how long to glow for

[waiwurri]

hi, i am new to this forum so thank you all very much i have learnt a lot already. i have a boat with an ld28 in it and when it is not used for a while it starts up a bit rough. It has a manual glow timer so I am glowing it for 20 secs and then give it another 20 sec. This helps but is it going to damage the glow plugs . ?Look farward to your thoughts. Thanks Pete.

[LD28 Owner]

The Nissan Marine LD-20M/LD-28M Owner/Operator Manual instructs us to turn the key to the preheat position for 10 to 15 seconds and then turn the key to the start position. The manual then confidently states: "This will start the engine."

In the case of my marine LD 28 the engine coughs on the first go around, fires but stops after the second 10-15 second glow plug shot and then always starts on the third try. All three crankings are with the "throttle wide open" and I'm prepared to pull the "throttle" back as soon as the engine is running.

In the end, I have run the glow plugs for 30 or 40 seconds each time I start the engine.

I check the glow plugs every year and I've not killed one yet.

It is interesting that there are at least three LD28 glow plug wiring plans (marine, industrial and automotive).

The marine wiring plan is simple. My keyed ignition switch on the factory panel has four positions: Off, a glow plug spring loaded position that is held in position for the required 10 to 15 seconds, a spring loaded start position that cranks the engine and the on position that that results from ending the cranking position.

The design prevents the glow plugs from being operated while the engine is cranked.

The Industrial Manual has two glow timer schemes both of which have a "Fast Glow Control Unit" to manage the whole process.

The first industrial scheme has the control unit turning on a pilot light and heating up the glow plugs for 15 seconds. When the pilot light goes out, the engine can be cranked. It appears that the glow plugs stay on while the engine is cranked.

The second Industrial Manual glow timer scheme adds a period of glow plug operation through a Dropping Resistor after cranking has ended and, one assumes, the engine is running. The length of the post-starting glow plug operation depends upon engine water temperature.

The automotive glow plug scheme is much like (the same?) as the second industrial scheme.

In an off line discussion with another LD28 marine owner we decided that the standard marine wiring program had the most conservative glow plug plan and we could improve upon that plan by taking the glow plug operation off the ignition switch and on to a push button. This change would allow the operator to energize the plugs for 15 seconds count and then continue to operating them while starting the engine.

The push button might also allow us to overheat the glow plugs and destroy them.

[rlaggren]

I strongly suspect that the marine engine has different glow plugs than the auto. From what I've read here I believe that repeated 15 sec heats would kill an auto plug. 30-40 secs for sure.

FWIW

Rufus

[waiwurri]

Thanks for the info. I dont think the engine is a marine as it has been installed in the boat at a latter date and the manifold has been made. After the second glow its starts first time with minimal throttle. I know there are different voltages of plugs and I dont know how to tell what ones I have

Its there a way of telling what type I have without taking them out ? Thanks Pete..

[LD28 Owner]

My glow plugs are stamped "12V" on one of the faces on the hex.

See

[LD28 Owner]

My glow plugs are stamped "12V" on one face of the hex portion of the plug-- easy to see when pulled out way more difficult when installed.

BTW If you haven't already, take a look at "LD28 Glow Plug Info" under the "LD Section Index" at the top of the NissanDiesel homepage. There is also some discussion of the timing issues.

Also: I'd love to see a picture of the fabricated manifold.

[overrated]

Are you sure the fuel not is pulled back from the fuelpump because of air sucking in to the fuel lines because of bad hoses? Or bad ventilation of the fueltank that causes vacum? On my ld28 i have to glow two times at a total of 15 seconds at -30 degrees celcius.

[waiwurri]

that is a possibility that I didnt think of. It starts worse in the winter. I did have a small leak on top of one of the injectors a while ago but tightened it and it stopped but I will check that again also. Thanks for the feed back.

[rlaggren]

You know the leak _out_ isn't the problem, right? It's the leak _in_ (air) tha causes problems - and you can't see that leak unless you sub in a short piece of clear hose near the IP and watch for bubbles.

Rufus

[waiwurri]

Hi thank you for the info. in regard to air getting into the fuel line if I put a clear piece of hose in the fuel return to the tank would this show the air or would it all expell though the injectors. Thanks Pete