Fuel Pump Going South?

[Scoobum]

Checked the line off fuel pressure at the track Saturday and it was down two pounds...secon d time this has happened this year. I've got the fuel pressure gauge mounted on the hood but it was hard to see exactly what it was reading going down the track(vibration). Anyway, is this a sign that the pump is weakening? If not...what would be causing this? I was showing 1.2 KR at the top of the track...02's were 808 at 20 PSI. All other SM numbers are normal.

[Steve Wood]

808 is usually pretty rich.  The drop in pressure could be the gauge being affected by the temperature, a tired gauge, the regulator, or maybe the pump.  Unless you have an expensive, high tolerance gauge, they can often be plus/minus 10%.  I would keep my eye on it and the 02s and see if you see a correlation between the two if there is more change.

[1KWIKSIX]

Checked the line off fuel pressure at the track Saturday and it was down two pounds...secon d time this has happened this year. I've got the fuel pressure gauge mounted on the hood but it was hard to see exactly what it was reading going down the track(vibration). Anyway, is this a sign that the pump is weakening? If not...what would be causing this? I was showing 1.2 KR at the top of the track...02's were 808 at 20 PSI. All other SM numbers are normal.

Hey Brad,

How do you like the new 6262 DBB Turbo with ported S Shroud?

Any comments from the "seat of your pants" experience?

After you get it shaken down & are sure you don't have any fuel pressure problems....an y plans on cranking her up to 26# boost?


dave

[Scoobum]

808 is usually pretty rich.  The drop in pressure could be the gauge being affected by the temperature, a tired gauge, the regulator, or maybe the pump.  Unless you have an expensive, high tolerance gauge, they can often be plus/minus 10%.  I would keep my eye on it and the 02s and see if you see a correlation between the two if there is more change.

The gauge is anyones guess...as I picked it up used with the braided line ,fittings, basically plug-n-play. It's an Autometer. The FP regulator is from Accufab...and is new this past spring. The pump would be two years old...with quite a few passes on it. Might be one of the bad Walbros.

[Steve Wood]

doubt that...they fall off a lot quicker than that if you drive the car a bit..if you trailered it, maybe

[Scoobum]

Steve, with me working 6 days a week, I haven't been to the track in prolly 6 weeks. I've been driving the car on the street regularly...bu t I never get into enuf boost to bring the alky on. Is it possible the alky in the tank has gone bad? I put a half tank of fresh gas in it before I left for the track.

[Steve Wood]

I kinda doubt it...alky does absorb water and if it is very humid, it might eventually get a lot of water in the reservoir, but, even then, it should still do a good job.  Most other cars use 50-50 mix alky/water..we are kinda the odd ball on using straight alky.  One of my cars sat for over a year before I fixed the flex plate and it still worked well...but, we are usually not humid here....it was 17% the other afternoon...bi t wetter at night...maybe 45%

[Scoobum]

Myself and the guys I race with have a private track rental coming up shortly. I gotta try and nail this down before the last big event. I wanna bump the boost up a couple pounds and pull some fuel. Thanks for your help.

[Steve Wood]

remember that too much alky and not enuf boost will also trigger the knock sensor...at 20 psi, you need only a hint of alky

[Scoobum]

Good point Steve. Norbs and I have it coming on at 14 PSI...wonderin g if we should have it turn off a little earlier (less density). Final plan is to run it at 22 PSI and I'd like the 02's in the 770's...depending on what the plugs look like. I'm open to any suggestions.

[Steve Wood]

on my cars, I run 25-26 and my 02s are around 740 on both.  that corresponds to about 10.9 AF


Note that this works for me...but, I tune for no knock whether using wb or the factory-numbers be damned...there are no magic numbers, but, I find a given car with a given sensor will be pretty consistent in the range...once that range is determined.

[motorhead]

Brad you are worrying too much... just run it.

FWIW, I run a rather expensive pressure transducer for tracking fuel, big time expensive AFPR, and unknown double-pumper pumps; and still have to re-adjust the fuel pressure based on the season. I use an external FP gauge from Crappy Tire to baseline my fuel pressure, I usually hook up a battery charger to the car to create a steady voltage and jumper the fuel pumps to set the pressure... this helps clean up some variables found when the car is running.

Plus, I don't have to touch the vacuum line.