now what,,,, fuel?

[sportster96blk]

here's what i have, qwick fuel 650 carb,duel feeds from Holley regulator, 3/8 fuel line ,jegs 130 gph fuel pump and large filter now for the problem fuel pressure wont regulate when at 1/2 throttle or more there are bubbles in front fuel bowl . can i have a bad fuel pump or be over pumping the capacity of the fuel line ....george

[NVEGAR8D]

Hi,
i had a problem like that with an older 2bbl v8 vega . the line was so close to the exhaust pipe that the gas boiled at that area before it got to the carb. the motor would start to cough and sputter untili eased off the speed a bit and it was ok again. i ended up putting an asbestos rap in the spot and cured it .
nick75vega

[Wizeguyrc]

Where is the pump mounted? Do you have a sump in the rear or front of the tank? Is the pump being gravity fed or do you have it trying to pull fuel out of the top of the tank?
Or did Jegs have the pump made by the lowest bidder in China..lol

Tracy

[chevy art]

george alot of time the holley regulators go bad. not saying thats problem but keep it in mind. if for some reason you mount the fuel pump upside down it will still work, but will cavitate the fuel and eventually burn the pumnp out.. wisrguy may have called it in relation with the rear pickup and sump area. what exactly do you have for a rear tank or cell and how is it scavenged from this cell or tank. if you could describe your whole system in back, then perhaps one of thew guys could make a better call for you. also ,does this happen right away, or only after the car heats up. probably only a minor problem, so if you let us know your specs we will try and help art

[sportster96blk]

well i remade the sump out 3/8 brake line and bent the pipe the same way it was originally and it picks up fuel from the bottom of rear side of the tank. it does get close to the header on the passengers side but i have it wrapped in flexible heat wrap should with stand 500 to 1000 degrees of heat. I'm thinking about rerunning braided line and finding a way around that header so it wont be that close just to eliminate that scenario. jegs is sending me another pump to try ill be installing it Saturday cant get the braided fuel line till Monday. I'm sure my pick up is good ,I'm either boiling or starving it of fuel or both. I'm going to start with them. thanks guys i need all the thoughts on this i can get ....george

[Wizeguyrc]

If I'm understanding correctly, you do not have a sump in the bottom of the tank, but have a 3/8" line that is pulling as the original design.
I can't speak for the Jegs pump as I have never used one, but some of those pumps are designed to be gravity fed and have a hard time "pulling"
fuel and keeping up with supply and demand at higher rpm. When I was speaking of a sump, I meant as pictured below.
I had the same problem out of my 64 Chevelle. At high rpm, 4000 and higher, the car was running out of fuel. Low pressure, etc.
I added a front angled sump with baffles in the tank and it took care of the problem. While my Holley pump would do the job at low rpm, it couldn't pull enough fuel at W.O.T. After I made it gravity fed, I was good to go.
This may not be your problem. It's usually something simple. Just don't rule this out.

Tracy

[sportster96blk]

well Ive tried to remove my crush fitting to see if i was getting air there and no. heat doesn't seem to be it either so i think i need to add the rear sump as wizeguyrs pictured in the photo above and see if that solves it. know just to find someone who welds on gas tanks. installing my fuel pump vertical helped a lot much quieter.on goes the battle

[chevy art]

hey sportster. if you put the sump on you will need someone to solder it, and not weld it due to type of metal used on gas tanks. learned that one from Bill K . ill bet your problem is due to a little known fact that if you take the sock off the fuel pickup and just put the line back down in there with the tube being parallell with the bottom it will bubble up like crazy when the tank starts getting low. what you must do without the sock is to put the line straight down (at right angles with the bottom of tank). and have it about maybe a 1/4 inch from the bottom. learned this out of a tech tip in Hot Rod Magazine a few years ago. also when you put the electric fuel pump in make sure you run it off of a relay and you can still trigger the relay with that oil pressure safety switch that goes to the stock fuel pump (i assume you are running your setup something like this, and make sure you have the best ground possible for the fuel pump./ PS the sumps you buy from jegs or moroso are a little too wide and will fall into the area of the tank straps. you will probably have to custom make one, and you really only need one bung in it. you may not even need to do this. try what i said with the pickup strsaight down, or look at speedphreakes project journals.. that guys car runs fast as hell and if you look, he drilled one hole in the FRONT side of the tank and put a bulkhead type fitting in there(no welding) and it is gravity fed out the bottom to his awaiting electric fuel pump.let us know how things work out art

