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Flooding on SU HS-4, what am I doing wrong?

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Mark - didn't mean to sound like I was jumping on you. I appreciate the thought!

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no worries Rob. my thought stemmed from the fact that there is 1/2 the area to hold back the same amount of pressure. sounds logical to me.

mark
 
Thom - I have an inline fuel filter about 2' from the carb and an aluminum heat shield. I was tinkering with the carb while it was running yesterday and it was relatively cool. No gunk visible in teh bottom of the float bowl Good thoughts though!

BTW, I should mention I don't have a needle float as shown on the exploded diagrams I've seen. It's a ball valve on this carb.
 
Weee, got the latest goodies do you, sigh.
 
Someone explain fuel pressure regulators to me.

I took the one I had back to autozone, long story short, it doesn't work as advertised but it does apear to work.

The top of the regulator has a knob that varies the tension on a spring (I'll explain it's internals in a second) The knob has settings on it, 0.5 through 5.5, that are supposed to represent approximate psi. At any setting between 0.5 and 2, I get NO FLOW through the regulator. However, at 2.5 & above, I do get flow, and it's easier to blow air through it the higher the numerical setting.

As for the internals, just inside the intake line, is a ball valve that is pressed upwards (closed) by a spring below it. Above the ball valve is a diapram that acts upon the valve. If the diaphfram is pushing down, it opens the valve. If it is pusing down less than the spring below the ball, it closes. Make sense so far. The fuel passes through the ball valve (when open), and then leaves the output port. As fuel pressure builds, it pushes against the diaphram and closes the valve. I gather this is how it's intended to regulate pressure.

Now above the diapram, there is a second spring acting upon it's center (where it acts against the ball valve). The knob I turn effectively turns a plate inward towards the diaphram or outwards, away from it. The diaphram is in it's most downward tension at the low settings and there is less tension at the higher settings.

Presently at any setting below 2, the ball valve is closed. Once closed, you cannot open the valve by applying more pressure on the inlet, only by increaseing pressure on the outlet, which acts upon the diaphram. In other words, it won't work.

Assuming you have flow through the ball valve at rest, it then acts as a pressure regulator, since as pressure increases on the outlet, fuel will push upward on the diapram, alowing the ball valve to close. As pressure then falls though consumption, the ball again opens.

As far as I can tell, this regulator is effectively mislabled. 2psi is infact 0 psi. 5.5psi is effectively 2.5psi.

What I can't decide is, would this be a manufacturing defect, or is this an effect of my altitude. I'm at 4500' above sea level. This translates to approximately 2psi less atmospheric pressure than at sea level. Coincidence? I'm thinking probably so, since the diapram can be acted upon by air on both sides, so there isn't a sealed container with 1ATM in it causing this unit to malfunction.

It's really bugging me I don't know why this thing is built this way. Someone set me straight, my head is starting to hurt....
 
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BTW, I should mention I don't have a needle float as shown on the exploded diagrams I've seen. It's a ball valve on this carb.

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Hi Rob,
So far, you have described an intermittent condition of both float bowl overfilling & underfilling. Ball valve type inlets have several different versions, each of which the seat has to be at a specific distance from the lid. Also the actual required float setting will vary. Any deviation from optimum can cause the float/ball to bind in various open or closed positions with erratic operation.

Ball valves work well for some folks in some carbs & not well for other combinations.

I would suggest going back to the exact float needle & seat that are specified for your carb & setting the float level & float drop exactly by the book. This would eliminate any possibility of erratic float valve operation. Varying the fuel pressure may be just complicating the real problem.
D
 
"Someone explain fuel pressure regulators to me"

Yep, the way I understand things your altitude does indeed make a difference if the regulator is baised upon outside air pressure. For example it will have less air pressure to push against the higher you go. How much, beats me. Would think you would need a pressure gage to make sure.

