yarddog

Long story short:

Had a crank but no start condition. Finally narrowed it down to a fuel issue.

The power feed to my fuel pump relay is only "on" when the key is in the "run" position but is off when cranking. It's been this way forever and was never an issue until now. I hope I haven't been slowly killing the VP I worked so hard to build a bullet proof fuel system for . Anyway it seems to start and run fine now when I have full voltage to the fuel pump when cranking.

I need a power feed to trigger the relay that is off when the key is in the accessory and off position by on when in run and crank positions. Any ideas?

BigIron70

The stock pump has 2 modes of operation: Mode 1: 100 percent duty-cycle with a minimum pressure of 10 psi except when the engine is cranking. Mode 2: 15 percent duty-cycle with maximum pressure of 7 psi with the engine cranking

The 15 percent duty-cycle is used to limit injection pump inlet pressure until the engine is running.

The transfer pump is self-priming: When the key is first turned on (without cranking engine), the pump will operate for approximately 1/4 second and then shut off. The pump will also operate for up to 25 seconds after the starter is engaged, and then disengaged and the engine is not running. The pump shuts off immediately if the key is on and the engine stops running.

Tate

Find the wire that triggers the fuel heater relay. Its hot in run and start position. I use it to power my shut off solenoid.

KATOOM

Before you do anything, what makes you think there's something wrong? Maybe the fuel pump is fine but you've acquired a leak in the return fuel line somewhere. That would make more sense. And having the fuel pump not pump while cranking is not going to harm the VP. Matter of fact, there is a factory flash which enables that feature since over pressurizing the VP during cranking was even a problem on stock fuel systems. You just dont hear to much about it.

yarddog

This was my first thought too so I cleaned and checked all the connections and replaced all the lines running in the frame that I couldn't see. After I did this it still will only start when the FP is running on crank.

All my problems started during our last cold snap when the filter jelled. The truck has had a hard/no start condition ever since. Before then it always started almost instantly.

I'm at a loss

KATOOM

That right there would stop me from bothering with when the pump cycles. I wouldnt blame the fuel pump since it sounds to me as if your fuel pump's trying to tell you something. Its obviously something which happened during/after the freeze and if the issue arose only after your filters froze then I'd definitely be looking at fuel lines, fittings, injector o-rings, etc..... What did you use or do to ungel the system? Maybe we need that "long" version you left out.

PaulDaisy

Powering the LP from a run-only circuit is the way to go. When I had mine wired to a crank-run circuit the truck had a hard to start when hot in hot weather condition. Moving to a run only circuit resolved the issue.
I bet the problem is elsewhere.