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#1
10-10-2010, 09:32 AM
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Car acts like it is running out of fuel on big end, suggestions?
I have 30+ passes on my current fuel system and have had NO issues till yesterday .
I went to BOP day at Cordova and my first three runs were good 11.78 11.82 & 11.84 @ 113mph. Then it started to fall on its face ,lay over on the top end charge (3rd gear only)til I let off the throttle for 2 secs then it would recover and pull thru the big end. I took the regulator apart to inspect looked good . I made 3 more runs problem still there . So .. Until I can get my electric pressure gauge mounted back in the car ( had fuel pressure set to 6 psi ) to see whats going on . What part of my fuel system is failing? This set up has been flawless in different weather conditions ,different fuel levels (always run with more than a half tank ). I'm running all RobbMc stuff.. 1/2" pick up in the tank to filter to 1100hp mech. pump deadheaded to RobbMc regulator .All 1/2" lines . holley 850 carb. Floats ? pump going bad ,regulator??
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69 Grand Prix 428 H.O. loaded "J" 11.51 @ 116 |
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#2
10-10-2010, 10:32 AM
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Running an alternator?
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John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates |
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#3
10-10-2010, 12:04 PM
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Yes , it's a street car .
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69 Grand Prix 428 H.O. loaded "J" 11.51 @ 116 |
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#4
10-10-2010, 12:48 PM
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Need to check the fuel pressure at load. (while going down the track)
May be losing PSI, using a return style regulator is better. Try bumping the pressure up and making another pass. Also check how much fuel it flows in a minute, need at least a gallon.
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John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates |
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#5
10-10-2010, 01:47 PM
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How much gas in the tank?
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#6
10-10-2010, 01:57 PM
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In the original post he states he always has a half a tank.
Robert
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67 Firebird 467 cubic inches 7.71 @ 92 in the 1/8 and 11.69 @ 115 in the 1/4. |
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#7
10-10-2010, 02:00 PM
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Have you checked your filter? I was just going over your post and noticed that you said if you get off of it and get back on it that the car will recover. Just throwing it out there as I had a car do the same thing and it was a filter.
Robert
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67 Firebird 467 cubic inches 7.71 @ 92 in the 1/8 and 11.69 @ 115 in the 1/4. |
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#8
10-10-2010, 02:06 PM
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What size of vent?
Any popping or sputtering? Lst time you changed your plugs?
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68 Firebird Are you running with the wind or breaking it? |
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#9
10-10-2010, 02:50 PM
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It runs clean everywhere ,idle, part throttle ,pulls hard always except when I get to 1000' then it just pukes till I let off for a bit then will run out back door.
I bumped the pressure up to 7 psi. no change .(taking reading w/inacurate gauge under hood  )I will check plugs and filter . I made many runs with this fuel set up and this issue just poped up out of the blue. I will get my electric gauge mounted in the car so I can check fuel pressure through out the run.
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69 Grand Prix 428 H.O. loaded "J" 11.51 @ 116 |
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#10
10-10-2010, 04:51 PM
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Add 1 vote for inadequate or malfunctioning tank venting.
 As soon as I got turned around on the big end I'd pull over to the side on the return road and I'd jump out and try opening the gas cap and see if I got a big rush of vacuum outta the tank to see if it's a venting problem. Just be careful doing that,you dont wanna end up wearing a couple of gallons gas. Also agree that checking the fuel filter(s) would be a good idea as well,that SOP most anytime there seems to be a fuel problem. FWIW Bret P. |
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#11
10-10-2010, 05:16 PM
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Quote:
Robert
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67 Firebird 467 cubic inches 7.71 @ 92 in the 1/8 and 11.69 @ 115 in the 1/4. |
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#12
10-10-2010, 06:08 PM
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Good way to check SC.
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68 Firebird Are you running with the wind or breaking it? |
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#13
10-11-2010, 01:42 AM
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Do you have a screen on your fuel PU in tank? Do you have an older fuel cell or foam inserts in your hard tank that are coming apart from age or alcohol? Might be clogging the PU on hard use and then dropping off when you shut down.
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#14
10-11-2010, 02:45 AM
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As others have said, you really need to know the PSI under load. If you let off and it recovers it's running out of fuel. You'll just have to work through it. Check the vent, then filter, clogged fuel line, regulator, pump or even something partially blocking the fuel flow in the carb.
You'll figure it out, good luck. Take it EZ, Brett
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#15
10-12-2010, 10:16 PM
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UPDATE
Ok... I pulled the RobbMc filter apart and found some crap in there .
 Plus I had it on "backwards" (duh) Anyway , I put my electric gauge in the car, set the fuel pressure to 6 1/2 and went for a blast. Ran it thru the gears up over 100 mph and steady 6-6 1/2 psi .Pulled hard  So.. I should be good , can't wait to go to the track now Thanks for all the suggestions.
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69 Grand Prix 428 H.O. loaded "J" 11.51 @ 116 |
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