But what the heck, put it on a low setting like 5 if you can see that that opens the valve a bit and give it a go. If it is adjustable you can play with it as you go along.

In my mind this would only be a stop gap fix for a proper fuel pump.
 
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The top of the regulator has a knob that varies the tension on a spring (I'll explain it's internals in a second) The knob has settings on it, 0.5 through 5.5, that are supposed to represent approximate psi....

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Rob,

Is this a chromed unit slightly smaller than the palm of your hand, and with inlet and outlet ports 180 degrees from each other? If so, I'm going to pass along a recommendation Bugeye58 (Jeff) gave me a couple of years ago. Get rid of it! He was adamant about it too. Seems they are finicky, erratic, and can even come apart while in use with the ensuing safety (fire) problems.

So what regulator to use? Get yourself a Holley fuel pressure regulator part #12-804. This is a low pressure adjustable 1-4 psi unit that many racers use and has proven reliable over the years. You should be able to pick one up at your local parts store for less than $25.00. Here is a link to Holley's web site:

Holley Fuel Pressure Regulators

You can also get these at Jegs (www.jegs.com) or Summit Racing (www.summitracing.com). Here is a direct link to the listing at Summit (and lots of info on the regulator too):

Summit Racing Holley Fuel Pressure Regulator

Hope this helps! /ubbthreads/images/graemlins/cool.gif

Tim
 
Dave - I think you are correct. I checked my float level and the distance from the float to the lid was high by 4mm (it was almost 9mm from the lip). I removed one of the washers so it was back to 4-5mm from the lid. I also tried a setting around 3mm from the lid. Couldn't determine which was better. But playing with the regulator settings, it seems I either flood or starve the carb, there's no middle ground.

Tim - That is the type of regulator I'm toying with and I'm going to take your advice. This little bugger has too much resistance. I can't get it to a good position. it's starving my carb at low pressure settings....I'm planning on placing an order with summit for that holley regulator and also a carter rotary vane pump. This little facet doesn't seem to cut it anymore.

So, at this point, I'm looking at a new regulator and pump. I'm curious if I should also consider replacing that ball valve in the float with a needle type from moss?

Guess I'll try the pump and regulator first and go from there unless someone advises otherwise.
 
What engine do you have? Most Spridgets take an HS2 carb. This is supposed to run on 1.5-2.5 pounds, and yes, that can be the problem with replacement pumps. One common thing that makes these carbs do this is a clog in the vent line on the bowl. There needs to be an open vent line on each bowl, otherwise it will trap an air bubble and prevent the float from coming up to shut off the needle valve, which makes sense if your fuel level in the float bowl is low. The later cars in the US (70 California, 71 Federal) have a connection from the float bowl vent to the charcoal canister, which can be clogged, which again can prevent the bowl from operating normally. (BTW, later cars--72->--have the anti-runon solenoid connected to the charcoal canister system, which will give you the opposite problem if it's malfunctioning--fuel can't flow out of the bowl.)
 
It's a 1500, single HS-4 instead of the ZS.

The vent/overflow line is presently connected to a return line to the tank. I don't have a charcoal canister anymore.


I haven't checked if the hardline is clogged or anything...Should I just run that overflow/vent down to the base of the engine bay? Any better ideas than what I've already done?
 
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One common thing that makes these carbs do this is a clog in the vent line on the bowl. There needs to be an open vent line on each bowl, otherwise it will trap an air bubble and prevent the float from coming up to shut off the needle valve, which makes sense if your fuel level in the float bowl is low.

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/ubbthreads/images/graemlins/thumbsup.gif /ubbthreads/images/graemlins/cheers.gif /ubbthreads/images/graemlins/thirsty.gif /ubbthreads/images/graemlins/driving.gif

You nailed it!

Tried blowing air through the return line to the tank and although air can flow through it, it presents quite a bit of resistance. Removed the vent line from the carb, runs great!

Going to tinker with it more tomorrow, but that was the problem!
 
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