In-line Non Return Valve (fuel)

My car takes a fair bit of cranking to get started. As it's an easy enough job to carry out, I was thinking of fitting an in-line non return valve, for a "belt & braces" approach.

My question to the sage ones, where best to fit the valve, as close to the pump as possible at the rear of the car, or as close to the fuel rail/injectors as possible?

FWIW, its a system which returns fuel to the tank.

Richard.

The check valve should be located as close to the fuel pump output as practical.

Thanks David,

Can you explain why? If I hadn't asked the question I would have fitted it closer to the fuel rail where the pressure is required most.

Richard.

Since you seem to have a large delay while the fuel lines fill with fuel, why not keep the largest possible volume at pressure. Your pump will have less work to do before suppling the pressure you need.

Thanks David, that makes perfect sense.

Richard.

Be mindful if you don't have a fuel pressure sensor and compensated tune or closed loop correction/engine protection set up it could significantly limit the effective high load flow capacity of the pump and lean you out, especially if it's a boosted application with high final rail pressure on boost.

Unless you have an accumulator in the system (such as as much soft line as possible and a pulse damper) or an actual accumulator putting a non-return will make pressure drop fast if there is no fuel flow.

Is your pump prime actually timing out while you are cranking (3 or 5 secobds from memory on some ecus)? I'd personally prefer to mount a momentary switch in the cabin in parallel with the ecu trigger to the fuel relay (or ammend the ecu/PDM priming logic to maintain pump power while starter circuit was active) so you can keep the pump powered for as long as it takes to start without adding a restriction to the fuel system, also have consistent fuel delivery pressure for atomisation and half a chance to tune out cold start issues without going in circles.

Changing ecu logic is potentially free or the cost of an extra sense wire to the start circuit if you can't do logic via sensed crank rpm.

A momentary switch and wiring should be less than $5 and your time. I would do everything in my power to avoid derating the fuel system unnecessarily.

If this is a sudden change in behaviour I'd be checking the battery is maintaining voltage under crank load, you aren't losing coolant into the combustion chamber and fuel pressure regulator is working as usual.