Starting Problem, Air In Fuel Rail?

[89CAL]

Hi

I'm having a minor issue with cold start when the car has been sitting for a while. I wasnt to worried about it but recently I went overseas for nearly 3 weeks and when I got back the car would only just start and ran horribly for about 5 mins

normally but it will either fire first time and die straight away, then next time it fires up alright and idles perfect

Or

fires up, idles jump up and down about 500rpm (between about 500-1000rpm) a few times then it idles perfect.

I had a FPR laying around so decided to change mine in the off chance something was wrong with it. When I pulled mine out I noticed the fuel was slowly bubbling as if there was air trapped in the rail. Left for a while there was no fuel visible through the hole for the FPR

So it looks to me like over time the fuel drains back through the pump to the tank, but I didnt think this should happen. Was fairly sure the pump has a check valve to stop this happening inside it (I have a Tomei intank pump, same as Nismo)

Car also has 555cc Nismo injectors and 255rwkw. Fuel filter replaced not to long ago (Z201 from memory).

I'm wondering if the check valve in the pump has failed or something, or if perhaps I'm missing something.

Thanks

[DVS JEZ]

Does holding the throttle open slightly help?

[89CAL]

Does holding the throttle open slightly help?

When starting? I will try that next time. Are you thinking AAC? because I've pulled it apart and cleaned it not so long ago.

[DVS JEZ]

Its a good way to diagnose if its too rich or too lean. If holding the throttle open helps then its too rich on start up. If hinders then too lean.

[89CAL]

Its a good way to diagnose if its too rich or too lean. If holding the throttle open helps then its too rich on start up. If hinders then too lean.

Makes sense

I'll try and remember to do that next time I start it in the morning

can you confirm theres a check valve/anti return valve in the Fuel pump to stop fuel flowing back through it?

[DVS JEZ]

Yes there normally is. I have not seen a tomei though

[89CAL]

To easy, Thought so

I'll see what happens next time I start up

[DVS JEZ]

Any luck?

[89CAL]

Adding some throttle had no real effect on startup. Certainly didn't improve it anyway

[DVS JEZ]

Ok so it may be too lean on start up which can be caused by the fuel pump voltage. Try the rewire or atleast earth the fuel pump negative direct to the chassis ground

[89CAL]

I'll have a look tomorrow (if I remember) and make up a little jumper lead to earth it to chassis.

Or I might just do the full re-wire while I'm there

But I have tried priming the car constantly before startup (If I hold my key just before it starts the fuel pump constantly primes) with no improvement

But worth a shot anyway