PRT FumeFX doesn't render

Krakatoa for 3ds Max
1

I created a Fuel based FFX simulation, saving the channels Fuel and Velocity. Then I created a PRT FumeFX loader, connected my FFX grid to it and made sure there are particles drawn in the viewport right where I was expecting them. There are also two 3dsMax standard spotlights in the scene. Now, if I hit Render on Krakatoa, it reads the particles (according to the render log), calculates the lights but doesn’t show any particles in the render, just black frames.
There are also no particles visible in the alpha channel. I played a bit with density, but it didn’t help anything…no particles in the rendering whatsoever. Then I tried increasing the particle cloud’s density by using Subdivision with a value of two. Now, Krakatoa takes significantly more time for calculating, but again…black frames and nothing visible in the alpha. We are using 2.1.3.47998.

For debugging reasons, I put some PFlow particles into the scene…Krakatoa renders them like a delight, but not my PRT FumeFX particles. I double checked PRT FFX | PFD is activated, color is overridden to white and 'm running out of ideas.
I also opened an old scene on a different computer, also a Fuel Based (Export: Fuel, Velocity, Temperature), created a PRTFumeFX and connected that to the Grid. Again, particles become visible as expected in the viewport, when rendering the frames remain black.

Any idea what might be going on there?

EDIT: Ok, I found out I am stupid and I could use the Fuel stuff only when activating Generate Emission from FumeFX Fire (plus Use Emission) and so Krakatoa will read the Fire channel. But is there a way (via KCM) I could turn my Fuel into Density? I want Krakatoa just to read the particle’s position data and render that (just like when rendering smoke), without any fancy emission type of thing.

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You can select the PRT FumeFX and open the Particle Data Viewer. Take a look at the particle it reports and at their channels (and post a screenshot of PDV here if you want).
Additive rendering is achieved in Krakatoa by setting the Emission channel to the Color channel, while Color and Absorption are both set to black. But if the Color channel is also black, the emission will be zero and nothing will show up. Also, the Density channel might be 0.0 too. So look at these channels (if present) and try to override Color to be non-black and Density to be non-zero. This is all that is needed for volumetric rendering.

In general, PRT FumeFX was meant for rendering the Smoke and Fire channels, not Fuel. I have never tried to render a Fuel-only simulation, so we are both on new ground here.