[Wizeguyrc]

I made the sump in the above picture and tig welded it using standard wire. I've never had to solder or braze any steel gas tank. Most tanks I see done have been mig welded. The only bad thing about putting a fitting in the front is that you have to keep a decent amount of fuel in the tank to make sure the fitting doesn't get "uncovered" under hard acceleration, cornering, etc. Which is a pain in the azz for a street car. You can cut the tank apart and add baffles around the fitting area, but that's alot of work. I made the sump face forward in my 64 Chevelle and I had to add baffles behind and around the fitting area to make sure I didn't "uncover" the fitting while driving on the street.

Tracy

[chevy art]

tracy i was suggesting adding the line in front end as it is very simple to get at right down through the hole where the pickup goues in and just drill hole and the fitting goes in with the fiber washers and its done. i know you need to keep gas in there or it will starve for gas. what were the dimensions of the sump you made. if my tank is good(thats coming out real soon to check it) then i will make a sump, and if you say it can be welded in (tig or mig?) then thats how ill have it done. did you cut the rectangle out close to the size of the sump, or did you drill a few big holes arount the size of the sump and leave a little metal(framing) around the hole, and did you do some sort of baffling in that sump area(is it really necessary). i want to use a single # 10 bung coming out of sump. ( aluminum or steel?)( russell male or female fitting?). thanks for info art

[Wizeguyrc]

Yes. I understand and agree with what you are saying on the sock, etc. I was speaking about the other car your referred to and the bulkhead fitting in the bottom, front.
The sump is slightly less than the inside width of the straps. Maybe 1/4" total. Around 2" deep.
You are right, Todd drilled 1 1/2" holes instead of cutting out the entire area. No baffles were added for the rear sump and the fittings are common 1/2" NPT, steel fittings from the local hardware store.
Another good tig rod for this kind of stuff is silicon bronze. The stuff cuts in like melted butter and is real good for anyone just learning how to tig.

Tracy

[chevy art]

thanks tracy. i will let my welder buddy know the welding rods you mentioned and i will get my tank down and cleaned out(if its in good shape) and im sure it is as my 75 vega has zero rust issues. i will make a few practice sumps out of coil stock aluminum(real light guage) and then go for the finished product. always appreciate your help art

[HAULIN' IT]

(1) Are you having this bubble problem only with the car running? (2) Does the fuel pressure do strange if the car is sitting still when brought up to 1/2 throttle? (3) Does it do this when the car is just getting warmed up?
What I'm getting at is: Unless you have done WAY more testing than it sounds like in this post...I think your jumping to conclusions that a sump is a cure.
When you say "won't regulate" (4) Do you mean that it has higher than normal fuel pressure? A sump or lack there of CAN'T fix this! It can only insure you have the needed fuel volume so the pressure doesn't fall off...not raise it in some way.
You were on the right track in your original post. Try soaking a towel in cold water & tiewrap it to the hose/tube in question & repeat your testing.
(5) What is the pre-set pressure of the pump? (6) Is this the standard in the bottom, out the Two sides - cheapy Holley regulator?
My Two cents, Don't pull the tank out yet. Answer questions 1 through 6 & we can come up with some ways to check this farther. Lorne

[sportster96blk]

well i added braided line for 95% of the entire fuel line just to remove possibility i had air leaks all so re-plumed the pickup tube and i have the original sock on it with a piece of 3/8 rubber tube making it fit on the 3/8s line so i should have the 1/4 inch space on the bottom of the tank. i did some adjustments to my float level and air fuel mixture and was able to get good power though out the entire rpm range but am not able to regulate the pressure (set it at 8 have it go to 12 reset it at 8 have it drop to 3) its a jegs race pump runs 130gph with a professional products fine filter and tank sock all hooked to that single in double out Holley regulator (didn't think it was a cheap one though) the gas does not pass any heat making sources now( found a way around the headers) engine runs very cool so i think i can rule out percolation.im beginning to think it might be my regulater is there a better one then holley ?.......george

[chevy art]

george jegs and summit sell a rebuild kit fot the holley regulator. its real cheap and its just a diaphram that you change. do it right in place in a few minutes. im going to rebuild mine next week just as a precaution,,, mine has been working ok for 15 years, but i know guys that had problems in a short time.try the rebuild before getting another. if you change to another you may have to change lines around because a new on may be shaped differently good luck art