nope, I don't think you can get the flamestart from Napa. it's a 'custom' perkins
part (but i'm sure it's made by someone else - I just don't know who). TAD diesels sells I think, probably on fleabay as well.
It's essentially a glow plug
and a length of fuel line (pipe) with some fittings and a thermally controlled valve. it gets installed in the air intake manifold, right under the intake cap.
The fuel line (a small length of hard fuel tubing) runs from the fuel filter
block on the engine, and gets charged at low pressure with fuel when the engine is running.
The next time you go to start it, first you hit the glow plug
button (you'll have to install this and wire it to your battery/12vdc - use a fuse and wire capable of slightly more than 20 A - 25-30 should do).
When the glow plug reaches temp, the thermally controlled valve opens and dumps the contents of the tube (an ounce or so of fuel) onto the red-hot end of the glow plug, and of course it ignites, essentially lighting
a small fire in your air intake. usually takes 4-6 seconds to get 'ignition'.
then you hit the starter; the burning flame gets sucked into the cylinders and pre-heats, and helps initial firing along.
primitive? Yup. so is the rest of the engine, but it works.
The flamestart is the "OEM" solution to cold weather
starting on the 4-108.
If I were you, I'd try the decompression trick with your engine. Take the cover off the air intake (it usually is pretty loosely clamped there), and cover the intake port with your palm, get a good seal. hit the starter, and the engine will crank -trying to suck your hand in. it will crank really quite quickly - like nearly twice the speed of a normal crank (because you are creating a vacuum in the cylinders that is helping)- but won't fire until you remove your hand and give it air for compression.
I've found this little trick works really well on marginal perkins
engines - 4-108's especially. it gets the HP pump spinning much faster, which gives better fuel delivery to the injectors, so you get better fuel atomization right when you need it. Spinning faster also heats the engine up better internally, gets you better oil
pressure and therefore better lubrication on startup; and it actually reduces the load on the starter momentarily while you keep it partially decompressed. good for batts that are nearly dead or starters that are on their last legs.
you will end up with a little black ring of soot on your palm, and a red hickey in the middle where the engine tried to suck out your blood... but it goes away fast
...a little shot of WD40 into the manifold before you decompress it never hurts either.
wait - did you say it needs gasoline vapors to start when its warm too? that ain't right.
if that's the case, and it's spinning fast enough when trying to start, you've either got poor compression or poor fuel delivery. check compression (with a gauge in the injector ports). could be worn or busted rings. since you will have the injectors out to do this, then get them serviced. and hell, if you're going to an injector shop, take the HP pump to them too and get that checked out.