All 3 runs A/F goes from normal to 20:1 third way down the track?
05-08-2011, 06:57 AM
#1
All 3 runs A/F goes from normal to 20:1 third way down the track? First 2 runs (1/4 mile track) on Nitrous everything seemed normal at launch....A/F 12:1 and falling until approx third way down the track A/F shoots up to 20:1 and the A/F Safety Switch in my Progressive kicked off the Nitrous. Figured issue could be in the stand alone so did a naturally aspirated run and the exact same thing happened. The car did not stutter or bog..I just got out of it based on the A/F readings (I have 2 A/F guages and both registered the 20:1). Drove the car home with no issues..runs fine. I'm no mechanic but I'm thinking fuel pump...but replaced only a year ago with walbro 225 and hot wire kit. Appreciate anyone elses opinions....TKS!
05-08-2011, 08:58 AM
#2
You could be sucking the fuel bucket dry due to a lack of fuel in the tank, or the venturi system not functioninig properly. The pump could be going bad or there could be an internal leak in the tank causing a pressure loss.
You should be running a fuel pressure gauge to see if the pressure drops.
This is valuable info to have. The air fuel gauge is good as it tells you that your engine is going to be damaged, but the pressure gauge can tell you the cause. Also you should be letting out of the throttle around 14:1 before permanant damage is done.
You should be running a fuel pressure gauge to see if the pressure drops.
This is valuable info to have. The air fuel gauge is good as it tells you that your engine is going to be damaged, but the pressure gauge can tell you the cause. Also you should be letting out of the throttle around 14:1 before permanant damage is done.
05-08-2011, 09:45 AM
#3
Thanks Lonnie! You could be sucking the fuel bucket dry due to a lack of fuel in the tank, or the venturi system not functioninig properly. The pump could be going bad or there could be an internal leak in the tank causing a pressure loss.
You should be running a fuel pressure gauge to see if the pressure drops.
This is valuable info to have. The air fuel gauge is good as it tells you that your engine is going to be damaged, but the pressure gauge can tell you the cause. Also you should be letting out of the throttle around 14:1 before permanant damage is done.
You should be running a fuel pressure gauge to see if the pressure drops.
This is valuable info to have. The air fuel gauge is good as it tells you that your engine is going to be damaged, but the pressure gauge can tell you the cause. Also you should be letting out of the throttle around 14:1 before permanant damage is done.
05-14-2011, 07:55 AM
#4
Mystery of spiking A/F solved! Went ahead and installed new fuel pump from racetronix which showed producing 62 pounds at the fuel rail vs 58 pounds per specs (vs 55 on previous). Anyway, hooked up fuel pressure guage and took for a run showing 62 llbs fuel pressure the whole time but experienced the exact same A/F spike after a few seconds on WOT. Went on to clean the MAF and no change. At this point hooked up a scanner which created even more confusion as it was showing fuel being pulled when both my A/F guages showed lean! This was the clue we were looking for though and decided to swap out the oxygen sensor for the A/F guage and bingo there was the issue! In the end a faulty oxygen sensor was making me and the Nitrous cut-off switch think the car was running lean when it was not. Thought I would share in case anyone else comes across this issue.....
05-14-2011, 08:21 AM
#6
Nitrous cut-off set at 12.7:1 I probably was not very clear on this point. The Nitrous cut-off is set at 12.7:1 and cuts off the nitrous flow at the exact second is reads this value. The A/F was jumping up to 20:1 (maximum reading) so fast there is no time to react before you see this happen. That's exactly why I invested in the protection of the nitrous cut-off switch which has saved my motor many times!
