Three months ago I changed an injector pump
on a 4 JH4, not sure if they are similar. I th ink they are.
There is a thread here on that painful experience.
I don't know about there being a retaining clip. I had three studs with nuts, one of which was impossible to get a wrench on. Used a big screwdriver and hammer to move the nut. Not pretty.
Here is a word of advice not related to your question. If your engi he is like mine, and I think it is, you need to carefully mark the gears before removing the pump and then be careful to not rotate the engine
. there is an idler gear
between the crank shaft drive gear
and the pump gear. If you loose the relationship between th see three you loose your timing.
To your question, look for three nuts holding the pump to the forward housing. There is Lso a bracket under the pump holding it, that is not obvious.
Then some other stuff had to be moved, or at least relaxed, to allow reward movement.
It was not easy and clearly not designed for field maintenance
I'm on an I pad and can't find my earlier post back in late May.