Ok today i will be installing a fuel pressure guage. My question is now that i am running nitrous i am very worried that the stock pump will be dying. Now i did a search and i came up with a stock system would be 13-15 at idle. am i correct? Now when i goose it a little what should the pressure be at? Should it go down or stay the same or go up? I have made my regulator adjustable and i bumped up the pressure and it is running super rich. and i would like to know an ideal STOCK seting due to the jet chart being for stock pressure. I know it is always better to run it fat than lean but fuel injection is a little different to me. I would like to run it like 1/2psi more than stock to insure a little richer mixture. So i would like to know what GM "says" stock is. Thanks-Joe

 

the stock bin assumes stock FP. i would set it at 13-14 lbs. your regulator should maintain that at WOT if pump is up to task. an upgrade to a walbro(190?) might be a good idea. how old is pump? are you tuning? i see the cam in sig. now you are adding nitrous on top of a potentially lean condition if that cam/motor needs more fuel on top. seems like a risky proposition adding nitrous, that is, on a cammed motor with unk state of tune. i would consider a dyno run with WB02 to see where your A/F is at WOT before you add the juice.

 

oh it runs good with spray. It is just it is really fat. im trying to lean it out. It has a stock tune and runs fine. I wiull see what the F.P. is at during lunch and get back with ya. I have no idea how old the pump is. I bought the whole car as it sits minus the new trans, and rear end and the nitrous for $800 so i cant complain. If it blows up i have another TBI 305 at home to drop in. Right now it is just experimental. so 13-14 is good?

 

ok. I pulled a plug and it is still black. Maybe from before still. Anyways, the fuel pressure is at 12psi all around (idle and WOT) so my worries about the pump are gone. But why is it still running rich. It has dried the plug out (last time it was wet with fuel) since i have added the 4* advance timing. Should i go up 1 psi or leave it alone?

 

hmmm. maybe someone can chime in. i dont think that cam is all that radical? is it possible the map sesnsor is reading lack of vac at idle(higher MAP than stock) and adding fuel? due to cam profile? or did the prior owner swap injectors or chip?

 

he said that he didnt swap injectors or chip. All he said was an
LT-1 cam, timing advance, headers, and new fuel pump relay.

 

pull the part number off injector and do a search to determine what injector in there. seems odd a stock injector would run pig rich. possible map sensor failing? check for codes.

 

or coolant temp sensor possibly bad? seems should throw a code however.

 

it does throw a code every once and a while. I will see if i can pull it for you. Do you do the paperclip in the two top left terminals? It throws a code every time i get on it at the track. I never thought to pull it and see because it goes away when i cool it down.

 

take to auto zone or whomever and they will do for free. it may have 2 diffeerent codes .my jump of terminals makes it blink and it drives me nuts so i have wife count the blinks and pauses. she is already nuts.

 

ok, i went and pulled the codes with a paperclip and got a code 42 and a code 44. I dont know what they are but ill do a search. Maybe you guys can tell me a cure for them?

 

Stock fuel pressure is anywhere from 9-13 PSI. The following info is straight from a Haynes manual:

Code 42- EST (Electronic Spark Timing)-Poor electrical connection, open or short in circuit, defective ignition module, defective ECM (doubt this one). This code generally refers to a timing issue.

Code 44- Lean exhaust-Lean condition caused by malfunctioning carburetor/fuel injector, vacuum leak, low fuel pressure, etc.: defective TPS, defective MAP, defective oxygen sensor: defective ECM.

 

yeah well the code 42 i think is from my timing being advanced. But the code 44 could be Any of those. I think it is the map sensor from not enough vaccum from the LT1 cam as RONNY said. Is there any way to fix this rich condition?

 

is it rich all the time, or only on the nitrous? if it isn't rich all the time, then don't touch the fuel pressure. just adjust the jetting accordingly. if it is rich all the time, you will either need to lower the FP, or change it in the chip. the lt1 cam should should give you MAP errors, i idle at 55kpa, no issues.

the code 42 is likely from disconnecting the ESC to set the timing, disconnect the battery for a while, and that code should go away. code 44 is low o2 voltage. i would hook a voltmeter up to your o2, and see what it is doing. it is likely that your o2 is bad.

 

yeah it does run rich all of the time. What should i lower it too? Maybe 10-11psi?

 

well, first, if the o2 is going bad, and really reading lean. the computer is going to try to add fuel. That would be my #1 concern right now. get rid of the codes, before trying to crutch it by the FP.

 

good idea thanks dewey

 

well i called autozone and they have a bosch one for $20 so i think ill just replace the o2 sensor.

 

i would suggest getting a delco unit. the bosches are problematic at best.

 

really?? I had new bosch ones on my S-10 and man did it ever run better than the delco stock ones. granted they were new but i ran nitrous through them and didnt throw a code after that. Dont you have nitrous dewey?

 

i saw in another post that you do. Can you post a few pics of it here?

 

In my living room, its not in the car yet. I havea stumble that comes in about 5k, i want to clear that up before i spray. and i need to get a blow-down tube.

 

ahhh blowdown tube is something i dont have either. Im friends with the tech guys here and they will let me go without one.