Where the heck is my fuel pressure goin? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 01-17-2009, 04:33 PM
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Where the heck is my fuel pressure goin?

Recently I changed out my Speed Demon 750 in favor of another Barry Grant offering, the Six Shooter tri-power. It went on easily and although it was second hand, it didn't seem to be causing any grief, at least at first.

I noticed that my fuel curve was running real fat and spending a while in the shop trying to get it reset something caught my eye that I cannot explain, nor resolve as yet. I use a Holley 110gph mechanical pump and a regulator set at 6. When the engine is cool, the gauge shows the desired 6lbs of pressure and I set the center carb up accordingly. As the engine gets up to operating temperature, the fuel pressure gauge starts to drop off and ends up near to 1-2lbs. Once the engine cools off a bit, the fuel pressure again reads 6lbs but again, drops off when it gets up to normal temp.

To date I have taken the following steps to no avail.

1. Replaced the inline fuel filter.
2. Replaced the regulator
3. Replaced the mechanical pump with another (still mechanical).
3. Traced out all my fuel lines and eliminated all the rubber sections with formed metal pieces. Also looked for any area where the fuel line could be affected by exhaust heat and only found one over the passenger rear hump and repaced that with metal as well and insulated it.

Any ideas at what is causing this problem, because it is eating my lunch. I can't say for sure I wasn't having a similar problem with the four barrel setup as I had some tuning issues with it as well that I suspect are related. I would really like to retain the tri-power.

Thanks for any and all interest....Carl in Riverview, FL

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Old 01-17-2009, 04:44 PM
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fuel pressure?

What brand of guage are you using? Most of the cheaper, mount near the carb or regulator, liquid filled guages are known to have this problem. they will read low when they get heated by underhood heat.
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Old 01-18-2009, 08:25 AM
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RE: liquid fuel gauge

I was not aware of that aspect regarding liquid gauge. Mine is not a cheaper model but is liquid just the same. I can't imagine it being that sensitive but funnier things do happen. It has been dropping even though the hood was open the whole time. I will check that option out. Thanks for replying.
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Old 01-18-2009, 08:36 AM
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Throw the liquid filled gauge in the trash. They do not work well under the hood.
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Old 01-18-2009, 08:52 AM
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RE: liquid fuel gauge

That's two against the gauge. I did some other browsing though older blogs here and found several with the same problems. I will change out the gauge and see what happens. Thanks again for the help.
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