fuel issues

[mechanized]

so i have a new to me 99gst with many mods and car has alot of potential but previous owner didnt seem to have direction with the car. so i spent the day yesterday straightening out wiring issues and such but biggest problem now is that the car has crazy fuel pressure (90+) according to the gauge at the regulator. ordered a new gauge and waiting on that. it has a high volume fuel pump(not sure of brand), 560cc injectors, aem regulator and aem high flow fuel rail. the idle is terrible, car is running rich and has a knock. thinking of taking the fuel system back to factory and starting all over again since it didnt come with any kind of way to control fuel pressure besides the regulator. it did come with a safc2 but isnt working so cant use that to try to calm it down. is this a good idea or would i be better off getting dsmlink to get at least the idle straightened out. seems to me that he was modding the car just randomly without actually finishing anything. any help would be appriciated...thanks!

 

[91talonts1]

The regulator is the only thing that's supposed to control fuel pressure. As long as the regulator is not being overrun, all you need to do is adjust the regulator to bring fuel pressure down to 43psi with the pump running and the vacuum line disconnected. It should run much better if pressure really is at 90psi now.

You will benefit from a way to tune for those 560s as you'll be running a little rich. But the safc should be capable of those minor adjustments if you can get it to work, I've never messed with one.

 

[mechanized]

thanks 91...was messing with the regulator yesterday but i dont think that the gauge at the regulator is working right which is why i ordered a new one. ill try getting it down somemore today. when i was searching around for some threads for help i found some generic tunes for the safc but since its not working right its tough to tell if im headed in the right direction. thanks again

 

[91talonts1]

Yeah not at all uncommon for one of those little regulator mounted gauges to be off. Just in case you didn't know, loosening the jam nut then turning the adjustment rod counter clockwise will lower pressure, clockwise to raise it.

 

[mechanized]

thank you!

 

[pat white]

if you have an wide band o2 sensor n gauge and ur running rich you can drop ur fuel pressure below stock to compensate for those bigger injectors ...shpuld work just moniter the air fuel ratio and don't get leaner than 11:1...anyone see a problem with this?

 

[mechanized]

I'll give it a shot then Pat when I get the new gauge...I think I have it tuned down now, doesn't smell like a gas station but the old gauge must be stuck at 90 cuz it hasn't changed....thanks for the help

 

[Coppermitsu]

At 90psi I'd think your gonna blow those injectors apart pretty quick is that at idle or?

 

[mechanized]

hey copper....i cant say for sure now that it was running that high since the gauge at the regulator is broke...i do have it backed off and according to the wideband its running lean but still has a bad tap/knock...new gauge should be here soon so then ill know for sure...just wondering if theres a bent valve...

 

[Coppermitsu]

Hard to say hope not, if check over everything externally then if you still don't find it pull the valve cover n look real close at the valvetrain for wear.
Food for thought widebands rear a average ratio not exact so you could be leaner or richer than what it's shows not by much but a wot pull on what's already showing lean could be all it takes.

What regulator is on it now

 

[mechanized]

its an aem, he also put the high flow aem rail on too

 

[Coppermitsu]

Surprised that would break

 

[mechanized]

Ok...so hopefully someone can still help me here...new fuel pressure gauge came today and I got off work early so put that in..tuned pressure to 42-44...and let it idle..still idling rough...still has knock...and looks and smells like fuel dripping from exhaust joint...not quite sure what direction to head here???

 

[mechanized]

Could I have an injector open? Was checking timing and replaced plugs and #4 was definitely wet...or maybe not firing? Sorry thinking out loud here

 

[Patchez_]

yes your injectors are all open too long for the size the best way to deal with that is to go back to stock and run ecm at stock or you have a couple options, on the 98+ models they had an updated flash-able ecm from the factory meaning you could buy software called evoscan and flash the stock computer to run your bigger injectors and also data log and tune. the other option would be to get a eeprom ecu from a 95-96 dsm and have ecmlink.com mod it and run link which is easier to use and has more info available. is the knock lifter tick or bottom end knock? there may already have been too much fuel thru the oil from running rich causing internal damage. in your position i would take the bottom end apart and blueprint/rebuild or at least compression, leakdown test and check crank end play to get an idea of what life is left in the motor so you can tune from there.

 

[mechanized]

thanks Patchez...for now till i get some other things fixed ill just buy a set of factory injectors..much appriciated

 

[mechanized]

just an update here...pulled valve cover and checked things out...checked timing etc...things look good, have a 4g64 spyder parts car so just to be sure i pulled injectors out of that even though i know the cc is not as much as what i need and stuck them in...no more knock/ tap while cranking...no excess fuel everywhere so it makes me feel much better about the injector solution...thanks alot for the help, if anyone has a set of 450,s laying around let me know if you wanna get rid of them...thanks!