Fuel reg & holley carb problems [Archive] - Chevelle Tech

: Fuel reg & holley carb problems

Jan 28th, 08, 11:39 PM
Having a couple of issues with my fuel system :

1. I can't seem to get my fuel pressure below 9 psi, no matter what I do with my regulator. See attached pictures. When the adjusting screw is all the way in, or all the way out, no change in fuel pressure. Which, coincidentally brings us to problem number 2.

2. When starting my engine, I have my Holley Blue electric pump wired to a oil pressure cut out switch (5 psi op cutout). This in turn is wired to a toggle switch inside the car for manual on/off option. It's been working properly until today, when the switch wouldn't turn it on or off...even when I disconnected it completely :confused:

This has really got me perplexed. I do run the pump through a relay, battery feed, pump feed, ground, and hot line from relay to o.p. cutout switch.

Sounds crazy, but how could the switch work before, and now not ? I know the pump is pumping because I had a friend watch the pressure gauge. Bizarre.

3. This is the biggest headache. I run a Holley 750 dual feed, and I'm getting major grief over it. The problems started with gas geysering out of the front bowl.

So I swapped the needle and seat front to back...voila, the back bowl is spouting now. Ok, buy new needle and seat and replace. :sad: Guess what ? Now I've got gas gushing out of both the front and rear bowls. :confused: I even replaced both needle and seats front and rear.

Are they spouting because I can't get my fuel pressure below 9 psi with my regulator issues ?

Any suggestions would be appreciated. I've got to go clean up, as I reek of gas from my afternoon antics.

Thank you. :)

Just an example of how I had the regulator set. Motor not running in example photos.

regulator fully threaded in ...still 9psi


regulator all the way out...still 9psi


Jan 29th, 08, 12:22 AM
Wow John! The one thing that I can think of is that regulator being bad. What brand and model regulator is it? And did you buy it new, or was it from someone else? Is it a dead head regulator, or a bypass style?

Jan 29th, 08, 12:48 AM
On point number 3, check for sunken floats.

Jan 29th, 08, 12:50 AM
Thanks for the reply, Billy.

Reg was new in box when I bought the Holley Blue pump.

I don't know much about it. Best I can tell, one line in, and two out. One to my carb feed, and the other to the fuel solenoid for my nitrous plate.

I think I'm going to take it apart and blow it out. Same for my float bowls.

Jan 29th, 08, 12:52 AM
IF I recall correctly those Holley regs when you back out the set screw it drops fuel pressure. Run it in and it raises fuel pressure. I'd back off the set screw and rap on the main body of the regulator with a rubber or cow hide mallet. Sometimes on the holley regs they will stick if you run the set screw in too tight or too far. If this does'nt work it may be the diaphragm is old and cracked letting fuel bypass unregulated. You can get a rebuild kit from just about any speed shop or call jegs or summit. That style holley fuel psi reg if it is a standard pressure unit is only good for a 1 - 4 psi range. Max pressure units are good for 4.5 - 9 psi. Running nitrous you would be better served to invest some money in a new better quality fuel psi regulator. You don't want to skimp on fuel supply when the dental gas is flowing.Here a link to jegs for a look at the holley regs and a rebuild kit.http://www.jegs.com/webapp/wcs/stores/servlet/product_10001_10002_745059_-1_10323

Jan 29th, 08, 2:52 AM
Thanks Chris. According to the Jegs link, I've got the cheap reg. It came with the pump, and apparently it should have been the better one.

Oh well, gives me something to play with tomorrow.

That and the crazy wiring demons I've got with the pump switch.

Bob West
Jan 29th, 08, 7:51 AM
Do you have a filter inline betweem the tank and pump? It sounds like you're getting dirt in your needle and seat, and possibly whats messing with your regulator too.

Jan 29th, 08, 11:44 AM
Yes, Bob. Large cannister filter within a foot of my tank.

Jan 29th, 08, 5:57 PM
Got a replacement regulator under warranty. http://www.jegs.com/webapp/wcs/stores/servlet/product_10001_10002_18328_-1

For those unsure, the directions say, turn set screw clockwise (in) to increase pressure, and turn counter clockwise (out) to reduce pressure.

This should help reduce the fountain issue.

We'll let you know.

Jan 29th, 08, 7:47 PM
Please check your floats. I chased this same thing a year ago. I did replace my Holley regulator. But in the process of swapping needles/seats during my diagnosis, I managed to damage a float that had been good just a month prior during a carb rebuild.

Nine psi is too much for a Holley needle/seat, but if you get it the the range of 8 or so and still have the fountain, it could be in the carb.

Tom Mobley
Jan 29th, 08, 8:03 PM
see if you can get it to 5psi, and if that solves the problem. If it does you can cheat it up to 7 or so. 9 won't work.

Jan 30th, 08, 12:17 AM
Replaced the regulator, and had it set to 5psi. Took the old reg apart, and couldn't see anything obviously wrong with it, but sent it back under warranty anyways. So that has problem #1 solved.

Problem #2, unable to turn off pump with switch, I also figured out. My toggle switch cuts the power to the ign. side of the op switch, which is a constant ign supply.

The reason it was still pumping while cranking. even with the switch off, is it gets a hot feed from the cranking side of the solenoid while cranking to open the switch at 5psi and above.

I believe that if it had fired, and I stopped cranking it, it would have stopped getting power from that side of the solenoid. Then my toggle switch would have killed the ign. power, and the pump would then die.

I think I made it sound more complicated than it is.

As for problem #3, I'm still spewing gas out the carb, but at least now it's narrowed down to the carb. Gotta love process of elimination.

Pulled the needle and seats again, they look fine. I think it must be sticky float bowls. That seems like the only logical choice now.

I'll pull the bowls tomorrow and see what mysteries lie within.

Jan 30th, 08, 10:32 PM
Drop your floats in a little pan of fuel and see if they float, that's what I've done.

I have also mocked up my MityVac pump to a pressure gauge and then into the fuel inlet of the carb. This way you can see exactly the pressure that overcomes the needle. Do with with the bowls full of fuel and you'll know if you are holding pressure or not by watching the gauge. Do each side separately. Much safer this way than with the car running and flammable fuel coming out the top.

Jan 31st, 08, 2:40 AM
Thanks everybody for their help on this one.

I pulled the bowls off tonight, and there was a little bit of black dirt like substance in there. What was most significant was how far out of whack the floats were.

I reset them, with the bowls upside down, and set both primary and secondary floats to center of each bowl. They weren't closing the seat before.

I overlook this critical adjustment when I was chasing the faulty regulator. It was too late to start it, ( I had to give my neighbors a break tonight...open headers at bedtime 3 nights in a row would have them calling the cops), so I'll flash it up tomorrow. I am certain this is going to be problem solved.

Thanks all, again.

Feb 1st, 08, 12:57 AM
Thanks all for your suggestions and help.

Fired up tonight, nice and clean. No longer a fire hazard.

I love it when things work out like they should.

On to body work now.

Feb 1st, 08, 1:21 AM
You have patient neighbours. Mind you if they are like most of the retired folks on the island, no one would have heard it anyway.;);):):D:yes:;):yes::)

syracuse elkyman
Feb 1st, 08, 4:02 AM
them holley regulators were a constant problem for me in the past (they don`t like to be dead-headed) but I got rid of them in favor of a by-pass system with moroso ...works great now & I`m not supporting holley no more !!