Glow Plugs for an AD21

[dkirsop]

This post describes two versions for installing glow plug pre-heaters in the Albin AD21 engine. The glow plugs function to assist in a cold start by preheating the intake air. This replaces the factory options of: cranking till the cows come home; or using diesel starter fluid to blow up your engine. I should mention that the AD21 has a common air intake manifold for both cylinders which makes this modification fairly straight forward.

Version 1

Has been in use in my boat for the past three years. The glow plug is a wire wound heater element type mounted in the air filter/flame arrestor device. Here is a picture of the glow plug as it comes out of the package. The plug is a Champion 167 ch3. Based on my experience this type of plug is very tolerant of long activation times upwards of 30 seconds or more.

Plug1.jpg

The picture below shows the plug as it appears in the engine. The plug is axially aligned with the axis of the air intake manifold. This allows the filter/flame arrestor to be rotated on the manifold without changing the alignment of the glow plug.

Version1.jpg

A starter solenoid is used to activate the glow plug. The high current connection to the solenoid is taken from the battery connection to the starter motor. Note that the glow plug draws approximately 20 amps. I use #8 wire for the high current conductor on both versions. A 12 volt activation current is provided from a momentary contact switch on the dashboard; #14 wire is ample for this purpose. I have removed the filter/flame arrestor to better illustrate the solenoid wiring and placement.

Solenoid.jpg

The next shot shows the glow plug when looking through the port that connects to the air intake manifold. A well torqued nut complete with lock washer holds the glow plug in. Note that the air horn baffle had to be slightly trimmed (the crescent shaped cut) to allow access with a deep socket wrench. I used a bi-metal hole saw that was a close fit with the inside diameter of the intake port to do this. The intake port serves as a steadying guide and light pressure is applied to the hole saw to avoid grabbing while cutting.

Inside.jpg

This installation has worked well. It really simplifies the cold start process. I activate the glow plug for 20-30 seconds. Then wait another 20 - 30 seconds to allow the residual heat to permeate the air in the manifold before cranking the engine. Usually the engine will start on the first try. I have seldom had to repeat the process except in early spring or late fall conditions. I do not use the boat in winter.

Version 2

This is my attempt at a cleaner installation which was part of an engine rebuild described in an earlier thread "Heart Surgery for Sea Quill". This installation is a variant on a similar installation that is on the emergency power generator for my home. In this version I have installed two 'pencil type' glow plugs inside the air intake manifold. Each glow plug is aligned with the intake port for each cylinder. The glow plugs are NGK Y-207T. Here is a picture of the plug.

Plug2.jpg

The manifold was drilled and threaded to accept the plugs. What appears to be a nut closest to the manifold is only a spacer, drilled out to take up some of the threaded shaft depth of the glow plug.

Version2.jpg

Again, power is supplied through a starter relay as described above.

I have only used this setup once after the rebuild was complete when testing the engine. One of the plugs burnt out when I held the momentary contact switch too long. In fairness this was a difficult start due to the temperature, presence of oil in the cylinders and the need to bleed air from the system. Also, the engine is tight and has not been broken in. I will report on the operation later this year after I have used it a while. I would say the best way to use this set up is in cycles of 4 seconds on and 6 seconds off, repeating several times in sequence prior to attempting an engine start in order to avoid plug failure.
My reasons for this installation is: it places the heat closer to the cylinder intakes, the glow plugs are less expensive and it looks neater. If it fails to meet my expectations then I will revert to Version 1.

I hope other users of the AD21 find this article useful. For what it's worth I really like this engine. It is rated for continuous duty and will last a very long time in service. My boat is hull 1013 which corresponds to 1971 as its production year. The engine is now 46 years old and the bearings and bores were all within specification when I did the rebuild. Only rings and valves needed attention. The castings are of a quality you will not find today.

[WillieC]

I knew this would be good. Textbook clean and elegant.
Now I need a common intake manifold to replace the three individual air horns on the MD3B and 17C engines.

17C air cleaners.jpg

Hmm. I have NINE of these air cleaners to work with. Surely I can make a common airbox with a single filter. However, the draw of three glowplugs seems a bit excessive. What do you think?

I completely agree with your assessment of the AD21. Yours will go another fifty years.

Nice work, Dave. Thanks!

[dkirsop]

Or, place a glow plug in each air cleaner and wire all three together similar to what is shown for Version 2.

