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Why or why not Glow Plugs?

steelypip

Active member
769
68
28
Location
Charlottesville, VA
Good question. The MEP002/003 has them along with intake heaters. Don't know why they don't exist on the MEP-004. I suspect there was some durability or qualification item that lead them to using an ether shot system, manifold heaters, or whatever.
 

PeterD

New member
622
6
0
Location
Jaffrey, NH
Glow plugs are only used in engines that have 'pre-combustion chambers'. For direct injection engines (where the fuel is injected directly into the cylinder) glow plugs are not used.

Examples of direct injection engines are the Dodge truck's Cummins diesel, and the Hercules engines in the MEP-004 and MEP-005. The Dodge uses a heater grid in the intake instead of glow plugs, while the Hercules engines use an 'ether' starting aid for very low temperatures. I've toyed with a grid heater for the MEP-004, and I'm sure it could be done without too much trouble--but a block heater is certainly the easiest solution.

Glow plugs, though common, are not universal by any means. Some engines that do use glow plugs include automobile diesels (such as VW and Benz) and the 6.2/6.5 engines found in a number of trucks and buses.

There's nothing wrong with glow plugs, but without a pre-combustion chamber it is physically impossible to fit them into the combustion chamber. As well, the pistons in a direct injection engine such as the Hercules are radically different. They do have a small dished out combustion area in the top of the piston, with a very interesting ball like structure in the center. (Think a small ball (1/8 in diameter?) on a very short spike.) The ball gets heated and helps fire off the fuel once the engine is running.

BTW, the MEP-004 is a 4-cylinder engine, the MEP-005 is a 6-cylinder engine. Both engines are virtually identical, the 6-cylinder engine just has two more cylinders 'grafted' on to it... (Or, looking the other way, the 4-cylinder engine has the last two cylinders lopped off... :razz:)

The MEP-006 also has a 6-cylinder engine, but it is not a Hercules, and the MEP-006 is turbo charged.

Yes, I do have an MEP-004, have rebuilt it (the engine) so I'm rather familiar with them. I also have a number of diesel trucks (Hummers) with 6.5 engines (which I also rebuild).

Without glow plugs, without any form of heating, the MEP-004 will start reliably at about 20 degrees. Once colder than that, you need to heat the block, and run a good winter grade oil (or a synthetic) that has good cold viscosity. The secret to starting these is cranking speed, so oil in the winter months can be more critical. In my setup, I keep the MEP-004 in the shop in the winter so it is warmer than the outdoors environment. If I need it, I tow it out and crank it up.
 

m139h2otruck

Member
569
5
16
Location
NH
Actually, the military is using glow plugs on the newer 6v53T Detroit Diesel engines in the updated M113 personal carriers. They must have gotten sick of the older Bendix style thermo-start systems that the original 6v53 engines had and went to the glow plugs like the 6.2/6.5 GMC engines.

The simplest system for heating intake air is the Lucas Thermostart. Uses a little heater/valve plug like unit that goes in the intake manifold, connected to the return fuel (low pressure) line for fuel and a switched 12 or 24 volt source. Crank the engine, heat the plug/valve, fuel runs onto the hot element and a fire starts in the intake. Had one on a Long tractor and it would start at below zero every time. Have pictures somewhere of a unit I put on a 2-53 Detroit. Will try to post.
 

m139h2otruck

Member
569
5
16
Location
NH
It's a Lucas style (aftermarket) Thermostarter. Tractor Supply stocks them for Ford and M-F tractors. Just hook it to a low or no pressure fuel source and apply voltage (12 VDC in this case) to the element terminal and the heat coil inside glows red and opens a little needle valve which lets fuel drip out onto the hot coil. Instant fire in the intake!! Do this only while cranking the starter or the fire goes out from lack of air. Do this as required for a cold start and it should fire off at almost any low temp in the lower 48 states. As noted above, we had a Long tractor w/ a 45hp Perkins copy engine w/ one of these in the intake and it would start at below zero temps within in 2-4 trys.
 

m139h2otruck

Member
569
5
16
Location
NH
Just have to be sure you get the right voltage, the TSC ones are 12 volt. On line, I have seen them for 24 volt @ about the same price, $28-35/each.
 

Wolf.Dose

Active member
1,062
9
38
Location
Boehl-Iggelheim, Germany
There are direct injection Diesel engines arround this world WITH glow plugs, for example the OM 314 V or OM 352 A or OM 602 DE 29 LA or OM 501 LA/III, OM 501LA/IV, OM 502LA/III, OM 457hLA/III, OM 457hLA/IV and simelar. The glow plugs are active during could idle to reduce the emmission. The glow plugs are not needed for starting. For starting at very low temperatures there is a aspirating air preheater in use.
Wolf
 

PeterD

New member
622
6
0
Location
Jaffrey, NH
Wolf, I wonder how they fit into the head on those engines... I'll have to see if I can dig up an illustrated manual for one of those engines.
 
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