Crappy starting after sitting and fuel psi question

[Zukifreek]

Ok so I've been battling a hard starting issue. When it sits especially if the fuel level is lower and the nose is uphill it cranks alot before firing. I tightened all the connections and don't see any leaks. Can one of you guys video your fuel psi gauge on a cold start up so I can see how your truck reacts? Mine will sometimes jump to 20psi for a brief half second while the wait to start is on before cranking and then it will drop right down to 0. I have started bumping the starter without starting the engine and allowing the pump to prime the system. Then letting the preheat cycle do it's thing. It seems to start better when I do that but not always. This is starting to pee me off...lol I'd like to put a switch in so I could manually turn the lift pump on before I crank it. Maybe I should change the overflow valve on the VP...it might be original still???

[War Eagle]

My 2nd gen also started hard this last weekend, Seems to have similar characteristics as you explained.I will be interested in what you find out. I did the once over and didn't find anything obvious but was thinking I must be bleeding off pressure and letting air in some where.

[LiveOak]

Put a manual guage on your fuel system to verify that pressure. Sometimes the indicated pressure on the in cab guage can be incorrect due to a faulty isolator or sending unit. At 20 psi, your fuel pressure is at the low end of being marginally high. If the reading in the cab is actually showing low, the fuel pressure could be considerably higher. High fuel pressure can cause hard starting issues. Target fuel pressure should be in the 18 psi range. Compare what both guages are saying. I am going on the presumption that you have already checked for any codes. Here is a decent primer on troubleshooting. Hope this helps. http://www.bluechipdiesel.com/vp44diagnostichelp.html

[dripley]

Definite sign of an air leak somewhere. Mine was leaking at the return tee and the banjo bolt at the rear of the engine. That will allow the air in and let the fuel go back to the tank. Running the lift pump before starting just pushes fuel back in where it belongs. I replace the orings on the tee and the sealing washers on the banjo bolt on the back of the head. Every once in awhile it will still happen(1 in 100 starts maybe), just not enough to make me go find it. When my engine does not hit in the first second and a half, I just let the lift pump run for a cycle and it starts right up. When you first turn the key on the ECM will bump the fuel pump and you will see the pressure spike and fall right back off to 0. This is normal. The fuel system does not hold any pressure unless the truck is running.

[LiveOak]

Rather than have you sort through the entire troubleshooting section. This is the particular scenario I was thinking of:

HARD START COLD, LONG CRANK TIMES, AND INSTANTLY RUNS SMOOTHLY This is typically due to a cracked or broken diaphragm inside the Injection Pump. To test for this try disconnecting the electrical power from the Lift Pump BEFORE turning the key on, and see if it starts better. This happens because the electric lift pump pushes air which is always in the fuel chamber inside the VP44 pump, through the crack or break in the diaphragm, into the mechanical high pressure pump and it becomes air-bound until it rotates enough times to bleed out the air. If it starts better without an electric Lift Pump, it is because the electric Lift Pump hasn’t forced air into the mechanical high pressure pump through the crack or break in the diaphragm, which is what separates the fuel chamber from the high pressure pump. This failure requires a VP44 replacement to fix the problem.

Excessively high lift pump pressure can cause the diaphram to crack thus causing the hard start issue and the percieved air leak/priming issue.

[dripley]

LiveOak is right, this also a possibility. Check your cranking pressure also. It should only be about 1/2 of your normal running pressure. Mine idles at just over 19 and cranks at about 10. I will be keeping my fingers crossed that it is an air leak and not the vp.