Pressure sound in Fuel rail?

[CosmoE36]

i understand that with the ignition on but the motor not started the fuel rail and injectors are under pressure, but mine sounds lie i have a injector stuck open.

with my ignition on (car not started) you can hear this HISSING and of course it goes away as soon as i pull the fuel pump fuse.


first i unplugged the injectors from the injector clips so they are not recieving ANY power. put the fuel pump fuse back in and i can stil hear the HISS.

the sound seemd to be coming from the rear of the rail like the last 3 injectors thats at least where it sounded louder? so i took the rear 3 injectors and swapped them up front and put the front injectors in the back. bolted everything down (did not plug the injector clips back in yet) and after the fuel primed back up to the rail the HISS is back.


now i have left the ignition on for say about 10-15 min and went to start the car and it fired right up. so i assume that my cylinders are not flooding out.


i could have sworn before the motor build that the rail and injectors didint hiss like this before. im hoping its just the PRESSUE in the rail and thats all im hearing.

any thoughts on this or ways to test injectors to see if they are stuck open?

[card counter]

This will not cost you anything but time.Take the back 3 injectors and move them to the front and front to the back then listen and see where the sound is coming from.I really dont think the injector is stuck open what do your afrs look like at idle

[StreuB1]

Depending on you fueling setup.......your existing fuel system will make ALOT of noise due to the massive amount of fuel now flowing through it.

I have dual intank 255's, -8 lines, huge rail and an aeromotive A1000 FRP. You can hear the fuel surging thru the FPR and rail with the hood closed and the pumps running.

You can also hear the pumps 10' away. ;)


And in my opinion......its a defined hissing/slooshing noise.....just sounds like alot of fluid flowing thru something. lol

[CosmoE36]

Depending on you fueling setup.......your existing fuel system will make ALOT of noise due to the massive amount of fuel now flowing through it.

I have dual intank 255's, -8 lines, huge rail and an aeromotive A1000 FRP. You can hear the fuel surging thru the FPR and rail with the hood closed and the pumps running.

You can also hear the pumps 10' away. ;)


And in my opinion......its a defined hissing/slooshing noise.....just sounds like alot of fluid flowing thru something. lol



yes the sound you describe is what i hear. i hear a Swooshing of Fluid moving through the entire rail.


is itpossible that my stock FPR might have bit the dust?

all i have are bosch green top 42 lb injectors with stock fuel rail, lines and fuel pump for now. (Walbro is in the mail)



i actually pulled the injectors out but left them in the fuel rail so i could see the tips of them. i put the fuel pump fuse back in and the loud soudn of fluid came back but i saw no fuel come through any of the injectors. its almost like my fuel pump is PUSHING fuel through the rail and back through the return line ona continuous cycle even though the motor is not running.


also one mroe bit of info.

i started my car (which started just fine) backed out into the street. turned the motor off but lef the ignition on and pop the hood and the noise was gone. it was nice and quite like it used to be, i started the car it started fine turned it back off left ignition on and the noise was back. i was like wtf.

i almost thought the issue had resolved itself. its like fuel is getting PAST the stock FPR and just rushing through the rail back through the return line.


oh yea my AFRs at idle are at about 15-16 back and forth run a little lean at idle but that should be fine. theres no RIch fuel smell at idle or from the exhaust

[StreuB1]

Your fuel pump primes for 15 seconds when the key is in the accessory position. Once you turn it the pumps run for 15seconds and then shut off.

What you are hearing is the fuel in the rail. When you turned the car off.......the pump stopped and the fuel stopped flowing.

:)

Sounds like nothing is wrong; just a little paranoia. ;)

[CosmoE36]

Your fuel pump primes for 15 seconds when the key is in the accessory position. Once you turn it the pumps run for 15seconds and then shut off.

What you are hearing is the fuel in the rail. When you turned the car off.......the pump stopped and the fuel stopped flowing.

:)

Sounds like nothing is wrong; just a little paranoia. ;)


i dont think this is paranoia lol. i can leave my car sitting with the ignition on and the fuel pump does not shut off after 15 seconds. i left the ignition on for about 25-30 min tonight while trying to pinpoint the noise and fuel was rushing through the rail the entire time

i know the fuel pump primes for 15 seconds and it shoudl shut off and i should not hear fuel going through the rail for 30 min non stop lol.

i would be very happy if it was just paranoia.. i am glad its not my injectors sticking open i feel much better after finding that out.

i suppose i will try replacing the FPR with another unti and see if it helps any.


heres another idea.


what would the outcome be if i got the rubber fuel lines under the intake mani mixed up..

there are 2 metal hard fuel lines and one line from the Fuel flter goes to one and one going back to the tank goes to the other, if i got them mixed up is it possible fuel could be traveling the wrong way through the rail and the wrong way through the FPR? i dont thk the car would even start if i had the feed and retunr lines mixed up. just throwing that out there

[Shuasha]

doubtful it would cause any issues at your power levels.

[StreuB1]

If yer pump is RUNNING for THAT long you have a fuel pump relay latched ON.

Pull the pump relay, the noise should go away. Throw it away and replace it.

PM Tom BMWperson. He's got a few actually.

[CosmoE36]

If yer pump is RUNNING for THAT long you have a fuel pump relay latched ON.

Pull the pump relay, the noise should go away. Throw it away and replace it.

PM Tom BMWperson. He's got a few actually.

hmm i hear what your saying.. this is good direction. wha oes LATCHED ON mean?

and if this was the case wouldnt i notice an issue with the motor running? or no?

so it looks like is a toss up betwen bad FPR and bad fuel pump relay..

are the relays known for going bad in E36's? i hope they arent that expensive.

i can only assume having a fuel pump relay latched on can wear out the fuel pump over time?

[fritzintn]

My fuel pump relay never really shuts off either from what I can tell on one of mine (which confused me since I thought it wasn't turning on at first since i never heard it 'stop'). Might just be a weird 95 quirk.

I'd pull the rail off once more (I know it's a pain) and check the rear return line. It's a bitch to get to, and when pulling up on the rail to get the #5/6 injectors in you may have gotten it loose. Even with a fairly snug clamp, fuel will still eek out a bit if it's not perfect (my front line does this a bit).

[ParadigmGuy]

Latched on just means that the relay doesn't disengage. It would be constantly engaged so the fuel pump would constantly be running. Relays are normally VERY expensive, somewhere in the area of $10-$30.

[CosmoE36]

My fuel pump relay never really shuts off either from what I can tell on one of mine (which confused me since I thought it wasn't turning on at first since i never heard it 'stop'). Might just be a weird 95 quirk.

I'd pull the rail off once more (I know it's a pain) and check the rear return line. It's a bitch to get to, and when pulling up on the rail to get the #5/6 injectors in you may have gotten it loose. Even with a fairly snug clamp, fuel will still eek out a bit if it's not perfect (my front line does this a bit).


o know its not the injectors or the rer fuel line gong to the rail at the rear of the motor. i pulled the rail up and i could see the rear fuel line there was no fuel spewing out. also there is no fuel smell like you smell with a fuel leak. and also even though fuel dries pretty fast i saw no wet areas at al anywhere at front or rear of the fuel rail or under he manifold when i looked under there.




i wil try swapping Relays first to se if that helps any. hopefully its just the relay is old and malfunctioning.