Jump to content
SAU Community

Popped The Vacuum Line Of The Fuel Pressure Reg N Got Detonation...


Recommended Posts

Hey people.

So on the weekend i was giving my car some WOT. 2nd gear wound out fine but just after i got into 3rd it pinged- 1/4 of a second's worth, i got off the gas straight away. Sounded like 5 or so audible knocks before i got off the gas.

Turns out the vacuum line off my fuel pressure regulator popped off... Im putting it down to deteriorated vacuum line and a tune at a new boost level (18psi).

Since then iv reconnected the vacuum hose.

Car seems to start, run and drive fine still so Im assuming that the momentary detonation didnt do any damage... (tho i havent given it any WOT yet till i replace the vacuum lines)

any thoughts on what would have caused this? deteriorated line not holding the 18psi or something more sinister?

any thoughts on whether i would have done damage and how to check for it? im thinking that if i had done a ringland or a head gasket id know about it? (there is not smoke or anything coming out the pipe and no oil etc in the coolant)

cheers

J

The problem is that audible ping isnt always what kills the motor, its inaudible ping thats happening when you least realise it..

My concerns are if the fuel pressure would drop enough to actually make it lean out and detonate... Or if the tune is just on the edge as is....

My recommendations are that you do a comp test (and leakdown if you want) to gauge if the motor is in as good health as it was prior, then run the car up on another dyno and have the opperator monitor knock and the AFR's.

If all is good then dont worry and press on.

you would have bigger issues with the car leaning out massively when the line comes off the pressure regulator, once you take into account 18psi of boost the fuel pressure difference is only ~27psi instead of the 45 it should be (as the regulator adds 1psi of fuel pressure for every 1psi of boost to keep the difference in pressure at ~45psi)

as long as you didnt keep thrashing it without the reg connected to vac/boost the chances of it having melted something is fairly low.

Isnt it that its 1psi added to the base pressure for every psi boosted?

Meaning he would have more like 65psi rail pressure at 18psi boost?

yeah, I think titan was referring to you have to subtract the amount of pressure in the inlet, so 65psi rail pressure - 18psi boost pressure = 47psi effective rail pressure

Something like that, I wonder if the riser is for failsafe or if it actually needs it to run the injectors right...

Either way I am not convinced the vac hose is all that made it ping, sounds like the tune is either pretty hard or too close to the edge.

it is needed to keep the fuel flow linear(ish) to injector opening time, otherwise, say you have 45psi rail pressure and 45psi boost pressure, no fuel will flow out of the injector due to no pressure differential

cheers peeps.

Im going to replace the lines today and then take it for a drive and see if there are any anomolies indicating problems/damage. All feels fine so far so god damn are my fingers crossed...

Yeah as said the difference between 27psi and 45psi relative fuel pressure is a lot and definitely something I would expect to cause it to run lean.

Hopefully it was brief enough to not cause any damage!

As far as a cause for it, yeah just old or crappy vacuum lines. Definitely replace them, I really like the Turbosmart range of vacuum hose as its nice and soft and seems to hold on really well.

Also make sure there is enough length in the hose so that when the engine twists/moves that its not putting too much tension on the hose.

Is there already a clamp on that vacuum hose? If not get one.

Yeah as said the difference between 27psi and 45psi relative fuel pressure is a lot and definitely something I would expect to cause it to run lean.

Hopefully it was brief enough to not cause any damage!

As far as a cause for it, yeah just old or crappy vacuum lines. Definitely replace them, I really like the Turbosmart range of vacuum hose as its nice and soft and seems to hold on really well.

Also make sure there is enough length in the hose so that when the engine twists/moves that its not putting too much tension on the hose.

Is there already a clamp on that vacuum hose? If not get one.

cheers mate.

yeah going to go and get those blue silicon ones. Also def going to put a clamp on it! f*kn hell. Such a small thing that can have disastrous consequences...

cheers mate.

yeah going to go and get those blue silicon ones. Also def going to put a clamp on it! f*kn hell. Such a small thing that can have disastrous consequences...

