Fuel line check valve size in mm

[dannyn424]

I have an 023 fuel pump and frequently have hard starts if left overnight, but occurs intermettently. I surmise that the pressure bleeds out from the fuel line overnight (sometimes after parking for a while) and want to install an outside check valve. I ordered an 8mm check valve for the fuel line? Is that the right size. I have one for the bosch fuel pump if its not on already. Thanks.

The hard start causes misfire codes and eventually throws car into limp mode. Thanks!!

[034Motorsport]

Fuel line on the B5 S4 is indeed 8mm ID, which is pretty much 5/16", the SAE equivalent.

[dannyn424]

Thanks Max!!!

[MonkeyKing]

I just installed the 044 drop-in from 034, and have long starts after the cars sits for a few hours. The drop-in kit came assembled with a check valve, but will adding another inline valve to the fuel line on top of the tank help? If I add an inline check valve, should I remove the one on the pump, or just leave it? Can someone post a link to which check valve I should buy? I searched for bmw part number 16 14 9 068 988, but can't find it for sale anywhere.

Why doesn't the check valve that comes with the 034 kit work?

[S4James]

I noticed that those BMW units leaned out my fuel mixture half a point or more at WOT...

[dannyn424]

I noticed that those BMW units leaned out my fuel mixture half a point or more at WOT...

Good to know james..... I really need a ride in a local stg 3 to see how much powa im puttn down..near fairfield cty...

[034Motorsport]

I just installed the 044 drop-in from 034, and have long starts after the cars sits for a few hours. The drop-in kit came assembled with a check valve, but will adding another inline valve to the fuel line on top of the tank help? If I add an inline check valve, should I remove the one on the pump, or just leave it? Can someone post a link to which check valve I should buy? I searched for bmw part number 16 14 9 068 988, but can't find it for sale anywhere.

Why doesn't the check valve that comes with the 034 kit work?

Some cars are just more finicky then others. My car has the 034Motorsport Drop In 044 fuel tank kit and started up without hesitation every time no matter what. Install the same kit into another car, and they'll get warm start issues.

However, in general, it's not a cold start issue but is usually experienced when you shut off the car while hot and then try to start it again soon after.

Actually throwing codes and going into limp mode is different and sounds like you may have an issue with the outlet connection at your fuel pump.

[dannyn424]

Im pretty sure the misfire codes pop up if it takes too long to crank and or fails to crank.. it well then start up on second try....

[Timtheguru]

Im pretty sure the misfire codes pop up if it takes too long to crank and or fails to crank.. it well then start up on second try....

These bots need to go...

[richmonds4]

If the rail doesnt stay pressureized after shut down ,
Then the fuel can vapor lock in the rail .
This can cause hard start and missfires .
I Put in a in line fuel guage in mine , now i can watch and see if its bleeding down !

[dannyn424]

If the rail doesnt stay pressureized after shut down ,
Then the fuel can vapor lock in the rail .
This can cause hard start and missfires .
I Put in a in line fuel guage in mine , now i can watch and see if its bleeding down !

If this is indeed the case, will installng my external one way check valve on the fuel line fix the problem? Thanks.

[Caddy7]

It should!!

Whitch line on the pump is the line that this should be mounted on? Anyone have a pic?