cylinder positioned sort of like a spark plug. Just ask the guy you were speaking with if he could show you one on a 12 valve. LOL!

 

[fox]

Just explain to him that there are two types of diesels.

One, like he is refering to is indirect injection. The other is direct injection.

Direct injection sprays the fuel into the piston.

Indirect sprays in into a pre-chamber, which feed the main chamber.

direct injection is more efficient, starts better, and is simpler to build.

Tell him CUMMINS did it RIGHT.

 

[EKlem]

As suggested above, spend a little underhood time with him and he will see that there are not any. There are no wires going to the head in any place that would allow them to be for glow plugs.

 

[RVTRKN]

fox, I think you hit it right on the head, the direct injection explanation is the best way to explain it without insulting him. I'll try to check in with the 12 valve crowd from time to time, I'll learn more of the basics.



Thanks Steve

 

[KOG]

But you can have glow plugs with either direct or indirect injection engines. It's just that Cummins chose to use a grid heater in the intake instead.

 

[DieselDoghouse]

KOG is right and to extend the discussion (and ventilate my own ignorance). There are 3 common ways to "enrich ignition" for a diesel:



1. glow plugs - which preheat, heat the initial air and enhance combustion. I am not aware that they can be active while running in a direct injection engine and therefore they are a starting aid only.



2. Flame front heaters - common on Yanmar style engines such as the compact util tractors viz. Deere 650 - 950's Think of a cigarette lighter through which you drip diesel to heat the intake manifold like a BBQ starter with rabies - again a starting aid only!



3. Intake grid heaters - which preheat any incoming combustion air to enhance combustion and therefore are a starting aid and initial run aidto reduce emissions. THAT is why Cummins chose this method and why our trucks have electrical systems that 'pulse' for the first 3 minutes, or until road speed = 18 mph or engine speed reaches 1800 rpm. This method was also used on the larger displacement John Deeres and others.



Show this to your friend - he may be smarter than you might think!!