Brill_C-37M_Bus

Sticking Carb Needle Valve... Fuel Pump PSI too High?

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Hello everyone,

 

I have a question before I replace my fuel pump.  My bus has a Holley 852-FFG 2-barrel carburetor, which has a problem with its needle valve sometimes not closing, flooding the cylinders and vapor-locking the engine.  I know my fuel pump is not original, so I’m wondering if a fuel pump with too high a shutoff PSI could be making this problem worse.  I do plan to rebuild the carb, but want to get some road testing done before then, and I need to replace the fuel pump anyway.

 

The factory manual from ACF-Brill Motors lists my original fuel pumps as Autopulse parts, 12v, 2 PSI pressure, 10-15 gallons/Hour.  My current fuel pump (from previous owner) is a Facet Posi-Flo 60106, which is also 12v, but 4-7 PSI and 32 gallons/hour.  Does that seem excessive?  I can get a similar model Facet pump with 1.5-4 PSI shutoff pressure and up to 25 GPH flow.  I’ve looked for lower-rated pumps, but I don’t see any that I trust yet.

 

I’ve looked into the original pumps, but the sports car and super car market has driven the prices for Autopulse pumps through the roof, and I’m uncertain about their longevity with ethanol fuels.  Any advice would be greatly appreciated!

 

 

-Steven

 

 

 

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Most auto parts stores have cheap inline regulators that might do the task.

Cool bus. I had a Brill way back when, but it had been fitted with a 500 Cadillac and a motor home conversion. It must have originally had some sort of flat engine.

I had to put an under drive on the turbo 400. The builder completely missed the gear ratio calculations and I was screwed if I got stuck at the bottom of a hill.

Fun stuff.

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Posted (edited)

2X on the fuel pressure regulator.  I had a 1972 Mustang, rebuilt the carb, lost track of how many times, 2 new fuel pumps, still too much pressure to close the needle valve consistently.  I put in a fuel pressure regulator, never had another problem.

Edited by Graham Man (see edit history)
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Posted (edited)

Many floats and  needles can handle that pressure and if yours is flooding, then it's obviously it's not jamming the needle shut, it's more likely the float level is too high before the needle shuts fuel flow off.  

 

Any increase in fuel pressure will raise the float level.  And, it can cause flooding if it's enough of an increase. If you have the specs for what your carb's float level should be, you can try lowering the float level by bending the float arm nearest to the float.  General rule of thumb is,....  however much you change the distance measured at the horizontal center line of the float is how much the float level will change.  

 

Paul

Edited by PFitz (see edit history)
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Holley makes a GOOD fuel pressure regulator with a bypass.

 

(Opinion) stay away from the dial type inexpensive inline regulators found at your FLAPS.

 

You might try changing the float setting, but with 4~7 psi on that carb, I doubt it will help. Rather than bend the float, remove the float valve seat, and change the thickness of the float valve seat gasket to adjust the float.

 

Jon.

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Posted (edited)

Thanks guys.  I’ll admit, changing the carb float setting is totally foreign to me, I’ve never done any work like it.  I know my manual goes into extreme detail on carb work, so I suspect I could learn float adjustment when I rebuild the carb.  Or do you think it’s worth it for me to look up how to adjust the float and just try that by itself, rather than wait and do a full rebuild?

 

I’ll look for the Holley pressure regulator.  So I should set that to the 2PSI that the system was originally set up for?

 

Edit: I think I found a regulator that might work.  I wonder if this first one is an actual Holley part.

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F173723755033

 

The second one clearly isn’t.  Anyone have any experience with this QFT brand? https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F202605124354

Edited by Brill_C-37M_Bus (see edit history)

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You are on the right track.

Even with a carb and/or fuel pump rebuild you may want to leave this inline.

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Posted (edited)

I ran a Napa 12 volt 4psi pump on 6 volts to get 2 psi without a fuel pressure reg. works great. Just a thought.

Edited by Steves Buick
computer glitch half way through "thought" (see edit history)

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FYI.

For anyone that must use an electric pump, Summit Racing sells a low pressure 6 volt pump that is best for any float needle type carbs. It's rated 2-4 psi. Adding an inline pressure regulator to lower a too-high fuel pressure just adds one more thing that can fail.

 

https://www.summitracing.com/parts/atx-e8902

 

Paul

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I agree with the idea that fewer aftermarket parts are better.  But getting 6v DC on an exclusively 12v vehicle will involve another aftermarket part, so I’m going to go for the pressure regulator.  My hope is to someday tear out the modern pump and regulator and put a 2PSI Autopulse in... once I save enough to not be afraid of their ridiculous price tag!

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Just rereading your post.  I assumed you rebuilt the carb?  Most likely your float is not adjusted correctly, causing the flooding.  I would rebuild the carb or have it done my guess is your problems will go away.  

 

PS after rebuilding a few carburetors with my new sonic cleaner, I would never do one again without it.

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On 8/15/2019 at 1:37 AM, Steves Buick said:

I ran a Napa 12 volt 4psi pump on 6 volts to get 2 psi without a fuel pressure reg. works great. Just a thought.

 

Several people are doing this in the club, and have had no issues, but I am told the pump should be replaced often as they will fail without warning. That said, others have told me they are on the same pump for ten or more years. I called Carter Fuel Systems to ask them to make me a pump for a specific application and they declined. They use to do it and stopped several years ago. It seems they are particularly worried about six volt pumps being installed in airplanes and all the liability that goes along with it. 

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