Fuel pressure builds after a short while |
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Fuel pressure builds after a short while |
Seabird |
Aug 4 2014, 08:41 AM
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#1
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Member Group: Members Posts: 165 Joined: 21-November 13 From: United States Member No.: 16,683 Region Association: South East States |
Hello all!
Having some on going difficulties with my fuel system. Last time at the track I had a lean running condition when under load on the 1-2 bank. Swapped a gasket once back home and now can't replicate the problem. Decided I was going to refresh a few components as a precautionary measure. Fuel regulator (as this is where the split happens between the left and right carbs), fuel pressure gauge (the old one was well old), and adding a spare carb to my track side spares. Previously I had not had a problem with fuel pressure per the gauge. After swapping in a fresh Holley 12-804 and an oil filled gauge I was unable to regulate the pressure down to 3 psi. Was not able to regulated it lower than 15 psi for that matter. A little research on the web indicated that the 12-804 and the higher pressure 12-803 sometimes get mislabeled. So I bought a rebuild kit which came with both springs. Swapped the new low pressure spring into the new regulator. Initially I could get the pressure in the 3 lb range but after a sort while the pressure would creep up. To make matters worse if I bounce the throttle I actually can watch the fuel pressure drop off (IMG:style_emoticons/default/hissyfit.gif) The fuel pump is a Holley blue top so it has a max pressure of 14 psi. My next track day is 2 Saturdays from now so I need to sort this soon. Has anyone else run across this before? Thanks, Miguel |
stugray |
Aug 4 2014, 02:51 PM
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#2
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Advanced Member Group: Members Posts: 3,825 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
Just this last weekend (first time on the track) I was having a similar issue.
Car would run great for ~10 minutes hard, then start to bog at WOT and not have the same pep. Hard to tell if it is a lean or rich condition (murphy's law = datalogging was not working when this happened for AFR & EGTs). I suspect a fuel pressure problem. I have the holley red pump & regulator up front with the fuel cell, 3/8" steel line through the tunnel and a pressure gauge at the splitter in the back where they split and go to dual fuel filters & 40 IDFs. I have nice new lines everywhere except from the fuel filters to the carbs. Damn those weber fuel inlets being 5/16" / 8-9mm! I will definitely be replacing the weber inlet hosebarbs with AN fittings...( anyone know the drill & tap size for that?) I am even considering putting in a fuel pressure sensor and logging it with everything else. It is not heat soak as I have the phenolic spacers, tall intakes, and carbs are cool to the touch when I come in. |
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