Converting an internal combustion engine to run only on hydrogen instead of running on petrol/diesel is actually possible in principle. We will explain two ways here, but there are more.

 

When you say "possible", it is in quotation marks. Always when you have to convert/rebuild/modify, it is always much more than you had initially expected. At the time of this writing, no pre-made conversion kits have yet been found on the market, perhaps there never will be either.

 

The next question that comes up is which engine type and model year to convert, but we will stick to completely general explanations without going too deep into the smallest detail. There are companies today that makes conversion kits for CNG, compressed natural gas, LNG, Liquefied natural gas and this gasses are very similar to hydrogen gas.[1]


[1](Dimitriou and Tsujimura, 2017)