ignatz

I have one of these installed and it appears to be a pretty slick product ....



... except for one thing - the regulator doesn't work. At the left hand side near the blue return fitting, there is a jam nut visible and an adjustment screw that purports to regulate the pressure. What I thought was a fuel pump problem in another post appears to be the regulator in this fuel log. The adjustment screw simply turns in place and the pressure goes up and down by maybe 1/2 psi. The return line seems to be wide open.

I am wondering what I could be doing wrong here, or whether this thing is malfunctioning. Any users out there?

S10xGN

iTrader: (11)

Can't see the regulator or how it's plumbed, can you pan back a bit and reshoot? Could be trash under the seat or plumbed wrong...

ignatz

s10: Very little to see, but here you are



Just a screw that does little to nothing. It doesn't even go in and out so the underlying mechanism is mysterious to me. This is probably common hardware and I wonder if other regulators have their adjustment screws simply turn? Next step is to take it apart as I haven't gotten any help on the help line.

As to plumbing, the fitting to the left returns to the vent in the tank.

S10xGN

iTrader: (11)

On a real regulator, the screw puts pressure on a spring-loaded diaphragm that controls flow through an orifice. I see no way for that to happen with this setup. Are there no instructions for it? I'd keep the log, add a real regulator to the back end, and then you'll have adjustablilty...

MikeFSKSpeed

iTrader: (37)

Ive had an issue with those holding pressure in the past myself. Id put a separate regulator myself.

ignatz

I don't have any resolution on this yet. I did manage to get through to someone at Prestolite who was a little more knowledgable. He agreed that the adjustment screw ought to do a little more than nothing. Gave me instructions as to where to send it for repair. I spoke with Mike F (thank you for that, Mike) at S-K Speed, who said it's "worth a shot" at repair!

Kylel

iTrader: (2)

I have that same fuel log on my carb'd 6.0. When I first started using it I thought the screw worked like a regular external regulator, but it doesn't. Turning the screw just raises/lowers the pressure. imagine that the screw is like a camshaft lobe- turn it clockwise and the valve opens up further, keep turning it clockwise and the valve closes, keep turning it and it will open again, etc. You have to watch the fuel pressure gauge as you turn the screw slowly to set the pressure in the right spot.

Also, what size return line are you running? Is your return line big enough? I have an 8an feed and a 10an return on mine, and I can set to zero pressure. Just throwing some ideas out there.

S10xGN

iTrader: (11)

This would make it a "flow restrictor" and not a regulator. A regulator has an internal feedback contol loop that "sees" the inlet pressure and continually adjusts to hold a set outlet pressure. What you have is an adjustable restriction that does none of this. If your fuel pressure changes (like when a filter starts plugging) the outlet pressure will be different as well as the flow. It's a pretty piece, but of little use as a regulator.

ignatz

What you describe, Kylel, is the way I've seen the screw operate, and the way I've tried to set the pressure by watching the gauge with the engine running. The screw doesn't go in and out at all and perhaps the so called regulator is simply a butterfly valve. I think mine must be mostly wide open all the time and the screw doesn't do hardly anything. If this does regulate somehow, maybe I have a busted spring. However this is my first time use of a brand new part. I'm going to pull it apart and see what's in there in a day or two.

Let's see, you said "Is your return line big enough?". These are the stock Corvette lines, 3/8" feed and 1/4" vent/return. I would have to pull the body off to change them and once in a lifetime is plenty, thank you.

I measure my pressure as set to 6.0 psi with the return line closed. When I calculate the cross sectional area of the lines, area of the return is very roughly half of the feed line. And the pressure goes to about half. Not having majored in fluid mechanics, maybe that's just coincidence.

If I can get to the inside of it I'll try to get a picture.

Kylel

iTrader: (2)

It sounds like you are describing a dead-head regulator- does a return-style regulator work the same way? Isn't it just an adjustable restriction also?

My screw doesn't go in and out either- just turns. It's connected to an eccentric (like the cam lobe idea). I don't believe there is a spring in there. I don't know how low I can regulate my fuel pressure (can't remember off the top of my head) but it won't regulate down if fuel flow is so large that the fuel can't return as fast as it's being pumped because of a too-small return line. What fuel pump are you using?

ignatz

All these things have restrictors. The only thing that makes them "regulators" is a spring that measures force. Mine won't regulate "up". Wide open, best I can tell. I've had my share of problems, probably ignorance on my part aggravated by the way this thing doesn't work as advertised. The pump I originally started with was an edelbrock 1792 (160 GPH). The fuel pressure would go down near zero and the only explanation I can come up with is that it was cavitating. I downsized to a 1791, (120 GPH) and shut off the return line. It stays pretty consistent at 6 psi unless I "get on it". It doesn't really support my motor. I need overcapacity on the pump and regulation on the return. So far I have neither.

S10xGN

iTrader: (11)

It describes both types, but a return type is far better if for nothing else other than cooler fuel. I have a Holley "black" pump with -10 suction and -8 discharge that puts out 14# with a Barry Grant return-style regulator set at 5#. The rest of the lines are all -8 and 1/2" SS tubing.

ignatz

Nailed it Kylel! look at this picture from the regulator end



It is exactly a cam and I assume it is pushing on some sort of spring loaded piston. I can see it move in and out as I turn the screw. Do not know why it does so little. Guy at Mallory said don't try to repair it myself. Not sure what I can do to test it some more.