Go OEM unless you *know* the brand is good. There's a lot of crap silicon hoses out there.

takes a lot more pressure. remember we are talking pounds per square inch..... not a massive amount of force in that little hose, a cable tie done tight will hold it.

but I agree nissan could have tried harder there (however Evos are the same - i think they all use JECS items?)

just cable tie it up with a small black one..

I cabled tie all the hoses up tight just in case any decide to come off.. I replaced all the spring clamps with screw clamps (yeah I am anal aye?)

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Good luck on the weekend mate
    • Must have been an absolute nightmare to drive when the power steer was out, the rack ratio/wheel size/caster is all set up for power assistance
    • Welcome to SAU, what are you looking at buying?
    • I checked the injectors again (1 and 2, since they’re easiest to access) to make sure they weren’t clogged. Even though the entire fuel system had been cleaned, I wanted to be certain. Everything looked clean, so I reinstalled and connected everything. When I started the car to confirm everything was okay, it immediately revved up high, so I shut it off straight away. I checked to see if I’d missed a vacuum hose or something, but everything was connected. On the second attempt, the car ran without the high idle, but I noticed a distinct “compressed air” sound coming from the engine bay. Tracing the sound, I pushed injector #6 forward slightly and the noise stopped — it turned out it wasn’t seated properly, despite the fuel rail being bolted down. While holding it in place, the car idled steadily without stalling and ran for over 5 minutes. At this point, I pulled all six injectors out just in case I hadn’t seated them correctly or dirt had gotten onto the O-rings. Unfortunately, I discovered that I had damaged 3 out of 6 injectors (the OEM 270cc ones) during installation. So yes, this was my fault. Since only the pintle caps were damaged, I’ve ordered a Fuel Injector Service Kit from NZEFI to refurbish them. In the meantime, I reinstalled my new injectors – the car now idles fine for over 15 minutes without stalling. I have not attempted to drive it so far. It’s not perfect yet, as it hesitates when the throttle is pressed, but it’s a big improvement. Unplugging the IACV with the new injectors idles at around 800rpm, even with the IACV screw tightened fully. But this is probably due to tune.
    • I wanted to try and preserve the front bumper as long as possible, they're not cheap and are made to order in Japan. Taking inspiration from my previous K11 Micra build where I made an undertray for the Impul bumper, I did the same for this BN Sports bumper but a little slimmed down.  This time round I only made a 'skid plate' (if that's the correct wording/term) for just the bumper surface area, the Micra version covered the gap like an undertray. Starting off with a sheet of mild steel approx. 0.9mm thick 4ft x 2ft in size. I traced around the bumper, cut it out and cleaned the edges. Luckily I was able to get two halves from one piece of metal In the video I installed it as is, but I've since then I've removed it to spray and add a rubber edging trim. The rubber trim is suitable for 1-2mm and it's a really nice tight fit. The bolts had to be loosened due to the plates being too tight against the bumper, the trim wouldn't push on I used some stainless M6 flat headed bolts for a flusher finish (rather than hex heads poking down), I believe this style fastener is used for furniture too incase you struggle to source some. The corner's are a little wider, but this may be an advantage incase I get close to bumping it  The front grill got some attention, finally getting round to repairing it. Upon removal one fixing pulled itself out of the plastic frame, one side is M8 that fixes inside of the frame, where as the other side is M5. Not knowing I could get replacements, I cut down an M8 bolt, threaded it inside the frame along with a decent amount of JB Weld.  The mesh was replaced to match the bumper. One hole on the bonnet/hood had to be drilled out to 8mm to accommodate the new stud, once the glue had set it could be refitted. I think the reason the grill was double meshed was to hide the horn/bonnet latch (which makes sense) but I much prefer it matching the bumper Bumper refitted and it's looking much better IMO The Youtube video can be seen here: https://www.youtube.com/watch?v=bVZP35io9MA
×
×
  • Create New...