Fuel Pressure ?

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Fuel Pressure ?

Post  bigjohn2007 on January 1st 2014, 12:19 am

With the engine off and the BG400 pump on after the reg it showing 12 psi.I got it started and set reg 12-704 on 7psi and float about half way in sight glasses.When i go back next day and try start it act as it flooded with one pump and pop back in carb so i check fuel pressure it on 12 psi.Motor run good after u get it fired up but getting it running is a mess.Timing set on 32 degrees.I cant figure it out after getting motor together i got bum out on it but now im trying again so any help i'll be thankful.
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Re: Fuel Pressure ?

Post  69F100 on January 1st 2014, 12:38 am

I always set mine to the bottom of the sight hole but with the regulator should only show 7 psi if that where you have it set when you shut the pump off it should go to zero pressure. Your regulator might be bad if you have another one try it and see if stops it at 12psi it is pushing by the needle and seat and flooding it.
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Re: Fuel Pressure ?

Post  bigjohn2007 on January 1st 2014, 12:46 am

i got a 12-803 u think it hold the pressure of that big pump?
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Re: Fuel Pressure ?

Post  69F100 on January 1st 2014, 12:59 am

bigjohn2007 wrote:i got a 12-803 u think it hold the pressure of that big pump?

That is the same regulator I had when I ran gas I did have a problem with it when I put it on but it had been sitting for a while Rick AKA 557 mazda took it apart and we clean it and I never had another problem out of it. It wouldn't regulate the pressure right take the 4 screws out of the bowl part and take it apart and make sure it clean.
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Re: Fuel Pressure ?

Post  69F100 on January 1st 2014, 1:03 am

bigjohn2007 wrote:i got a 12-803 u think it hold the pressure of that big pump?


IT should hold the pressure be worth trying I see you had a different one listed in the 1st post. I still have my 12-803 in my trailer as a back up.
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Re: Fuel Pressure ?

Post  bigjohn2007 on January 1st 2014, 1:16 am

Thanks good idea i try it Cool 
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Re: Fuel Pressure ?

Post  Larry Williams on January 1st 2014, 3:29 am

I had a similar problem turned out to be the size of the return line. i had a - 8 needed a - 10


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Re: Fuel Pressure ?

Post  bigjohn2007 on January 1st 2014, 5:46 am

Larry Williams wrote:I had a similar problem   turned out to be the size of the return line.  i had a - 8  needed a - 10


Thanks Larry i'll check that too...
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Re: Fuel Pressure ?

Post  maverick on January 1st 2014, 9:57 am

According to the catalogs, your regulator is a deadhead (non-return) style.  I would definitely use a return-type regulator with ample sized return line (at least an eight)  Also, the BG400 has an adjustable bypass (16 to 25 psi.)  I'd also set that at its minimum bypass pressure.

Also, I've found that some fuel cells come with #6 return line fittings installed.  If you need a #8, using adapter fittings to put a larger line on a #6 still leaves you with a #6 sized return.  Doing it right requires reaming the hole in the fuel cell and installing a #8 fitting. A return line that's too small will cause pressure to creep up.

Just a few things to check.
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Re: Fuel Pressure ?

Post  norm on January 1st 2014, 10:49 am

Where is the gauge mounted? If its liquid filled and mounted in the engine compartment , the engine heat will make the gauge read incorrectly. With it cold put a heat gun on it and watch the needle climb. Mine is in the engine compartment and I only look at the gauge with it dead cold. After it gets some heat I disregard it. No good if you spray, need a gauge inside with an isolator.
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Re: Fuel Pressure ?

Post  bigjohn2007 on January 2nd 2014, 9:43 pm

It is but the reading is before car ever startup so no heat but i see what your saying and makes another good point......
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Re: Fuel Pressure ?

Post  bigjohn2007 on January 4th 2014, 6:57 pm

Changed reg. to day and it still creeping as long as i leave pump on it raising.I ran reg like this with same pump on old motor no problem.Check line from pump to cell it right what else can it be??
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Re: Fuel Pressure ?

Post  maverick on January 4th 2014, 7:55 pm

I'm guessing that you're going to get pump bypass pressure to the carb if you're using a deadhead regulator.  I think it wants a return line.
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Re: Fuel Pressure ?

Post  bigjohn2007 on January 5th 2014, 12:37 am

Readup on this sounds as this is why it so hard to start to might be pushing past needle and seats making it very hard to start like it flooding also.


Last edited by bigjohn2007 on January 5th 2014, 1:40 am; edited 1 time in total
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Re: Fuel Pressure ?

Post  bigjohn2007 on January 5th 2014, 1:39 am

What type regulator would u guys recommended?part # please
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here are two.

Post  460pulling on January 5th 2014, 2:18 am


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Re: Fuel Pressure ?

Post  69F100 on January 5th 2014, 2:44 am

I am at work right now so cant get the # but it is a mallery with a return line with the vac port if you get one with vacume port / boost make sure it is one that works off vacume. Mine has to have pressure in the port for it to increase the fuel pressure it is for a turbo setup. Had thought about putting a small tub in the header but got to thinking about the heat and flame from the exhaust might not work to good with regulator and alky at the carb.
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Re: Fuel Pressure ?

Post  bigjohn2007 on January 5th 2014, 2:58 am

The 12-803bp looks like a good deal.How are yall tapping in the fuel cell for the return at the top with bulkhead fitting?How big line do i need run?
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Re: Fuel Pressure ?

Post  69F100 on January 5th 2014, 3:09 am

The top is good place mine is in the bottom I need to move it to the top so it dont airate the fuel so much I got 1/2" on the return
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Re: Fuel Pressure ?

Post  supervel45 on January 5th 2014, 3:28 am

bigjohn2007 wrote:Readup on this sounds as this is why it so hard to start to might be pushing past needle and seats making it very hard to start like it flooding also.
With the fuel pump on, engine off, is any fuel dripping from the boosters? I have had dead head regulators creep up, but not this high. For a bandaid type deal your could fire the engine and then hit the fuel pump, and see if it starts easier.

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Re: Fuel Pressure ?

Post  maverick on January 5th 2014, 7:24 am

bigjohn2007 wrote:The 12-803bp looks like a good deal.How are yall tapping in the fuel cell for the return at the top with bulkhead fitting?How big line do i need run?

Yep. Bulkhead fitting. I just use a unibit (stepped drillbit) to open up the hole, making sure to keep the cuttings out of the tank. It helps to turn the cell upside down and drill from the underside.
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Re: Fuel Pressure ?

Post  bbf-falcon on January 5th 2014, 12:59 pm

My pump has a bypass port @the pump,and I go from there to the tank.

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Re: Fuel Pressure ?

Post  bigjohn2007 on January 5th 2014, 3:07 pm

bbf-falcon wrote:My pump has a bypass port @the pump,and I go from there to the tank.
Is your pump a BG 400 that be nice if i could do this.I know i have a guage on the pump to show line pressure.thanks
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Re: Fuel Pressure ?

Post  bigjohn2007 on April 5th 2014, 3:35 pm

bbf-falcon wrote:My pump has a bypass port @the pump,and I go from there to the tank.
What psi are you running from the pump to the regs?
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Re: Fuel Pressure ?

Post  bbf-falcon on April 6th 2014, 11:37 pm

Sorry,don't recollect at this time. Changing pushrods right now ,will get back later.

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