Fuel Draining Back To Tank

[89CAL]

Seem to have a problem with fuel on the pressure side of the system draining back to tank when the car is switched off and left for a while. I am away from work for 7 days and when I come back it takes a bit to start the first time and recently it runs a bit rough for a bit after the car is started. When driving it has a small miss, but it goes away fairly quickly

I believe it is a problem with the fuel draining back to tank and just wondering if anyone has found anything similar and knows why it might be happening

I was away for nearly a month once and the car idled horribly (Sounded like it had a super lumpy cam) for about 5 minutes. But usually when I'm away for a week its not as big a problem as the issue goes away quickly and its not so bad if started daily, but I would like to fix it. I've found check valves for fuel systems but most seem to be for Carb and low pressure fuel systems. I dont really want to start forking out for braided lines and JIC fittings etc for the fuel system, would rather a barb fitting check valve etc

Just after anyone who has had a similar problem or is it just something you have to live with?

Thanks

[Marcus89]

I don't have a check valve in my system. It doesn't seem to affect my car other than when it's warm and I turn it off and come back like an hr later can sometimes struggle to start. Cold start is perfect though

[89CAL]

I never used to have the problem, it started probably a year and a half to two years ago.

[StevenCJR31]

is your fpr working properly?

[Kinks]

changed your fuel pump? or maybe the internal check valve has failed..

stock pumps have a check valve as do some aftermarkets. I know for a fact that bosch 040 has no check valve and I had hard-starting problems as soon as I put one in. had to pull it out and put a speedflow check valve in just above the pump and it has started first time every time since then.

[89CAL]

Have a Nismo Pump, and have done for about the last 4 years or so. Never had the problem to start with

I did change the FPR with another stock one a while ago, just cant remember quite when. (if it was before or after the problem started)

I have another rail and FPR with new Nismo 740's going on soon

Might disconnect the return line with the car off and see if anything comes out of the FPR at some point

[Shoota_77]

I'm going with return valve in the fuel pump. If you can, put a fuel pressure gauge between the pressure reg and the fuel pump and see if it drops off.

[89CAL]

Do the Nismo pumps have a built in non return valve in the pump? Or is it the little part that comes with the kit? I played with it a bit and decided it wasnt a check valve so I didnt put it in. Will have to see If I can adapt a fuel pressure gauge in there. Think I can, have an old gauge from work at home just have to get some barb fittings and chuck it in somewhere

Your talking about fuel pressure dropping off to quickly when the engine is turned off? or is the FPR supposed to keep a small amount of fuel in the pressure side? I imagine the FPR drains through an orrifice when the car is turned off to drain the pressure out of the system, but having never had a fuel pressure gauge in there I'm not 100% sure on what it should do

Thanks

[Hanaldo]

I think you will find your problem is something else entirely man, I've got a fuel pressure gauge on mine and the pressure begins draining off almost immediately after switching the car off. Takes less than 5 minutes or so to drain off all the pressure. I don't have issues starting no matter how long the car sits for. Regardless, surely you prime your fuel pump before starting?

[89CAL]

Yeah it seems like fuel drains out of the injectors and then when starting theres an air lock in the injectors or something.

Might pull the fuel pump out when the car is off the road for a look. Might all come good with new injectors and the other fuel rail and FPR yet

[89CAL]

I'll update this thread

I pulled the rail off today and noticed on the inlet side of the fuel rail, pretty much all of the fuel had drained back, Then pulled the return line off the fuel regulator and there was fuel and a little bit of pressure. Some air and fuel came out, had to block it off.

My fuel tank doesnt really pressurise anymore so not real sure if this is normal or not. Car had been sitting in the shed for about a week before I pulled the rail off.

If this is normal I think I wont really worry about it I think. Have another rail with new injectors and fuel reg on it so something there might fix it anyway lol

Not sure if the fuel damper could be the issue, seems unlikely but dont know much about fuel dampers

Edited September 16, 2013 by 89CAL

[Hanaldo]

Sounds normal to me. Unless you have a check valve in your feed line, there is nothing holding pressure there. Whereas in the return line, your pressure reg will hold some pressure.

Not sure how correct I am, but that sounds right to me. My return line usually has a little bit of fuel in there when I pull it off.

[Ben C34]

Also sounds right to me. When the pump primes it wouldn't take half a second to fill the line up again.

[89CAL]

Yeah the only odd thing I thought was that the little bit of pressure I described was on the tank side of the reg. But this may just be how the fuel line is run (fuel gravity feeding back towards the front when a line is removed)

Yeah I'll just live with it I think, it's not that annoying unless I havent driven the car for a while