Hey all, new here and looking for some expirenced insight.
Truck: 1995 F150 351W 2wd Auto.
Fresh Top End job- only mod GT40 Lightning Heads.

The problem: cranks up perfect when cold but has a long lag time when cranking hot. Cant tell if it makes a difference feathering the pedal or just holding down the switch till she busts off.
Note: I have had this issue since I purchased the truck 2 years ago so it is not related to the fresh top end job.

I have searched all over the forums here and others for insights to this issue.

What I have replaced is literally everything now, and all Motorcraft. To be detailed:

• Coolant sensor- both
• Ignition switch module
• Ignition module on fender (had grey one and per forums installed black one)
• TPS Sensor and calibrated to 0.98
• Idle Air Control
• New complete Spectra Disy
• Complete Tune up including coil/ ignitor
• Intake Air Temp (BWD unable to find Ford)
• Fuel Pres Regulator & Filter & Injectors
• New Magnaflow y-pipe w/ cat and all exhaust (to rule out a stopped up cat)
• Lastly have run 10 & 12 degrees on timing with no discernable difference.

I have tested and tested everything guys, and everthing was replaced when I did the motor work.
Again I had this issue before the motor work and before switching to the Black Ignition Module (per write-ups all over the internet regarding grey vs black)

Now lastly: I just did a fuel pressure test again, to see if anything has changed. (Dual Tank)
My results on both pumps: When Hot

• Turning key to on position pressure climbs to about 20, cycle it once more and climbs to 30. Turned to start and busted off after a few seconds but not immediately.
• Running Pressure between 28/30
• Openning throttle while running 1/4 turn all the way to wide open the gauge needle drops about 5 psi momentarily then picks up back to 28/30. Have not seen a higher pressure than 30 on any loads/ throttle openings.
• Remove regulator vac line gauge goes to 40 psi. Reatched vac line gauge stayed at 40 psi with load or idle- odly.
• Took gauge off and repeated from start with the exception of the vac line test and all same results, psi 28/30.

Now to me it seems like both fuel pumps are weak but I really want an experienced conclusion or second opinion. The motorcraft pumps are very pricey, and it just baffles me that both pumps/ tanks have the exact same readings. I dunno guys maybe im just over thinking it, but any feedback would be greatly appreciated.

I thank you in advance and apologize for the novel, best regards.
Nash

 

Is sure sounds like you have no fuel at the injectors when the engine is warm. Fuel pumps will not come on with a warm engine, fuel pressure is held by the fuel regulator on the outlet side and fuel pump check valves on the inlet side. What I did to verify a similar problem after to many no starts at the gas pumps was to run a wire from the fuel pump relay to a momentary push button (like a door bell) switch. By holding it down for a second while cranking, it'd pop right off. That wire just runs from the hot side of the relay directly to the pump, bypassing the "control" circuitry. I ran a fuel pressure gauge into the cab with stainless line, right off the test port on the fuel rail. After that, I really don't recall the fix, as it was at least 15 years ago, but it was frustrating for a while