Fuel pressure drops down track with elec. pump.......
#730705
06/21/10 10:02 PM
06/21/10 10:02 PM
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Joined: Oct 2005
Posts: 2,611 Elbridge, NY
Dart1031
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I need some opinions on this one...... I noticed the other day that my fuel pressure gauge was down to 3lbs. of pressure from the 1/8 mile on. It's a Mallory pump, not sure which model cause of the way it's mounted in the car I can't see a number on it. It was all ready in the car when I got it. This is a "back up" car and I'm not pulling it apart unless I have to, lol. The only thing I can think of that's causing this is because the gauge is tapped into the fuel line at the carb, not the regulator. At idle, and up to the 1/8, it's at 7lbs. Does this make sense, or could it be another problem? Also, the car runs fine and pulls the whole way down the track. It doesn't act like it has low pressure, but the gauge is telling me it does. Thanks in advance for any help!
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Re: Fuel pressure drops down track with elec. pump.......
[Re: BobR]
#730709
06/21/10 10:53 PM
06/21/10 10:53 PM
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Joined: Oct 2005
Posts: 2,611 Elbridge, NY
Dart1031
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Sorry, long day..... It's a 3/8" fuel line from the tank to the carb. Mallory pump, Fram canister filter(new element), stock tank, 3/8" pick up, Holley reg., Holley 750, shift at 6,500. Anything else you need to know?
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Re: Fuel pressure drops down track with elec. pump.......
[Re: Bob_Coomer]
#730710
06/21/10 10:59 PM
06/21/10 10:59 PM
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Joined: Oct 2005
Posts: 2,611 Elbridge, NY
Dart1031
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Quote:
Next time your at the track, raise the float level about 1/2-3/4 turns out on the bowls, and increase fuel pressure to 8-8 1/2 lbs..see if the car responds with any increase in MPH....If it does, there might be a fuel starvation problem.
Thanks Bob, I'll give that a shot.
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Re: Fuel pressure drops down track with elec. pump.......
[Re: Dart1031]
#730711
06/21/10 11:02 PM
06/21/10 11:02 PM
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Joined: Oct 2004
Posts: 5,620 long island NY
Ari440
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long island NY
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Quote:
Sorry, long day..... It's a 3/8" fuel line from the tank to the carb. Mallory pump, Fram canister filter(new element), stock tank, 3/8" pick up, Holley reg., Holley 750, shift at 6,500. Anything else you need to know?
1/2 fuel line and get rid of the fram fuel filter for a inline screen type fuel filter
1.39 9.85 - 137 mph
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Re: Fuel pressure drops down track with elec. pump.......
[Re: Dart1031]
#730712
06/22/10 02:01 AM
06/22/10 02:01 AM
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Joined: Aug 2003
Posts: 43,364 Bend,OR USA
Cab_Burge
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I Win
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Fuel consumption is much greater in the last half of the 1/4 mile than the first 1/8 mile do to rpm acceleration per second, the first 1/8 you go through two or three gears, the last 1/8 is usually done in high gear only. The Fram canister can be a limiting factor on the supply side, check it to see if it is plug up full of trash or debris A friend of mine ended up substanially increasing his fuel volume by adding another Fram in parelel from the tank to the pump by adding a Y to the inlet side of the pump from the two filters If you can swing it use a better in line 40 micron or larger in line race fuel filter instead of one Fram or two Frams
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Fuel pressure drops down track with elec. pump.......
[Re: Dart1031]
#730714
06/22/10 07:24 AM
06/22/10 07:24 AM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Basically you could have a couple of issues.... If the pressure held good before then its a pump MAYBE going bad(doubt it) or the suction side cant supply the pump with enough fuel
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Re: Fuel pressure drops down track with elec. pump.......
[Re: Thumperdart]
#730717
06/22/10 12:13 PM
06/22/10 12:13 PM
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Joined: Jan 2003
Posts: 25,200 Upper Midwest
MoparforLife
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Upper Midwest
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Quote:
Quote:
Fuel consumption is much greater in the last half of the 1/4 mile than the first 1/8 mile do to rpm acceleration per second, the first 1/8 you go through two or three gears, the last 1/8 is usually done in high gear only. The Fram canister can be a limiting factor on the supply side, check it to see if it is plug up full of trash or debris A friend of mine ended up substanially increasing his fuel volume by adding another Fram in parelel from the tank to the pump by adding a Y to the inlet side of the pump from the two filters If you can swing it use a better in line 40 micron or larger in line race fuel filter instead of one Fram or two Frams
That be me and I picked up way more flow w/the two filters but I`d toss those and get something better and less restrictive. Yesturday I changed out my cannister filter and installed an Earls in line screen filter and my gauge read 1/2 lb. more pressure when I fired it up.
Less restrictive will generally mean a more open filter with less filtering. Also remember more pressure doesn't always translate into more volume. In a carburated engine that doesn't require pressure to operate like injectors I prefer larger line size and more volume over higher pressure.
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Re: Fuel pressure drops down track with elec. pump.......
[Re: Dart1031]
#730718
06/22/10 08:46 PM
06/22/10 08:46 PM
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Joined: Oct 2005
Posts: 2,611 Elbridge, NY
Dart1031
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Thanks again for the replies Mr. P..... This car is fairly new to me, and I just noticed this issue last weekend. It may have happened before and I never noticed it. BobR.... No idea if the sock is in the tank. I bought the car with this fuel system. I saw the car run 11.70's before I bought it and I "assumed" everything worked OK. The way the pump is mounted I can't read the model number. I'll try and remove it this weekend to verify. drjay0...... That's how the pump is mounted. I know for a fact the car had 5 gallons of fuel that day. I don't think the pickup would become uncovered with that much fuel, but maybe it did.
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Re: Fuel pressure drops down track with elec. pump.......
[Re: MR_P_BODY]
#730720
06/22/10 09:57 PM
06/22/10 09:57 PM
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Joined: Jul 2005
Posts: 8,647 ELYRIA,OH
blownzoom440
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Joined: Jul 2005
Posts: 8,647
ELYRIA,OH
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Quote:
I think its time to pull the fuel system to check out what you have and to correct where its not up to par
maybe even flow test it with a ball valve into a jug.
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