This truck has 78,800 original miles and has new plugs, plug wires, coil pack, air filter, oil change, new oil filter, and new gas cap. Been having trouble for quite some time with slow start. It does have a P0442 error code hence the new cap that didn't solve the code. I don't know if the P0442 has any bearing on the hard/slow to start problem.

Looking at the slow to start problem I just did a fuel pressure test. If I turn the key on but don't start after about a second or so the pressure climbs right up to 65lbs. Once I start, it stays steady at 65lbs. If I shut it off, the pressure drops back to 0 in about 10 seconds so it doesn't hold pressure. If I let it sit and the start it, the engine is slow to start and the pressure is about 15lbs during cranking until the engine starts. It then comes up to 65lbs right away. Is this normal operation or is there a bad fuel pressure regulator or fuel pump going bad? What would cause the rapid leak down of fuel pressure?

Thanks....

 

Welcome to the forum

No, not normal operation
System should hold pressure at 35-45psi for MONTHS

Running pressure should be 55-65psi

When you turn on the key the fuel pump only runs for 2 seconds, its a safety thing, that adds about 10psi of pressure

Cranking speed is 200RPM
Computer will not start fuel pump full time until engine has started, its above 400rpms

But you can turn on the key, count to 3, then turn off the key and turn it back on again to get another 2 seconds of run time, do this 3 times to get 30psi, then try to start engine

In the gas tank is the Fuel Pump and the Fuel Pressure Regulator(FPR), both are on the Fuel Pump Assembly
The Fuel pump has a built in Check Valve(back flow preventer) so when its off fuel can't flow back into the pump from the filter/engine
FPR has the same setup it prevents fuel under 65psi from flowing into the tank
So unless you SMELL gasoline at the fuel filter or in the engine bay then the pressure is being lost in the Fuel Pump assemble in the tank



The 2 second thing
If there was an accident and a fuel line broke the engine would stall and electric fuel pump would shut off, engine is under 400rpm
If that didn't happen and battery was still connected and driver incapacitated(key still on) then fuel pump would just keep pumping out fuel until tank was dry, which would NOT be a good thing, lol

 

Thanks for the info. Is the check valve part of the fuel pump itself, that is, if you replace the fuel pump (instead of the whole assembly) will that include the check valve? Also, could this check valve problem be the reason for the P0442 error code?

 

Yes, check valve is inside the fuel pump not a separate part
If you are losing pressure when engine is off you would replace the whole assemble, fuel pump and FPR, because either could be at fault
But check the hoses inside the tank, a crack or pinhole will cause same symptom, pressure lose and no leak outside the tank


P0442 Evaporative Emission Control System Leak Detected (small leak)
This is an EVAP system code so no, not related to fuel pressure

 

Thanks for all the help. I am back to close this thread with the results. I pulled the bed off. I ran a 2x4 under the wheel wells and lifted it straight up and pulled the truck forward making sure everything was clear of the truck. I replaced the fuel pump assembly to resolve the fuel pressure issue. When I took the fuel filler neck loose to lift the box, the steel fuel vent line where it connects at the hose from the tank broke off. It had mostly rusted through and broke the rest of the way when moving it out of the way. I replaced the fuel filler neck assembly after replacing the fuel pump assembly. I am guessing there was a little rust through causing a EVAC leak right where the vent hose connected to the fuel filler neck assembly. Anyway, the fuel pressure now holds above 50lbs for a long period of time and the "hard to start" condition is fixed with the fuel pump assembly replacement. EVAC code P0442 has been fixed and no longer shows up with the fuel filler vent hose fix. It is working great now in all respects. Thanks again.