2002 Frontier Crew Cab 4x4 SC hard start

[Davidlorang]

Recently purchased the above truck and have been doing a lot of work on it. I’m a diy mechanic so lots of learning along the way. Truck was in need of maintenance on a lot of things. 197,000 miles on it. Long story short I replaced the distributor and plugs and wires. Timed it as per the Haynes manual. Hood sticker said 10 degrees btdc. Truck runs very well now (used to sputter and shake at lights). My issue is when the engine is cold it will fire right up (within the forst 1-2 seconds of turning over. Like a vehicle should). When the engine is warm I have discovered it does not want to start unless I turn the key to the ON position for about 3 seconds before I start to crank it over. It always starts if I do this but has to crank for 2-3 seconds. My thoughts-
1- possible fuel pressure issue? But why not at cold temps? (Replaced the charcoal canister, fuel filter, and fuel pump when I had the bed off).
2- faulty part in the brand new O’Reilly distributor? I have seen other threads on this being a possible issue but it’s brand new?
3- Some other sensor or timing issue? Mass airflow? (Truck runs well just a quirky start).

TIA

[VStar650CL]

The first thing I'd check is the Fuel Pressure Regulator. Pull the FPR vacuum line and see if there's fuel in it, if so the diaphragm is shot. That will cause balky warm starts, but won't affect cold starts when it wants to be rich anyway.

[Davidlorang]

I installed a new FPR. (That’s a real treat on the 3.3!). It was bad as I had fuel out of the vacuumn line. However the vehicle still has a hard time starting when warm. Still have to turn the key on for 2-3 seconds before cranking. Any other ideas?

[VStar650CL]

That sounds like a fuel pump issue. All the only other things which commonly cause a prolonged crank aren't likely to respond to the key being left on.

[Davidlorang]

So I think we’ve narrowed it down to a fuel pressure loss or something related to the fuel delivery system. Ideas on how to test this? Fuel injector leaking? Check valve bad? (Is that built into the pump on the 3.3?). Crack in the fuel lines in the tank? Vapor lock? Very strange that it would only do it when the engine is warmed up and after it has been sitting for 10 mins or longer. Again once the fuel pump runs for 4 seconds it will start.

[VStar650CL]

Most parts stores will rent you a fuel pressure gauge, or you can get a China-cheap set off Amazon or eBay for about $25. Before you do anymore guessing, I'd just get a gauge and take a look.

[Davidlorang]

Plot thickens! I attached a fuel pressure gauge on the output side of the fuel filter. KoEo the pump gets pressure up to about 40psi. If I turn the key off, the pressure drops to 0 in about 8-10 seconds. If I turn the key on and start the vehicle I maintain about 36psi. As soon as I shut the vehicle off, pressure drops to 0 in 8-10 seconds. I believe the fuel should stay pressurized?? I cannot find any leaks on the vehicle so I’m assuming I have a check valve in the tank not working or a leak in a hose in the tank? I did replace the fuel pump when I had the box off and maybe a line is leaking or I did something wrong? Is the check valve built into the pump?

[VStar650CL]

It should hold pressure for a lot longer than that. I'm not sure on your Frontier, but on most of the models with fuel filters the check valve is part of the filter, there may or may not be one in the pump. That's why almost all filters have a direction arrow. You might try a new one, maybe that's your whole problem.