My engine is hard starting?

We use to be able to get in start it up and drive away, then I noticed it needed to warm up some then it would drive or the pedal might go to the floor and shut off the engine. Like now one day of draining the battery trying to start it. I tried starting fluid, nothing, recharge. I did the full throttle cranked it over and it would run at 450 rpm but at full pedal or it would shut off. It is a motorhome built of a 1992 Toyota truck one ton frame. Please, not head gaskets, replaced plugs and it does have spark and I do not believe you sloped a timing belt 45 psi fuel after the filter, sprays at banjo fitting. Can it be a fuel pressure regulator? Filter was clean so fuel lines should be fine I would assume. Are the injectors prone to sensor damage or suggestions. Thank you

But when it starts up, it is perfectly fine. It will fire right up and stay running. I just asked my dad about the fuel pump though and said that we have not looked at that yet

No codes given. As I said it will start at full throttle, and will get up to temp running on all cylinders, but @ low rpm, if put in gear ( auto transmission) I bet it would die, I did feather it half throttle to full throttle and it once came up to full throttle, I backed off not to over rev the engine it went back to as mentioned low rpm. But no codes. Filter was changed I can see thru the old filter a screen mess, clean after I blew it out by mouth. My only thought not knowing much. Regulator, all the injectors. As said sprays at all banjo fittings, New plugs, old looked good, has to be lack of fuel. Right? Any known sensors I can jump or suggested go bad? Thanks

So what your telling me, is that I should install this gauge and take a look at the fuel pump/ pressure? How much does this usually run for just parts, considering I could do it myself.

Does the air flow meter have a test? It did back fire and blew off that intake tube to intake to it?Mass air flow or the one at butterfly? Culprits?

Awesome. Well ill let you know what happens after I do that. Because just this morning, it took over 20 cranks to get it going. Then after my class, it only took one turn. Sound like the fuel pressure?

Recently bought the vehicle had this issue before I purchased. Has had many repairs prior to and since I purchased it as follows. Timing set, water pump, complete tune up ie, plug wires cap rotor and coil pack. Due to stripped fuel line fittings at both inlet &outlet of fuel filter it had not been serviced for over 2 yrs. However I recently changed it and it was definitely plugged it made a noticeable difference but still starts hard when cool. After running 10min. Starts fine as long as it is warmed up. Also has check engine light on intermittently. It will be off for several days and randomly come on and back off. Eng. Light will also come on if the pickup is let run for extended periods. I have not yet checked O2 sensor. Please help