Going Lean. Please help
Thread Starter
Pro
Joined: Oct 2007
Posts: 708
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From: Mandeville LA
Going Lean. Please help
I noticed in the last few weeks that my tune has shown an increase of injector duty cycle so I decided to look into it. It went from 85-86% - 90-91%. The only change I made was going back to a stock converter. My car is a H/C/I car that makes around 435 rwhp and has the l92/76 setup with LS7 injectors and stock fuel pump. I hooked up a BAP that will run only when a switch is on when I plan to spray the car. Attached you will find a screenshot of a bad lean spot I found today. It was 17.2 A/F. Not very safe .lol While I was trying troubleshoot the car, I attached a fuel pressure gauge to watch fuel pressure. fuel pressure is around 45psi until I nail it and it goes to 40psi. (Thats the screenshot you see below). I tried it again with the BAP on and the pressure went from 45 to 43.5. Do you guys think the fuel pump is going bad? Thats the only thing I can think of. I was thinking that the pump was starting to crap out and the injectors are trying to compensate for it. The car has 30k miles on it. What do you guys think? 
Safety Car
Joined: Dec 2000
Posts: 3,767
Likes: 5
From: Jacksonville Fl
Well, the lean spike happenned when the injector duty cycle had no change, meaning it's not leaning out from PCM, it's from lack of fuel.
Is your tank full when you run? Fuel slosh in the tank uncovering the pickup or a bad pickup sock can do it. It could even be a wiring problem to the fuel pump, or a pump relay not liking the accelleration.
Is your tank full when you run? Fuel slosh in the tank uncovering the pickup or a bad pickup sock can do it. It could even be a wiring problem to the fuel pump, or a pump relay not liking the accelleration.
Last edited by BBA; Aug 9, 2008 at 12:54 AM.
Safety Car
Joined: Jun 2004
Posts: 3,560
Likes: 739
From: panama city beach florida USA
St. Jude Donor '09
i dont know the specs off hand but the test is fuel line off and into a clean container then fuel pump on for say 10 seconds .you should have x amount of fuel. if ya cant find the specs let me know and i will try to find them. usualy if it fails this test its fuel filter.another test is to put an amp meter in place of fuel pump fuse and see how much the pump draws [amp wise]
Safety Car
Joined: Dec 2000
Posts: 3,767
Likes: 5
From: Jacksonville Fl
I would not suspect fuel volume, it was fine, dropped out and came back on. If the pump could not keep up, it would stay lean, not come back.
It's a slosh or fuel pickup problem or an electrical problem to the pump. Could be a loose wire connector, bad relay, etc...
It's a slosh or fuel pickup problem or an electrical problem to the pump. Could be a loose wire connector, bad relay, etc...
Thread Starter
Pro
Joined: Oct 2007
Posts: 708
Likes: 0
From: Mandeville LA
Thanks for the input guys. What is the fuel pressure supossed to be? I thought it would be higher than 45psi. It should never drop when I floor it. I can watch it drop on a fuel pressure gauge. Tank is 3/4 fuel. It is only going lean a split second. I also heard that the car does not have a fuel filter. I need to check into that. I am going to do some more testing and log voltage of car.
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