Motor runs lean on spray

**Whiteboycntdnce** · 12-16-2007, 05:44 AM

Had the car on the dyno about a month or 2 ago... I have a 125 shot (wet) on the car, when the system engages, the motor bucks hard then sprays, but the wideband was showing 17.5:1 a/f ratio. Obviously... Not good

My tuner has told me to get a racetronix fuel pump, he believes the stock pump can't handle the extra load, so I'm going to go ahead and do that. He has also told me he has tuned a couple of cars that even after a fuel pump upgrade the nitrous systems still turn the motor dangerously lean.

Has anyone else had this problem? Im buying the pump later today and when it's shipped here I plan on installing them going back to the tuner and dyno. Just wanna get some input on this issue and see if anyone else has had the same problem?

**mrr23** · 12-16-2007, 07:39 AM

i've been 200 on a stock fuel pump. it's possible your stock pump is on the way out and that's why the lean issue is there. one way to make sure, is to attach a fuel pressure gauge and see what happens when you hit the nitrous. if it's dropping below 50 psi, you have a pump issue. if it doesn't, then you have other issues.

things to look at:
make sure the outlet part of the nozzle is pointed directly at the TB
make sure the fuel solenoid is opening

**Whiteboycntdnce** · 12-16-2007, 08:48 AM

I wasnt in the car when it was on the dyno, and my tuner was looking at the laptop I have an electric fuel pres. guage but NO ONE saw what the psi is =x I might take it out today and give it one shot and pay attention to the guage.

**Frost** · 12-17-2007, 05:34 AM

Originally Posted by Whiteboycntdnce

....
My tuner has told me to get a racetronix fuel pump, he believes the stock pump can't handle the extra load, so I'm going to go ahead and do that. He has also told me he has tuned a couple of cars that even after a fuel pump upgrade the nitrous systems still turn the motor dangerously lean....

Not several, just one other... tuned a wet kit recently that ALWAYS went lean. Owner replaced: fuel pump, harness, line to fuel noid, replaced fuel noid, tried a plate and 2 different end nozzles, replaced hose from noid to nozzle, rewired hot and ground to both noids, tests fine off the car but goes dead lean when sprayed. Tried with no fuel jet in nozzle and plate too. Everything on the fuel side was replaced; FPG senders is at the rail and fuel pressure twitched a lb or two. Never could figure this out so it was fueled manually through a different process.

With the issue your car had, I was focused on the wideband to end the pulls early, so I couldn't see where the fuel pressure was headed.

I can catch up with you on the street to mess with it sometime if you have any ideas or get anything changed up.

**Whiteboycntdnce** · 12-17-2007, 11:33 AM

^--- There ya' go haha

**mrr23** · 12-18-2007, 12:33 PM

i wonder if the hole where the schrader valve has some left over material from assembly restricting it?

**Frost** · 12-18-2007, 02:07 PM

testing just the fuel side (bottle off) and with or without a jet in the nozzle, fuel pours out.

**mrr23** · 12-18-2007, 02:08 PM

weird.

**Frost** · 12-18-2007, 03:22 PM

I have owned 4 different wet setups in the past (only 1 an ls1 setup) reaching back to 1994, and have installed and tuned a biggity buttload of them. NEVER seen anything like that before.

Just threw it out so Tim (original poster) was aware of it, as I was working on that setup at the same time as his. It's been ongoing for over a year with no resolution and basically everything being replaced one part at a time

Sure hope his isn't the same. I am telling him that his pump is suspect because after getting him tuned to a nice comfy 12.9:1, his injector duty cycle was 92% and his car is STOCK other than a lid. High IDC can be pointing to loss of fuel pressure. Either way, once the car has headers/cam and possibly heads and the jug, it's gonna need a pump and harness.

**Whiteboycntdnce** · 12-18-2007, 04:11 PM

:::cough:::lid/LTs/ORY/Catback:::cough:::

**Frost** · 12-18-2007, 05:07 PM

Originally Posted by Whiteboycntdnce

:::cough:::lid/LTs/ORY/Catback:::cough:::

Sorry I had your setup mixed up with another black SS from the same time.

I do remember that you have a 2000, so you unfortunately have the small injectors, so I guess 92% isn't out of line, but it's still quite high for the mods.

Does anyone here have any other suggestions for the violent lean hit he takes other than pump and harness replacement? It isn't just a lean spike, it stays lean.

**Whiteboycntdnce** · 12-19-2007, 03:59 AM

blah i actually JUST put the LTs and ORY on... BUT... What would it take (if this is another problem wet setup) to transform it to a dry shot? Just run the n20 lines to the airbox and scrap the fuel portion of the setup?

**Frost** · 12-19-2007, 06:23 AM

Originally Posted by Whiteboycntdnce

blah i actually JUST put the LTs and ORY on... BUT... What would it take (if this is another problem wet setup) to transform it to a dry shot? Just run the n20 lines to the airbox and scrap the fuel portion of the setup?

for dry, the nozzle should be in the neck of the lid for best results, HOWEVER, you MUST step up in injectors, as yours are almost maxed out and that is how dry is fueled

If I'm not mistaken, didn't we even try to spray with the fuel jet taken out completely?

**Whiteboycntdnce** · 12-19-2007, 09:16 AM

No... We were running short on time so I think we got 2 passes done, and then we had to call it quits. ..... Looks like I'm just gonna keep my fingers crossed and hope this racetronix fuel pump does the job!

**leftout** · 12-19-2007, 12:59 PM

I have seen where the piston has swollen on the fuel solenoid before because the fuel was getting warm, but usually it swells shut, but possibly this one is just enough to restrict the opening. should check this and if the piston is rubber replace with teflon.