How To Diagnose Faulty Injector?

[sweetr33]

Hey guys im having some headaches with my R33 GTST. I put a sard fuel pressure reg on it on wednesday night n bumped the pressure up to 52psi at idle. 10psi more than stock reg showed, anyhow it ran fine for one day. Idled normal and ran beautifully on boost. Until the next day it developed a misfire.At cruise and idle would run on 5 cyls but on acceleration would clear itself up n run on 6.

basically i compression tested my engine all readings are the same so scratch that. i swapped coil packs around and number 2 was still the problem so scratch out coil packs. Had a look at all my plugs n they were all very black n number two was soaking wet.

Whacked 6 brand new plugs in there n started it up, after it cleared itself it ran on 6 cyls. had fuel pressure set at 36psi, as soon as i started to bump pressure above 42psi it started to run on 5 cyls again and number two n was still the cylinder misfiring.

Also another thing to note is my idle hunts sometimes when the misfire occurs, like its got a major air leak, 500rpm to 1500rpm n so forth until it stalls. but this isnt all the time. tried squirting water around the intake manifold on number twon injectors to see if it was sucking in air from the seal but no difference. Im stumped, anyone know the symptoms for a faulty injector??

[Adriano]

just wondering why you would want to increse fuel pressure over stock, they run rich as from the factory.

[r33_racer]

why dont you swap injectors? Move no2 to say no3 and vice versa and see if the problem moves to cylinder 3...

Why are you bumping the fuel pressure up so high? You running an aftermarket turbo, trying to do a manual tune on it so you can run higher boost? Or is it knocking or something?

[sweetr33]

ok basically the reason i am trying to bump the pressure up is because i had it on the dyno n it made 346hp at the wheels but was running a tad lean top end so was trying to avoid buying injectors for now coz they are expensive, thought a fuel reg may work as a cheaper option coz i want to sell the car but now i have this issue, n the reason i dont change injectors around is coz its one hell of a mission to get the rail out to swap them over. cheers

[Abo Bob]

I think it's either that or take them all out to be cleaned and flow tested. Costs about $20 each injector.

[sweetr33]

yeah i had them all ultrasonically bathed n flow checked before i put them in when i build the motor 10k ago. Is there an easy way to get the rail out on the Rb25 engines? looks like a nightmare :s

[rob82]

Did you retune the light load, idle and cruise conditions? By going from 38 to 50psi you've introduced about 15% more fuel every where. The 02 sensor will pull some of the fuel out of it but that is too much of a pressure increase.

[sweetr33]

its still running stock computer wont it self adjust??

[sweetr33]

ended up finding the problem wasnt injector, it was the new sard fuel pressure reg i'd put on, fuel was passing through the regulator into the vacuum line n being sucked into the front of the manifold n straight into number two pot hence the over fueling in that cylinder mainly but fouling plugs, and rough idle. Take vacuum line off top of reg and theres a constant stream of fuel coming out. took a day of driving to give way but yeah. shouldnt overlook new bits hey :s

[Mr. Oizo]

wtf, was it faulty? or did you buy a cheapo one from ebay?

[sweetr33]

yeah it was faulty, it was a sard reg so not just a cheapo

[Mr. Oizo]

Did you buy it from ebay?