[WillieC]

Round portion is full of filter media, intake horns are about the size of the glow plugs. Still pondering.

[WillieC]

Thinking of making an extension out of pipe between head and air cleaners. 2" nom. pipe is a bit large for fitting over the head connection.. 1-1/2" is a bit small to fit inside the air filter and make it clamp. But, I have rude and crude welding skills so I will try a few tricks. The idea is to give me something solid enough to drill and tap for the glow plug, not ignite the filter or require modification of the filter itself. Thinking of having the glow plug hang below this extension, since heat rises. The plug would simply project into the airpath to the intake valve, hopefully without setting the doghouse cover on fire. Check this out for how it was done in the old country:

https://www.youtube.com/watch?v=NeDvCVS38hk

Here is some info on the Y207-T you suggested:
Voltage 11
Port Type M5/3Nm
Cone Pitch 63
Thread Size M 12x1,25
Total Length 58
Spanner size 12 mm
Tightening Torque 22
Rated Current 14
Glow Plug Type after-glow capable
Glow Plug Type Pencil-type Glow Plug
Fitting Depth 21
Failure Moment 45

14A x 3= 42A. Would probably run one large wire at least #6 from starter to solenoid, (fuse?) then run three smaller, separate wires from solenoid to plugs.
21mm fitting depth would fit nicely in 1-1/2" pipe nipple and not block air passage enough to matter a whit.

Does failure moment 45 mean, run it at short bursts of 5 seconds, as you suggested? 45 (seconds?) and it is toasted?

You have inspired me, and the weather is too crappy for bottom painting.

[dkirsop]

I think 45 seconds would definitely toast it. I came up with the 4-5 second rule by observing the glow plug while activating it on the battery. It gets really hot, really fast. Given that the engine will be cold when you use it, the wire run is short and the load doesn't peak like a motor, I think you can safely connect all 3 plugs using a common #8 wire. Sounds like you have a plan!

[WillieC]

See how I adapted this plan on my MD17C.

viewtopic.php?f=28&t=9381&p=63197#p63197

Thank you, Dave!

[denchen]

Only as a suggestion, but my old boat had a Perkins engine and the cold start was by a `Heater glow plug`. It works by allowing a bit of diesel through and then starting a small fire in the air intake. This side of the pond the glow plugs are about $10.00. My old Perkins would start no matter how cold and was never any problem. As stated above, only a suggestion.

[WillieC]

I posted a youtube link to the Perkins method earlier.

Here it is, not easily adaptable to three individual intakes, methinks.

https://www.youtube.com/watch?v=NeDvCVS38hk

I paid about $10 for each of the Autolite 1101, matching application to the NGK Y207-T that dkirsop used.

[dkirsop]

I promised an update after a season of use on this modification. Both Version 1 and Version 2 perform well. I had used Version 1 for 2 prior seasons before trying out Version 2.

Version 1 is most tolerant of user abuse. You can hold the button down for minutes if you want without burning out the plug. This system requires activation times of about 1 minute when starting from cold. Version 1 is more difficult to construct due to the placement of the plug in the flame arrestor.

Version 2 is based on a 20 second activation time. Any longer and the plugs might burn out. However, the heat source is closer to the cylinders and this system works consistently with the shorter activation time. Version 2 is easier to construct.

In summary, both systems perform well.

[WillieC]

So here we are in October and the WillieC. is still on the hook. Beautiful weather forecast for this week again and I will be out there. I have not installed my super duper glow plug intake port extensions as I have not needed them at all this summer. And number three cylinder, farthest forward, will jam the intake manifold up against the angled section of the doghouse where it tapers toward the galley door. The fiberglass could be massaged a bit without too much trouble. (I had a little practice this summer with fiberglass. Don't ask.)

Now, we do get some stupendous sunny days even in winter here, so I might just need those glow plugs after all. I would need to finish up the wiring after I start doing the wiring.

Dave, so glad to hear about your excursions this summer and that the AD is running so well. I am pretty pleased with the MD17C as well. Hoping to avoid the bent pushrod issue that some have experienced with these Volvo Pentas.

[dkirsop]

I rewired my boat three years ago. I am just now collecting all my sketches, notes and photos so I can finish the wiring diagram this winter. You will enjoy many hours sitting on the head staring at the panel. The big decision is whether to protect only the circuits (as per the original) or fit a central fuse system similar to an automobile.

You will also have many happy hours practicing yoga in cramped spaces - enjoy!