Doug,
There are three different Onan 5.5 units.
It probably did have a fuel pump - I'll get back to that.
Without knowing the model and the age, that is a stopper.
I am guessing that it is a gas engine because it has spark plugs, but some of the Onan 5.5s are diesel and some are LP.
Collect the data plate and search the web, there is probably a manual -service or at least operators - available somewhere.
If the unit is more than 10yo, replace all the fuel lines and then test the fuel pump. There probably is one, but it may have been murdered by the alcohol that the put in what is now sold as motor fuel.
I have had to deal with this on all of my old generators.
Matt
Matt & Mary Colie
A sailor, his bride and their black dogs (one dear dog is waiting for us at the bridge) going to see some dry places that have Geocaches in a coach made the year we married.